Body temperature

Physiology and regulation

The body temperature is the difference between the amount of heat produced by body processes and the amount of heat lost to the external environment:

Heat produced – Heat lost = Body temperature

Despite extremes in environmental conditions and physical activity, temperature-control mechanisms keep the body’s core temperature (temperature of the deep tissues) relatively constant (Figure 28-1). Surface temperature fluctuates depending on blood flow to the skin and the amount of heat lost to the external environment. While there is no single temperature that is ‘normal’ for all people, the body’s tissues and cells function best within a relatively narrow temperature range, the normal range being approximately 36.2–37.5°C (Gordon and Craft, 2011).

FIGURE 28-1 Ranges of normal temperature values and abnormal body temperature alterations.

From Potter PA, Perry AG 2013 Fundamentals of nursing, ed 8. St Louis, Mosby.

Nurses can use knowledge of temperature-control mechanisms to understand and promote temperature regulation. The balance between heat lost and heat produced, or thermoregulation, is precisely regulated by physiological and behavioural mechanisms.

Neural and vascular control

Body temperature is controlled in the anterior portion of the hypothalamus (preoptic area) at a set-point that is normal for each individual. This thermoregulatory centre is monitored by peripheral thermoreceptors in the skin and mucous membranes and central thermoreceptors in internal organs including the hypothalamus. A fall in environmental temperature activates heat-production mechanisms such as vasoconstriction of blood vessels to reduce blood flow to the skin and extremities. When vasoconstriction is ineffective in preventing additional heat loss, compensatory heat production is stimulated through voluntary muscle contraction and muscle shivering. Disease or trauma to the hypothalamus or to the spinal cord, which carries hypothalamic messages, can cause serious alterations in temperature control.

Heat production

Heat production within the body is the by-product of metabolism, skeletal muscle tone and contraction, and chemical thermogenesis. Metabolism refers to the chemical reactions in all body cells. Chemical reactions require energy in the form of adenosine triphosphate (ATP). Any ATP metabolic process results in the production of heat. Food is the main fuel source for metabolism; its energy is transferred to ATP which in turn transfers energy to body cells. The amount of energy used for metabolism is the metabolic rate. When metabolism increases, additional heat is produced and vice versa.

Heat loss

Heat loss and heat production occur simultaneously. The skin’s structure and exposure to the environment result in constant normal heat loss through radiation, conduction, convection and evaporation (see Figure 28-2). Diaphoresis is profuse sweating associated with an elevated body temperature, physical exertion, exposure to heat, and mental or emotional stress.

FIGURE 28-2 Mechanisms of heat loss from the body.

Modified from Guyton AC, Hall JE 2011 Textbook of medical physiology, ed 12. Philadelphia, Saunders.

Behavioural control

Individuals voluntarily act to maintain a comfortable body temperature when exposed to temperature extremes. The ability of a person to control body temperature depends on the degree of temperature extreme, the person’s ability to sense feeling comfortable or uncomfortable, thought processes or emotions and the person’s mobility or ability to remove or add clothes. Body temperature control is difficult if any of these abilities are absent or lost. Infants can sense uncomfortable warm conditions, but need help to change their environment. Older adults may need help in detecting cold environments and minimising heat loss. Illness, a decreased level of consciousness or impaired thought processes all result in an inability to recognise the need to change behaviour for temperature control. When temperatures become extremely high or low, health-promoting behaviours such as removing or adding clothing have a limited effect on controlling temperature.

An essential aspect of the nurse’s role is the assessment and modification of variables that place patients at high risk of ineffective thermoregulation.

Factors affecting body temperature

Age

At birth the newborn leaves a warm, relatively constant environment and enters one in which temperatures fluctuate widely. Extra care is needed to protect the newborn because their temperature-control mechanisms are immature. A newborn loses up to 30% of body heat through the head and therefore needs to wear a cap to prevent heat loss. When protected from environmental extremes, the newborn’s body temperature is maintained within the range of 35.5–37.5°C.

The older adult has a narrower range of body temperatures than the younger adult. The average body temperature of older adults is approximately 36°C. Older adults are particularly susceptible to temperature extremes because of deterioration in control mechanisms, particularly poor vasomotor control (control of vasoconstriction and vasodilation), reduced amounts of subcutaneous tissue, reduced sweat gland activity and reduced metabolism.

Exercise

Muscle activity requires an increased blood supply and increases carbohydrate and fat breakdown. This increased metabolism increases heat production and thus body temperature. Prolonged strenuous exercise, such as long-distance running, can temporarily raise body temperatures up to 41°C.

Hormone level

Women generally experience greater fluctuations in body temperature than men. Menstrual cycle hormonal variations cause body temperature fluctuations. When progesterone levels are low, the body temperature is a few tenths of a degree below the baseline level; the lower temperature persists until ovulation occurs. During ovulation, greater amounts of progesterone raise the body temperature to previous baseline levels or higher. These variations can predict the most fertile time to achieve pregnancy.

Body temperature changes also occur in women during menopause (cessation of menstruation). Postmenopausal women may experience periods of intense body heat and sweating lasting from 30 seconds to 5 minutes with an intermittent increase in skin temperature of up to 4°C (hot flushes). This is due to the instability of the vasomotor controls for vasodilation and vasoconstriction (Brashers, 2006).

Circadian rhythm

Body temperature follows a circadian pattern, peaking late afternoon (1800–2200 hours) and falling early morning (0200–0400 hours). Interestingly, temperature patterns are not automatically reversed in people who work at night and sleep during the day; it takes 1–3 weeks for the cycle to reverse. In general, the circadian temperature rhythm does not change with age.

Stress

Physical and emotional stress increase body temperature through hormonal and neural stimulation. These physiological changes increase metabolism, which increases heat production.

Environment

Environment influences body temperature. If temperature is assessed in a very warm room, a person may be unable to regulate body temperature by heat-loss mechanisms, and the body temperature will be elevated. If the person has just been outside in the cold without warm clothing, body temperature may be low because of extensive radiant and conductive heat loss. Infants and older adults are most likely to be affected by environmental temperatures, because their thermoregulatory mechanisms are less efficient.

Fever

Fever (or pyrexia) occurs as a part of the inflammatory response caused by trauma, surgery, infection, immune responses and tissue damage. For example, in the immediate postoperative period it is common for a patient to develop a fever as part of the normal inflammatory response to surgery. During fever, white-blood-cell production is stimulated and there is a decrease in the concentration of iron in the blood plasma, suppressing bacterial growth. Fever also stimulates the production of antiviral interferon.

Fever is a host defence response, a febrile response, to invasion from exogenous pyrogens, including microbial pathogens such as bacteria, viruses, mycobacteria and fungi as well as non-microbial antigens such as inflammatory agents and drugs. During the febrile response, the set-point in the thermoregulatory centre is reset to maintain a higher level of body temperature. This higher temperature is maintained through increased heat production, especially through peripheral vasoconstriction and behavioural measures such as covering oneself with blankets in response to chills even though the body temperature is elevated.

The febrile response is a coordinated series of events to defend the body against these invading organisms through the intentional elevation of the body’s core temperature—a mean 1°C increase in body temperature (for that specific measurement site). For example, normal axillary temperature ranges from 34.7–37.4°C with a mean of 36.5°C; 1°C above the mean is 37.5°C. However, body temperature can be raised by excessive clothing, physical activity, hot weather and the digestion of food. Hyperthermia—passive heat gain greater than the body’s capability to dissipate heat—is distinct from fever and the two should not be confused. Temperatures accepted as representative of fever are (El-Radhi and others, 2009):

• rectal temperature	≥ 38.0°C
• oral temperature	≥ 37.6°C
• axillary temperature	≥ 36.5°C
• tympanic temperature	≥ 37.6°C.

The widespread and continued prevalence of the febrile response in mammals, reptiles, amphibians and fish suggests that fever is an adaptive response, even though it places substantial demands on the body through increased metabolic demands. In humans and most mammals, fever has an upper limit ranging from 41°C to 42°C. When humans are in a thermoneutral environment, febrile rises in body temperature tend to range from 0.5°C to 3°C, with most infections producing fevers between 38.5°C and 40.5°C, and an average fever of 39.5°C.

Three phases of fever

The cold phase begins as the hypothalamic set-point is reset to a higher level (see Figure 28-3). This phase lasts approximately 10–40 minutes, during which all heat-producing mechanisms are activated and there is a rapid, steady rise in temperature. Heat production increases oxygen demands by 3–5 times normal resting levels, contributing to a hypermetabolic state. In this state there are associated increases in heart and respiratory rates and thirst. Vasoconstriction causes the skin to look pale with cyanotic nail beds, and to feel cool and dry. During this period, the person experiences chills and rigors, and feels cold even though the body temperature is rising.

FIGURE 28-3 Effect of changing the set-point of the hypothalamic temperature control during a fever.

Modified from Guyton AC, Hall JE 2011 Textbook of medical physiology, ed 12. Philadelphia, Saunders.

During the hot phase the body has reached a new set-point and maintains the body temperature at this new higher temperature. The length of this phase depends on the time it takes to eradicate the pyrogenic cytokines responsible for the raised set-point. Higher temperatures in this phase are maintained through a balance in heat production and heat loss. Skin is flushed and warm and the individual feels hot. Basal metabolic rate remains high, so tachycardia and thirst continue. Other symptoms associated with this phase include drowsiness, headache, photophobia, reduced activity and appetite, feelings of weakness and/or restlessness and sometimes convulsions. This phase ends when the underlying cause of fever has been treated and/or eliminated by the body, resulting in a decrease in set-point to normal.

The defervescence phase or the ‘breaking’ of the fever occurs when there is a sudden decline in circulating pyrogenic cytokines and resetting of the hypothalamic set-point back to normal. Heat loss mechanisms take over and heat production is inhibited. The skin feels warm and is flushed due to vasodilation and sweating, which can exacerbate existing dehydration. Finally, the temperature returns to normal and the patient becomes afebrile.

Patterns of fever

In the past, patterns of fever were used to assist in diagnosis, although there is much less focus given to these patterns during febrile illnesses today. There are only a few diseases that show a specific pattern of fever, yet the same disease may also present as a different pattern. Today, diagnosis of febrile illnesses is based on laboratory investigations, enabling an accurate diagnosis even before a specific fever pattern emerges.

Benefits and costs of fever

Fever is beneficial in a normal healthy person in the home setting, but seriously ill children and adults can become severely compromised by the additional physiological strain of fever. For every 1°C above normal temperature, there are associated physiological changes. Metabolic, heart and respiratory rates increase by 13%, 20 beats per minute and 4–5 respirations per minute, respectively. There is an associated increase in oxygen consumption of 10–12% and an insensible fluid loss of 20%. Increased fluid loss associated with reduced intake leads to dehydration, the most common and dangerous side effect of fever. During the cold stage, blood pressure increases and glomerular filtration rates decrease; this reverses during the hot phase. Increased urine output assists in the removal of the additional metabolic wastes from the catabolic febrile state.

When fever is prolonged, the risk of dehydration increases and anorexia, secondary to generalised weakness and malaise, is common. Psychological effects include apathy, confusion, delirium and withdrawal from people and activities. These physiological and psychological effects of fever are important considerations for nurses and those caring for febrile children and adults. Fever should be reduced in those who are placed at risk due to the additional physiological burden from the febrile response. This includes children and adults who are seriously ill, and those who have cardio-respiratory, neurological or metabolic disorders or are malnourished, dehydrated or have epileptic lesions and may not tolerate the additional physiological demands during fever. In children, fever may trigger convulsions in those with a seizure disorder or a predisposition to febrile convulsions.

Febrile convulsions

Febrile convulsions were defined as:

a seizure in association with a febrile illness in the absence of a central nervous system (CNS) infection or acute electrolyte imbalance in children older than 1 month of age without prior afebrile seizures

by the International League Against Epilepsy (1993). Approximately 30–40% of children who have one febrile convulsion will have another.

Most febrile convulsions (75–85%) are simple, lasting less than 10 minutes. Complex febrile convulsions lasting longer than 15 minutes occur in 9% of cases. Simple febrile convulsions are brief (<15 minutes), bilateral, tonic–clonic seizures of short duration followed by a brief postictal period after which the child readily returns to their pre-morbid baseline state. Complex febrile convulsions are focal, unilateral or prolonged seizures lasting longer than 15 minutes or multiple convulsions within the same illness. Febrile convulsions longer than 30 minutes indicate febrile status epilepticus and occur in 5% of febrile convulsions. Large epidemiological studies have concluded that simple febrile convulsions are benign, common events in children without a history of afebrile convulsions or intracranial involvement associated with rectal temperatures above 38°C.

Febrile convulsions are precipitated by any febrile illness (e.g. otitis media, pneumonia, tonsillitis or influenza) or environmental factors that raise the body temperature. Immunisations such as diphtheria–pertussis–tetanus and measles are environmental precipitants of febrile convulsions. In children who have an environmentally precipitated febrile convulsion, 50% have a genetic predisposition to febrile convulsions.

Less than 2–5% of all children under the age of 5 years will have a febrile convulsion. Predictors of an initial febrile convulsion are a febrile convulsion in a first- or second-degree relative, neonatal discharge at 30 days or later, very pre-term birth, parental report of slow development, more febrile episodes per year, or attending day care. In children with a febrile illness, additional factors include the peak temperature during the illness and the underlying illness. For example, gastroenteritis has a lower risk for febrile convulsions than otitis media or other causes of fever.

No long-term effects have been identified in children aged 6–12 years following febrile convulsions. Large epidemiological studies report that measures to prevent additional febrile convulsions are unlikely to alter the long-term outcome of most children who have a febrile convulsion.

Management of febrile children

Fever does not always need to be treated, although it should be treated in those it places at risk of further complications. Fever has a role to play in supporting the body’s defence against invading pyrogens, although there is consensus that temperatures above 40°C should be avoided, as there are reduced immunological benefits at these temperatures (Walsh, 2008).

Appropriate management of febrile children includes careful observation of the child’s response to fever, preventing dehydration, supporting the febrile response and reducing distressing symptoms such as pain and discomfort with recommended doses of analgesics. Carers can determine the degree of illness from the child’s interactions with the environment. This is achieved through observing the child’s alertness, playfulness or irritability and consolability, in addition to physical observations such as petechiae, bulging fontanels, nasal flaring and response to stimuli. If a child is shivering and vasoconstricted in a warm environment, it is safe to assume their thermostatic set-point has been raised. If they become flushed and perspire, cooling mechanisms are functioning.

It is important for carers to be watchful when administering antipyretics to dehydrated or severely malnourished children and those with hepatic or renal impairment. In a febrile, irritable, uncomfortable child, analgesia is warranted. Antipyresis is warranted in children with underlying neurological or cardiopulmonary disease (Walsh, 2008). Parents learn to manage fever from healthcare professionals, drawing on their knowledge. This makes it imperative that healthcare professionals have current fever management knowledge based on the latest scientific evidence (see Box 28-2).

BOX 28-2 ADVICE FOR PARENTS WHEN CARING FOR A FEBRILE CHILD

• Mild to moderate fever is beneficial and supports the immune system.

• Observe the child: focus on the child’s wellbeing rather than temperature.

• Make the child comfortable.

• Dress the child in light clothing.

• Encourage fluids: small, frequent drinks of clear liquid (e.g. water or diluted juice).

• Reduce activity.

• Light blanket for children who are cold or shivering.

• Selectively reduce fevers with medications when fever is:

— greater than 39.0°C and associated with discomfort

— 40°C or higher and

— in all children who are irritable, miserable or appear to be in pain.

• Medication dosages for children up to 6 years:

— paracetamol 15 mg/kg every 4 hours up to 4 times a day, maximum 1 g/day

— ibuprofen, always administer with food or milk, check labelling as dosage is age-related until 2 years (not recommended in some countries to children younger than 2 years), then 10 mg/kg 3–4 times a day, maximum of 1.2 g/day

— aspirin should be avoided.

• Do not continue giving regular medication for >48 hours without having the child assessed by a medical or nurse practitioner.

• Seek advice from your healthcare provider if there is no improvement in 48 hours, or if the child:

— is febrile and under 6 months of age

— looks ‘sick’, pale, lethargic or weak

— suffers severe headache, neck stiffness or light hurts their eyes

— has breathing difficulties

— refuses to drink

— persistently vomits

— shows signs of drowsiness

— suffers pain

— has a rash of red-purple spots.

