Etiology

Tracheomalacia is a floppy trachea due to lack of structural integrity of the tracheal wall. The tracheal cartilaginous rings normally extend through an arc of approximately 320 degrees, maintaining rigidity of the trachea during changes in intrathoracic pressure. With tracheomalacia, the cartilaginous rings may not extend as far around the circumference, may be completely absent, or may be present but damaged, and often the membranous posterior trachea is wider than usual. These abnormalities can result in excessive collapse of the trachea during expiration. Tracheomalacia may be congenital (tracheoesophageal fistula or bony dysplasia syndromes) or acquired (long-term mechanical ventilation). Tracheomalacia must be differentiated from extrinsic tracheal compression by masses or vascular structures. In some patients, localized tracheomalacia may persist after the trachea has been relieved of compression by a mass lesion or abnormal blood vessels. Viral infections may exacerbate tracheomalacia, leading to coarse expiratory wheezing and barky cough. The expiratory noises of tracheomalacia are often mistakenly ascribed to asthma or bronchiolitis, and the barky cough is often misdiagnosed as croup.

Clinical Manifestations

With tracheomalacia, the tracheal collapse may only be apparent during forced exhalation or with cough. It is commonly aggravated by respiratory infections. The airway collapse may cause recurrent coarse expiratory wheeze and a prolonged expiratory phase. Infants with severe tracheomalacia may completely collapse their tracheas during agitation, resulting in cyanotic episodes that resemble breath-holding spells. The voice is normal, as is inspiratory effort. In older children, the hallmark sign is a brassy, barky cough due to the vibration of the tracheal walls. This cough can be loud, persistent, and it is often misdiagnosed as croup.

Treatment

Infants with mild-moderate tracheomalacia usually require no intervention. Tracheomalacia improves with airway growth as the lumen increases in diameter and the tracheal wall becomes more firm. In older children, tracheomalacia may manifest as a severe brassy cough, which is often aggravated by respiratory infections. The treatment of these older children is geared toward treating any precipitating cause for cough and providing supportive care. Children, especially infants, with severe tracheomalacia may require tracheostomy tubes to administer continuous positive airway pressure (CPAP), which serves to stent open the airway.

Epidemiology

Aspiration of foreign bodies into the trachea and bronchi is relatively common. The majority of children who aspirate foreign bodies are under 4 years of age. Most deaths secondary to foreign body aspiration occur in this age group. Because the right mainstem bronchus takes off at a less acute angle than the left mainstem bronchus, foreign bodies tend to lodge in right-sided airways. Some foreign bodies, especially nuts, can also lodge more proximally in the larynx or subglottic space totally occluding the airway. Many foreign bodies are not radiopaque, which makes them difficult to detect radiographically. The most common foreign bodies aspirated by young children are food (especially nuts) and small toys. Coins more often lodge in the esophagus than in the airways. Older children have been known to aspirate rubber balloons, which can be life-threatening.

Clinical Manifestations

Many children who aspirate foreign bodies have clear histories of choking, witnessed aspiration, or physical or radiographic evidence of foreign body aspiration. However, a small percentage of patients have a negative history because the aspiration went unrecognized. Physical findings observed with acute foreign body aspiration include cough, localized wheezing, unilateral absence of breath sounds, stridor, and, rarely, bloody sputum.

Most foreign bodies are small and quickly expelled, but some may remain in the lung for long periods of time and may come to medical attention because of persistent cough, sputum production, or recurrent pneumonia. Foreign body aspiration should be in the differential diagnosis of patients with persistent wheezing unresponsive to bronchodilator therapy, persistent atelectasis, recurrent or persistent pneumonia, or chronic cough without another explanation. Foreign bodies may also lodge in the esophagus and compress the trachea, thus producing respiratory symptoms. Therefore, esophageal foreign bodies should be included in the differential diagnosis of infants or young children with persistent stridor or wheezing, particularly if dysphagia is present.

Diagnostic Studies

Radiographic studies will reveal the presence of radiopaque objects and can also identify focal air trapping, especially on expiratory views. Thus, when foreign body aspiration is suspected, expiratory or lateral decubitus chest radiographs should be ordered. In addition, fluoroscopy may be helpful, especially in children who cannot perform expiratory views. If there is strong evidence of foreign body aspiration, the patient should undergo rigid bronchoscopy. Flexible bronchoscopy can be used to locate an aspirated foreign body and may be useful when the presentation is not straightforward, but foreign body removal is best performed via rigid bronchoscopy.

