Rib cage and chest shape

The cross-sectional shape of the infant thorax is cylindrical and not elliptical as in adolescents or adults. The ribs of the newborn infant are relatively soft and cartilaginous compared with the more rigid chest wall of older children and adults. They are also placed horizontally in relation to the sternum and vertebral column compared with the more oblique rib angle of adults (Fig. 10.1). The bucket handle rib movement seen in older children and adults is therefore not possible. As the infant grows, and begins to develop an upright posture, the ribs develop a more oblique angle and the transverse diameter of the rib cage increases. The adult chest shape is achieved by 3 years of age (Openshaw et al 1984).

Figure 10.1 Normal chest radiograph.

The intercostal muscles are poorly developed in infancy and contraction of the intercostal muscles is inefficient at improving thoracic volumes either by increasing the anteroposterior or transverse diameters of the chest. Increased ventilatory requirements have to be met by increasing the respiratory rate rather than depth (Konno & Mead 1967).

Diaphragm

The angle of insertion of the infant diaphragm is horizontal compared with older children or adults, placing it at a mechanical disadvantage. The infant diaphragm has a lower relative muscle mass and a lower content of high-endurance muscle fibres, and thus is much more vulnerable to fatigue.

Maximal diaphragmatic activity during severe respiratory distress or respiratory obstruction leads to an inward movement of the lower rib cage instead of a downward movement of the diaphragm, as well as intercostal and sternal recession (Muller & Bryan 1979). Despite these disadvantages, the diaphragm is the main muscle of inspiration in the infant, since the intercostals are poorly developed. Ventilation in the infant is also more affected by impaired diaphragmatic function, for example by abdominal distension, hepatomegaly or phrenic nerve damage.

Preferential nasal breathing

The shape and orientation of head and neck in babies (large head, prominent occiput, short neck, large tongue, smaller retracted lower jaw, high larynx) mean that the airway is prone to obstruction in young infants. Young infants up to about 6 months of age are preferential nasal breathers and studies suggest that up to half of all neonates are unable to breathe through their mouths, except when crying, for the first few weeks of life (King & Booker 2004) The small nasal passages account for between 30% and 50% of the total airway resistance in neonates. The narrowest portion of the nasal airway has a cross-sectional area of about 20 mm². Therefore, even a small amount of swelling or obstruction of the nasal passages of infants compromises breathing considerably and causes a disproportionate and detrimental effect on the work of breathing. Some young infants with upper respiratory tract infections and partial obstruction of their nasal passages can develop respiratory distress.

Position of larynx

In the newborn infant, the larynx and hyoid cartilage are higher in the neck and closer to the base of the epiglottis, being at the level of C3 in a premature infant and C4 in a child compared with C5–6 in the adult. The larynx descends with age, but its high position enables the infant to feed and breathe simultaneously for approximately the first 4 months of age.

This high position also provides some protection of the airway in infants younger than 4–6 months because it acts as a valve, which helps keep food in the mouth until the pharyngeal swallow is initiated. The airway has less anatomical protection as the larynx assumes its lower position in the neck and is not as directly protected by the epiglottis. Then, poor closure of the airway or partial paralysis of the vocal folds may become more evident and coughing, choking or aspiration may occur.

Airway diameter

The neonatal trachea is short (4–9 cm) and directed downward and posteriorly. The diameter of the trachea in the newborn is 4–5 mm and the diameter of an infant trachea is only about one-third that of an adult. This makes respiratory resistance higher and the work of breathing greater. Since the resistance to airflow through a tube is directly related to the tube length and inversely related to the fourth power of the radius of the tube, halving the radius of the trachea will increase its resistance (reduce flow) 16 times. Tracheal swelling as a result of endotracheal intubation or suction can therefore dramatically increase resistance to breathing. These factors give the lungs less reserve, so that a well-oxygenated infant with upper airway obstruction can become cyanotic in a matter of seconds.

In contrast to adolescents and adults, the narrowest part of the infant’s airway is not the vocal cords, but the cricoid ring. Thus an uncuffed endotracheal tube provides a larger internal diameter compared with a cuffed tube and in children will successfully seal against in the circular subglottic ring. However, the inflexible cricoid ring also leaves children more vulnerable to mucosal oedema and post-extubation stridor. The right main bronchus is less angled than the left, making right mainstem intubation more likely.

At birth there is no further increase in the number of airways formed but there is growth and development in their size. In the first few years of life there is a significant increase in the diameter of the larger, more proximal airways (Hislop & Reid 1974). The smaller, more distal airways do not increase in diameter until nearer 5 years of age. This higher peripheral airways resistance is exacerbated by respiratory infections, which cause inflammation of the airways, for example in bronchiolitis, or in the presence of secretions.

Bronchial walls

The bronchial walls are supported by cartilage, which begins to develop from 12 weeks’ gestation and continues throughout childhood. The cartilaginous support of an infant’s airways is much less than that of an adult, and predisposes the airways to collapse. The bronchial walls contain proportionally more cartilage, connective tissue and mucous glands than do those of adults, but less smooth muscle; this makes the lung tissue less compliant. The lack of bronchial smooth muscle, particularly in the smaller bronchioles, may be one reason for the lack of response to bronchodilators under the age of 12 months. The β-receptors in infants are also immature, which further reduces any response to β-adrenergic bronchodilator therapy (Reid 1984). The high proportion of mucous glands in the major bronchi of infants makes the airways more susceptible to mucus obstruction.

Cilia

At birth the cilia are poorly developed, which increases the risk of secretion retention, especially in the premature infant. The airway obstruction caused by secretions in a neonate is much greater than in an adult whose airways are relatively large.

Alveoli and surfactant

The respiratory system is not fully developed at birth, even in the term neonate, and postnatal maturation continues for a significant time. Although by 20–27 weeks’ gestation lung acinar have formed, several types of epithelial cells can be differentiated, and the air–blood barrier is thin enough to support gas exchange; true alveoli develop only after about 36 weeks’ gestation. A term newborn has an average of 150 million alveoli. The remainder of the eventual average of 400 million alveoli develop after birth, the vast majority within the first 2 years of life. Both the number and size of alveoli continue to increase postnatally until the chest wall stops growing. By 4 years of age, the adult number of 300 million may exist, although growth can continue until 7 years of age. The smaller alveolar size of an infant makes the infant more susceptible to alveolar collapse, and the smaller number of alveoli reduces the area available for gaseous exchange (Reid 1984).

Pulmonary surfactant is a mixture of phospholipids (90%) and apoproteins (10%), which act to reduce surface tension at the air–liquid interface in the alveolus, thereby preventing collapse of lung parenchyma at the end of expiration. Type II alveolar cells synthesize and secrete surfactant from 23 to 24 weeks’ gestation. In preterm newborns, a deficiency of surfactant is a major factor in the development of neonatal respiratory distress syndrome (RDS). Male gender is a risk factor for neonatal RDS, bronchopulmonary dysplasia (BPD) and mortality. Boys with neonatal RDS seem to have more health problems than girls during the neonatal period.

Collateral ventilation

Collateral ventilation is the means by which a distal lung unit can be ventilated, despite blockage of its main airway. Collateral ventilatory pathways are achieved by a network of interconnecting pathways linking different structures. Respiratory bronchioles are linked by channels of Martin. Canals of Lambert connect respiratory and terminal bronchioles with alveoli and their ducts; and adjacent alveoli are joined by openings in the alveolar wall, called pores of Kohn (Menkes & Traystman 1977). However, none of these pathways exists at birth. The pores of Kohn develop between years 1 and 2, and the canals of Lambert do not appear until about 6 years of age. The collateral ventilatory channels between alveoli, respiratory bronchioles and terminal bronchioles are poorly developed until 2 and 3 years of age, predisposing towards alveolar collapse.

Internal organs and lymphatic tissue

The lymphatic tissue (adenoids and tonsils) may be enlarged in the infant and the tongue is also relatively large. These factors may contribute to upper airway obstruction. The heart and other organs are also relatively large in infants, leaving less space for lung expansion. The heart can occupy up to half the transverse diameter of the chest in chest radiographs.

Height and exposure to air pollution

Because children breathe more rapidly compared with adults and because they spend more time outdoors being physically active, they tend to be more exposed to outdoor air pollution and allergens than do adults and have greater deposition of particulate matter. Their reduced height means they are also more exposed to vehicle exhausts and heavier pollutants that concentrate at lower levels in the air. There is substantial evidence linking air pollution with respiratory health problems and children are more vulnerable (Brauer et al 2007, Pénard-Morand et al 2005).