Adapted from Walsh A 2008 Fever management in children. Aust J Pharm 89(4):66–9.

Hyperthermia

Hyperthermia is an elevated body temperature related to the body’s inability to promote heat loss or reduce heat production. Whereas fever is an upward shift in the set-point, hyperthermia results from an overload of the body’s thermoregulatory mechanisms (Guyton and Hall, 2011). Any disease or trauma to the hypothalamus can impair heat-loss mechanisms. Malignant hyperthermia is a hereditary condition of uncontrolled heat production, occurring when susceptible people receive certain anaesthetic drugs.

Prolonged exposure to the sun or high environmental temperatures can overwhelm the body’s heat-loss mechanisms and depress hypothalamic function. These conditions cause heatstroke, a dangerous heat emergency with a high mortality rate. People at risk include the very young and very old; a diagnosis of cardiovascular disease, hypothyroidism, diabetes or alcoholism; people taking medications that decrease the body’s ability to lose heat (e.g. phenothiazines, anticholinergics, diuretics, amphetamines and beta-adrenergic receptor antagonists); and those who exercise or work strenuously (e.g. athletes, construction workers and farmers). Signs and symptoms of heatstroke include hot, dry skin, body temperature sometimes as high as 45°C, tachycardia, hypotension, giddiness, confusion, delirium, excessive thirst, nausea, muscle cramps, visual disturbances and even incontinence. Victims of heatstroke do not sweat because of severe electrolyte loss and hypothalamic malfunction. Heatstroke with a temperature greater than 40.5°C produces tissue damage to the cells of all body organs. The brain may be the first organ affected, because of its sensitivity to electrolyte imbalances. As the condition progresses, a person becomes unconscious with fixed, non-reactive pupils. Permanent neurological damage occurs unless cooling measures are rapidly started.

Hypothermia

Heat loss during prolonged exposure to cold overwhelms the body’s ability to produce heat, causing hypothermia. In hypothermia the body at first increases metabolic rate (to increase heat production), increases vasoconstriction (to decrease heat loss), shunts blood from the peripheral vascular bed to the core (to reduce heat loss) and increases shivering (to increase heat production). Hypothermia is classified by core temperature measurements (Box 28-3). Some people are more prone to hypothermia than others (Box 28-4). It can be caused unintentionally, such as by falling through the ice of a frozen lake. Hypothermia may also be intentionally induced during surgical procedures, to reduce metabolic demand and the body’s need for oxygen.

BOX 28-3 CLASSIFICATION OF HYPOTHERMIA

Mild	33.1-36°C
Moderate	30.1-33°C
Severe	27-30°C
Profound	< 27°C

BOX 28-4 PATIENTS AT RISK OF HYPOTHERMIA

NEONATES

Can lose as much as 4.5°C immediately after delivery, as a result of heat evaporation. They also have a larger surface-to-mass ratio and a small amount of subcutaneous tissue.

OLDER PATIENTS

Often have a decrease in level of thyroxine and therefore a decreased ability to increase metabolic rate and heat production. Have a decreased ability in vasomotor response, including decreased ability to produce heat through shivering.

PATIENTS WITH ALCOHOL PROBLEMS

Alcohol increases peripheral vasodilation (increases heat loss), and long-term use may affect the hypothalamic response to cold.

SURGICAL PATIENTS

Patients can lose as much as 0.3°C per hour by loss of heat through an open cavity in a theatre where the ambient temperature is less than the body temperature. Anaesthetics block the activity of shivering and decrease the body’s ability to produce heat.

Hypothermia usually develops gradually and may go unnoticed for several hours. When skin temperature drops to 35°C, the person suffers uncontrolled shivering, loss of memory, depression and poor judgment. As the body temperature falls below 34.4°C, cyanosis occurs, and heart and respiratory rates and blood pressure fall. If hypothermia progresses, cardiac dysrhythmias, loss of consciousness and unresponsiveness to painful stimuli occurs. In cases of severe hypothermia, a person may demonstrate clinical signs similar to death (e.g. lack of response to stimuli and extremely slow respirations and pulse). The assessment of core temperature is critical when hypothermia is suspected. A special low-reading thermometer may be required, because standard devices often do not register below 35°C.

Frostbite occurs when the body is exposed to subnormal temperatures. Ice crystals forming inside the cell can result in permanent circulatory and tissue damage. Areas particularly susceptible to frostbite are the earlobes, tip of the nose, and fingers and toes. The injured area is white, waxy and firm to the touch, and sensation is lost in the affected area. Intervention includes gradual warming measures, analgesia, and protection of the injured tissue.

Sites for measuring body temperature

There are several sites for measuring core and surface body temperature. The non-invasive sites used most commonly for temperature measurement include the tympanic membrane, mouth and axilla (Box 28-5). The rectum is an invasive site, which is occasionally used.

BOX 28-5 CORE AND SURFACE TEMPERATURE MEASUREMENT SITES

CORE

Tympanic membrane

Oesophagus

Urinary bladder

Pulmonary artery

SURFACE

Skin

Axillae

Oral

Oral, axillary and skin temperature sites rely on effective blood circulation at the measurement site. The heat of the blood is conducted to the thermometer probe. Non-invasive chemically prepared thermometer patches can also be applied to the skin.

Tympanic temperature relies on the radiation of body heat to an infra-red sensor. Tympanic temperature is considered a core temperature because the tympanic membrane shares the same arterial blood supply as the hypothalamus.

The temperature obtained varies, depending on the site used, but should be between 36°C and 38°C. Research findings from numerous studies are contradictory; however, it is generally accepted that rectal temperatures are usually 0.5°C higher than oral temperatures, and axillary temperatures are usually 0.5°C lower than oral temperatures (Guyton and Hall, 2011). Each of the common temperature measurement sites has advantages and disadvantages (Box 28-6). The nurse chooses the safest and most accurate site for the patient (Skill 28-1). The same site should be used when repeated measurements are necessary.

BOX 28-6 ADVANTAGES AND DISADVANTAGES OF SELECT TEMPERATURE MEASUREMENT SITES

TYMPANIC MEMBRANE SENSOR

Advantages:

• Easily accessible site

• Minimal patient repositioning required

• Very rapid measurement (2–5 seconds)

• Can be obtained without disturbing or waking patient

• Unaffected by oral intake of food, fluids, smoking

• Can be used for tachypnoeic patients

• More accurately reflects core temperature than any other method (Nimah and others, 2006).

Disadvantages:

• Requires removal of hearing aids before measurement

• Should not be used with patients who have had surgery of the ear or tympanic membrane

• May have lower readings with cerumen impaction (Lu and others, 2010).

ORAL

Advantages:

• Accessible—requires no position change

• Minimal patient repositioning required

• Provides accurate surface temperature reading

Disadvantages:

• Affected by ingestion of fluids or foods, smoke and oxygen delivery (Guyton and Hall, 2011)

• Should not be used with patients who have had oral surgery, trauma, history of epilepsy or shaking chills

• Should not be used with infants, small children or confused, unconscious or uncooperative patients

• Risk of body fluid exposure

• Uncomfortable for patients with nausea

AXILLA

Advantages:

• Safe and non-invasive

• Can be used with newborns and uncooperative patients

Disadvantages:

• Long measurement time

• Requires continuous positioning by nurse

• Lags behind core temperature during rapid temperature changes

• Requires exposure of thorax

• Not recommended to detect fever in infants and young children

SKIN

Advantages:

• Inexpensive

• Provides continuous reading

• Safe and non-invasive

• Does not require disturbing of patient

• Can be used for neonates

• Easy to read

Disadvantages:

• Lags behind other sites during temperature changes, especially during hyperthermia

• Adhesion can be impaired by diaphoresis or sweat

• Can be affected by environmental temperature

• Unreliable during chill phase of fever

Guyton AC, Hall J 2011 Textbook of medical physiology, ed 12. Philadelphia, Saunders.; Lu S-H, Leasure A-R, Dai Y-T 2010 A systematic review of body temperature variations in older people. J Clin Nurs 19(1–2):4–16.; Nimah MM, Bshesh K, Callahan JD and others 2006 Infrared tympanic thermometry in comparison with other temperature measurement techniques in febrile children. Pediatr Crit Care Med 7(1):48–55.

SKILL 28-1 Measuring body temperature

DELEGATION CONSIDERATIONS

Temperature measurement can be delegated to enrolled nurses (ENs).

• Inform EN of the frequency of temperature measurement.

• Determine that EN is aware of the reportable levels for patient.

• Inform EN of the need to report any abnormalities that should be reconfirmed by the nurse.

EQUIPMENT

• Appropriate thermometer

• Pen, observation chart

• Plastic thermometer sleeve or disposable probe cover

STEPS				RATIONAL
1. Assess for signs and symptoms of temperature alterations and for factors that influence body temperature.				Physical signs and symptoms may indicate abnormal temperature. Nurse can accurately assess nature of variations.
2. Determine any previous activity that would interfere with accuracy of temperature measurement. When taking oral temperature, wait 15-20 min before measuring temperature orally if patient has smoked or ingested hot or cold liquids or foods.				Smoking or oral intake of food or fluids can cause false temperature readings in oral cavity.
3. Determine appropriate temperature site and device for patient.				Chosen based on patient requirements, advantages and disadvantages of each site (see Box 28-6).
4. Explain how temperature will be taken and importance of maintaining proper position until reading is completed.
5. Perform hand hygiene.				Reduces transmission of microorganisms.
6. Help patient assume comfortable position that provides easy access to temperature site.				Ensures comfort and accuracy of temperature reading.
7. Obtain temperature reading.
	A. Oral temperature measurement with electronic thermometer
	(1)Put on oral probe cover			Use of oral probe cover, which can be removed without physical contact, minimises need to wear gloves.
	(2)Remove thermometer pack from charging unit. Attach oral probe (blue tip) to thermometer unit. Grasp top of probe stem, being careful not to put pressure on the ejection button.			Charging provides battery power. Ejection button releases plastic probe cover from tip.
	(3)Slide disposable plastic probe cover over thermometer probe until cover locks in place (see illustration).			Soft plastic cover will not break in patient’s mouth and prevents transmission of microorganisms between patients.
Step 7A(3) Sliding disposable probe cover over thermometer probe.
		(4)Ask patient to open mouth; then gently place thermometer probe under tongue in posterior sublingual pocket lateral to centre of lower jaw.		Heat from superficial blood vessels in sublingual pocket produces temperature reading. With electronic thermometer, temperatures in right and left posterior sublingual pocket are significantly higher than in area under front of tongue.
		(5)Ask patient to hold thermometer probe with lips closed.		Maintains proper position of thermometer during recording.
		(6)Leave thermometer probe in place until audible signal occurs and patient’s temperature appears on digital display; remove thermometer probe from under patient’s tongue.		Probe must stay in place until signal occurs to ensure accurate reading.
		(7)Push ejection button on thermometer stem to discard plastic probe cover into appropriate receptacle.		Reduces transmission of microorganisms.
		(8)Return probe to storage position of thermometer unit.		Protects probe from damage. Returning probe automatically causes digital reading to disappear.
		(9)Perform hand hygiene.		Reduces transmission of microorganisms.
		(10)Return thermometer to charger.		Maintains battery charge.
	B. Axillary temperature measurement with electronic thermometer
		(1)Draw curtain around bed and/or close door.		Provides privacy.
		(2)Position patient lying supine or sitting.		Provides easy access to axilla.
		(3)Move clothing or gown away from shoulder and arm.		Exposes axilla for correct thermometer probe placement.
		(4)Remove thermometer pack from charging unit. Be sure oral probe (blue tip) is attached to thermometer unit. Grasp top of probe stem, being careful not to apply pressure on the ejection button.		Charging provides battery power. Ejection button releases plastic cover from probe.
		(5)Slide disposable plastic probe cover over thermometer probe until cover locks in place.		Soft plastic cover prevents transmission of microorganisms between patients.
		(6)Raise patient’s arm away from torso, inspect for skin lesions and excessive perspiration. Insert probe into centre of axilla, lower arm over probe and place arm across patient’s chest (see illustration).		Maintains proper position of probe against blood vessels in axilla.
Step 7B(6) Axillary temperature measurement.
		(7)Leave probe in place until audible signal occurs and temperature appears on digital display.		Probe must stay in place until signal occurs to ensure accurate reading.
		(8)Remove probe from axilla.
		(9)Push ejection button on thermometer stem to discard plastic probe cover into appropriate receptacle.		Reduces transmission of microorganisms.
		(10)Return probe to storage position of thermometer unit.		Protects probe from damage. Returning probe automatically causes digital reading to disappear.
		(11)Help patient assume a comfortable position.		Restores comfort and promotes privacy.
		(12)Perform hand hygiene.		Reduces transmission of microorganisms.
		(13)Return thermometer unit to charger.		Maintains battery charge.
	C. Tympanic membrane temperature with electronic thermometer
		(1)Help patient assume comfortable position with head turned towards side, away from nurse. Right-handed people should obtain temperature from patient’s right ear. Left-handed people should obtain temperature from patient’s left ear. The less acute the angle of approach, the better the probe seal.		Ensures comfort and exposes auditory canal for accurate temperature measurement.
		(2)Remove thermometer handheld unit from charging base, being careful not to apply pressure on the ejection button.		Base provides battery power. Removal of handheld unit from base prepares it to measure temperature. Ejection button releases plastic probe cover from tip.
		(3)Slide clean disposable speculum cover over otoscope-like lens tip until it locks into place, being careful not to touch lens cover.		Lens cover must be unimpeded by dust, fingerprints or earwax to ensure clear optical pathway.
		(4)Insert speculum into ear canal following manufacturer’s instructions for tympanic probe positioning:		Correct positioning of the probe with respect to ear canal ensures accurate readings.
			a. Pull ear pinna backwards for a child, up and out for an adult.	The ear tug straightens the external auditory canal, allowing maximum exposure of the tympanic membrane.
			b. Move thermometer in a figure 8 pattern.
			c. Fit probe snugly into canal and do not move.
			d. Point towards nose.
		(5)As soon as probe is in place depress scan button on handheld unit. Leave thermometer probe in place until audible signal occurs and patient’s temperature appears on digital display.		Depression of scan button causes infra-red energy to be detected. Otoscope tip must stay in place until signal occurs to ensure accurate reading.
		(6)Carefully remove speculum from auditory meatus.
		(7)Push ejection button on handheld unit to discard plastic probe cover into appropriate receptacle.		Reduces transmission of microorganisms. Automatically causes digital reading to disappear.
		(8)If a second reading is necessary, replace probe lens cover and wait 2-3 min before inserting the probe tip.		Lens cover must be free of cerumen to maintain optical path.
		(9)Return handheld unit to charging base.		Protects sensory tip from damage.
		(10)Help patient assume a comfortable position.		Restores comfort and sense of wellbeing.
		(11)Perform hand hygiene.		Reduces transmission of microorganisms.
8. Discuss findings with patient as needed.				Promotes participation in care and understanding of health status.
9. If temperature is assessed for the first time, establish temperature as baseline if it is within normal range.				Used to compare future temperature measurements.
10. Compare temperature reading with patient’s previous baseline and acceptable temperature range for patient’s age group.				Normal body temperature fluctuates within narrow range; comparison reveals presence of abnormality. Improper placement or movement of thermometer can cause inaccuracies. Second measurement confirms initial findings of abnormal body temperature.

RECORDING AND REPORTING	HOME CARE CONSIDERATIONS
• Record temperature in observation chart. Measurement of temperature after administration of specific therapies should be documented in narrative form in progress notes. • Report abnormal findings to nurse in charge or medical practitioner.	• Assess temperature and ventilation of patient’s environment to determine existence of any environmental condition that may influence outcome of patient’s temperature reading.

Thermometers

The types of thermometers used for determining body temperature are electronic and disposable. The nurse must be skilled in the use of the selected measurement device.

ELECTRONIC THERMOMETERS

The electronic thermometer consists of a rechargeable battery-powered display unit, a thin wire cord and a temperature-processing probe covered by a disposable plastic sheath (Figure 28-4). One form of electronic thermometer uses a pencil-like probe. Separate non-breakable probes are available for oral and rectal use. The oral probe can also be used for axillary temperature measurement. Within 20–50 seconds of insertion, a reading appears on the display unit. A sound signals when the peak temperature reading has been measured.