Prevention

The best approach to preventing foreign body aspiration is to educate parents and caregivers. Before molar teeth have erupted, infants and children should not be given nuts, uncooked carrots, or other foods that may be easily broken into small pieces and aspirated. Additionally, tiny toys are at risk for being aspirated by young children. Sound parental judgment is required to determine at what age and stage of development small objects should be accessible to children.

Etiology

Primary ciliary dyskinesia (PCD, immotile cilia syndrome) is an inherited disorder in which ultrastructural abnormalities in the cilia result in absent or disordered movement of the cilia. This disorder affects approximately 1:19,000 persons. There are many reported abnormalities in ciliary structure, but the most common are due to defects in the dynein arms, ultrastructural features that provide energy via adenosine triphosphatase (ATPase), which is necessary for ciliary motility.

Diagnostic Studies

PCD is confirmed by electron microscopy of respiratory cilia. The cilia may be obtained from scrapings/biopsy of nasal or airway epithelium, although results may be difficult to interpret because chronic infection and inflammation may lead to ultrastructural abnormalities in nasal cilia. The measurement of nasal nitric oxide has been used as a screening tool for PCD. Low nasal nitric oxide values (<200 parts per billion) are consistent with PCD, while values greater than 400 parts per billion make the diagnosis less likely. However, the validity of nasal nitric oxide assays as a diagnostic test for PCD has not been fully substantiated.

Treatment

Treatment is geared toward treating infections and improving clearance of respiratory secretions. Sinus surgical procedures are often done to manage chronic sinusitis, but their benefit is questionable. Most children require placement of pressure equalization (PE) tubes for management of recurrent otitis media. Chest physiotherapy and prompt treatment of bacterial infections are helpful, but the course of the disease tends to be slowly progressive.

Etiology

Pulmonary edema is the seepage of fluid into the alveolar and interstitial spaces. At the alveolar-capillary interface, capillary hydrostatic forces and interstitial osmotic pressures tend to push fluid into the airspaces, while plasma osmotic pressures and tissue mechanical forces tend to move fluid away from the airspaces. Under normal circumstances, the sum of these forces favors absorption, so the alveolar and interstitial spaces remain dry. Fluid entering the alveoli is normally removed by pulmonary lymphatics. Pulmonary edema forms when transcapillary fluid flux exceeds lymphatic drainage. Reduced left ventricular function leads to pulmonary venous hypertension and increased capillary hydrostatic pressure, and fluid moves into the interstitial space and alveoli. Fluid initially enters the interstitial space around the terminal bronchioles, alveoli, and arterioles (interstitial edema), causing increased lung stiffness and premature closure of bronchioles on expiration. If the process continues, fluid then enters the alveoli, further reducing compliance and resulting in intrapulmonary shunting (alveolar units that are perfused but not ventilated). Decreased ventilation (hypercarbia) is a late finding.

Pulmonary edema is most commonly due to heart failure from left ventricular or biventricular dysfunction. Pulmonary hypertension and associated cor pulmonale (right ventricular dysfunction) do not usually cause pulmonary edema as the increased vascular resistance is proximal to the capillary bed. Pulmonary edema may occur with excessive swings in intrathoracic pressure, as seen after tracheal foreign body aspiration or severe obstruction from hypertrophied tonsils and adenoids (postobstructive pulmonary edema). Pulmonary edema may also be present in conditions with decreased serum oncotic pressure (hypoalbumenemia), after administration of large volumes of intravenous (IV) fluids, especially if there is capillary injury, with ascent to high altitude (high altitude pulmonary edema), and after CNS injury (neurogenic pulmonary edema).

Clinical Manifestations

The clinical manifestations of pulmonary edema are dyspnea, tachypnea, and cough (often with frothy, pink-tinged sputum). As the edema worsens, there is increased work of breathing, hypoxemia, and diffuse inspiratory crackles can be heard on auscultation.

Diagnostic Studies

Chest radiographs may reveal diffuse hazy infiltrates, classically in a perihilar pattern, but these findings may be obscured by underlying lung disease. Interstitial edema (Kerley B lines) may be seen, especially at the lung bases.

Treatment and Prognosis

Treatment and prognosis depend on the cause of the pulmonary edema and response to therapy. Patients should be positioned in an upright posture and given supplemental O₂. Diuretic therapy and rapidly acting IV inotropic agents may be helpful in cardiogenic pulmonary edema. Continuous positive airway pressure (CPAP) or intubation with positive pressure ventilation using high positive end-expiratory pressures (PEEP) may be required.