Respiratory compliance

Respiratory compliance is a measure of the pressure required to increase the volume of air in the lungs and reflects a combination of lung and chest wall compliance. The lung compliance of a child is comparable to that of an adult, being directly proportional to the child’s size. However, compliance is reduced in the infant because of the high proportion of cartilage in the airways. The premature infant, who lacks surfactant, demonstrates a further significant decrease in compliance. The chest wall of an infant is cartilaginous and therefore very soft and compliant in comparison with the more calcified and rigid adult structure. The intercostal muscles are also less well equipped to stabilize the rib cage during diaphragmatic contraction. Neonates therefore have an imbalance between a relatively low outward recoil of their chest wall and normal inward elastic recoil, which means that they are prone to airway collapse. An awake, spontaneously breathing neonate will maintain its functional residual capacity (FRC) by active measures including laryngeal braking, the initiation of inspiration before the end of passive expiration (intrinsic PEEP) and persistent inspiratory muscle activity throughout the respiratory cycle. These active mechanisms are lost during anaesthesia and result in a fall in FRC, airway closure, atelectasis and ventilation/perfusion mismatch.

Closing volume

The closing volume is the lung volume at which closure of the small airways occurs. This volume plus the residual volume (the volume of gas left in the lungs following maximum expiration) is known as the closing capacity (CC). In the adult, CC is less than FRC, i.e. the volume of gas left in the lungs following tidal expiration, whereas in the infant it is greater than FRC. The higher closing volumes apparent in infants are due to greater chest wall compliance and reduced elastic recoil of the lungs than in the adult. Therefore, airway closure may occur before the end of expiration, e.g. during expiratory chest vibrations, putting the infant at a much greater risk of developing widespread atelectasis, especially in the presence of lung disease, where lung volume is further reduced. In the event of respiratory distress, the infant grunts on expiration, adducting the vocal cords in an attempt to reduce the amount of gas expired, thus maintaining a higher FRC and minimizing alveolar collapse (Pang & Mellins 1975). Re-inflation of alveoli, once collapsed, is more difficult in the infant, who has to work considerably harder to overcome the effects of the compliant chest wall.

Ventilation and perfusion

In the adult, both ventilation and perfusion are preferentially distributed to the dependent lung. The best gas exchange and ventilation/perfusion match will therefore be in the dependent region of the lung (Zack et al 1974). In the infant, however, ventilation is preferentially distributed to the uppermost lung (Davies et al 1985), whereas the perfusion remains best in the dependent regions. This leads to greater gas exchange in the uppermost lung (Heaf et al 1983) but an imbalance between ventilation and perfusion (Bhuyan et al 1989). In acutely ill children with unilateral lung disease, oxygenation may be optimized by placing the ‘good’ lung uppermost. However, this is contrary to the goal of improving ventilation to the diseased lung and facilitating secretion clearance, in which positioning and postural drainage would require the diseased lung to be uppermost. The therapist would have to balance their decision based on the stability, tolerance and current therapeutic priorities.

The difference in ventilation distribution between infants and adults is most likely due to the more compliant rib cage of the infant, which compresses the dependent areas of lung. In addition, while in the adult the weight of the abdominal contents provides a preferential load on the dependent diaphragm and therefore improves its contractility, in the infant this does not happen. The effect on both hemidiaphragms is similar, due to the abdomen being so much smaller and narrower (Davies et al 1985). It has been shown in adults that, when the diaphragm is inactivated, e.g. when ventilated under anaesthetic, the ventilation distribution changes to that of an infant (Rehder et al 1972). It is not yet known exactly when the ventilation distribution in the infant changes to that of an adult, but it may be as late as 10 years of age.

Oxygen consumption, cardiac output and response to hypoxia

Infants have a higher resting metabolic rate than adults and consequently have a higher oxygen requirement. Children have a higher cardiac output and oxygen consumption per kilogram than adults; in infants this may exceed 6 ml/kg/min, twice that of adults. They support this higher output with a higher baseline heart rate but lower blood pressure than adults.

Neonatal myocardium has a large supply of mitochondria, nuclei and endoplasmic reticulum to support cell growth and protein synthesis, but these are non-contractile tissues, which render the myocardium stiff and non-compliant. This may impair filling of the left ventricle and limit the ability to increase the cardiac output by increasing stroke volume (Frank Starling mechanism). Stroke volume in infants is therefore relatively fixed and the only way of increasing cardiac output is by increasing heart rate.

The sympathetic nervous system is not well developed predisposing the neonatal heart to bradycardia. An infant responds to hypoxia with bradycardia and pulmonary vasoconstriction, whereas the adult becomes tachycardic with systemic vasodilation. The bradycardic response in infants is probably due to myocardial hypoxia and acidosis, but leads to an immediate reduction in cardiac output and the development of further hypoxia.

Although anatomical closure of the foramen ovale can occur as early as 3 months of age, the channel remains ‘probe patent’ in 50% of children up to 5 years of age, and persists in about 30% of adults. Similarly, anatomical closure of the ductus arteriosus usually occurs between 4 and 8 weeks of age. Any stimulus, such as hypoxia or acidosis, that causes an increase in pulmonary vascular resistance during the neonatal period may allow these two potential channels to reopen, resulting in right-to-left shunting and increasing hypoxia (King & Booker 2004).

Muscle fatigue

The respiratory muscles of infants tire more quickly than those of adults due to a much smaller proportion of fatigue-resistant muscle fibre (Keens & Ianuzzo 1979). There are two main muscle fibre types, type I and type II. Type I muscle fibres are slow twitch, high oxidative and slow to fatigue. Type II fibres are fast twitch, slow oxidative and tire quickly. Of the muscle fibres in the adult diaphragm, 55% are type I compared with only 30% in the infant. Premature infants tire even more easily as, at 24 weeks’ gestation, only 10% of their muscle fibres are fatigue resistant (Muller & Bryan 1979). Excessive muscle fatigue results in apnoea. By 12 months of age the number of type I fibres equals that of an adult.

Breathing pattern and rapid eye movement sleep

Irregular breathing patterns and episodes of apnoea are relatively common in neonates, especially if premature, and are related to immature cardiorespiratory control. Short spells of apnoea can be considered normal in these circumstances, but need careful monitoring as they may reflect hypoxic conditions.

During rapid eye movement (REM) sleep there is a reduction in postural tone and tonic inhibition of the infant’s intercostal muscles such that the rib cage is even less well equipped to counteract the contraction of the diaphragm during inspiration (Muller & Bryan 1979). This reduces the efficiency of respiration, causes a drop in functional residual capacity and increases the work of breathing, predisposing the infant to apnoeic episodes (Muller & Bryan 1979). The premature infant is most at risk, spending up to 20 hours a day asleep, 80% of which may be in active REM sleep compared with 20% in adult sleep.

Response to cold

Paediatric patients have an increased surface area per kilogram and lose heat to the environment more readily than adults. This is compounded by cold intravenous fluids, dry anaesthetic gases and exposure. Non-shivering thermogenesis in brown adipose tissue is the major mechanism of heat production during the first few months of life. Brown fat is specialized tissue located in the posterior of the neck, along the interscapular and vertebral areas, and surrounding the kidneys and adrenal glands. Metabolic heat production can increase up to two and a half times during cold stress. Shivering is a less economical form of heat production but does occur in severely hypothermic neonates. Hypothermia is a serious problem that can result in increased oxygen consumption, cardiac irritability and respiratory depression (King & Booker 2004).

Clinical signs

Clinical signs of respiratory distress are listed in Box 10.1.

Box 10.1 Clinical signs of respiratory distress

Recession

Recession

– intercostal

– subcostal

– sternal

Nasal flaring

Tachypnoea

Expiratory grunting

Stridor

Cyanosis

Abnormal breath sounds

Cardiac

Tachycardia/bradycardia

Hypertension/hypotension

Other/general

Neck extension

Head bobbing

Pallor

Reluctance to feed

Irritability/restlessness

Altered conscious level

Headache

Recession occurs when high negative intrathoracic pressure during inspiration pulls the soft, compliant chest wall inward. It may be sternal, subcostal or intercostal. Mild recession may be normal in preterm infants but in older infants is a sign of increased respiratory effort.

Nasal flaring is a dilatation of the nostrils by the dilatores naris muscles and is a sign of respiratory distress in the infant. It may be a primitive response attempting to decrease airway resistance.

Tachypnoea (respiratory rate greater than 60 breaths/min) may indicate respiratory distress in infants. Normal values are listed in Table 10.1.

Table 10.1 Normal values

Grunting occurs when an infant expires against a partially closed glottis. This is an automatic response which increases functional residual capacity in an attempt to improve ventilation.

Stridor is heard in the presence of a narrowing of the upper trachea and/or larynx. This may be due to collapse of the floppy tracheal wall, inflammation or an inhaled foreign body. It is most commonly heard during inspiration, but in cases of severe narrowing it may be heard during both inspiration and expiration.

Cyanosis refers to the bluish colour of the skin and mucous membranes caused by hypoxaemia. In infants and young children it is an unreliable sign of respiratory distress as it depends on the relative amount and type of haemoglobin in the blood and the adequacy of the peripheral circulation. For the first 3–4 weeks of life, the newborn infant has an increased amount of fetal haemoglobin, which has a higher affinity for oxygen than adult haemoglobin. The result is a shift of the oxygen saturation curve to the left in infants.