FIGURE 28-4 Electronic thermometer. Blue probe is for oral or axillary use. Red probe is for rectal use.

From Potter PA, Perry AG 2013 Fundamentals of nursing, ed 8. St Louis, Mosby.

Another form of electronic thermometer is used exclusively for tympanic temperature (Figure 28-5). An otoscope-like speculum with an infra-red sensor tip detects heat radiated from the tympanic membrane. The head is stabilised, the ear pulled straight back (children) or up and back (adults), and within 2–5 seconds of placement of the speculum in the auditory canal a reading appears on the display unit. A sound signals when the peak temperature reading has been measured.

FIGURE 28-5 Tympanic thermometer with probe cover being inserted into auditory canal.

Image: iStockphoto/tbradford.

The greatest advantages of electronic thermometers are ease of insertion, readings within seconds, being easy to read and the plastic sheath being unbreakable and ideal for children. Their expense is a major disadvantage.

DISPOSABLE THERMOMETERS

Disposable, single-use thermometers are thin strips of plastic with a temperature sensor at one end. The sensor consists of a matrix of dot-like indentations that contain chemicals which melt and change colour at different temperatures. They are used for oral or axillary temperatures, particularly with children (Figure 28-6). Single-use thermometers are inserted the same way as any oral or axillary thermometer. The thermometer is removed after 3 minutes and read after waiting about 10 seconds for the colour change to stabilise.

FIGURE 28-6 Disposable, single-use thermometer strip.

From Potter PA, Perry AG 2013 Fundamentals of nursing, ed 8. St Louis, Mosby.

Another form of disposable thermometer is a temperature-sensitive patch or tape. Applied to the forehead or abdomen, the patch changes colour at different temperatures. Both forms of disposable thermometers are useful for screening patients, especially infants, for altered temperature, and are not appropriate for monitoring temperature therapies.

Interpretation of results

Interpretation of temperature readings is based on norms, patient baseline temperature and clinical situation as well as the nurse’s knowledge of pathophysiology. An important part of the process of making a nursing diagnosis is identifying the cause or aetiology of the problem, as well as the defining characteristics relevant to the patient.

Nursing interventions

Prevention is the key for patients at risk of altered body temperature. The very old and the very young are most at risk of developing altered body temperature, because of a lack of ability to modify the environment in conjunction with ineffective thermoregulation mechanisms. Other people at risk include those who are debilitated by trauma, stroke, diabetes, drug or alcohol intoxication, sepsis, Raynaud’s disease and alterations in mental health status. People without adequate home heating, shelter, diet or clothing are also at risk.

Prevention involves educating patients, family members and friends. Nursing interventions for diagnoses of hyperthermia and hypothermia are directed towards promoting balance between heat production and heat loss. Level of activity, temperature of the environment and clothing are all considered. For example, avoiding strenuous exercise in hot, humid weather; drinking fluids such as water or clear fruit juices before, during and after exercise; wearing light, loose-fitting, light-coloured clothes; avoiding exercising in areas with poor ventilation; wearing a hat when outdoors; and gradual exposure to hot climates. The ability of an elderly patient or the mother of an infant to explain appropriate actions to take during hot weather is important in monitoring the elimination of a risk factor and in demonstrating the success of patient and family education.

Managing fever

The goal of fever management is to reduce heat production, increase heat loss and prevent complications (see Box 28-7). The procedures used to intervene and treat an elevated temperature depend on the fever’s cause, its adverse effects, its intensity and duration. Following consultation with the medical practitioner, the nurse may be required to obtain samples of urine, blood or sputum or wound-site specimens for culture and sensitivities to determine the cause of fever and direct treatment.

BOX 28-7 NURSING MEASURES FOR PATIENTS WITH A FEVER

ASSESSMENT

• Obtain core temperature during each phase of febrile episode.

• Assess for contributing factors such as dehydration, infection or environmental temperature.

• Identify physiological response to temperature:

— Obtain all vital signs

— Observe skin colour

— Assess skin temperature

— Observe for shivering and diaphoresis

— Assess patient comfort and wellbeing.

INTERVENTION (UNLESS CONTRAINDICATED)

• Obtain blood cultures if indicated. Blood specimens are obtained to coincide with temperature spikes when the antigen-producing organism is most prevalent.

• Initiate therapies to minimise heat production.

— Reduce the frequency of activities that increase oxygen demand such as excessive turning and ambulation.

• Allow rest periods.

— Limit physical activity.

• Initiate therapies to maximise heat loss;

— Reduce external covering on patient’s body to promote heat loss through radiation and conduction. Do not induce shivering.

— Keep clothing and bedclothes dry to increase heat loss through conduction and convection.

• Initiate therapies to meet requirements of increased metabolic rate:

— Provide supplemental oxygen therapy if indicated to improve oxygen delivery to body cells.

— Provide measures to stimulate appetite and offer well-balanced meals.

— Provide fluids (at least 3 L per day for patient with normal cardiac and renal function) to replace fluids lost through insensible water loss and sweating.

• Initiate therapies to promote patient comfort:

— Encourage oral hygiene because oral mucous membranes dry easily from dehydration.

— Control temperature of the environment without inducing shivering.

• Identify onset and duration of febrile episode phases.

• Examine previous temperature measurements for trends.

• Initiate health teaching as indicated.

Antipyretics such as paracetamol or non-steroidal anti-inflammatory drugs (NSAIDs, e.g. indomethacin) may be prescribed to reduce fever. Paracetamol increases heat loss by reducing the production of prostaglandins in the brain and spinal cord. Other medications that effect body temperature include corticosteroids. This group of medications acts within cells to prevent the release of chemicals that are normally involved in producing immune and allergic responses, resulting in inflammation. Consequently, they affect the body’s ability to fight infection and are not used to treat fever. It is important, however, to be aware of their effect in suppressing the immune system and masking the typical signs of infection.

Non-pharmacological therapy for fever includes methods that increase heat loss by evaporation, conduction, convection or radiation. Nursing measures are aimed at enhancing comfort, reducing metabolic demands and providing nutrients to meet increased energy needs (Box 28-7). Nursing measures to enhance body cooling must avoid the stimulation of shivering. Traditionally, nurses have used tepid sponge baths and cooling fans; however, use of these methods over antipyretic medications may lead to shivering. Shivering is counterproductive because of the heat produced by muscle activity. Vigorous shivering can increase energy expenditure up to 400% (Guyton and Hall, 2011). Shivering intensity ranges from palpable but not visible to violent extremity contractions.

Children and older adults are at risk of dehydration because they can quickly lose large amounts of fluids in proportion to their bodyweight. Prevention of dehydration is managed by accurate documentation of intake and output records, daily weighs and adequate fluid intake. Identifying preferred fluids and encouraging oral fluid intake is an important nursing intervention. It is recommended that antipyretics such as paracetamol in combination with tepid sponge baths is the most effective approach to reducing fever rather than using paracetamol alone (Joanna Briggs Institute, 2010). Care must be taken, however, not to induce shivering. Tepid sponging is not recommended for fever reduction in children (Joanna Briggs Institute, 2009).

Managing hypothermia

The priority treatment for hypothermia is to prevent a further decrease in body temperature. Wet clothes are removed and replaced with dry clothing, and the person is wrapped in blankets. When the patient reaches an emergency department, treatment depends on the severity of the condition. Warmed intravenous fluids, heating blankets, and warm fluids may be used. Patients are monitored closely for cardiac irregularities and electrolyte imbalances. In the acute care setting, patients undergoing surgery may become hypothermic as a consequence of the cooler operating room environment and the effects of the anaesthetic (Kurz, 2008). To avoid the complications associated with hypothermia, use of a warming system such as circulating water garments or forced-air warming are more effective than using extra blankets (Galvão and others, 2010).

Clinical decision making: body temperature

Knowledge of the physiology of body temperature regulation positions the nurse to assess the patient’s response to temperature alterations and to intervene safely and effectively. Independent measures can be implemented to increase or minimise heat loss, to promote heat conservation and to increase comfort. Many measures can also be taught to family members, parents of children or other caregivers.

If treatment is effective, body temperature will return to a normal range, other vital signs will stabilise and the patient will report a sense of comfort. The hypothermic patient will also demonstrate a temperature and other vital signs within the normal ranges and report feeling comfortable.

SAMPLE NURSING CARE PLAN

ELEVATED BODY TEMPERATURE

ASSESSMENT

Mr Coburn is a 45-year-old man being treated for pneumonia. His skin is warm and dry to touch. His face is flushed, and he appears to have laboured breathing. He reports that he smokes one packet of cigarettes per day and recently began expectorating yellow-green sputum. Vital signs obtained are: blood pressure 116/62 mmHg, radial pulse 98 beats per minute, regular and bounding; respiratory rate 26 breaths per minute; SpO₂ 98% on room air; tympanic temperature 39.2°C.

NURSING DIAGNOSIS: Altered body temperature (febrile) related to infectious process.

PLANNING

GOALS	EXPECTED OUTCOMES
Patient will regain normal range of body temperature within next 24 hours.	Body temperature will decline at least 1°C within next 8 hours.
Patient will attain sense of comfort and rest within next 48 hours.	Patient will report increased satisfaction with rest and sleep pattern.
	Patient will report increase in energy level within next 3 days.
Fluid and electrolyte balance will be maintained during next 3 days.	Intake will equal output within next 24 hours. No evidence of postural hypotension during ambulation.

INTERVENTIONS^†	RATIONALE
Fever treatment
• Educate patient to reduce external coverings and keep clothing and bedclothes dry.	Promotes heat loss through conduction and convection.
• Educate patient to monitor temperature at home and administer paracetamol every 4 hours as prescribed for temperature over 39°C.	Antipyretics reduce set point.
• Educate patient to limit physical activity and increase frequency of rest periods over next 2 days.	Activity and stress increase metabolic rate, contributing to heat production.
• Educate patient to increase oral fluids of choice.	Fluids lost through insensible water loss require replacement.

^†Intervention classification labels from Bulechek GM, Butcher HK, McCloskey Dochterman J 2008 Nursing interventions classification (NIC), ed 5. St Louis, Mosby.

EVALUATION

Ask patient to identify temperature and describe energy level.

Ask patient about sleep patterns.

Obtain lying, sitting and standing blood pressures.

Ask patient about any dizziness with posture changes.

Ask patient to track and report intake and output.

• CRITICAL THINKING

Marcia, aged 40 years, had a hysterectomy this morning. As you collect her vital signs this evening you note her body temperature is 37.8°C. Marcia asks you if this is normal. How would you respond? Explain the relevance of Marcia’s temperature. What additional assessment will you conduct?

Pulse

Physiology and regulation

The pulse is the palpable bounding of blood flow noted at various points on the body. It is an indicator of the fluid wave created by ventricular contraction and therefore of the adequacy of circulatory status. Electrical impulses originating from the sinoatrial (SA) node travel through heart muscle to stimulate cardiac contraction. Approximately 60–70 mL of blood (stroke volume) enters the aorta with each ventricular contraction. With each stroke-volume ejection, the walls of the aorta distend, creating a pulse wave that travels rapidly towards the distal ends of the arteries. When a pulse wave reaches a peripheral artery, it can be felt by palpating the artery lightly against underlying bone or muscle. The number of pulsing sensations occurring in 1 minute is the pulse rate.

The volume of blood pumped by the heart during 1 minute is the cardiac output (CO). Cardiac output is the product of the heart rate (HR) and the ventricle’s stroke volume (SV), that is:

CO = HR × SV

In an adult the heart normally pumps 5 L of blood per minute. A change in HR or SV does not always change the CO or the amount of blood in the arteries. Mechanical, neural and chemical factors regulate the strength of heart contractions and the heart’s SV. If the HR increases, the body will respond by decreasing SV to maintain CO. Alternatively if the SV increases, the body will decrease HR to maintain CO. For example, if a person’s heart rate is 70 beats per minute and the stroke volume is 70 mL, the cardiac output is 4.9 L per minute. Box 28-8 shows what happens to SV if the heart rate drops to 60 beats per minute.

BOX 28-8 CARDIAC OUTPUT DETERMINATION

Pulse rate × Stroke volume = Cardiac output

70 beats per minute × 70 mL/beat = 4.9 L/min

60 beats per minute × 85 mL/beat = 5.1 L/min

When mechanical, neural or chemical factors are no longer able to alter SV, a change in HR will result in a change in blood pressure. As HR increases without a change in SV, there is less time for the heart to fill and blood pressure will decrease. An abnormally slow, rapid or irregular pulse may alter CO. The heart’s ability to meet the demands of the body’s tissue for nutrients is determined by palpating a peripheral pulse or by using a stethoscope to listen to heart sounds (apical heart rate).

While several arteries can be assessed for pulse rate (Skill 28-2), the radial and carotid arteries are usually the most practical sites at which to palpate the pulse (Figure 28-7). Other peripheral pulses such as the brachial or femoral arteries are assessed when surgery or treatment has impaired blood flow to a body part, there are clinical indications of impaired peripheral blood flow or when a focused cardiovascular physical examination is conducted (Table 28-1). When CO declines significantly, peripheral pulses weaken and are difficult to palpate. The carotid site is the best in this situation because the heart will continue delivering blood through the carotid artery to the brain as long as possible.

SKILL 28-2 Assessing the radial and apical pulses

DELEGATION CONSIDERATIONS

Pulse measurement can be delegated to enrolled nurses who are informed of:

• appropriate patient position when obtaining apical pulse measurement

• appropriate duration of radial and apical pulse count

• patient history or risk of irregular pulse

• frequency of pulse measurement

• the usual reportable levels for the patient

• the need to report any abnormalities.

EQUIPMENT

• Stethoscope (apical pulse only)