Etiology

Pulmonary arterial hypertension (PAH) may be primary or acquired. The most common cause is chronic hypoxia. Alveolar hypoxia results in local pulmonary vasoconstriction and PAH. Pulmonary hypertension is also seen with chronic lung disease, upper airway obstruction resulting in obstructive sleep apnea and hypoxemia, pulmonary thromboembolism, exposure to high altitude, and in autoimmune diseases (e.g., scleroderma). Acquired PAH can also be due to excessive pulmonary blood flow due to left-to-right cardiac shunting (see Chapter 143). With prolonged PAH, irreversible changes may occur in the intima and media of the pulmonary arterioles. Idiopathic pulmonary arterial hypertension (previously called primary pulmonary hypertension) is a disorder in which the changes in the pulmonary vasculature are not due to an identifiable underlying cause. It has been associated with mutations in the bone morphogenetic receptor 2 (BMPR2) gene and the use of anorectic weight loss drugs. There is an approximately 2:1 female predominance.

Pulmonary arterial hypertension strains the right side of the heart, which leads to hypertrophy and dilation of the right ventricle. This may result in cor pulmonale, a condition in which right-sided heart failure leads to hepatic congestion, fluid retention, and tricuspid insufficiency. In severe cor pulmonale, the ventricular septum may be displaced toward the left ventricle, hindering left ventricular function. The most common causes of cor pulmonale in children are chronic lung diseases, especially severe bronchopulmonary dysplasia and scleroderma, and severe untreated obstructive sleep apnea (with chronic hypoxia).

Clinical Manifestations and Diagnostic Studies

Pulmonary arterial hypertension should be suspected whenever there is prolonged hypoxemia or hemodynamically significant left-to-right cardiac shunting. In addition to the other physical findings associated with pulmonary and cardiac diseases, an accentuated pulmonary component of the second heart sound may be heard in the left second intercostal space. Definitive diagnosis is made by cardiac catheterization, but echocardiography may confirm the presence of right ventricular hypertrophy, ventricular dysfunction, and tricuspid insufficiency and can be used to estimate the pulmonary artery pressures.

Treatment and Prognosis

In acquired pulmonary arterial hypertension, it is important to treat the underlying condition. The relief of hypoxemia with supplemental O₂ therapy is essential. Heart failure may require treatment with diuretics and restrictions of salt and fluid intake. Vasodilator therapy (sildenafil) is helpful in some patients, and inhaled nitric oxide can be used short term. Continuous IV infusions of prostacyclin may be helpful both acutely and chronically. The use of endothelium antagonists may be beneficial. Unfortunately, many patients with the idiopathic form of PAH have progressive courses, and lung or heart-lung transplantation may be the only treatment option.

Etiology

Pulmonary hemorrhage is a rare but potentially life-threatening condition in children. It can be due to bleeding from the airways (hemangiomas, bronchial vessel bleeds) or from diffuse capillary bleeding (alveolar hemorrhage). Alveolar hemorrhage is usually due to diffuse capillary disruption/inflammation caused by autoimmune disorders and after bone marrow transplantation. Airway bleeding can be due to airway hemangiomas, pulmonary arteriovenous malformations (as with hereditary hemorrhagic telangectasia), and bronchial artery collaterals, which develop in some patients with chronic lung infections, especially cystic fibrosis. Idiopathic pulmonary hemosiderosis is a rare disorder characterized by recurrent alveolar bleeding, iron deficiency anemia, and hemosiderin-laden macrophages in the lung. Red blood cells are phagocytosed by alveolar macrophages and the hemoglobin is converted to hemosiderin, which, with the use of special iron-staining techniques can be identified microscopically within the alveolar macrophages. Hemosiderin-laden macrophages may be identified in bronchoalveolar lavage or lung biopsy specimens. Although the term hemosiderosis is sometimes used interchangeably with pulmonary hemorrhage, it is a pathologic finding that results from bleeding anywhere in the lung, airway, pharynx, nasopharynx, or mouth leading to hemosiderin accumulation in the lung. Pulmonary hemorrhage is a preferable term for bleeding from an intrathoracic source.