Auscultation of the infant and young child is sometimes complicated by the easy transmission of sounds. In the infant who is ventilated, referred sounds such as water in the ventilator tubing may be transmitted to the chest. In the older child, secretions in the nose or throat may lead to referred sounds in both lung fields. Wheezing in the younger child or infant may be due to bronchospasm, but could also be due to retained secretions partially occluding smaller airways. It is sometimes very difficult to hear breath sounds in the spontaneously breathing preterm infant.

Cardiac manifestations of respiratory distress include an initial tachycardia and possible increase in systemic blood pressure. This changes with worsening hypoxia to bradycardia and hypotension.

Neck extension in an infant with respiratory distress may represent an attempt to reduce airway resistance.

Head bobbing occurs when infants attempt to use the sternocleidomastoid and the scalene muscles as accessory muscles of respiration. It is seen because the relatively weak neck extensors of infants are unable to stabilize the head.

Pallor is commonly seen in infants with respiratory distress and may be a sign of hypoxaemia or other problems, including anaemia.

Reluctance to feed is often associated with respiratory distress and infants may need to take frequent pauses from sucking when tachypnoeic.

Alterations in levels of consciousness should be noted. A reduction in activity may be due to neurological deficit or as a result of opiate analgesia but may also be due to hypoxia. It may be accompanied by an inability to feed or cry. Irritability and restlessness may also be indicative of a hypoxic state.

Other relevant observations

The behaviour of a child can often give important clues about their respiratory status. Agitation or irritability may be a sign of hypoxia, while the child in severe respiratory distress may be withdrawn and lie completely still.

It is important to note muscle tone in the infant or child with respiratory distress. A hypotonic child may have increased difficulty with breathing, coughing and expectorating, while hypertonia may also be associated with difficulty in clearing secretions.

Abdominal distension can cause or exacerbate respiratory distress, because the diaphragm is placed at a mechanical disadvantage. In infants this is of greater concern as the diaghragm is the primary muscle of respiration.

Precautions for chest percussion and vibratory techniques

In children with dietary deficiencies, liver disease, bone mineral deficiency (e.g. rickets) or coagulopathies, manual techniques should be applied with caution. Manual techniques may not be appropriate in extremely premature infants and specific issues related to this group of patients are discussed later.

Chest percussion has been reported to cause an increase in bronchospasm in adults with chronic lung disease (Campbell et al 1975, Wollmer et al 1985). Premedication with bronchodilator therapy may reduce this effect but in severe cases percussion should be avoided.

Airway clearance for children with neurological and neuromuscular impairment

Impaired cough, as a consequence of weakness from neuromuscular disease such as Duchenne muscular dystrophy and spinal muscular atrophy or neurological impairment, can cause serious respiratory complications including atelectasis, pneumonia, airway obstruction and acidosis (Miske et al 2004). Chronic respiratory insufficiency and respiratory failure will ultimately result from chronic weakness of respiratory muscles, shallow breathing and ineffective cough. For these children, independently performed airway clearance techniques are not usually feasible, but options such as the ‘cough assist’ (mechanical insufflation/exsufflation device) and other non-invasive forms of positive pressure ventilation are safe and well tolerated in this client group, with growing evidence to support their efficacy (Chatwin et al 2003, Panitch 2006, Vianello et al 2005). They are discussed more comprehensively in Chapters 5 &11. Not all patients with neuromuscular disease are good candidates for the use of non-invasive respiratory aids. Potential contraindications include an inability to manage oropharyngeal secretions, mental status changes or cognitive impairment, and cardiovascular instability. For some patients, including those with the most severe spinal muscular atrophy, sole reliance on non-invasive methods of assisted cough and ventilation is inadequate, and they may require repeated episodes of intubation and mechanical ventilation in the intensive care unit to prolong survival (Birnkrant 2002).

Saline instillation

Saline instillation into the tracheal tube of ventilated patients aims to loosen thick or sticky secretions to facilitate easy removal with suction (Schreuder & Jones 2004). Evidence for the practice is variable and therefore saline should be used only where there is a clear indication. Some suggest that saline instillation at best is not effective and at worst is harmful (Blackwood 1999, Hagler & Traver 1994, Kinloch 1999, McKelvie 1998, Ridling et al 2003), while others suggest it is well tolerated even in infants and may be helpful in removing secretions adherent to the chest wall (Shorten et al 1991). Other mucolytics (N-acetylcysteine) in aliquots of 0.5–5 ml may be used to enhance secretion clearance. Larger quantities of irrigants are sometimes used as part of bronchoalveolar lavage procedures.

Aetiology

Children are more likely to develop asthma if parents or close relatives are asthmatic or atopic. There is an important link between atopy and bronchial hyperreactivity, and children with asthma often have other atopic features such as eczema, food allergy, hay fever or urticaria. Exposure to specific allergens such as house dust mite, pollen and animal dander can precipitate bronchospasm and wheeze. Exercise, particularly running, can precipitate an acute attack (exercise-induced asthma, EIA), as can emotional upset or upper respiratory tract infections.

Management

The mainstay of asthma treatment is drug therapy. There are agreed guidelines on the management of asthma (British Thoracic Society & Scottish Intercollegiate Guidelines Network (SIGN) 2003, National Asthma Education and Prevention Programme (NAEPP) 2002). The aims of therapy are to obtain optimal asthma control with few or no symptoms, undisturbed sleep, normal lung function with no limitation to daily activity and no severe, acute exacerbations. Poor asthma control has been attributed to suboptimal adherence to treatment guidelines both by physicians and families (Rabe et al 2004).

Short-acting inhaled β₂-agonists may be all that is required in children who have mild intermittent asthma, but inhaled corticosteroids are the mainstay of asthma therapy in those with persistent symptoms and are given in addition to short-acting β₂-agonists. Administration of corticosteroids by the inhaled route is safer and results in fewer systemic effects. It is important when using inhaled corticosteroids in children that growth is carefully monitored. In more severe asthma, long-acting β₂-agonists should be added to the treatment regimen. Leukotriene receptor antagonists may also be useful in a proportion of cases. Higher doses of inhaled corticosteroids may be needed. The use of continuous (preferably alternate day) oral steroids for prophylaxis is rarely needed nowadays. More severely affected children may require them intermittently on a continuous daily basis, for short periods, during acute exacerbations.

Inhalation of asthma medications provides effective topical therapy, which usually requires smaller doses and has fewer systemic effects. However, the method of drug delivery is very important and has been extensively reviewed (O′Callaghan 2000).

The choice of device depends both on the drug to be delivered and the patient, particularly in relation to age. In children the preferred method for delivery of both inhaled corticosteroids and β₂-agonists is by metered dose inhaler (MDI) along with a spacer device. Metered dose inhalers can be manually or breath-actuated and contain a mixture of propellant and drug which is emitted at a high velocity. Breath-actuated devices require an adequate inspiratory flow to trigger the device and the manual devices require coordination of the actuation of the device with inspiration. This makes them inherently difficult to use in children and therefore a valved spacer device should be incorporated into the system. The spacer allows the infant or child to inhale from a reservoir of drug within a chamber.

In babies, a facemask is required and should be held gently over the nose and mouth with the device held upright, at an angle greater than 45°, to ensure the valve is open. The drug can then pass effectively through the open valve to be inhaled (Fig. 10.7A & B). Once the child is older (usually from the age of 2 or 3), the spacer device can be used conventionally with a mouthpiece (Fig. 10.7C). The click of the valve opening will be heard with each breath. It should be noted that different spacer devices have been shown to deliver varying drug doses (Barry & O′Callaghan 1996).

Figure 10.7 Administration of bronchodilator by spacer device to (A) an infant; (B) a teddy bear, to familiarize a young child with the device; (C) a young child.

Nebulized drug delivery systems for asthma are now rarely used in the home setting. They may be used in circumstances where medication cannot be delivered effectively using an MDI and spacer and in severe cases or during an acute exacerbation. It is preferable to use a mouthpiece (if the child is able) so as to avoid drug deposition on the face.

Children with a severe asthma attack usually display signs of acute respiratory distress; they may not be able to complete a sentence in one breath or may not be able to talk, and infants show difficulty in feeding due to breathlessness. The respiratory rate is usually high (>30/minute age 5 years and above, >50/minute - age 2–5 years) and the child is tachycardic. Obvious wheezing may not necessarily be present. In life-threatening attacks, when airway obstruction in the presence of hyperinflation is severe, the airflow may be so low that wheezing is not heard, the respiratory rate is lower than expected and the chest is ‘silent’. The child may be cyanotic and is often exhausted. Children with either severe or life-threatening asthma require immediate admission to hospital. It is important to note that if nebulized bronchodilator therapy is given during an acute attack it should be oxygen driven to avoid hypoxaemia (Inwald et al 2001).