• Wristwatch with second-hand or a digital display

• Pen, observation chart

• Alcohol swab

STEPS			RATIONALE
1. Determine need to assess radial or apical pulse:			Certain conditions place patients at risk of pulse alterations. Heart rhythm can be affected by heart disease, cardiac arrhythmias, onset of sudden chest pain or acute pain from any site, invasive cardiovascular diagnostic tests, surgery, sudden infusion of large volume of intravenous fluid, internal or external haemorrhage and administration of medications that alter heart function.
	a. Note risk factors for alterations in apical pulse.
	b. Assess for signs and symptoms of altered stroke volume and cardiac output such as dyspnoea, fatigue, chest pain, orthopnoea, syncope, palpitations (person’s unpleasant awareness of heartbeat), jugular venous distension, oedema of dependent body parts, cyanosis or pallor of skin.		Physical signs and symptoms may indicate alteration in cardiac function.
2. Assess for factors that normally influence apical pulse rate and rhythm:			Allows for accurate assessment of presence and significance of pulse alterations.
	a. Age		Acceptable range of pulse rate changes with age (see Table 28-2).
	b. Exercise		Physical activity requires an increase in cardiac output that is met by an increased heart rate and stroke volume.
	c. Position changes		Heart rate increases temporarily when changing from lying to sitting or standing position.
	d. Medications		Antiarrhythmics, sympathomimetics and cardiotonics affect rate and rhythm of pulse; opioid analgesics and general anaesthetics slow heart rate; central nervous system stimulants such as caffeine increase heart rate.
	e. Temperature		Fever or exposure to warm environments increases heart rate; heart rate declines with hypothermia.
	f. Emotional stress, anxiety, fear		Results in stimulation of the sympathetic nervous system, which increases heart rate.
3. Determine previous baseline apical rate (if available) from patient’s record.			Allows nurse to assess for change in condition. Provides comparison with future apical pulse measurements.
4. Explain that pulse or heart rate is to be assessed. Encourage patient to relax and not speak.			Activity and anxiety can elevate heart rate. Patient’s voice interferes with nurse’s ability to hear sound when apical pulse is measured.
5. Perform hand hygiene.			Reduces transmission of microorganisms.
6. If necessary, draw curtains around bed and/or close door.			Maintains privacy.
7. Obtain pulse measurement.
	A. Radial pulse
		(1)Help patient assume a supine or sitting position.	Provides easy access to pulse sites.
		(2)If supine, place patient’s forearm straight alongside or across lower chest or upper abdomen with wrist extended straight (see illustration). If sitting, bend patient’s elbow 90 degrees and support lower arm on chair or on nurse’s arm. Slightly flex the wrist with palm down.	Relaxed position of lower arm and extension of wrist permits full exposure of artery to palpation.
		(3)Place tips of first two fingers of hand over groove along radial or thumb side of patient’s inner wrist (see illustration).	Fingertips are the most sensitive parts of hand to palpate arterial pulsation.
Step 7A(2) Measuring radial pulse in supine patient.			Step 7A(3) Position of fingertips for obtaining radial pulse.
		(4)Lightly compress against radius, obliterate pulse initially and then relax pressure so pulse becomes easily palpable.	Pulse is more accurately assessed with moderate pressure. Too much pressure occludes pulse and impairs blood flow.
		(5)Determine strength of pulse. Note whether thrust of vessel against fingertips is bounding, strong, weak or thready.	Strength reflects volume of blood ejected against arterial wall with each heart contraction.
		(6)After pulse can be felt, look at watch’s second- hand and begin to count rate; when second-hand hits number on dial, start counting with 0, then 1, 2 and so on.	Rate is determined accurately only after nurse is assured pulse can be palpated. Timing begins with 0. Count of 1 is first beat palpated after timing begins.
		(7)If pulse is regular, count rate for 30 s and multiply total by 2.	A 30 s count is accurate for rapid, slow or regular pulse rates.
		(8)If pulse is irregular, count rate for 60 s. Assess frequency and pattern of irregularity.	Inefficient contraction of heart fails to transmit pulse wave, interfering with cardiac output, resulting in irregular pulse. Longer time ensures accurate count.
Critical decision point: If pulse is irregular or rapid, assess for pulse deficit that may indicate alteration in cardiac output. Count apical pulse while colleague counts radial pulse. Begin apical pulse count out loud to simultaneously assess pulses. If pulse count differs by more than 2, a pulse deficit exists.
	B. Apical pulse
		(1)Help patient into supine or sitting position. Move aside bedclothes and gown to expose sternum and left side of chest.	Exposes portion of chest wall for selection of auscultatory site.
		(2)Locate anatomical landmarks to identify the point of maximal impulse (PMI), also called the apical impulse. Heart is located behind and to left of sternum with base at top and apex at bottom. Find angle of Louis just below suprasternal notch between sternal body and manubrium; can be felt as a bony prominence. Slip fingers down each side of angle to find second intercostal space (ICS). Carefully move fingers down left side of sternum to fifth ICS and laterally to the left midclavicular line (MCL). A light tap felt within an area 1-2 cm of the PMI is reflected from the apex of the heart.	Use of anatomical landmarks allows correct placement of stethoscope over apex of heart, enhancing ability to hear heart sounds clearly. If unable to palpate the PMI, reposition patient on left side. In the presence of serious heart disease, the PMI may be located to the left of the MCL or at the sixth ICS.
		(3)Place diaphragm of stethoscope in palm of hand for 5-10 s.	Warming of metal or plastic diaphragm prevents patient from being startled and promotes comfort.
		(4)Place diaphragm of stethoscope over PMI at the fifth ICS, at left MCL, and auscultate for normal S1 and S₂ heart sounds (heard as ‘lub-dub’) (see illustration).	Allow stethoscope tubing to extend straight without kinks that would distort sound transmission. Normal sounds S1 and S₂ are high-pitched and best heard with the diaphragm.
Step 7B(4) Auscultating for heart sounds.
		(5)When S1 and S₂ are heard with regularity, use watch’s second hand and begin to count rate: when second hand hits number on dial, start counting with 0, then 1, 2 and so on.	Apical rate is determined accurately only after nurse is able to auscultate sounds clearly. Timing begins with 0. Count of 1 is first sound auscultated after timing begins.
		(6)If apical rate is regular, count for 30 s and multiply by 2.	Regular apical rate can be assessed within 30 s.
		(7)If heart rate is irregular or patient is receiving cardiovascular medication, count for 1 min (60 s).	Irregular rate is more accurately assessed when measured over longer interval.
		(8)Note regularity of any dysrhythmia (S1 and S₂ occurring early or later after previous sequence of sounds; for example, every third or every fourth beat is skipped).	Regular occurrence of dysrhythmia within 1 minute may indicate inefficient contraction of heart and alteration in cardiac output.
		(9)Replace patient’s gown and bedclothes; help patient return to comfortable position.	Restores comfort and promotes sense of wellbeing.
		(10)Clean earpieces and diaphragm of stethoscope with alcohol swab as needed (optional).	Controls transmission of microorganisms when nurses share stethoscope.
8. Discuss findings with patient as needed.			Promotes participation in care and understanding of health status.
9. Perform hand hygiene.			Reduces transmission of microorganisms.
10. Compare readings with previous baseline and/or acceptable range of heart rate for patient’s age (see Table 28-2).			Checks for change in condition and alterations.
11. Compare peripheral pulse rate with apical rate and note discrepancy.			Differences between measurements indicate pulse deficit and may warn of cardiovascular compromise. Abnormalities may require therapy.
12. Compare radial pulse equality and note discrepancy.			Differences between radial arteries indicate compromised peripheral vascular system.
13. Correlate pulse rate with data obtained from blood pressure and related signs and symptoms (palpitations, dizziness).			Pulse rate and blood pressure are interrelated.

RECORDING AND REPORTING	HOME CARE CONSIDERATIONS
• Record pulse, noting the site used, in observation chart. Measurement of pulse rate after administration of specific therapies should be documented in narrative form in progress notes. • Report abnormal findings to nurse in charge or medical practitioner.	• Assess home environment to determine room that will afford quiet environment for auscultating apical rate.

FIGURE 28-7 Location of pulse points in the body.

TABLE 28-1 PULSE SITES

SITE	LOCATION
Apical	Fourth to fifth intercostal space at left midclavicular line	Site used to auscultate for apical pulse
Brachial	Groove between biceps and triceps muscles at antecubital fossa	Site used to assess status of circulation to lower arm Site used to auscultate blood pressure
Carotid	Along medial edge of sternocleidomastoid muscle in neck	Easily accessible site used during physiological shock or cardiac arrest when other sites are not palpable
Dorsalis pedis	Along top of foot, between extension tendons of great and first toe	Site used to assess status of circulation to foot
Femoral	Below inguinal ligament, midway between symphysis pubis and anterior superior iliac spine	Site used to assess character of pulse during physiological shock or cardiac arrest when other pulses are not palpable; used to assess status of circulation to leg
Popliteal	Behind knee in popliteal fossa	Site used to assess status of circulation to lower leg
Posterior tibial	Inner side of ankle, below medial malleolus	Site used to assess status of circulation to foot
Radial	Radial or thumb side of forearm at wrist	Common site used to assess character of pulse peripherally and assess status of circulation to hand
Temporal	Over temporal bone of head, above and lateral to eye	Easily accessible site used to assess pulse in children
Ulnar	Ulnar side of forearm at wrist	Site used to assess status of circulation to hand Site also used to perform Allen’s test

If the radial pulse is abnormal, irregular or unattainable because of a dressing, a cast or patient-prescribed medication affecting the heartbeat, the apical pulse is assessed. The brachial or apical pulses are the best sites for assessing an infant’s or young child’s pulse because other peripheral pulses are deep and difficult to palpate accurately.

Interpretation of pulse

Assessment of the pulse includes measurement of the rate, rhythm, strength and equality. Before measuring a pulse, the patient’s baseline rate is reviewed for comparison (Table 28-2). When assessing the pulse, it is important to consider the variety of factors influencing the HR (Table 28-3). A combination of these factors may cause significant changes. Consideration needs to be given to postural changes, which cause changes in pulse rate because of alterations in blood volume and sympathetic activity. The HR temporarily increases when a person changes from a lying to a sitting or standing position. If an abnormal rate is detected while palpating a peripheral pulse, the next step is to assess the apical rate. The apical rate provides a more accurate assessment of cardiac contraction.

TABLE 28-2 ACCEPTABLE RANGES OF HEART RATE

AGE GROUP	HEART RATE (BEATS PER MINUTE)
Infants	120–160
Toddlers	90–140
Preschoolers	80–110
School-agers	75–100
Adolescents	60–90
Adults	60–100

TABLE 28-3 FACTORS INFLUENCING PULSE RATES

FACTOR	INCREASE PULSE R ATE	DECREASE PULSE R ATE
Drugs	Positive chronotropic drugs such as adrenaline	Negative chronotropic drugs such as digitalis
Emotions	Acute pain and anxiety increase sympathetic stimulation, affecting heart rate	Unrelieved severe pain increases parasympathetic stimulation, affecting heart rate; relaxation
Exercise	Short-term exercise	A conditioned athlete who participates in long-term exercise will have a lower heart rate at rest
Haemorrhage	Loss of blood increases sympathetic stimulation
Postural changes	Standing or sitting	Lying down
Pulmonary conditions	Diseases causing poor oxygenation
Temperature	Fever and heat	Hypothermia

Apical rate

The apical rate is assessed by listening to the heart sounds with a stethoscope (see Box 28-9). The first and second heart sounds (S₁ and S₂) are identified. At normal rates, S₁ is low-pitched and dull, sounding like ‘lub’. S₂ is higher-pitched and shorter, creating the sound ‘dub’. Each set of heart sounds is counted as one heartbeat. Using the diaphragm or bell of the stethoscope, count the number of heart sounds occurring in 1 minute. When auscultating an apical pulse, it is only possible to assess pulse rate and rhythm.

BOX 28-9 USING A STETHOSCOPE

• The five major parts of the stethoscope are the earpieces, binaurals, tubing, bell chestpiece and diaphragm chestpiece.

• To ensure the best reception of sound:

— the earpieces should fit snugly and comfortably and follow the contour of the ear canal, pointing towards the face

— the binaurals should be angled and strong enough so that the earpieces stay firmly in the ears without causing discomfort.

• As longer tubing decreases the transmission of sound waves, the polyvinyl tubing should be flexible and about 30 cm in length. The tubing should be thick-walled and moderately rigid to eliminate transmission of environmental noise and to prevent the tubing from kinking, which distorts sound-wave transmission.

• Stethoscopes can have single or dual tubes. Dual tubes promote sound clarity by minimising the number of turns the sound wave makes before reaching the earpiece.

• The diaphragm is the circular, flat portion of the stethoscope chestpiece covered with a thin plastic disc. It transmits high-pitched sounds created by the high-velocity movement of air and blood.

— Position the diaphragm to make a tight seal against the patient’s skin.

— Enough pressure is exerted to leave a temporary red ring on the patient’s skin when the diaphragm is removed.

• The bell is the bowl-shaped chestpiece usually surrounded by a rubber ring. The ring avoids chilling the patient with cold metal when placed on the skin. The bell transmits low-pitched sounds created by the low-velocity movement of blood. Heart and vascular sounds are auscultated using the bell.

— To test, lightly tap to determine which side is functioning. Newer stethoscope models have one chestpiece that combines features of the bell and diaphragm. When light pressure is exerted the chestpiece is a bell, whereas exerting more pressure converts the bell into a diaphragm.

— Apply the bell lightly, resting the chestpiece on the skin. Compressing the bell against the skin reduces low-pitched sound amplification and creates a ‘diaphragm of skin’.

• The bell and diaphragm are rotated into position on the chestpiece, depending on which part you choose to use.

• The diaphragm or bell must be in proper position during use for the nurse to hear sounds through the stethoscope.

• The stethoscope is a delicate instrument and requires proper care for best functioning.

— The earpieces should be removed regularly and cleaned of cerumen.

— The bell and diaphragm are cleaned of dust, lint and body oils.

— The tubing should be kept away from the nurse’s body oils. Avoid draping the stethoscope around the neck next to the skin. Cleaning the tubing with mild soap and water is the recommended cleaning method.

Rhythm

Normally, a regular interval occurs between each pulse or heartbeat. An interval interrupted by an early or late beat or a missed beat indicates an abnormal rhythm or arrhythmia. Arrhythmia threatens the heart’s ability to provide adequate cardiac output, particularly if it occurs repetitively. If an arrhythmia is present, the regularity of its occurrence should be assessed. Arrhythmias may be described as regularly irregular or irregularly irregular. To diagnose arrhythmia, the medical or nurse practitioner may order an electrocardiogram as well as other cardiac investigations. Children often have a sinus arrhythmia, which is an irregular heartbeat that speeds up with inspiration and slows down with expiration. This is a normal finding and can be verified by having the child hold their breath; the heart rate should then become regular.

An inefficient contraction of the heart that fails to transmit a pulse wave to the peripheral pulse site creates a pulse deficit. To assess a pulse deficit, the nurse and a colleague assess radial and apical rates simultaneously and then compare rates. The difference between the apical and radial pulse rates is the pulse deficit. For example, an apical rate of 92 with a radial rate of 78 leaves a pulse deficit of 14 beats. Pulse deficits are frequently associated with dysrhythmias.

Strength

The strength or amplitude of a pulse reflects the volume of blood ejected against the arterial wall with each heart contraction and the condition of the arterial vascular system leading to the pulse site. Normally the pulse strength remains the same with each heartbeat. Pulse strength may be graded or described as strong, weak, thready or bounding.

Equality

Pulses on both sides of the peripheral vascular system should be assessed. For example, both radial pulses are taken and the characteristics of each compared. A pulse in one extremity may be unequal in strength or absent in many disease states (e.g. peripheral arterial disease). All symmetrical pulses can be assessed simultaneously except for the carotid pulse. Both carotid pulses should never be assessed at the same time because excessive pressure may occlude blood supply to the brain.

Clinical decision making: pulse characteristics

Assessment of heart rate determines the general state of cardiovascular health and the response to other system imbalances. For example, changes in body temperature, fluid status, respiratory function or metabolism will typically involve a change to some degree in heart rate, rhythm and/or strength. Common abnormalities in pulse are tachycardia, bradycardia and dysrhythmias. Tachycardia is an abnormally elevated heart rate, above 100 beats per minute in adults. Bradycardia is a slow heart rate, below 60 beats per minute in adults. This means that there is a wide range of normal of 60–100 beats per minute.

Knowledge of cardiovascular physiology is fundamental to assessment of the patient’s response to alterations in heart rate, rhythm and/or strength and to intervene safely and effectively. When interpreting pulse rate, consideration must be given to the patient’s pattern over time. For example, if a patient’s pulse rate has been averaging 72 beats per minute over the last 4 hours but then increases to 96 beats per minute, even though 96 is within the normal range, the increase from 72 to 96 is considerable and must be further investigated.

• CRITICAL THINKING

You assist Mrs Wong, aged 82 years, with her shower and then walk back to her room with her. You note that her breathing is laboured and sounds ‘wheezy’. When you take her pulse you note that it is 120 beats per minute and has an irregular rhythm.

1. What additional assessment will you conduct? Explain your selection. What advice will you give Mrs Wong?

2. Identify the actual and potential nursing problems for Mrs Wong. What nursing interventions will you implement to ensure her safety?

Respiration

Physiology and regulation

Knowledge of the structure and function of the respiratory system in combination with understanding of the patient’s clinical situation and the implications for the respiratory system facilitate accurate assessment of respirations. Human survival depends on the ability of oxygen (O₂) to reach body cells and for carbon dioxide (CO₂) to be removed from the cells. Respiration is the mechanism the body uses to exchange gases between the atmosphere and the blood and between the blood and the cells. Respiration involves ventilation (the movement of gases into and out of the lungs), diffusion (the movement of oxygen and carbon dioxide between the alveoli and the red blood cells) and perfusion (the distribution of red blood cells to and from the pulmonary capillaries), and can be affected by various factors (Box 28-10).

BOX 28-10 FACTORS INFLUENCING CHARACTER OF RESPIRATIONS

EXERCISE

• Exercise increases rate and depth to meet the body’s need for additional oxygen and to rid the body of carbon dioxide.

ACUTE PAIN

• Pain alters rate and rhythm of respirations; breathing becomes shallow.

• Patient may inhibit or splint chest wall movement when pain is in area of chest or abdomen.

ANXIETY

• Anxiety increases rate and depth as a result of sympathetic stimulation.

SMOKING

• Chronic smoking changes the lung’s airways, resulting in increased rate of respirations at rest when not smoking.