Clinical Manifestations

Most children with pulmonary hemorrhage present with hemoptysis. When evaluating a child with hemoptysis, it is important to rule out extrapulmonary sources of bleeding, including hematemesis and bleeding from the nasopharynx or mouth, as these are more common than true pulmonary hemorrhage. In addition to hemoptysis, the presenting signs and symptoms of pulmonary hemorrhage include cough, wheezing, shortness of breath, pallor, fatigue, cyanosis, and fever. Episodic pulmonary hemorrhage frequently manifests as recurrent respiratory symptoms associated with pulmonary infiltrates on chest radiographs. Symptomatic airway hemorrhage may result in significant hemoptysis with few radiographic changes, while alveolar bleeding often causes profound respiratory symptoms, hypoxemia, diffuse infiltrates on radiographs, and minimal hemoptysis. Some patients experience a localized bubbling sensation in the chest, which may be helpful in differentiating local from diffuse sources of pulmonary bleeding. Physical examination findings may include locally or diffusely decreased breath sounds, cyanosis, and crackles on auscultation.

The differential diagnosis of pulmonary hemorrhage includes alveolar and airway bleeding. The causes of alveolar (capillary) bleeding include idiopathic pulmonary hemosiderosis, diffuse alveolitis (capillaritis) secondary to autoimmune disease (Goodpasture syndrome, Wegener granulomatosis, systemic lupus erythematosus, polyarteritis nodosa), clotting disorders, veno-occlusive disease, diffuse alveolar injury (smoke inhalation), and cardiac conditions associated with elevated pulmonary venous and capillary pressures (mitral stenosis). Rarely, a previously well infant will present with life-threatening acute alveolar hemorrhage. Often no cause is found, and once the acute episode resolves, the infant returns to normal. Most of these infants never have a second bleeding episode. Hemoptysis can have cardiovascular, pulmonary, or immunologic causes (Table 136-2).

Diagnostic Studies

It is important to perform a thorough upper airway examination to rule out epistaxis. Sometimes this requires nasopharyngoscopy. If extrapulmonary sources of bleeding have been excluded, then other diagnostic tests to consider are chest radiographs, CT angiogram of the chest, bronchoscopy, echocardiogram, and evaluation for rheumatologic/autoimmune diseases, especially Goodpasture disease, Wegener granulomatosis, Schönlein-Henoch purpura, and systemic lupus erythematosus.

Treatment

The management of acute episodes of pulmonary bleeding includes the administration of supplemental O₂, blood transfusions, and, as is often the case with acute alveolar hemorrhages, mechanical ventilation with PEEP to tamponade the bleeding. Attempts should be made to identify the cause of the bleeding. Treatment is directed toward the underlying disorders and providing supportive care. In bronchial arterial bleeding, arteriography with vessel embolization has been shown to be successful.

Etiology

Pulmonary embolism is rare in children. When it occurs, it is often associated with indwelling central venous catheters, oral contraceptives, or hypercoagulable states. In adolescents, trauma, obesity, abortion, and malignancy may lead to deep vein thromboses (DVT) and pulmonary embolism.

Clinical Manifestations

Because the pulmonary vascular bed is distensible, small emboli, even if multiple, may be asymptomatic unless they are infected (septic emboli) and cause pulmonary infection. Large emboli may cause acute dyspnea, pleuritic chest pain, cough, and hemoptysis. Hypoxia is common, as are nonspecific ST-segment and T-wave changes on the electrocardiogram (ECG). The P₂ heart sound may be increased, and an S₄ sound may be present.

Diagnostic Studies

Although the chest x-ray is usually normal, atelectasis or cardiomegaly may be seen. The measurement of D-dimers can be used as a screening test, but it must be interpreted in light of the probability of a pulmonary embolism. If the D-dimer is normal and the probability for embolism is low, then no further workup may be necessary. However, if the D-dimer is elevated, or if it is normal but the probability of embolism is moderate or high, then the diagnostic test of choice is a CT angiogram of the chest. Ventilation-perfusion scans may be helpful in the diagnosis by revealing defects in perfusion without matching ventilation defects, but they are difficult to perform in young children. Doppler or compression ultrasonography can be useful in assessing patients for lower extremity deep vein thromboses (DVTs). For definitive diagnosis of pulmonary embolism, the gold standard is still pulmonary angiography, though with the improvement in CT angiography, angiograms are now rarely necessary. Children with pulmonary embolism without an obvious cause should be evaluated for hypercoagulable states, the most common of which is factor V Leiden.

Treatment

Once a pulmonary embolism is suspected, the patient should be anticoagulated, usually with low-molecular-weight heparin. All patients should receive supplemental O₂, and it is important to treat the predisposing factors. Thrombolytic therapy and surgical resection of emboli are rarely indicated. Occasionally an inferior vena caval filter needs to be placed to prevent recurrent emboli.