Exercise-induced asthma

Exercise-induced asthma (EIA) is a common symptom associated with childhood asthma. However there is considerable controversy around the subject of EIA. Seear et al (2005) in a study of 52 asthmatic children concluded that the clinical diagnosis of EIA was often inaccurate mainly due to the unreliability of children’s initial reporting of symptoms.

Physiotherapy

A crucial part of the management of asthma is education of the child and parents about the condition and its treatment. Often much of this is undertaken by the primary care team. The role of specialist nurses has also increased greatly in this field, although physiotherapists are sometimes still involved in teaching children how to take their medication.

Physiotherapists should also be able to advise on exercise, which is important in the asthmatic child to maintain general fitness. Improvements in aerobic capacity following exercise programmes have been documented in asthmatic patients (Bingol Karakoc et al 2000, Matsumoto et al 1999, Neder et al 1999), but there is no clear evidence to suggest that exercise training can influence the dose of medication required or improve asthma control in some other way (Carrol & Sly 1999). A systematic review of physical training in asthma concluded that physical training improved cardiopulmonary fitness, although it had no effect on lung function. No adverse effects of exercise were found and the authors stated that there are no reasons why those with asthma should not participate in regular physical activity (Ram et al 2005). A ‘warm-up’ should be recommended before starting vigorous activity (such as football, hockey, running), particularly in children with EIA. The use of a pre-exercise inhaled β-agonist may also be helpful.

A systematic review of the use of breathing exercises was also not conclusive as to the efficacy of this form of intervention in asthma, primarily because the studies included used a wide variety of treatment interventions and outcome measures (Holloway & Ram 2004).

The child with acute asthma may need to be admitted to hospital and in severe cases may require mechanical ventilation (Chapter 9). Often the situation will resolve with careful medical management and appropriate respiratory support. Physiotherapy intervention is not always necessary. However, if problems arise, due to mucus plugging or retained secretions, chest physiotherapy may be of benefit. It is essential that bronchospasm is adequately controlled before physiotherapy techniques are started. Treatment should proceed cautiously and if bronchospasm increases, treatment should be discontinued until bronchospasm can be controlled. Although there is no routine indication for chest physiotherapy in asthma (Hondras et al 2000), children with persistent areas of lung collapse following an acute attack may respond well to an appropriate airway clearance technique. Parents may need to continue physiotherapy at home if bronchial hypersecretion persists.

Clinical features

The initial presenting symptoms are coryzal, such as the common cold. The infant develops a dry irritating cough and has difficulty in feeding. As the disease progresses, the infant becomes tachypnoeic and wheezy with signs of respiratory distress. The chest radiograph shows hyperinflation and patchy areas of collapse or pneumonic consolidation. Widespread inspiratory cre-pitations and expiratory wheezes can be heard on auscultation.

Management

Management of this condition is mainly supportive. The infant is given humidified oxygen via a head box as required. In those with severe respiratory distress, blood gas monitoring and even ventilatory support may be necessary. Intensive care management of the infant with acute bronchiolitis is discussed in Chapter 9.

Most infants have difficulty with feeding due to respiratory distress. Milder cases may tolerate small, frequent nasogastric feeds, although the nasogastric tube causes obstruction of one nostril and may itself significantly increase the work of breathing. For this reason some centres prefer to use orogastric tubes. Small-volume feeds lessen the risk of vomiting and aspiration. More severely affected infants may require intravenous nutrition.

Antibiotics are not required as the cause of the illness is viral, although they are often used if there is suspicion of secondary bacterial infection. The risk of this is increased if the infant is ventilated and many centres would use intravenous antibiotics for those requiring mechanical ventilation. Bronchodilators or inhaled corticosteroids have not been proven to be of any value in the treatment of acute bronchiolitis (Scottish Intercollegiate Guidelines Network 2006).

Ribavirin is an antiviral agent, which may be effective in reducing severity and duration of the disease. It is delivered as an aerosol by a small particle aerosol generator for long periods (> 3–5 days). The drug is expensive and its efficacy has not been proven and it is therefore not currently recommended for use in acute bronchiolitis in infants (Scottish Intercollegiate Guidelines Network 2006).

Physiotherapy

Physiotherapy is not indicated in the acute stage of bronchiolitis when the infant has signs of respiratory distress. Studies that have examined the efficacy of physiotherapy intervention compared to no treatment in these patients have not shown any benefit in terms of the course of the disease (Nicholas et al 1999, Webb et al 1985). A systematic review based on the results of three randomized controlled trials concluded that chest physiotherapy using vibration and percussion techniques does not reduce length of hospital stay, oxygen requirements, or improve the clinical severity score in infants with acute bronchiolitis who are not under mechanical ventilation and who do not have any other comorbidity (Perrotta et al 2005). The ventilated infant with bronchiolitis needs careful assessment, and physiotherapy techniques should be applied only when sputum retention or mucus plugging is a problem.

Clinical features

The disease starts with coryza lasting 7–10 days during which the child is most infectious. The cough then becomes paroxysmal and can be provoked by crying, feeding or any other disturbance. It is particularly bad at night. The spasms of coughing may cause hypoxia and apnoea, especially in infants, and may lead to further problems such as convulsions, intracranial bleeding and encephalopathy.

At the end of the coughing spasm, the inspiratory whoop may occur followed by vomiting, when thick, tenacious sputum can be expectorated. This phase of paroxysmal coughing may last for 6–8 weeks and is exhausting for the child and parents. The Chinese call pertussis the ‘100-day cough’.

Bronchopneumonia is the most common complication, particularly in infants, and is due to the primary disease itself or to secondary bacterial infection with other organisms such as Staphylococcus, Haemophilus or Pneumococcus. The chest radiograph in severe cases shows hyperinflation and patchy areas of collapse and consolidation.

Management

Most children with pertussis will be managed at home. Infants and children with pneumonia may need admission to hospital. Treatment is supportive. Minimal handling in a quiet environment is essential for the infant with pertussis in order to reduce disturbance, which may precipitate coughing spasms. Nutritional and fluid support should be given throughout the stage of paroxysmal coughing. Antibiotics do not affect the course of the disease, but erythromycin may reduce infectivity and it can also be given prophylactically to close contacts. A small number of cases, particularly infants who have had frequent apnoeic attacks or hypoxic convulsions, will need intensive care and mechanical ventilation.

Physiotherapy

Any physiotherapy manoeuvre, during the acute phase, can precipitate the paroxysmal cough with its complications. Treatment is therefore contraindicated in children during this stage.

If the child or infant requires ventilation, physiotherapy is very important to remove the extremely tenacious secretions, which easily block large and small airways and endotracheal tubes. The paroxysmal cough is not a problem when the child is paralysed in order to be ventilated.

When the stage of paroxysmal coughing is over, there may occasionally be persistent lobar collapse. This lung pathology often responds to an appropriate airway clearance technique. Parents can be taught how to treat the child at home.

Clinical features

Presenting signs are pyrexia, dry cough, tachypnoea and not infrequently recession of the ribs and sternum. The chest radiograph shows areas of consolidation. Chest signs are often minimal compared with the degree of illness. Children with underlying pulmonary disease are particularly at risk from pneumonia.

Management

Treatment is supportive with adequate fluid intake and humidified oxygen, if required. In younger children it is impossible to distinguish between viral and bacterial pneumonia and broad-spectrum antibiotics are usually given.

Physiotherapy

In many cases of pneumonia there is consolidation of lung tissue with no excess secretions and there is no evidence that physiotherapy is of benefit (Stiller 2000). Where sputum retention is a problem, an appropriate airway clearance technique may be used. Copious amounts of sputum may be cleared in one treatment, following which the pyrexia may settle and the child will feel better. Reassessment of the child is often necessary, as retention of secretions may become a recurrent problem as the pneumonia resolves.

Physiotherapy

Although these children do not always have a primary problem with bronchial secretions, immobility and the presence of a chest drain can result in retained secretions and a weak cough. Airway clearance may be necessary, using an appropriate technique. Breathing exercises and advice on coughing are also important parts of treatment. As soon as the clinical condition allows, the child should be encouraged to mobilize as much as possible.

Clinical features

The presenting symptoms are coryzal and later include fever, a harsh barking cough and a hoarse voice. Stridor, initially inspiratory only, is much worse at night and may become inspiratory and expiratory. Signs of respiratory obstruction are seen and the severely affected child may develop respiratory failure. The acute stage of respiratory obstruction may only last 1–2 days but the stridor and cough may continue for 7–10 days. Some children have recurrent bouts of croup.

Management

Mild cases can be managed at home. Extra humidity is often given, for example by sitting with the child in a warm steamy bathroom, although there is no objective evidence of benefit from inhaled moist air in emergency settings (Moore & Little 2006). More severely affected infants will be admitted to hospital and given humidified oxygen if hypoxic or distressed. Treatment is supportive, but with minimal handling as any disturbance that upsets the child will increase the laryngeal obstruction.