BODY POSITION

• A straight, erect posture promotes full chest expansion.

• A stooped or slumped position impairs ventilatory movement.

• Lying flat prevents full chest expansion.

MEDICATIONS

• Opioid analgesics, general anaesthetics and sedative hypnotics depress rate and depth.

• Amphetamines and cocaine may increase rate and depth.

• Bronchodilators slow rate by causing airway dilation.

NEUROLOGICAL INJURY

• Injury to the brain stem impairs the respiratory centre and inhibits respiratory rate and rhythm.

HAEMOGLOBIN FUNCTION

• Decreased haemoglobin levels (anaemia) reduce oxygen-carrying capacity of the blood, which increases respiratory rate.

• Increased altitude lowers the amount of saturated haemoglobin, which increases respiratory rate and depth.

• Abnormal blood cell function (e.g. sickle cell disease) reduces ability of haemoglobin to carry oxygen, which increases respiratory rate and depth.

Breathing is generally a passive process. Normally, a person thinks little about it. The respiratory centre in the brainstem regulates the involuntary control of respirations. Adults normally breathe in a smooth, uninterrupted pattern 12–20 times a minute.

Ventilation is regulated by levels of carbon dioxide, oxygen and hydrogen ion concentration (pH) in the arterial blood. The most important factor in the control of ventilation is the level of CO₂ in the arterial blood. An elevation in the CO₂ level causes the respiratory control system in the brain to increase the rate and depth of breathing; the increased ventilatory effort removes excess CO₂ by increasing exhalation. However, some patients with chronic lung disease have ongoing hypercapnoea and are known as CO₂ retainers. For patients with hypoxaemia (reduced levels of arterial oxygen) in association with chronic lung disease, controlled oxygen therapy is used. Through frequent patient monitoring, treatment is aimed at achieving oxygen saturation levels of 88–92% using the lowest amount of oxygen to achieve this (Kunisaki and others, 2007). In summary, the general principle is to use the least amount of oxygen for the most benefit.

Mechanics of breathing

Although breathing is normally passive, muscular work is involved in moving the lungs and chest wall. Inspiration is an active process. During inspiration, the respiratory centre sends impulses along the phrenic nerve, causing the diaphragm to contract. Abdominal organs move downwards and forwards, increasing the length of the chest cavity to move air into the lungs. The diaphragm moves approximately 1 cm, and the ribs retract upwards from the body’s midline approximately 1.2–2.5 cm. During a normal, relaxed breath, a person inhales 500 mL of air. This amount is referred to as the tidal volume. During expiration, the diaphragm relaxes and the abdominal organs return to their original positions. The lung and chest wall return to a relaxed position (Figure 28-8). Expiration is a passive process. The normal rate and depth of ventilation, eupnoea, is interrupted by sighing. The sigh, a prolonged deeper breath, is a protective physiological mechanism for expanding small airways and alveoli not ventilated during a normal breath.

FIGURE 28-8 Diaphragmatic and chest wall movement during inspiration and expiration.

From Potter PA, Perry AG 2013 Fundamentals of nursing, ed 8. St Louis, Mosby.

Assessment of respirations

The accurate assessment of respirations depends on recognition of normal thoracic and abdominal movements (Skill 28-3). During quiet breathing, the chest wall gently rises and falls. Contraction of the intercostal muscles between the ribs or contraction of the muscles in the neck and shoulders, the accessory muscles of breathing, is not visible. During normal quiet breathing, diaphragmatic movement causes the abdominal cavity to rise and fall slowly.

SKILL 28-3 Assessing respirations

DELEGATION CONSIDERATIONS

Respiration measurement can be delegated to enrolled nurses who are informed of:

• appropriate patient position when obtaining respirations

• appropriate duration of respiratory rate count

• patient history or risk of increased or decreased respiratory rate or irregular respirations

• frequency of respirations measurement

• the reportable levels for the patient

• the need to report any abnormalities.

EQUIPMENT

• Wristwatch with second-hand or a digital display

• Pen, observation chart

STEPS			RATIONALE
1. Determine need to assess patient’s respirations:
	a. Note risk factors for respiratory alterations.		Certain conditions place patient at risk of alterations in ventilation detected by changes in respiratory rate, depth and rhythm. Fever, pain, anxiety, diseases of chest wall or muscles, constrictive chest or abdominal dressings, gastric distension, chronic pulmonary disease (emphysema, bronchitis, asthma), traumatic injury to chest wall with or without collapse of underlying lung tissue, presence of a chest tube, respiratory infection (pneumonia, acute bronchitis), pulmonary oedema and emboli, head injury with damage to brain stem and anaemia can result in respiratory alteration.
	b. Assess for signs and symptoms of respiratory alterations such as bluish or cyanotic appearance of nail beds, lips, mucous membranes and skin; restlessness, irritability, confusion, reduced level of consciousness; pain during inspiration; laboured or difficult breathing; adventitious breath sounds (see Chapter 27), inability to breathe spontaneously; thick, frothy, blood-tinged or copious sputum produced on coughing.		Physical signs and symptoms may indicate alterations in respiratory status related to ventilation.
2. Assess pertinent laboratory values:
	A. Arterial blood gases (ABGs). Normal ABGs (values may vary slightly within institutions): pH 7.35–7.45 PaCO₂ 35-45 mmHg PaO₂ 80-100 mmHg SaO₂ 94-98%		Arterial blood gases measure arterial blood pH, partial pressure of oxygen (PaO₂) and carbon dioxide (PaCO₂) and arterial oxygen saturation (SaO₂), which reflects patient’s oxygenation status.
	B. Pulse oximetry (SpO₂). Acceptable SpO₂ > 95% on room air. 88-92% may be acceptable for patients with chronic obstructive pulmonary disease.		SpO₂ less than 85% is often accompanied by changes in respiratory rate, depth and rhythm.
	C. Full blood count (FBC). Normal FBC for adults (values may vary within institutions):		Complete blood count measures red blood cell count, volume of red blood cells and concentration of haemoglobin, which reflects patient’s capacity to carry oxygen and therefore influences interpretation of the results.
		(1)Haemoglobin: males 130-180 g/L; females 115-165 g/L.
		(2)Haematocrit: males 0.42-0.52%; females 0.35-0.47%.
		(3)Red cells: males 4.50-6.50 × 10¹²/L; females 3.90-5.60 × 10¹²/L.
3. Determine previous baseline respiratory rate (if available) from patient’s record.			Allows nurse to assess for change in condition. Provides comparison with future respiratory measurements.
4. Be sure patient is in comfortable position, preferably sitting or lying with the head of the bed elevated 45-60 degrees.			Sitting erect promotes full ventilatory movement.
Critical decision point: Patients with difficulty breathing (dyspnoea), such as those with heart failure or abdominal ascites or in late stages of pregnancy, should be assessed in the position of greatest comfort. Repositioning may increase the work of breathing, which will increase respiratory rate.
5. Draw curtain around bed and/or close door. Perform hand hygiene.			Maintains privacy. Prevents transmission of microorganisms.
6. Be sure patient’s chest is visible. If necessary, move bedclothes or gown.			Ensures clear view of chest wall and abdominal movements.
7. Place patient’s arm in relaxed position across the abdomen or lower chest, or place nurse’s hand directly over patient’s upper abdomen (see illustration).			A similar position used during pulse assessment allows respiratory rate assessment to be inconspicuous. Patient’s or nurse’s hand rises and falls during respiratory cycle.
Step 7 Position of hands for assessing respirations.
8. Observe complete respiratory cycle (one inspiration and one expiration).			Rate is accurately determined only after nurse has viewed respiratory cycle.
9. After cycle is observed, look at watch’s second-hand and begin to count rate: when second-hand hits number on dial, begin timeframe, counting 1 with first full respiratory cycle.			Timing begins with count of 1. Respirations occur more slowly than pulse; thus timing does not begin with 0.
10. If rhythm is regular, count number of respirations in 30 s and multiply by 2. If rhythm is irregular, < 12 or > 20, count for 1 full minute.			Respiratory rate is equivalent to number of respirations per minute. Suspected irregularities require assessment for at least 1 minute.
Critical decision point: Respiratory rate < 12 or > 20 requires further assessment (see Chapter 27) and may require immediate intervention.
11. Note depth of respirations, subjectively assessed by observing degree of chest wall movement while counting rate. Nurse can also objectively assess depth by palpating chest wall excursion or auscultating the posterior thorax after rate has been counted. Depth is described as shallow, normal or deep.			Character of ventilatory movement may reveal specific disease state restricting volume of air from moving into and out of the lungs.
12. Note rhythm of ventilatory cycle. Normal breathing is regular and uninterrupted. Sighing should not be confused with abnormal rhythm.			Character of ventilations can reveal specific types of alterations.
Critical decision point: Occasional periods of apnoea, the cessation of respiration for several seconds, are a symptom of underlying disease in the adult and must be reported to the medical practitioner or nurse in charge. An irregular respiratory rate and short apnoeic spells are usual in a newborn.
13. Replace bedclothes and patient’s gown.			Restores comfort and promotes sense of wellbeing.
14. Perform hand hygiene.			Reduces transmission of microorganisms.
15. Discuss findings with patient as needed.			Promotes participation in care and understanding of health status.
16. If respirations are assessed for the first time, establish rate, rhythm and depth as baseline if within normal range.			Used to compare future respiratory assessment.
17. Compare respirations with patient’s previous baseline and normal rate, rhythm and depth.			Allows assessment for changes in patient’s condition and for presence of respiratory alterations.

RECORDING AND REPORTING	HOME CARE CONSIDERATIONS
• Record respiratory rate and character in nurses’ notes and observation chart. Indicate type and amount of oxygen therapy if used by patient during assessment. Measurement of respiratory rate after administration of specific therapies should be documented in narrative form in nurses’ notes. • Report abnormal findings to nurse in charge or medical practitioner.	• Assess for environmental factors in the home that may influence patient’s respiratory rate such as secondhand smoke, poor ventilation or gas fumes.

Rate

Assessment of respiration can best be done immediately after measuring pulse rate, with your hand still on the patient’s wrist as it rests over the chest or abdomen. This approach allows assessment of the respiratory rate, pattern and depth without drawing the patient’s attention to the assessment. If the patient is aware, they may unintentionally alter their rate and depth of breathing. Observe a full inspiration and expiration when counting ventilation or respiration rate. The respiratory rate varies with age (Table 28-4). The usual range of respiratory rate declines throughout life.

TABLE 28-4 ACCEPTABLE RANGE OF RESPIRATORY RATES FOR AGE

AGE GROUP	RATE (BREATHS PER MINUTE)
Newborn	30-60
Infant (6 months)	30-50
Toddler (2 years)	25-32
Child	20-30
Adolescent	16-19
Adult	12-20

Ventilatory depth

The depth of respirations is assessed by observing the degree of excursion or movement in the chest wall. Ventilatory movements are described as deep, normal or shallow. A deep respiration involves a full expansion of the lungs with full exhalation. Respirations are shallow when only a small quantity of air passes through the lungs, and ventilatory movement is difficult to see. More-objective techniques are used if you observe that chest excursion is unusually shallow. Table 28-5 summarises types of respiratory alterations.

TABLE 28-5 ALTERATIONS IN BREATHING PATTERN

ALTERATION	DESCRIPTION
Apnoea	Respirations cease for several seconds. Persistent cessation results in respiratory arrest
Bradypnoea	Rate of breathing is regular but abnormally slow (fewer than 12 breaths per minute)
Biot’s respiration	Respirations are abnormally shallow for 2–3 breaths followed by an irregular period of apnoea
Cheyne-Stokes respiration	Respiratory rate and depth are irregular, characterised by alternating periods of apnoea and hyperventilation. Respiratory cycle begins with slow, shallow breaths that gradually increase to abnormal rate and depth. The pattern reverses, breathing slows and becomes shallow, climaxing in apnoea before respiration resumes
Hyperpnoea	Respirations are laboured, increased in depth and increased in rate (more than 20 breaths per minute). Occurs normally during exercise
Hyperventilation	Rate and depth of respirations increase. Respiratory alkalosis may occur
Hypoventilation	Respiratory rate is abnormally low, and depth of ventilation may be depressed. Hypercapnoea may occur
Kussmaul’s respiration	Respirations are abnormally deep, regular and increased in rate
Tachypnoea	Rate of breathing is regular but abnormally rapid (more than 20 breaths per minute)

Ventilatory pattern

Determine breathing pattern by observing the chest or abdomen. Diaphragmatic breathing results from the contraction and relaxation of the diaphragm and is best observed by watching abdominal movements. Men and children usually demonstrate diaphragmatic breathing. Women tend to use thoracic muscles to breathe; movements are observed in the upper chest. Laboured respirations usually involve the accessory neck muscles. When a foreign body or tracheal trauma interferes with the movement of air into the lungs, the intercostal spaces retract during inspiration. A longer expiration phase is evident when the outward flow of air is obstructed (e.g. in asthma).

With normal breathing, a regular interval occurs after each respiratory cycle. Infants tend to breathe less regularly. The young child may breathe slowly for a few seconds and then suddenly breathe more rapidly. While assessing respirations, estimate the time interval after each respiratory cycle. Respiration is regular or irregular in pattern.

Ventilatory sounds

An integral part of respiratory assessment is listening to the sounds of breathing. The sounds of stertor, stridor, wheezing and inspiratory grunt are indicators of a respiratory obstruction. Stertor, a snoring sound, occurs where secretions block the trachea and large bronchi. Stridor is an inspiratory wheeze or crowing sound occurring with upper airway obstruction (e.g. croup, inhalation of foreign objects, epiglottitis and tracheal trauma). Wheezing is a high-pitched musical sound occurring on expiration when there is a partial obstruction in smaller airways and bronchioles (e.g. bronchiolitis and asthma).

Respiratory monitoring devices that aid your assessment include the apnoea monitor and pulse oximeter. Apnoea monitoring is used frequently with infants in the hospital and at home to observe for prolonged apnoeic events. Leads attached to the infant’s chest wall sense movement; the absence of chest wall movement is interpreted by the monitor as apnoea and triggers an alarm.

Measurement of arterial oxygen saturation

Arterial oxygenation can be non-invasively measured using a pulse oximeter (Skill 28-4). Blood flows through the pulmonary capillaries where oxygen attaches to red blood cells. After oxygen diffuses from the alveoli into the pulmonary blood, most of the oxygen attaches to haemoglobin molecules in red blood cells. Red blood cells carry the oxygenated haemoglobin molecules through the left side of the heart and out to the peripheral capillaries, where the oxygen detaches.

SKILL 28-4 Measuring oxygen saturation (pulse oximetry, SpO₂)

DELEGATION CONSIDERATIONS

Oxygen saturation measurement can be delegated to enrolled nurses who are informed of:

• need to notify nurse immediately of any reading lower than SpO₂ of 90%

• appropriate sensor site, probe and patient position for measurement of oxygen saturation

• frequency of oxygen saturation measurements

• factors that can falsely lower SpO₂ (Box 28-12).

EQUIPMENT

• Oximeter

• Oximeter probe appropriate for patient and recommended by manufacturer

• Pen, observation chart

STEPS		RATIONALE
1. Determine need to measure patient’s oxygen saturation:
	a. Note risk factors for alteration of oxygen saturation.	Certain conditions place patients at risk of decreased oxygen saturation: acute or chronic compromised respiratory function, recovery from general anaesthesia or conscious sedation or traumatic injury to chest wall with or without collapse of underlying lung tissue, ventilator dependence, changes in supplemental oxygen therapy.
	b. Assess for signs and symptoms of alterations in oxygen saturation such as altered respiratory rate, depth or rhythm; adventitious breath sounds (see Chapter 27); cyanotic appearance of nail beds, lips, mucous membranes and skin; restlessness, irritability, confusion; reduced level of consciousness; laboured or difficulty breathing.	Physical signs and symptoms may indicate abnormal oxygen saturation.
2. Assess for factors that normally influence measurement of SpO₂, such as oxygen therapy, haemoglobin level and temperature.		Allows for accurate assessment of oxygen saturation variations. Peripheral vasoconstriction related to hypothermia can interfere with SpO₂ determination.
3. Review patient’s medical record for medical practitioner’s order or consult agency policy or procedure manual for standard of care.		Medical order may be required to assess oxygen saturation.
4. Determine previous baseline SpO₂ (if available) from patient’s record.		Baseline information provides basis for comparison and helps in assessment of current status and evaluation of interventions.
5. Explain purpose of procedure to patient and how oxygen saturation will be measured. Instruct patient to breathe normally.		Promotes patient cooperation and increases compliance. Prevents large fluctuations in minute ventilation and possible error in SpO₂ readings.
6. Assess site most appropriate for sensor probe placement (e.g. digit, earlobe) (see Box 28-11). Site must have adequate local circulation and be free of moisture.		Peripheral vasoconstriction can interfere with SpO₂ determination. Dark nail polish and acrylic nails impede sensor detection of emitted light and produce falsely elevated SpO₂.
7. Perform hand hygiene.		Reduces transmission of microorganisms.
8. Position patient comfortably. If finger is chosen as monitoring site, support lower arm.		Ensures probe positioning and decreases movement that interferes with SpO₂ determination.
9. Instruct patient to breathe normally.		Prevents large fluctuations in respiratory rate and depth and possible changes in SpO₂.
10. If finger is to be used, remove any fingernail polish with acetone from digit to be assessed. If earlobe is to be used, remove any earrings. Wash site, swab with alcohol and air-dry.		Ensures accurate readings. Opaque coatings decrease light transmission; nail polish containing blue pigment can absorb light emissions and falsely alter saturation.
11. Attach sensor probe to monitoring site. Instruct patient that clip-on probe feels like a clothes peg on the finger but should not hurt.		Pressure of sensor probe’s spring tension on a peripheral digit or earlobe may be unexpected.
Critical decision point: Do not attach probe to finger, ear or bridge of nose if area is oedematous or skin integrity is compromised. Do not attach probe to fingers that are hypothermic. Select ear or bridge of nose if adult patient has history of peripheral vascular disease. Earlobe and bridge of nose sensors are not used for infants and toddlers because of skin fragility. Disposable adhesive probes contain latex and should not be used if patient has latex allergy.
12. Turn on oximeter by activating power. Observe pulse waveform/intensity display and audible beep. Correlate oximeter pulse rate with patient’s radial pulse. Differences require re-evaluation of oximeter probe placement and may require reassessment of pulse rates.		Pulse waveform/intensity display enables detection of valid pulse or presence of interfering signal. Pitch of audible beep is proportional to SpO₂ value. Double-checking pulse rate ensures oximeter accuracy. Oximeter pulse rate, patient’s radial pulse and apical pulse rate should be the same.
13. Leave probe in place until oximeter readout reaches constant value and pulse display reaches full strength during each cardiac cycle. Read SpO₂ on digital display. Inform patient that oximeter will sound alarm if the probe falls off or if patient moves the probe.		Reading may take 10-30 s, depending on site selected.
14. If continuous Sp0₂ monitoring is planned, verify SpO₂ alarm limits and alarm volume, which are preset by the manufacturer at a low of 85% and a high of 100%. Limits for SpO₂ and pulse rate should be determined as indicated by patient’s condition. Verify that alarms are on. Assess skin integrity under sensor probe and relocate sensor probe at least every 4 hours (every 2 hours for a spring-tension probe).		Alarms must be set at appropriate limits and volumes to avoid frightening patients and visitors. Spring tension of sensor probe or sensitivity to disposable sensor probe adhesive can cause skin irritation and lead to disruption of skin integrity.
15. Discuss findings with patient as needed.		Promotes participation in care and understanding of health status.
16. If intermittent or spot-checking Sp0₂ measurements are planned, remove probe and turn oximeter power off. Clean probe following manufacturer’s instructions and store in appropriate location.		Batteries can be depleted if oximeter is left on. Sensor probes are expensive and vulnerable to damage.
17. Help patient return to comfortable position.		Restores comfort and promotes sense of wellbeing.
18. Perform hand hygiene.		Reduces transmission of microorganisms.
19. Compare SpO₂ readings with patient baseline and acceptable values.		Comparison reveals presence of abnormality.
20. Correlate SpO₂ with SaO₂ obtained from arterial blood gas measurements (see Chapter 39) if available.		Documents reliability of non-invasive assessment.
21. Correlate SpO₂ reading with data obtained from respiratory rate, depth and rhythm assessment.		Measurements assessing ventilation, perfusion and diffusion are interrelated.

RECORDING AND REPORTING	HOME CARE CONSIDERATIONS
• Record Sp0₂ value on patient progress notes and observation chart, indicating type and amount of oxygen therapy used by patient during assessment. Also record any signs and symptoms of oxygen desaturation in narrative form in progress notes. Measurement of SpO₂ after administration of specific therapies should be documented in narrative form in progress notes. • Report abnormal findings to nurse in charge or medical practitioner. Assessment of oxygen saturation after administration of specific therapies should be documented in narrative form in progress notes. • Record in progress notes patient’s use of continuous or intermittent pulse oximetry.	• Pulse oximetry is used in home care to non-invasively monitor oxygen therapy or changes in oxygen therapy.

RECORDING AND REPORTING

HOME CARE CONSIDERATIONS

• Record Sp0₂ value on patient progress notes and observation chart, indicating type and amount of oxygen therapy used by patient during assessment. Also record any signs and symptoms of oxygen desaturation in narrative form in progress notes. Measurement of SpO₂ after administration of specific therapies should be documented in narrative form in progress notes.

• Report abnormal findings to nurse in charge or medical practitioner. Assessment of oxygen saturation after administration of specific therapies should be documented in narrative form in progress notes.

• Record in progress notes patient’s use of continuous or intermittent pulse oximetry.

• Pulse oximetry is used in home care to non-invasively monitor oxygen therapy or changes in oxygen therapy.

The percentage of haemoglobin bound with oxygen in the arteries is the percentage of saturation of haemoglobin (or SaO₂). It is usually between 95% and 100%. SaO₂ is affected by factors that interfere with ventilation and perfusion (see Chapter 40). The saturation of venous blood (SvO₂) is lower because the tissues have removed some of the oxygen from the haemoglobin molecules. A normal value for SvO₂ is 70%. SvO₂ is affected by factors that interfere with or increase the tissues’ need for oxygen.

The pulse oximeter (see Box 28-11 and Figure 28-9) emits light wavelengths that are absorbed by the oxygenated and deoxygenated haemoglobin molecules. The light reflected from the haemoglobin molecules is processed by the oximeter, which calculates pulse saturation (SpO₂). SpO₂ is a reliable estimate of SaO₂ when the SaO₂ is over 70%, but is less accurate at saturations below 70% (McMorrow and Mythen, 2006). The measurement of SpO₂ is affected by factors that affect light transmission or peripheral arterial pulsations (Box 28-12). Selecting the appropriate probe is important for reducing measurement error (Box 28-11). Movement is the most common cause of inaccurate readings.

BOX 28-11 CHARACTERISTICS OF PULSE OXIMETER SENSOR PROBES AND SITES

REUSABLE PROBE

• Digit probe

• Easy to apply, conforms to various sizes

• Yields strong correlation with SaO₂

EARLOBE

• Clip-on is smaller and lighter though more positional than digit probe

• Greater accuracy at lower saturations

• Good when uncontrollable movements (e.g. hand tremors) are present

• Least affected by decreased blood flow

DISPOSABLE SENSOR PAD

• Can be applied to a variety of sites: earlobe of adult, nose bridge, palm or sole of infant

• Less restrictive for continuous SpO₂ monitoring

• Expensive

• Contains latex

• Risk that skin under adhesive may become moist and harbour pathogens

• Available in variety of sizes; can be matched to infant weight

FIGURE 28-9 Pulse oximeter with spring tension digit probe.

From Potter PA, Perry AG 2013 Fundamentals of nursing, ed 8. St Louis, Mosby.

BOX 28-12 Factors affecting determination of pulse oxygen saturation (S_pO₂)

INTERFERENCE WITH LIGHT TRANSMISSION

• Outside light sources can interfere with the oximeter’s ability to process reflected light.

• Carbon monoxide (caused by smoke inhalation or poisoning) artificially elevates SpO₂ by absorbing light similar to oxygen.

• Movement can interfere with the oximeter’s ability to process reflected light.

• Jaundice may interfere with the oximeter’s ability to process reflected light.

• Intravascular dyes (methylene blue) absorb light similar to deoxyhaemoglobin and artificially lower saturation.

REDUCTION OF ARTERIAL PULSATIONS

• Peripheral vascular disease (Raynaud’s disease, atherosclerosis) can reduce pulse volume.

• Hypothermia at assessment site decreases peripheral blood flow.

• Pharmacological vasoconstrictors (adrenaline, phenylephrine, dopamine) will decrease peripheral pulse volume.

• Low cardiac output and hypotension decrease blood flow to peripheral arteries.

• Peripheral oedema can obscure arterial pulsation.

It is important to know that if the patient is having pulse oximeter readings, it is vital that respiratory rates are measured and documented as well (Parkes, 2011). Vital sign measurement of respiratory rate, pattern and depth, along with arterial oxygen saturation using the pulse oximeter (SpO₂), allows assessment of ventilation, diffusion and perfusion. Each measurement provides cues in determining the nature of a patient’s problem.

Clinical decision making: respirations

Accurate measurement of respirations requires observation, palpation of chest wall movement and listening to sounds associated with inspiration and expiration. The patient’s usual ventilatory rate and pattern, the influence any disease or illness has on respiratory function, the relationship between respiratory and cardiovascular function, and the influence of therapies on respirations and the patient’s recent pattern are all critical to accurate assessment of respiration rate, pattern and depth. Because respiration is linked to the function of numerous body systems, it is critical to consider all variables when changes occur (Parkes, 2011).

• CRITICAL THINKING

Michael is 18 years old and was involved in a motor vehicle accident 6 hours ago, where he received chest and head injuries. On admission to the unit his respiratory rate was 22 breaths per minute. You note that his respiratory rate is slowly decreasing and your most recent measurement of his respirations is 12 breaths per minute.

1. What additional assessment will you perform? Explain your selection.

2. Identify the actual and potential nursing problems for Michael. What nursing interventions will you implement to ensure Michael’s safety?

You should consult Chapter 27 to help you identify the critical elements of assessment of Michael’s cognition and perception.

Blood pressure

Knowledge of the structure and function of the cardiovascular system in combination with understanding of the patient’s clinical situation and the implications for the cardiovascular system facilitate accurate assessment of a patient’s blood pressure. Blood pressure is the lateral force on the walls of an artery from the blood pulsing under pressure from the heart. Systemic or arterial blood pressure, the blood pressure in the system of arteries in the body, is a good indicator of cardiovascular health. Blood flows throughout the circulatory system because of pressure changes. It moves from an area of high pressure to an area of low pressure. The heart’s contraction forces blood under high pressure into the aorta. The peak of maximum pressure, when ejection occurs, is systolic blood pressure. When the ventricles relax, the blood remaining in the arteries exerts a minimum or diastolic pressure.

Even though most sphygmomanometers are now either aneroid (using no fluid) or electronic, the standard unit for measuring blood pressure is millimetres of mercury (mmHg). The measurement indicates the height to which the blood pressure can raise a column of mercury. Blood pressure is recorded with the systolic reading before the diastolic (e.g. 120/80 mmHg). The difference between systolic and diastolic pressure is the pulse pressure. For a blood pressure of 120/80 mmHg, the pulse pressure is 40 mmHg. The pulse pressure varies with arterial elasticity. Rigid vessels incapable of distension and recoil produce increased pulse pressure. Increased pulse pressure indicates increased stroke volume, decreased peripheral vascular resistance, or both. A decreased or narrow pulse pressure reflects reduced stroke volume, increased peripheral vascular resistance, or both.

Physiology of arterial blood pressure

Blood pressure reflects the interrelationships of cardiac output, peripheral vascular resistance, blood volume, blood viscosity and artery elasticity. Knowledge of these haemodynamic variables helps in the assessment of blood pressure alterations.

Cardiac output

A person’s cardiac output is the volume of blood pumped by the heart during 1 minute. The blood pressure (BP) depends on the cardiac output (CO) and the systemic vascular resistance (SVR):

BP = CO × SVR

When volume increases in an enclosed space, such as a blood vessel, the pressure in that space rises. As CO increases, more blood is pumped against arterial walls, causing the BP to rise. Cardiac output can increase as a result of an increase in heart rate, greater heart muscle contractility or an increase in blood volume. Changes in heart rate can occur faster than changes in muscle contractility or blood volume. An increase in heart rate may decrease diastolic filling time and end-diastolic volume. As a result, there is a decrease in blood pressure.

Peripheral resistance

The blood circulates through a network of arteries, arterioles, capillaries, venules and veins. Arteries and arterioles are surrounded by smooth muscle that contracts or relaxes to change the size of the lumen. The size of arteries and arterioles changes to adjust blood flow to the needs of local tissues. For example, when more blood is needed by a major organ, the peripheral arteries constrict, decreasing their supply of blood. More blood becomes available to the major organ because of the resistance change in the periphery. Normally, arteries and arterioles remain partially constricted to maintain a constant flow of blood. Peripheral vascular resistance is the resistance to blood flow determined by the tone of vascular musculature and the diameter of blood vessels. The smaller the lumen of a vessel, the greater peripheral vascular resistance to blood flow. As resistance rises, arterial blood pressure rises. As vessels dilate and resistance falls, blood pressure drops.

Blood volume

The volume of blood circulating within the vascular system affects blood pressure. Most adults have a circulating blood volume of 5000 mL. Normally, the blood volume remains constant. However, if volume increases, more pressure is exerted against arterial walls. For example, the rapid, uncontrolled infusion of intravenous fluids elevates blood pressure. When circulating blood volume falls, as in the case of haemorrhage or dehydration, blood pressure falls.

Viscosity

The viscosity of blood affects the ease with which blood flows through small vessels. The haematocrit, or percentage of red blood cells in the blood, measures blood viscosity. When the haematocrit rises and blood flow slows, arterial blood pressure increases. The heart must contract more forcefully to move the more viscous blood through the circulatory system.

Elasticity

Normally, the walls of an artery are elastic and easily distensible. As pressure within the arteries increases, the diameter of vessel walls increases to accommodate the pressure change. Arterial distensibility prevents wide fluctuations in blood pressure. However, in certain diseases, such as arteriosclerosis, the vessel walls lose their elasticity and are replaced by fibrous tissue that cannot stretch well. With reduced elasticity there is greater resistance to blood flow. As a result, when the left ventricle ejects its stroke volume, the vessels no longer yield to pressure. Instead, a given volume of blood is forced through the rigid arterial walls, and the systemic pressure rises. Systolic pressure is more significantly elevated than diastolic pressure as a result of reduced arterial elasticity.

Each haemodynamic factor significantly affects the others (Figure 28-10). For example, as arterial elasticity declines, peripheral vascular resistance increases. The complex control of the cardiovascular system normally prevents any single factor from permanently changing the blood pressure. For example, if the blood volume falls, the body compensates with an increased vascular resistance.

FIGURE 28-10 Haemodynamic factors that affect blood pressure.

Factors influencing blood pressure

Blood pressure is not constant, but is continually influenced by many factors during the day. One blood pressure measurement cannot adequately reflect a patient’s blood pressure. Even under the best conditions, blood pressure changes from heartbeat to heartbeat. Blood pressure trends, not individual measurements, guide nursing interventions. Understanding these factors ensures a more accurate interpretation of blood pressure readings.

Age

Normal blood pressure levels vary and gradually increase throughout life (Table 28-6). The level of a child or adolescent’s blood pressure is assessed with respect to body size and age (Hockenberry and Wilson, 2011). Larger children (heavier and/or taller) have higher blood pressures than smaller children of the same age. An adult’s blood pressure tends to increase with advancing age (Table 28-7). Older adults have a rise in systolic pressure related to decreased vessel elasticity.

TABLE 28-6 AVERAGE OPTIMAL BLOOD PRESSURE FOR AGE

AGE GROUP	BLOOD PRESSURE (MMHG)
Newborn (3000 g)	40 (mean)
1 month	85/54
1 year	95/65
6 years	105/65
10 –13 years	110/65
14 –17 yea r s	120/75
Middle adult	< 120/80

From National Institutes of Health: National Heart, Lung and Blood Institute (NHLBI) Joint National Committee 2004 The Seventh Report of the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure, Bethesda, MD, NHLBI.