Glucocorticoids (dexamethasone and budesonide) have rapid beneficial effects on symptoms (Russell et al 2004). Nebulized adrenaline may be given with careful observation, in case of rebound and an acute collapse, and has been shown to provide short-term relief, but is probably not useful in the long term. Antibiotics are not usually required unless there is more specific evidence of a bacterial cause, for example purulent secretions.

Very few children with croup who are admitted to hospital go on to require intubation to maintain the airway due to severe respiratory obstruction. A few of these, particularly infants, may also require some additional form of respiratory support, e.g. intermittent positive pressure ventilation or continuous positive airway pressure.

Physiotherapy

Physiotherapy is contraindicated in the non-intubated child with croup. Treatment may be required when the child is intubated, if secretions cannot be cleared by suction alone.

Clinical features

The onset is sudden, with a severe sore throat and high temperature. Stridor and dysphagia develop rapidly, the child is unable to swallow saliva and drools. The neck is held extended in an attempt to open the airway. Acute and possibly fatal obstruction of the airway can develop.

Management

The child with suspected epiglottitis should not be disturbed in any way. No attempt should be made to examine the throat, as this may precipitate acute life-threatening obstruction. Usual management is intubation with a nasotracheal tube. In extreme circumstances tracheostomy may be necessary, but should only be required for 3–4 days, following which there is usually complete recovery.

Physiotherapy

Physiotherapy techniques may be required in the intubated child, if secretions cannot be removed by suction alone.

Physiotherapy

Infants with CLD are particularly prone to chest infections and have an increased rate of hospital admission in the first 2 years of life. Physiotherapy may be indicated if secretion retention is a problem. However these infants often wheeze and may have airway collapse. Detailed assessment is important before any intervention. If wheezing is not too severe, careful treatment may be possible. Inhaled β₂-agonists may temporarily improve lung function in these babies (Ng et al 2001) and may be useful as a premedication before physiotherapy. Modified gravity-assisted positions with chest percussion may be useful in infants, but nasopharyngeal suction may be required if retained secretions are a cause for concern. In older children an appropriate airway clearance technique should be used, either during episodes of infection or if retained secretions are a persistent problem. Children, particularly infants in whom supplemental oxygen is delivered via nasal cannulae, often have a problem with thick, dry nasal secretions and may need humidification (Chapter 5).

Management

All children who have aspirated a foreign body into the airway should have an urgent rigid bronchoscopy for removal of the foreign body. If symptoms persist, a repeat bronchoscopy may be necessary to ensure complete removal. Rarely bronchoscopic removal may fail and thoracotomy may be required.

Physiotherapy

Physiotherapy is not indicated to attempt to remove the object before bronchoscopy. Usually physiotherapy is ineffective as the object is firmly wedged in the bronchus. However, if the object is dislodged by physiotherapy manoeuvres, it may travel up the bronchial tree and obstruct the trachea, leading to respiratory arrest.

Following bronchoscopy, gravity-assisted positioning and chest clapping may be necessary to clear excess secretions, particularly if the object has been aspirated for some time and secondary bacterial infection has occurred.

Physiotherapy

Improvements in survival in CF have been attributed to regular monitoring, attention to nutrition and early, aggressive multidisciplinary treatment of CF lung disease. Most babies and young children attending cystic fibrosis centres now have good nutritional status, with body mass index (BMI) within normal limits, and do not display any recognizable signs of respiratory disease. Traditionally, airway clearance (usually in the form of postural drainage (PD) and percussion) was instigated on diagnosis. This approach is still taken by many physiotherapists, although many centres no longer use the head-down tipped position in these babies, as a consequence of a small study which suggested that a head-down tip may exacerbate gastro-oesophageal reflux and may have both short- and long-term consequences to the child’s respiratory status (Button et al 2003, 2004). In addition, these babies often have very little in the way of secretions and justifi-cation for postural drainage with a head-down tip is questionable.

Although there is considerable evidence that inflammation and infection are present from an early stage in CF and that changes in lung function and structure occur long before the onset of obvious clinical signs, the early pathophysiological picture is not associated with copious secretions or other symptoms which respond to airway clearance therapy. This has led many to question the appropriateness of a routine daily airway clearance regimen in these babies and it remains unclear whether airway clearance treatments are effective in asymptomatic babies with CF or whether a routine regimen of chest physiotherapy should be instigated regardless of clinical status (Prasad & Main 2006). An alternative approach is that these babies are very carefully monitored and active treatment applied only when symptoms warrant it. Parents and carers should always be taught an appropriate airway clearance technique soon after diagnosis and this should be practised and expertise maintained. They should also be taught how to check the child’s chest and when to instigate treatment (Chapter 18). The importance of physical activity should be emphasized from the time of diagnosis. Even if the child is not receiving a daily regimen of airway clearance, parents should be encouraged to engage in some sort of physical activity on a daily basis, even in infancy. In addition to modified postural drainage and percussion (Fig. 10.8), the use of other airway clearance techniques such as positive expiratory pressure, assisted autogenic drainage and the use of physical activity (e.g. bouncing on a gym ball) are becoming more widely used in these babies (Chapter 5).

Figure 10.8 Modified postural drainage in an infant, using a facemask for percussion (A) in supine and (B) in sitting for the upper lobes.

As children grow older, they can begin to play a more active role in their treatment. Many different airway clearance modalities are now available and the treatment regimen should be individualized depending on clinical status, age and social circumstances. The overall physiotherapy treatment and the various airway clearance techniques are discussed in detail in Chapters 5 and 18.

Infection

The preterm infant is particularly vulnerable to infection. Early-onset sepsis can occur during the first days of life. Infection can occur at any time during a NICU stay and may occur as a complication of invasive therapies in immature immune systems. The most important means of preventing and reducing cross-infection is by meticulous attention to hygiene by both staff and visitors.

Physiological jaundice

Physiological jaundice is common in the normal full-term infant owing to the breakdown of fetal haemoglobin causing a raised level of unconjugated bilirubin in the blood. It usually begins 2 days after birth and disappears after 1 week to 10 days. High levels of unconjugated bilirubin may diffuse into the basal ganglia and lead to a condition called kernicterus, characterized by athetoid cerebral palsy, deafness and mental retardation. Preterm infants are particularly prone to developing jaundice and run an increased risk of subsequent kernicterus, though this condition is now extremely rare. Serum bilirubin levels are closely monitored and phototherapy may be required. Phototherapy units consist of white or blue lamps, which emit light of wavelength 400–500 nm. Light of these wavelengths oxidizes unconjugated bilirubin into harmless derivatives. Infants receiving phototherapy have to be nursed naked, which can cause problems of temperature control. There is also increased insensible fluid loss and a theoretical risk of eye damage, so eye shields are placed on the infant. Advances in technology have led to a new phototherapy system that enables effective treatment to be given without the inconveniences of conventional phototherapy. The BiliBlanket® system uses fibre optics to provide therapeutic light for the treatment of physiological jaundice, filtering out the more harmful ultraviolet and infrared light. The fibre optics are covered with a pad of woven fibres and the pad is placed directly against the baby. In severe cases of jaundice an exchange transfusion (where small amounts of blood are replaced by donor blood until twice the infant’s blood volume has been exchanged) may be required.

Nutrition

Adequate calorie intake and weight gain are important in preterm and low birthweight infants to avoid hypoglycaemia, persistent jaundice and delayed recovery from respiratory distress syndrome. Feeding should be started as soon as possible, either enterally in those who can tolerate it, or intravenously. Preterm infants have poor sucking, gag and cough reflexes so will be fed nasogastrically until these develop. Continuous infusion of milk may be preferable to bolus feeds, which can increase respiratory distress, regurgitation and aspiration because of abdominal distension. Feeds are often better tolerated when the infant is lying in the prone position. Orogastric tubes may be used rather than nasogastric ones in order to avoid blockage of the nostril in spontaneously breathing infants with respiratory distress.

Temperature control

Preterm and low birthweight infants have difficulty in maintaining their body temperature because they have a large surface area relative to their body mass and easily lose heat through the skin by evaporation and radiation. They also have a smaller proportion of brown fat in comparison with full-term infants. Hypothermia may cause acidosis, hypoglycaemia, increased oxygen consumption and decreased surfactant production. Infants should therefore be kept in a thermoneutral environment (incubators or under radiant warmers) to maintain body temperature. Heat shields may be used to reduce radiant heat loss and the ambient room temperature is kept high at 27–28°C. A core temperature of less than 36.5°C in preterm infants indicates that non-essential handling should be delayed until the infant’s temperature has risen. Infants, especially preterm babies, may have difficulty maintaining their temperature and are therefore nursed in incubators or under radiant warmers.

Pulmonary haemorrhage

Pulmonary haemorrhage is defined as acute intrapulmonary bleeding. It is relatively uncommon but may be a life-threatening event. Physiotherapy is contraindicated, although regular suctioning may be required to keep the airway clear. When fresh blood is no longer being aspirated, physiotherapy techniques may assist removal of residual blood. Prognosis is often poor.