TABLE 28-7 CLASSIFICATION OF BLOOD PRESSURE FOR ADULTS

DIAGNOSTIC CATEGORY	SYSTOLIC (mmHg)	DIASTOLIC (mmHg)
Normal	<120	<80
High normal	120-139	80-89
Hypertension^*
Grade 1 (mild)	140-159	90-99
Grade 2 (moderate)	160-179	100-109
Grade 3 (severe)	≥180	≥110
Isolated systolic hypertension	≥140	<90
Isolated systolic hypertension with widened pulse pressure	≥160	≤70

^*The diagnosis of hypertension should be based on multiple BP measurements taken on separate occasions.

Adapted from Heart Foundation of Australia (National Blood Pressure and Vascular Disease Advisory Committee) 2010 Guide to management of hypertension 2008: assessing and managing raised blood pressure in adults; updated December 2010. Online. Available at www.heartfoundation.org.au/SiteCollectionDocuments/HypertensionGuidelines2008to2010Update.pdf 27 May 2012. Data reproduced with permission. © 2010 National Heart Foundation of Australia.

Stress

Anxiety, fear, pain and emotional stress result in sympathetic stimulation, which increases heart rate, cardiac output and peripheral vascular resistance and ultimately increases blood pressure.

Medications

Some medications can directly or indirectly affect blood pressure. During blood pressure assessment, the nurse asks whether the patient is receiving antihypertensive or other cardiac medications, which lower blood pressure (Table 28-8). Opioid analgesics also lower blood pressure through their vasodilatory effect.

TABLE 28-8 ANTIHYPERTENSIVE MEDICATIONS

MEDICATION TYPE	NAMES	ACTION
Angiotensin-converting enzyme (ACE) inhibitors	Captopril (Capoten), enalapril (Vasotec), lisinopril (Prinivil)	Lower blood pressure by blocking the conversion of angiotensin 1 to angiotensin II, preventing vasoconstriction; reduce aldosterone production and fluid retention, lowering circulating fluid volume
Beta-adrenergic blockers	Atenolol (Tenormin), nadolol (Corgard), timolol maleate (Blocadren), propranolol (Inderal)	Combine with beta-adrenergic receptors in the heart, arteries and arterioles to block response to sympathetic nerve impulses; reduce heart rate and thus cardiac output
Calcium channel blockers	Verapamil hydrochloride (Calan), nifedipine (Procardia)	Reduce peripheral vascular resistance by systemic vasodilation
Diuretics	Furosemide (Lasix), spironolactone (Aldactone), metolazone, polythiazide, benzthiazide	Lower blood pressure by reducing reabsorption of sodium and water by the kidneys, thus lowering circulating fluid volume
Vasodilators	Hydralazine hydrochloride (Apresoline), minoxidil (Loniten)	Act on arteriolar smooth muscle to cause relaxation and reduce peripheral vascular resistance

Diurnal variation

Blood pressure levels vary over the course of a day. Blood pressure is typically lowest in the early morning, gradually rises during the morning and afternoon and peaks in late afternoon or evening. No two people have the same pattern or degree of variation. Students may find it interesting to have their blood pressure checked by a friend at intervals over 24 hours.

Gender

There is no clinically significant difference in blood pressure levels between boys and girls. After puberty, males tend to have higher blood pressure readings. After menopause, women tend to have higher levels of blood pressure than men of similar age.

Blood pressure measurement

Accurate technique is critical for gaining meaningful blood pressure readings (Plante, 2005; Wallymahamed, 2008). To ensure reliable blood pressure results, you will need to become familiar with the equipment and the principles of blood pressure measurement (Skill 28-5). The blood pressure is measured by auscultation or palpation. Auscultation is the most widely used technique. The process of taking a blood pressure reading will differ depending on your knowledge of the patient and their previous blood pressure readings. You will also need to learn how to use automatic blood pressure equipment, as this is readily available in most clinical venues. Finally, you will need to understand how to manage challenging situations by selecting the most suitable equipment and sites for measuring the blood pressure. Accurate recording and interpretation of results and knowledge of when to report changes are critical to patient safety.

SKILL 28-5 Measuring blood pressure (BP)

DELEGATION CONSIDERATIONS

Blood pressure measurement can be delegated to enrolled nurses who are informed of:

• appropriate patient position when obtaining blood pressure measurement

• alterations affecting the appropriate limb for blood pressure measurement

• appropriate-size blood pressure cuff for designated extremity

• patient’s risk of orthostatic hypotension

• frequency of blood pressure measurement

• reportable levels for the patient

• the need to report any abnormalities.

EQUIPMENT

• Aneroid or mercury sphygmomanometer

• Cloth or disposable vinyl pressure cuff of appropriate size for patient’s extremity

• Stethoscope

• Alcohol swab

• Pen, observation chart

STEPS			RATIONALE
1. Determine need to assess patient’s BP:
	a. Note risk factors for alteration in BP.		Certain conditions place patients at risk of BP alteration: history of cardiovascular disease, renal disease, diabetes, circulatory shock (hypovolaemic, septic, cardiogenic or neurogenic), acute or chronic pain, rapid intravenous infusion of fluids or blood products, increased intracranial pressure, postoperative conditions, toxaemia of pregnancy.
	b. Observe for signs and symptoms of BP alterations:
		(1)High BP (hypertension) is often asymptomatic until pressure is very high. Assess for headache (usually occipital), flushing of face, nosebleed, and fatigue in older adults.	Physical signs and symptoms may indicate alterations in BP. (See Table 28-6 for average optimal blood pressure for age.)
		(2)Low BP (hypotension) is associated with: dizziness mental confusion; restlessness; pale, dusky or cyanotic skin and mucous membranes; cool, mottled skin over extremities.
2. Determine best site for BP assessment. Avoid applying cuff to extremity when: intravenous fluids are infusing; an arteriovenous shunt or fistula is present; breast or axillary surgery has been performed on that side; extremity has been traumatised, is diseased or requires a cast or bulky bandage. The lower extremities may be used when the brachial arteries are inaccessible.			Inappropriate site selection may result in poor amplification of sounds, causing inaccurate readings. Application of pressure from inflated bladder temporarily impairs blood flow and can further compromise circulation in extremity that already has impaired blood flow.
3. Select appropriate cuff size.			Improper cuff size results in inaccurate readings (see Table 28-9). If cuff is too small, it tends to come loose while being inflated or results in false high readings. If the cuff is too large, false low readings may be recorded.
4. Determine previous baseline BP (if available) from patient’s record.			Allows assessment for change in condition. Provides comparison with future BP measurements.
5. Encourage patient to avoid exercise and smoking for 30 min before assessment of BP.			Exercise and smoking can cause false elevations in BP.
6. Have patient assume sitting or lying position. Be sure room is warm, quiet and relaxing.			Maintains patient’s comfort during measurement. The patient’s perception that the physical or interpersonal environment is stressful affect the BP measurement.
7. Explain to patient that BP is to be assessed and have patient rest at least 5 min before measurement. Ask patient not to speak when BP is being measured.			Reduces anxiety that can falsely elevate readings. Blood pressure readings taken at different times can be objectively compared when assessed with patient at rest. Talking to a patient when the BP is being assessed increases readings by 10-40%.
8. Perform hand hygiene. With patient sitting or lying, position patient’s forearm or thigh, supported if needed. For arm, turn palm up; for thigh, position with knee slightly flexed.			Reduces transmission of microorganisms. If extremity is unsupported, patient may perform isometric exercise that can increase diastolic blood pressure.
9. Expose extremity (arm or leg) fully by removing constricting clothing.			Ensures proper cuff application.
10. Palpate brachial artery (arm); see illustration or popliteal artery (leg). Position cuff 2.5 cm above site of pulsation (antecubital or popliteal).			Inflating bladder directly over artery ensures proper pressure is applied during inflation.
Step 10 Position of cuff above site of pulsation of brachial artery.
11. Apply bladder of cuff above artery by centring arrows marked on cuff over artery. If there are not centre arrows on cuff, estimate the centre of the bladder and place this centre over artery. With cuff fully deflated, wrap cuff evenly and snugly around extremity.			Loose-fitting cuff causes false high readings.
12. Position manometer vertically at eye level. Observer should be no further than 1 m away.			Accurate readings are obtained by looking at the meniscus of the mercury at eye level. The meniscus is the point where the crescent-shaped top of the mercury column aligns with the manometer scale. Looking up or down at the mercury results in distorted readings.
13. If you do not know the patient’s baseline BP, estimate systolic pressure by palpating the artery distal to the cuff, i.e. radial artery, with fingertips of one hand while inflating cuff rapidly to pressure 30 mmHg above point at which pulse disappears. Slowly deflate cuff and note point when pulse reappears. Deflate cuff fully and wait 30 s.			Estimating prevents false low readings, which may result in the presence of an auscultatory gap. Maximal inflation point for accurate reading can be determined by palpation. If unable to palpate artery because of weakened pulse, an ultrasonic stethoscope can be used. Deflating cuff prevents venous congestion and false high readings.
14. Place stethoscope earpieces in ears and be sure sounds are clear, not muffled.			Each earpiece should follow angle of ear canal to facilitate hearing.
15. Relocate brachial or popliteal artery and place bell or diaphragm chestpiece of stethoscope over it. Do not allow chestpiece to touch cuff or clothing.			Proper stethoscope placement ensures optimal sound reception. Stethoscope improperly positioned causes muffled sounds that often result in false low systolic and false high diastolic readings.
16. Close valve of pressure bulb clockwise until tight. Rapidly inflate cuff to 30 mmHg above palpated systolic pressure.			Tightening of valve prevents air leak during inflation. Inflation ensures accurate measurement of systolic pressure.
17. Slowly release pressure bulb valve and allow mercury or needle of aneroid manometer gauge to fall at rate of 2-3 mmHg/s.			Too rapid or slow a decline in mercury level or aneroid pressure can cause inaccurate readings.
18. Note point on manometer when first clear sound is heard. The sound will slowly increase in intensity.			First Korotkoff sound indicates systolic pressure.
19. Continue to deflate cuff, noting point at which muffled or dampened sound appears.			Fourth Korotkoff sound involves distinct muffling of sounds and is recommended as indication of diastolic pressure in children.
20. Continue to deflate cuff gradually, noting point at which sound disappears in adults. Listen for 10-20 mmHg after the last sound, and then allow remaining air to escape quickly.			Beginning of the fifth Korotkoff sound is recommended as indication of diastolic pressure in adults.
21. Remove cuff from extremity unless measurement must be repeated. If this is the first assessment of patient, repeat procedure on other extremity.			Continuous cuff inflation causes arterial occlusion, resulting in numbness and tingling of patient’s arm. Comparison of BP in both extremities detects circulation problems. (Normal difference of 5-10 mmHg exists between extremities.)
22. Help patient return to comfortable position and cover upper arm if prev ously clothed.			Restores comfort and promotes sense of wellbeing.
23. Discuss findings with patient as needed.			Promotes participation in care and understanding of health status.
24. Perform hand hygiene.			Reduces transmission of microorganisms.
25. Compare reading with previous baseline and/or acceptable value of blood pressure for patient’s age.			Checks for change in condition and alterations.
26. Compare blood pressure in both arms or both legs.			If using upper extremities, the arm with the higher pressure should be used for subsequent assessments unless contraindicated.
27. Correlate blood pressure with data obtained from pulse assessment and related cardiovascular signs and symptoms.			Blood pressure and heart rate are interrelated.

RECORDING AND REPORTING	HOME CARE CONSIDERATIONS
• Inform patient of value and need for periodic reassessment. • Record blood pressure on observation chart and in progress notes if necessary. Measurement of blood pressure after administration of specific therapies should be documented in narrative form in progress notes. • Report abnormal findings to nurse in charge or medical practitioner.	• Assess home noise level to determine room that will provide quietest environment for assessing BP. • Consider electronic blood pressure cuff for home if patient has hearing difficulties and if patient has sufficient financial resources.

Equipment

Before assessing blood pressure, you need to be confident in using a sphygmomanometer and a stethoscope. A sphygmomanometer comprises a pressure manometer, an occlusive cloth or vinyl cuff that encloses an inflatable rubber bladder, and a pressure bulb with a release valve that inflates the bladder. The aneroid manometer has a glass-enclosed circular gauge containing a needle that registers millimetre calibrations. Cloth or disposable vinyl compression cuffs contain the inflatable bladder and come in several sizes. The size selected is proportional to the circumference of the limb being assessed (Figure 28-11). Ideally, the width of the cuff should be 40% of the circumference (or 20% wider than the diameter) of the midpoint of the limb on which the cuff is to be used (National Institutes of Health, 2004). The bladder, enclosed by the cuff, should encircle at least two-thirds of the arm of an adult and the entire arm of a child. In children, the lower edge of the cuff should be above the antecubital fossa, allowing room for placement of the stethoscope bell or diaphragm. Blood pressure measurements will not be accurate unless the correct size of blood-pressure cuff is applied appropriately.

FIGURE 28-11 Guidelines for proper blood-pressure cuff size. Cuff width = 20% more than the upper arm diameter; or 40% of circumference and two-thirds of arm length.

From Potter PA, Perry AG 2013 Fundamentals of nursing, ed 8. St Louis, Mosby.

Before using a sphygmomanometer, inspect the parts of the release valve and the pressure bulb. The valve should be clean and freely moveable in either direction. If it sticks or becomes too tightly closed, the deflation of the pressure cuff will be hard to regulate. The pressure bulb is made of tough rubber and should be free of leaks. Aneroid manometers have the advantage of being lightweight, portable and compact, but the tendency for metal parts to expand or contract in response to environmental temperature changes can affect their reliability. Aneroid sphygmomanometers require biomedical calibration at routine intervals to verify their accuracy. Before using the aneroid model, be sure that the needle points to zero and that the manometer is correctly calibrated.

Principles of blood pressure measurement

Measurement of arterial blood pressure works on a basic principle of pressure. Blood flows freely through an artery until an inflated cuff applies pressure to tissues and causes the artery to collapse. After the cuff pressure is released, the point at which blood flow returns and sound appears through auscultation is the systolic pressure.

In 1905, Korotkoff, a Russian surgeon, first described the sounds heard over an artery distal to the blood pressure cuff:

1. The first Korotkoff sound is a clear rhythmical tapping corresponding to the pulse rate that gradually increases in intensity. Onset of the sound corresponds to the systolic pressure.

2. With the second Korotkoff sound, a murmur or swishing sound occurs as the cuff continues to deflate. As the artery distends, there is a turbulence in blood flow.

3. The third Korotkoff sound is a crisper and more intense tapping.

4. The fourth Korotkoff sound becomes muffled and low-pitched as the cuff is further deflated. Cuff pressure falls below the pressure within the vessel walls; this sound is the diastolic pressure in infants and children.

5. The fifth Korotkoff sound is an absence of sound. In adolescents and adults, the fifth sound corresponds to the diastolic pressure (Figure 28-12).

FIGURE 28-12 The sounds auscultated during blood-pressure measurement can be differentiated into five Korotkoff phases. In this example, blood pressure is 140/90 mmHg.

From Potter PA, Perry AG 2013 Fundamentals of nursing, ed 8. St Louis, Mosby.

In some patients the sounds are clear and distinct. In other patients, only the beginning and ending sounds are clear.

Initial blood pressure measurement

During the initial assessment, ask the patient to state their usual blood pressure. If they do not know, you can tell the patient after measuring and recording the blood pressure. This may also be a good opportunity for relevant patients to discuss optimal values of blood pressure, the risk factors for developing hypertension and the dangers of hypertension. At the initial assessment, blood pressure is measured in both arms. Normally there is a difference of 5–10 mmHg between the arms. In subsequent assessments, the blood pressure should be measured in the arm with the higher pressure. Pressure differences greater than 10 mmHg indicate vascular problems in the arm with the lower pressure.