Patent ductus arteriosus

Patent ductus arteriosus (PDA) occurs in up to a third of all preterm infants of less than 1500 g at birth (Zahka & Patel 2002). In the full-term infant the duct, which is a fetal circulatory vessel, closes within the first 24 hours of life. A persistent patent duct in the preterm infant may lead to increased pulmonary blood flow. If symptomatic, a PDA can be treated medically (using indomethacin) or surgically (with ligation), depending on the infant’s clinical status.

Periventricular haemorrhage and periventricular leucomalacia

The incidence of intraventricular bleeding in preterm infants is inversely proportional to birth weight, occurring most frequently and severely in the smallest and least mature infant. Haemorrhage in the capillaries in the floor of the lateral ventricles is common in very low birthweight infants. The bleeding may extend into the ventricles and subarachnoid space. Several factors contribute to the risk of bleeding. These include hypoxia, fluctuation in blood pressure and cerebral blood flow and venous congestion. Cerebral ultrasound scanning is used to diagnose periventricular bleeds and is often the only way that small bleeds are detected. Periventricular haemorrhage is graded according to the extent of the bleeding seen on the ultrasound scan:

Grade I	bleeding into the floor of the ventricle
Grade II	bleeding into the ventricle (intraventricular haemorrhage (IVH))
Grade III–IVH	with dilatation of the ventricle
Grade IV–IVH	and bleeding into the cerebral cortex causing areas of ischaemia.

The smaller bleeds (grades I and II) have a good prognosis. They usually require no treatment and have no long-term sequaelae. Neurological development following a grade I or II bleed seems to be similar to that of an infant with a comparable gestation. Larger bleeds may need treatment with shunting and the outcome is dependent on the grade of the bleed. More severe bleeds are associated with ischaemic brain damage and therefore have a high mortality and morbidity.

Periventricular leucomalacia (PVL) may occur on its own or associated with PVH. Ischaemia of cerebral tissue adjacent to the ventricles causes formation of cystic lesions. There is an association with neurological problems, particularly diplegia.

Respiratory distress

Respiratory distress syndrome (RDS) is a common complication of preterm infants, primarily caused by structural and biochemical immaturity of the lung, in particular a lack of surfactant. The incidence of RDS increases with decreasing gestational age. Symptoms can develop within 4 hours of delivery with sternal and costal recession, nasal flaring, grunting and tachypnoea. Steroids are usually administered to women in preterm labour in an attempt to enhance lung maturation (Roberts & Dalziel 2006).

Pulmonary surfactant production usually begins 36–48 hours after birth, regardless of gestational age. The more mature infant will start to recover at this time. Very preterm infants who have other problems compounding their respiratory distress or infants who have developed complications of treatment may require ventilatory support for much longer. Surfactant therapy has significantly altered the treatment of RDS. Both prophylactic and early surfactant replacement therapy have been shown to reduce mortality and pulmonary complications in ventilated infants with RDS. A systematic review has reported advantages of early surfactant replacement therapy with extubation to nasal continuous positive airway pressure (CPAP) (Stevens et al 2004).

As lung collapse in RDS is primarily caused by lack of surfactant, physiotherapy is not required for this condition. Secretions may become a problem after the infant has been intubated for more than 48 hours, owing to irritation of the tracheal mucosa by the endotracheal tube. These secretions may be cleared easily by suction alone. Physiotherapy may be indicated if suction is not adequately clearing secretions.

Respiratory distress in the preterm infant can also be caused by pneumonia. Organisms causing pneumonia may be bacterial, viral or fungal and may be acquired before, during or after birth. The most serious bacterial cause is group B streptococcus. The presenting features of this pneumonia are similar to RDS with an indistinguishable chest radiograph. Group B streptococcal pneumonia can be rapidly fatal unless antibiotic therapy is started early. For this reason all infants presenting with respiratory distress are given antibiotics.

Parent-infant bonding

Infants who have been resuscitated and require immediate admission to a NICU shortly after birth will not have had the chance for physical contact with their parents. Incubators and other equipment may be a further barrier to contact. Parents will need to be supported by the NICU team through this difficult period and should be encouraged to have as close contact as possible with their baby and help with routine care.

Neonatal mechanical ventilation

Prophylactic ventilation is often started from birth in infants <1000 g, although wherever possible CPAP delivered via nasal prongs would be the intervention of choice. Other indications for ventilation are: deteriorating blood gases (hypoxaemia or hypercapnia) despite a high F_iO₂, recurrent or major apnoea, major surgery pre- or postoperatively for congenital anomalies.

The goals of mechanical ventilation in the NICU are to achieve and maintain adequate gas exchange, to reduce the work of breathing and to minimize the risk of secondary lung injury. Achieving synchrony between the baby’s breathing pattern and the ventilator is important, as asynchrony is associated with alterations in arterial and cerebral blood flow and an increased incidence of pneumothorax. Attempts to achieve synchrony include fast ventilatory rates and paralysing agents to suppress the infant’s respiratory drive. Time-cycled, pressure-limited devices have largely been replaced by newer ventilators which offer pressure control or volume limitation and patient triggering (Donn & Sinha 2003). Volume-limited ventilation enables the measurement of very small tidal volumes and the provision of very low flows.

The use of high-frequency ventilation has also increased over the past decade. Whether high-frequency oscillation (Chapter 9) can reduce the incidence of bronchopulmonary dysplasia remains unclear, but it is regarded as a useful rescue technique.

Complications of mechanical support in neonates

Pneumothorax may be caused by many factors including high peak inspiratory pressures, high positive end-expiratory pressure and long inflation times or ventilator asynchrony. Predisposing factors include hyperinflation of alveoli occurring in conditions such as meconium aspiration and respiratory distress syndrome (RDS). A tension pneumothorax is likely to cause a sudden deterioration and usually requires immediate insertion of an intercostal drain. Very small pneumothoraces may not require drainage.

Pulmonary interstitial emphysema used to be common in preterm infants, with the incidence being inversely proportional to gestational age. It has been seen less frequently since the introduction of treatment of preterm infants with exogenous surfactant, which improves lung compliance. Pulmonary interstitial emphysema is still seen occasionally in infants who require long-term ventilation and who have uneven aeration and gas trapping.

Retinopathy of prematurity is a condition of preterm infants seen when the capillaries in the retina proliferate, leading to haemorrhage, fibrosis and scarring. In the most severe form, this may result in permanent visual impairment. The cause is unknown, but periods of hyperoxia (exact length of time unknown) with a P_aO₂ of above 12 kPa are thought to be a major predisposing factor (Roberton 1996). Careful oxygen monitoring is essential to attempt to prevent this condition.

Prolonged ventilatory support and oxygen dependency may result in bronchopulmonary dysplasia (BPD), discussed earlier in this chapter.

Meconium aspiration

Meconium aspiration usually occurs in full-term infants who become hypoxic due to a prolonged and difficult labour. Hypoxia causes the infant to pass meconium into the amniotic fluid and to make gasping movements, thereby drawing meconium into the pharynx. The irritant properties of meconium can cause a chemical pneumonitis and meconium aspiration can also lead to significant gas trapping and thoracic air leak. In severe cases it can result in secondary persistent pulmonary hypertension of the newborn (PPHN). A severely affected infant is likely to require mechanical venti-lation and may require extracorporeal membrane oxygenation.

Physiotherapy is very important when meconium aspiration has occurred in order to remove the extremely thick and tenacious green secretions. In milder cases treatment consists of gravity-assisted positioning, as tolerated, with chest percussion. Treatment is usually well tolerated soon after aspiration. In more severe cases where pneumonitis develops, these babies are often very sick, require significant respiratory support, do not tolerate handling and should only be treated with caution.

Congenital diaphragmatic hernia

Diaphragmatic herniation occurs when abnormal fetal development of the diaphragm weakens the muscular barrier. The abdominal contents (usually stomach or small bowel) are displaced into the thoracic cavity, posteriorly and most commonly on the left side. The incidence is approximately 1 in 3000 births with mortality rates up to 50% (Schultz et al 2007). The abnormality may be diagnosed antenatally by ultrasound or postnatally in significant defects when the infant presents with neonatal respiratory distress. A chest radiograph will show abdominal viscera in the thoracic cavity. Unless the herniation has occurred late in pregnancy, which is very unusual, there will be associated pulmonary hypoplasia on the affected side as the abdominal viscera occupy the space normally available for the growing lung. Pulmonary hypoplasia is the main determinant of survival. The contralateral lung is also smaller than expected because of compression due to mediastinal shift during fetal development. There are also commonly other associated anomalies such as persistent fetal circulation and abnormalities of the pulmonary vasculature.

The infant with diaphragmatic hernia is often very unwell, particularly as the bowel in the chest distends with air and further compresses the lungs, and requires immediate gastric decompression with simultaneous intubation and ventilation. Surgery is not usually carried out until the infant’s condition is stabilized and extracorporeal membrane oxygenation may be required to support the infant until surgery is possible. A systematic review has reported a reduction in early mortality with extracorporeal membrane oxygenation but no overall long-term benefit (Morini et al 2006). Surgical correction is via a laparotomy. The abdominal viscera are carefully returned to the abdominal cavity and the defect in the diaphragm is closed. High-frequency oscillation has been reported as a beneficial elective ventilation strategy but as yet there have been no large randomized controlled trials (Smith et al 2005).

Postoperatively, the infant may require ventilation for some time, depending on the amount of pulmonary hypoplasia. Prognosis is variable and mortality for isolated hernias is about 45% (Wenstrom et al 1991). Physiotherapy may be indicated if retention of secretions is a problem. Manual hyperinflation techniques should avoid generating excess pressures within the hypo-plastic lungs.

Congenital anomalies of the lung

Congenital conditions of the lung such as lobar emphysema, lung cysts and adenomata are relatively rare. They may be diagnosed by ultrasound antenatally or by chest radiography postnatally. Treatment may involve surgical resection (lobectomy) if the condition is severe, but in some cases the lesions appear to resolve spontaneously in infancy.

Acquired lobar emphysema and lung cysts are more common as complications of respiratory distress syndrome and its treatment. Many cases resolve with medical management, although some do require resection. Physiotherapy may be indicated postoperatively if there is sputum retention, but manual hyperinflation is contraindicated if cysts are present.

Oesophageal atresia and tracheo-oesophageal fistula

There are five recognized types of this anomaly. In the most common variety the oesophagus ends in a blind proximal pouch (atresia) and there is a fistula between the trachea and the lower section of the oesophagus. About 10% of affected infants have oesophageal atresia with a tracheal fistula. The incidence is approximately 1 in 3000 births (Depaepe et al 1993).

The infant presents postnatally with episodes of choking, coughing and respiratory distress due to an inability to swallow saliva or feeds and consequent aspiration into the larynx or trachea. It is often difficult to pass a nasogastric tube, which on chest radiograph appears curled in the upper oesophagus.

Surgical correction is usually attempted as soon as possible and involves division of the fistula and anastomosis of the ends of the oesophagus. Some anastomoses may have to be performed under tension and the infant has to be electively ventilated and paralysed with the neck kept in flexion postoperatively. In a few cases, where the gap between the two ends of the oesophagus is too large, primary anastomosis is not possible and a feeding gastrostomy is performed. Oesophageal anastomosis or replacement by colonic, jejunal or gastric interposition is delayed.

If recurrent or continuous aspiration occurs before corrective surgery, physiotherapy (in the head-up position) may be indicated to clear excess secretions or treat lung collapse due to reflux of gastric contents. Preoperatively the airway is often kept clear by continuous suction of the upper pouch and the infant should be nursed head-up to prevent reflux of gastric contents through the fistula.

Postoperatively, head-down postural drainage is contraindicated and patients are often nursed in the head-up position for the first few days, to reduce the risk of reflux. Care must be taken not to extend the neck, especially in patients with a tight oesophageal anastomosis. Naso- or oropharyngeal suction should not in general exceed the external distance between the nasal cavity and the ear. This distance is effective at producing cough and inadvertent damage to the oesophageal anastomosis is avoided.

Gastroschisis and exomphalos (omphalocele)

These conditions are relatively rare abdominal wall defects, occurring in approximately 1 : 5000 births (Baird & MacDonald 1982). Gastroschisis refers to a full thickness abdominal wall defect next to the umbilical opening, through which the small and large bowel herniate, not usually covered by a membrane. Exomphalos occurs when the anterior abdominal wall fails to close at the base of the umbilical cord, allowing the abdominal contents and sometimes the liver to herniate through the umbilical ring and develop externally in utero. A translucent membranous sac encloses the hernial contents. The defect is usually diagnosed antenatally by ultrasound and is classified as major or minor depending on whether the defect is bigger or smaller than 5 cm. Affected infants often have other major associated anomalies.

Immediately after birth, the abdominal contents are covered to prevent heat and fluid loss until corrective surgery can be undertaken. In most cases primary repair is possible but where the defect is large a staged procedure is required, with gradual reduction of the bowels into the abdominal cavity.

Postoperatively the infant may require ventilation as the tightly packed, rigid abdomen causes respiratory embarrassment and compromises venous return. Where a staged procedure is necessary, prolonged ventilation may be required. Some infants have impaired antenatal lung growth and a proportion continue to have abnormal lung function during infancy.

These infants are particularly at risk from retention of secretions and lobar collapse due to the distended abdomen and predominantly supine nursing position (with the abdominal contents suspended above the abdomen). If treatment is required, techniques that increase intrathoracic pressure and consequently intra-abdominal pressure, such as vibrations or manual hyperinflation, should be used very cautiously. Postoperative respiratory compromise, if related to increased abdominal pressure, is unlikely to respond to physiotherapy. A slightly head-up position may relieve the thorax of some of the weight of the abdominal contents and reduce the work of breathing.

Congenital heart problems in infants and children

Congenital heart disease is the most common congenital anomaly with the incidence of moderate and severe forms about 6 in 1000 live births, and of all forms about 75 in 1000 live births (Hoffman & Kaplan 2002). Roughly one-third of these will require surgical intervention, with the rest either resolving spontaneously or being haemodynamically insignificant. Major congenital cardiac defects can often be detected antenatally by ultrasound examination, while more minor defects may not be detected until the postnatal period. Diagnosis is usually confirmed by echocardiography. Postnatally most cardiac defects are amenable to surgery and overall mortality has fallen to less than 5% in the best units (Elliott & Hussey 1995, Stark et al 2000). Early complete repair is attempted whenever possible, with the majority of operations being performed in the first year of life.

Management of congenital heart defects must involve agreement between cardiologist, surgeon, family and the child, if he is old enough. Each aspect of the child’s care is an integrated process requiring the skills of a multidisciplinary team before, during and after surgery.

Palliative procedures

When a primary repair is not possible, palliative or staging procedures will provide temporary or extended relief of symptoms. They are usually indicated to deal with excessive pulmonary blood flow, inadequate pulmonary blood flow or inadequate mixing between oxygenated and deoxygenated blood in the heart.

Corrective surgery: closed procedures

Corrective surgery: open procedures

Open procedures require cardiopulmonary bypass, modified for children in terms of size, flow rate, perfusion, temperature and drugs (Elliott & Hussey 1995).

Ventricular septal defect (VSD).

Ventricular septal defects are the most common congenital cardiac lesions, defined by a hole in the septum that separates left and right ventricles. VSDs are often found in conjunction with other cardiac defects and the clinical presentation will depend on the size of the VSD and the presence or absence of other cardiac anomalies. Infants may present with congestive cardiac failure, recurrent chest infections and failure to thrive. More than half of all VSDs close spontaneously and do not require surgery (Elliott & Hussey 1995). However, as with ASDs, undiagnosed larger defects can lead ultimately to severe irreversible pulmonary hypertension.

VSDs (Fig. 10.12) are defined according to their position in either the perimembranous inlet, the trabecular portion or the muscular outlet of the ventricular septum. Primary repair is usually performed using synthetic or bovine pericardial patches via median sternotomy, with the cardiac approach varying according to the position of the defect. Conduction disturbances are common following surgery.

Figure 10.12 Ventricular septal defect, showing mixing of blood between the left and right ventricle: AO, aorta; PA, pulmonary artery; SVC, superior vena cava; IVC, inferior vena cava; RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle; LPA, left pulmonary artery; PV, pulmonary veins; LBV, left brachiocephalic vein.

Although operative mortality approaches zero for isolated septal defects, multiple VSDs or ‘Swiss cheese’ defects carry a higher risk (De Leval 1994a).

Tetralogy of Fallot.

The four components of Fallot’s tetralogy are classically described as a large VSD, right ventricular (infundibular) outflow or valve obstruction, overriding aorta and right ventricular hypertrophy (Fig. 10.13).

Figure 10.13 Tetralogy of Fallot, showing VSD, right ventricular hypertrophy, aorta overriding both ventricles and stenosis of the pulmonary artery: AO, aorta; PA, pulmonary artery; SVC, superior vena cava; IVC, inferior vena cava; RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle; LPA, left pulmonary artery; PV, pulmonary veins; LBV, left brachiocephalic vein.

Inadequate blood flow to the pulmonary circulation and preferential flow of deoxygenated blood to the aorta may cause cyanosis, but severity of symptoms will depend on the degree of obstructed pulmonary blood flow. The majority of infants are pink at birth but become progressively cyanosed as they grow. Periodic spasm of the infundibulum prevents blood flow to the lungs and may cause ‘spelling’ episodes in which infants become irritable. Continued crying leads to increasing cyanosis and eventual loss of consciousness. The spasm then relaxes and the child gradually recovers. These episodes are dangerous and may lead to death or cerebral anoxia. Older undiagnosed children may intuitively squat following exercise, which reduces blood flow to and from the lower extremities in an effort to compensate for the large oxygen debt accrued during physical activity. In the presence of cyanosis, this behaviour may suggest diagnosis of this defect.