Palpation technique

The palpation technique is often used by the admitting nurse when the patient’s usual blood pressure reading is unknown. This approach is useful for determining how high to inflate the cuff. The palpation technique is also used for patients whose arterial pulsations are too weak to create Korotkoff sounds. Severe blood loss and decreased heart contractility are examples of conditions that result in blood pressures too low to auscultate accurately. Only the systolic blood pressure can be easily assessed by palpation (Box 28-13). Although the diastolic pressure is difficult to determine by palpation, a subtle change in sensation, usually in the form of a thin, snapping vibration, marks the diastolic level. When the palpation technique is used, the systolic value and the manner in which it was measured are recorded (e.g. RA 90/–, palpated, supine).

BOX 28-13 PALPATING THE SYSTOLIC BLOOD PRESSURE

1. Apply blood-pressure cuff to the upper arm in the same manner as the auscultation method (Skill 28-5).

2. Continually palpate the radial artery.

3. Inflate blood pressure cuff 30 mmHg above the point at which the radial pulse can no longer be palpated.

4. Release valve and allow mercury to fall 2 mmHg/sec.

5. As soon as the radial pulse is palpable, note the manometer reading—this is the systolic blood pressure.

The palpation technique is used with auscultation in some instances. In some hypertensive patients, the sounds usually heard over the brachial artery when the cuff pressure is high disappear as pressure is reduced and then reappear at a lower level.

Auscultation

The best environment for blood pressure measurement by auscultation is a quiet room at a comfortable temperature. Although the patient may lie or stand, sitting is the preferred position. If auscultation is not performed correctly (Table 28-9), blood pressure readings will be incorrect. When unsure of a reading, a colleague should reassess the blood pressure.

TABLE 28-9 COMMON MISTAKES IN BLOOD PRESSURE ASSESSMENT

ERROR	EFFECT
Arm above heart level	False low reading
Arm below heart level	False high reading
Arm not supported	False high reading
Bladder or cuff too narrow	False high reading
Bladder or cuff too wide	False low reading
Cuff wrapped too loosely or unevenly	False high reading
Deflating cuff too quickly	False low systolic and false high diastolic readings
Deflating cuff too slowly	False high diastolic reading
Inaccurate inflation level	Inaccurate interpretation of systolic and diastolic readings
Inflating cuff too slowly	False high diastolic reading
Multiple examiners using different Korotkoff sounds for diastolic readings	False high systolic and low diastolic readings
Repeating assessments too quickly	False low systolic reading
Stethoscope applied too firmly against antecubital fossa	False low diastolic reading
Stethoscope that fits poorly or impairment of the examiner’s hearing, causing sounds to be muffled	False low systolic and false high diastolic readings

ULTRASONIC STETHOSCOPE

If unable to auscultate sounds because of a weakened arterial pulse, an ultrasonic stethoscope can be used (see Chapter 27). This stethoscope allows you to hear low-frequency systolic sounds, and is commonly used when measuring the blood pressure of infants and children and low blood pressure in adults.

Automatic blood pressure devices

Electronic devices are commonly used to determine blood pressure (Figure 28-13). Whereas the auscultatory technique relies on the detection of Korotkoff sounds, some electronic devices rely on the principle of oscillometry. The system includes either a microphone or a pressure sensor built into the inflatable cuff. The microphone or acoustic system hears Korotkoff sounds and registers diastolic and systolic readings. The pressure sensor or ultrasonic system responds to the pressure waves generated by the movement of blood through the artery. The sensor determines the initial burst of oscillations and translates the information into a systolic pressure reading. The diastolic pressure is measured when the oscillations are lowest, just before they stop (Rauen and others, 2008).

FIGURE 28-13 Automatic vital-signs monitor.

Image: Connex^® Vital Signs Monitor, courtesy of Welch Allyn.

Electronic devices work automatically and are applied when frequent blood-pressure assessment is required, such as in the critically ill or potentially unstable patient, during or after invasive procedures or when therapies require frequent monitoring (e.g. intravenous heart and blood pressure medications). However, some patient conditions are not appropriate for automatic blood pressure devices (Box 28-14).

BOX 28-14 PATIENT CONDITIONS NOT APPROPRIATE FOR ELECTRONIC BLOOD PRESSURE MEASUREMENT

• Irregular heart rate

• Peripheral vascular obstruction (e.g. clots, narrowed vessels)

• Shivering (e.g. postoperative shivering)

• Seizures

• Excessive tremors

• Inability to cooperate

• Blood pressure less than 90 mmHg systolic

The advantages of automatic devices are the ease of use and efficiency when repeated or when frequent measurements are indicated. The ability to use a stethoscope is not required. However, automatic devices are more sensitive to outside interference and are very susceptible to error. The microphone or pressure sensor must be positioned directly over the artery for proper function. Patient movements, vibration or outside noise can interfere with the microphone or sensor signal. The nurse should avoid speaking to the patient for at least 1 minute before initiating a blood-pressure recording—talking to a patient when the blood pressure is being assessed can increase readings by 10–40%.

A baseline blood pressure should be obtained using the auscultatory method before applying automatic devices. A comparison helps evaluate a patient’s status and allows proper programming of the device. Once the blood-pressure cuff is applied, the device is programmed to obtain and record blood-pressure readings at preset intervals. Alarm limits can be programmed to alarm if the blood-pressure measurement is outside desired parameters. If readings do not match your understanding of the patient’s situation and other assessment data, it is advised that a manual blood-pressure reading be taken to reduce the potential for error.

Position

The patient’s position during routine blood-pressure determination should be the same during each measurement to permit a meaningful comparison of values. Controlling factors responsible for artificially high readings, such as pain, anxiety or exertion, is an important part of blood-pressure measurement. The patient’s perception of a stressful physical or interpersonal environment will affect blood-pressure measurement. For example, blood-pressure measurements taken at the patient’s place of employment or in a medical practitioner’s office are often higher than those taken in the patient’s home.

Self-measurement of blood pressure

Some people measure their own blood pressure because of improved technology in home monitoring devices and a greater interest in health promotion. Portable home devices include the aneroid sphygmomanometer and electronic digital readout devices that do not require the use of a stethoscope. The electronic devices inflate and deflate cuffs with the push of a button. They may be easier to manipulate, but can easily become inaccurate and require recalibration more than once a year. Because of their sensitivity, improper cuff placement or movement of the arm can cause electronic devices to give incorrect readings.

Self-measurement of blood pressure has several benefits. Elevated blood pressure may be detected in people previously unaware of a problem, and people with high normal blood pressure can learn about the pattern of blood-pressure values. Patients with hypertension can benefit from participating actively in their treatment through self-monitoring, which may help compliance with treatment. The disadvantages of self-measurement include: improper use of the device; a patient may be needlessly alarmed with one elevated reading; and patients with hypertension may become overly conscious of their blood pressure and make inappropriate self-adjustment of medications.

Challenging situations

CHILDREN

Blood pressure in children changes with growth and development. The measurement of blood pressure in infants and children is difficult for several reasons:

• Different arm size requires careful and appropriate cuff-size selection. Do not choose a cuff based on the name of the cuff. An ‘infant’ cuff may be too small for some infants.

• Readings are difficult to obtain in restless or anxious infants and children. Delay at least 15 minutes to allow children to recover from recent activities and apprehension. Preparing the child for the blood-pressure cuff’s unusual sensation can increase cooperation. Most children will understand the analogy of a ‘tight hug on your arm’.

• Placing the stethoscope too firmly on the antecubital fossa can cause errors in auscultation.

• Korotkoff sounds are difficult to hear in children because of low frequency and amplitude. A paediatric stethoscope bell can be helpful.

ASSESSMENT IN THE LOWER EXTREMITIES

Dressings, casts, intravenous catheters, arteriovenous fistulas or shunts and axillary lymph node dissection can make the upper extremities inaccessible. Blood pressure must then be measured in the lower extremities. Comparing upper extremity blood pressure with that in the legs is also necessary for patients with certain peripheral vascular abnormalities.

The popliteal artery, palpable behind the knee in the popliteal space, is the site for auscultation. The cuff must be wide enough and long enough to allow for the larger girth of the thigh. Placing the patient in a prone position is best. If such a position is impossible, the patient should be asked to flex the knee slightly for easier access to the artery. The cuff is positioned 2.5 cm above the popliteal artery with the bladder over the posterior aspect of the mid-thigh (Figure 28-14). The procedure is identical to brachial artery auscultation. Systolic pressure in the legs is usually higher by 10–40 mmHg than in the brachial artery, but the diastolic pressure is the same.

FIGURE 28-14 Lower-extremity blood-pressure cuff positioned above the popliteal artery at mid-thigh with the knee flexed.

From Potter PA, Perry AG 2013 Fundamentals of nursing, ed 8. St Louis, Mosby.

Interpreting blood pressure readings

Two numbers are usually recorded for a blood-pressure measurement:

• the point on the manometer when the first Korotkoff sound is heard for systolic, and

• the point on the manometer when the fifth Korotkoff sound is heard for diastolic.

Some institutions recommend recording the point when the fourth sound is heard as well, especially for patients with hypertension. The numbers are divided by slashed lines (e.g. 120/80 or 120/100/80); the arm used to measure the blood pressure is noted (e.g. right arm (RA) 130/70); and the patient’s position when the pressure is assessed is recorded (e.g. sitting). The importance of obtaining an accurate blood pressure cannot be overemphasised, because many medical decisions and nursing interventions are made on the basis of blood-pressure findings.

The auscultatory gap typically occurs between the first and second Korotkoff sounds. The gap in sound may cover a range of 40 mmHg and thus may cause an underestimation of systolic pressure or an overestimation of diastolic pressure. The nurse must be certain to inflate the cuff high enough to hear the true systolic pressure before the auscultatory gap. Palpation of the radial artery helps to determine how high to inflate the cuff. The nurse inflates the cuff 30 mmHg above the pressure at which the radial pulse was palpated. The range of pressures in which the auscultatory gap occurs is recorded (e.g. BP RA 180/94 with an auscultatory gap from 180 to 160, sitting).

Hypertension

The most common alteration in blood pressure is hypertension. This is a major factor underlying deaths from strokes and is a contributing factor to myocardial infarctions. Hypertension is an often asymptomatic disorder characterised by persistently elevated blood pressure. The diagnosis of hypertension in adults is made when:

• an average of two or more diastolic readings on at least two subsequent visits is 90 mmHg (diastolic hypertension) or higher, or

• an average of multiple systolic blood pressures on two or more subsequent visits is consistently higher than 135 mmHg (systolic hypertension).

Categories of hypertension have been developed and determine medical intervention (see Table 28-7). One elevated blood-pressure measurement does not qualify as a diagnosis of hypertension. However, if the first blood-pressure measurement shows a high systolic or diastolic reading (e.g. 150/90 mmHg), repeated measurements are required.

Hypertension is associated with the thickening and loss of elasticity in the arterial walls. Peripheral vascular resistance increases within thick and inelastic vessels. The heart must continually pump against greater resistance. As a result, blood flow to vital organs such as the heart, brain and kidney decreases. People with a family history of hypertension are at significant risk. Obesity, cigarette smoking, heavy alcohol consumption, high sodium (salt) intake, sedentary lifestyle and continued exposure to stress are also linked to hypertension. The incidence of hypertension is greater in patients with diabetes, older adults and Indigenous Australians. Patients diagnosed with hypertension require education about blood-pressure values, long-term follow-up care and therapy, the usual lack of symptoms (the fact that it may not be ‘felt’), therapy’s ability to control but not cure hypertension and a consistently followed treatment plan that can ensure a relatively normal lifestyle (Heart Foundation of Australia, 2010).

Hypotension

Hypotension is generally considered present when the systolic blood pressure falls to 90 mmHg or below. Although some adults have a low blood pressure normally, for the majority of people low blood pressure is an abnormal finding associated with illness. Hypotension occurs because of the dilation of the arteries in the vascular bed, the loss of a substantial amount of blood volume (e.g. haemorrhage) or the failure of the heart muscle to pump adequately (e.g. myocardial infarction). Hypotension associated with pallor, skin mottling, clamminess, confusion, increased heart rate or decreased urine output is life-threatening and should be reported to a medical practitioner immediately.

Orthostatic hypotension, also referred to as postural hypotension, occurs when a normotensive person (one with normal blood pressure) develops symptoms and low blood pressure when rising to an upright position. When a healthy individual changes from a lying to a sitting to a standing position, the peripheral blood vessels in the legs constrict. Constriction of the lower-extremity vessels when standing prevents the pooling of blood in the legs due to gravity. When patients have a decreased blood volume, their blood vessels are already constricted. When a volume-depleted patient stands, there is a significant drop in blood pressure with an increase in heart rate to compensate for the drop in cardiac output. Patients who are dehydrated or anaemic or who have experienced prolonged bed rest or recent blood loss are at risk of orthostatic hypotension. Some medications can cause orthostatic hypotension, especially in older adults or young patients. Blood pressure should always be measured before administering such medications.

Orthostatic vital sign measurements include obtaining blood pressure and pulse with the patient supine, sitting and standing. When recording orthostatic blood-pressure measurements, record the patient’s position in addition to the blood-pressure measurement (e.g. 140/80 supine, 132/72 sitting, 108/60 standing). The readings are obtained 1–3 minutes after the patient changes position. In most cases, orthostatic hypotension is detected within 1 minute of standing. If orthostatic hypotension is assessed, the patient is helped to a lying position and the medical practitioner or nurse in charge is notified. While obtaining orthostatic measurements, observe for other symptoms of hypotension such as dizziness, weakness or light-headedness. Because the skill of orthostatic measurement requires critical thinking and ongoing nursing judgment, this procedure is not normally delegated to ENs.

Clinical decision making: blood pressure

Blood pressure is usually measured by using a sphygmomanometer and stethoscope. Changes in blood pressure occur in response to changes in the general state of cardiovascular health and/or in response to changes in other systems. Knowledge of the cardiovascular structure and physiology is critical to assessment and interpretation of blood-pressure changes in order to determine appropriate interventions. The assessment of blood pressure along with pulse assessment is used to evaluate the general state of cardiovascular health and responses to other system imbalances. Hypotension, hypertension, orthostatic hypotension, and narrow or wide pulse pressures are defining characteristics of certain problems and are considered along with other assessment data.

• CRITICAL THINKING

Joe has returned to the unit following abdominal surgery. His BP on return to the unit was 160/75 mmHg. You note that over the past 2 hours his BP has been slowly decreasing. The most recent recording shows 120/65 mmHg.

1. What additional assessment will you conduct?

2. Why do you think his blood pressure is dropping?

3. Identify the actual and potential nursing problems for Joe.

4. What nursing interventions will you implement to ensure Joe’s safety?

Guidelines for assessing vital signs

Research focus

Research abstract

Evidence-based practice

Recording vital signs

Body temperature

Physiology and regulation

Neural and vascular control

Heat production

Heat loss

Behavioural control

Factors affecting body temperature

Age

Exercise

Hormone level

Circadian rhythm

Stress

Environment

Fever

Three phases of fever

Patterns of fever

Benefits and costs of fever

Febrile convulsions

Management of febrile children

Hyperthermia

Hypothermia

NEONATES

OLDER PATIENTS

PATIENTS WITH ALCOHOL PROBLEMS

SURGICAL PATIENTS

Sites for measuring body temperature

CORE

SURFACE

TYMPANIC MEMBRANE SENSOR

ORAL

AXILLA

SKIN

DELEGATION CONSIDERATIONS

EQUIPMENT

Thermometers

ELECTRONIC THERMOMETERS

DISPOSABLE THERMOMETERS

Interpretation of results

Nursing interventions

Managing fever

ASSESSMENT

INTERVENTION (UNLESS CONTRAINDICATED)

Managing hypothermia

Clinical decision making: body temperature

ELEVATED BODY TEMPERATURE

ASSESSMENT

PLANNING

EVALUATION

Pulse

Physiology and regulation

DELEGATION CONSIDERATIONS

EQUIPMENT

Interpretation of pulse

Apical rate

Rhythm

Strength

Equality

Clinical decision making: pulse characteristics

Respiration

Physiology and regulation

EXERCISE

ACUTE PAIN

ANXIETY

SMOKING

BODY POSITION

MEDICATIONS

NEUROLOGICAL INJURY

HAEMOGLOBIN FUNCTION

Mechanics of breathing

Assessment of respirations

DELEGATION CONSIDERATIONS

EQUIPMENT

Rate

Ventilatory depth

Ventilatory pattern