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Some controversy exists about whether it is better to do primary repair or palliative shunt with repair when the child is older. Corrective surgery will involve closure of the VSD, resection of the hypertrophied infundibulum and reconstruction of the pulmonary arteries. Long-term results are good with actuarial survival of 93% at 15 years and good quality of life (Castenda 1994).

Transposition of the great arteries (TGA).

This defect is characterized by the aorta originating from the right ventricle and the pulmonary artery from the left (Fig. 10.14). Oxygenated pulmonary blood recirculates through the lungs without reaching the body and deoxy-genated blood recirculates through the body without reaching the lungs. The two closed circulations would quickly lead to death but there is usually a degree of mixing through the PDA and, if present, associated anomalies such as ASD or VSD. Babies therefore present soon after birth with cyanosis and immediate treatment aims include keeping the ductus arteriosus open with prostaglandins until surgery. Before corrective surgery, cardiac catheterization and balloon atrial septostomy may also be necessary.

Figure 10.14 Transposition of the great arteries. Shaded area shows either position of a patent foramen ovale or site of balloon septostomy allowing some mixing of oxygenated and deoxygenated blood between the systemic and pulmonary circulations: AO, aorta; PA, pulmonary artery; SVC, superior vena cava; IVC, inferior vena cava; RA, right atrium; LA, left atrium; RV, right ventricle; LV, left ventricle; LPA, left pulmonary artery; PV, pulmonary veins; LBV, left brachiocephalic vein.

The arterial switch operation has been performed with good results since 1985 and is the preferred option for simple TGA or for TGA with VSD. It is generally performed in the first 2–3 weeks of life, while the pulmonary vascular resistance is high and the left ventricle is ‘trained’ to receive the systemic workload. The aorta and pulmonary arteries (above the level of the coronary vessels) are transected and transferred to their correct anatomical positions. The coronary arteries are also transferred to their appropriate positions. Operative mortality is low (< 2%) and long-term results appear to be far superior to the earlier Mustard or Senning operations, which redirected blood flow via intra-atrial tunnels (Freed et al 2006).

Cardiac valve abnormalities

Transplantation surgery in children

The problems of cardiac, lung and heart-lung transplant surgery in children are similar to those in adults, and are discussed in detail in Chapter 15.

Trauma & head injury

Accidents are the most common cause of child death after the first year of life and 50% are road traffic accidents. Children who have been severely injured may require intensive care and mechanical ventilation, particularly after head injury.

In the acutely head-injured child the primary injury refers to the damage sustained during trauma caused by bleeding, contusion or neuronal shearing. Secondary injury is due to the resultant complicating events. These may be intracranial factors such as bleeding, swelling, seizures and raised intracranial pressure (ICP) or systemic factors such as hypoxia, hypercarbia, hyper- or hypotension, hyper- or hypoglycaemia and fever. In the United Kingdom, 90–95% of injuries are managed without the need for neurosurgical intervention (Tasker et al 2006). When required, for example in the presence of an acute subdural bleed, surgical evaluation should be facilitated immediately.

The most common presentation of acute, severe head injury in children is coma. Clinical scores, such as the paediatric modifications of the Glasgow Coma Scale (GCS) (Tasker 2000, Teasdale & Jennett 1974), allow bedside assessment of neurological function and the degree of impairment of consciousness in children. Such scores are designed to allow early identification of pathology when it is still potentially reversible by medical or surgical intervention.

Coma in children may present after a longer interval than in adults. Continued extradural bleeding following a relatively minor injury may lead to a deteriorating level of consciousness. Cerebral oedema may be focal or generalized; the latter may result in an increase in intracranial pressure and cause a more rapid deterioration.

Raised intracranial pressure

Raised intracranial pressure (ICP) represents an increase in the volume of the intracranial contents. In addition to trauma, it can be caused by space-occupying lesions or encephalopathy. Normal values for ICP fall below 15 mmHg. The cerebral perfusion pressure (CPP) is the driving pressure for cerebral blood flow and is defined as the difference between mean arterial blood pressure and ICP. It is a crucial parameter, which lies within the range of 50–70 mmHg. A variety of methods to monitor ICP can be used including intraventricular catheters, subdural or subarachnoid monitors and cerebral intraparenchymal catheters.

Once the child is stabilized, medical management aims to avoid or minimize secondary brain injury. Factors that may precipitate a rise in ICP, resulting in a potential fall in CPP, should be avoided. Intubation and mechanical hyperventilation have been sometimes been used to reduce ICP. This has been controversial as hyperventilation (and hypocapnia) may induce cerebral ischaemia. In general, this is still sometimes used for short periods during acute deterioration or when intracranial hypertension is unresponsive to other therapy.

The management of children with acute head injury has been reviewed extensively (Tasker 2001). Many of the strategies for management are similar to adults and discussed in Chapter 8.

Pulmonary problems following liver transplantation

Liver transplantation is used for chronic end-stage liver disease and fulminant hepatic failure. Shortage of paediatric donors means that more and more grafts are reductions of adult livers. In some situations one donor liver can be used for two patients. Postoperative complications include bleeding and splinting of the right side of the diaphragm. Patients invariably develop a pleural effusion which is usually right-sided but may be bilateral. Acute rejection is common 5–7 days post- transplant. Some patients develop chronic rejection and require retransplantation (Salt et al 1992).

Physiotherapists may have the opportunity to assess these patients preoperatively, but often patients with fulminant hepatic failure are operated on as an emergency or are too ill to be seen preoperatively.

Postoperatively, the risk of bleeding in some patients means that handling is kept to a minimum. Patients are assessed regularly and treated as appropriate. Following extubation, ambulation is encouraged as soon as possible. Large pleural effusions coupled with ascites mean patients are often very breathless and unable to mobilize.

Preoperative management

In some hospitals preoperative visits and handbooks are available which help to reduce some of the fear of being in hospital. Except in emergency admissions, it is desirable for children and their parents to be seen by a physiotherapist before their surgery. Appropriate explanation of postoperative procedures should be given at the level of the child’s age and understanding, but overloading the child with information they do not understand may increase stress and anxiety. It is important that parents understand the need for postoperative physiotherapy intervention as they can play an important role in encouraging postoperative mobility.

Physiotherapy assessment should include cardiores-piratory status and physical and motor development. The assessment of respiratory status provides an opportunity to evaluate postoperative risks and the need for preoperative treatment. If indicated, older children may be taught an airway clearance technique. Incentive spirometry can be useful in reducing atelectasis in children after cardiac surgery, especially those techniques specifically designed for children (Krastins et al 1982).

When a child has pre-existing pulmonary disease, for example cystic fibrosis, they may need to be admitted some time before surgery for prophylactic antibiotics and for effective airway clearance. Such children may require physiotherapy and suction in the anaesthetic room following intubation and before surgery (Tannenbaum et al 2007).

Several congenital cardiac anomalies are associated with a broader spectrum of embryological malformations, some of which result in developmental delay. These children may require long-term developmental follow-up. Any preoperative neurological problems or developmental delay should be documented and appropriate management plans formulated.

Postoperative management

In addition to the altered pulmonary dynamics and respiratory insufficiency seen after general anaesthesia, open heart surgery with cardiopulmonary bypass leads to further changes in respiratory function. The lungs may be compressed during surgery, contributing to atelectasis, loss of perfusion and diminished surfactant production, all of which contribute to poor respiratory compliance postoperatively. Children and infants should be regularly reviewed and treated as required.

As sedation is reduced and children are able to take a more active role in their treatment, effective pain relief is essential. Pain due to the incision and presence of intercostal drains may cause splinting of the chest wall and reduced excursion. Adequate pain relief can be provided through continuous infusion or patient-controlled systems in older children. It may be difficult to assess the severity of pain in children, although the development of specific paediatric pain scales has made it easier in recent years (Razmus & Wilson 2006). Children in pain can be withdrawn and immobile and infants in pain may be tachycardic and tachypnoeic. Some children who have a fear of needles will deny pain in order to avoid injections.

Treatment is directed towards early extubation and mobilization. When in bed, children should be comfortably positioned in alternate side lying or sitting upright and the ‘slumped posture’ should be avoided. As soon as possible, children should be sat out of bed and walking encouraged when appropriate. Drips, drains and catheters can all be carried to allow early ambulation. Attention to posture is important, particularly following thoracotomy when arm and shoulder exercises to the affected side are also essential.

If sputum retention is a problem postoperatively, airway clearance techniques may be required. A child may prefer not to have his wound supported or to support his own wound when coughing.

Acknowledgements

We would like to thank Dr Robert Dinwiddie and Catherine Dunne for their invaluable assistance with the preparation of this chapter.