The airway can be affected by congenital anomalies causing upper airway obstruction that can be relatively fixed (skeletal) or dynamic (soft tissue). (Please note that because only common pediatric upper airway disorders are discussed in this review, the term “airway” denotes upper airways only.) Further, the nose, larynx, and trachea have nonskeletal structural support that can have both fixed and dynamic components contributing to obstruction. Normally, air movement starts at the nasopharynx, travels past the soft palate and posterior to the tongue, through the hypopharynx (past the epiglottis), then through the larynx (thyroid cartilage, cricoid cartilage, vocal cords), and finally through the trachea and main bronchi (Figure 1).
Infants are obligate nasal breathers due to their low-lying posterior soft palate and enlarged epiglottis that results in close approximation of the hypopharynx and nasopharynx; this normal anatomical relationship reduces risk of aspiration. With growth in the first year of life, the space between the hypopharynx and nasopharynx increases. In general, minor reduction in the caliber of airways may have significant consequences in the form of increased obstruction and resultant elevated airway resistance (Poiseuelle's law states that the resistance is inversely proportional to the fourth power of the radius of the tube). The infant airway is also shifted more anteriorly, with the narrowest area at the level of the cricoid ring (making a funnel shape rather than a cylindrical laryngeal shape).
Common obstructive upper airway disorders in neonates and infants are choanal atresia, laryngomalacia, tracheomalacia, tracheal esophageal fistula, and vascular ring. Epiglottitis, laryngotracheobronchitis (croup), and obstructive sleep apnea (OSA) tend to occur in early childhood. Vocal cord dysfunction tends to occur in older children and adolescents. Table 1 describes the location, pathology, and associated diagnoses of some of the common pediatric upper-airway obstructive lesions, and the following text provides a brief description of selected disorders.
As the first point of contact for all pediatric patients, the general pediatrician plays a vital role for initial evaluation and for directing care to the appropriate subspecialists. As airway disorders can sometimes be potentially life-threatening, early recognition and management is essential. This article reviews the most common and most life-threatening pediatric airway disorders that may present as noisy breathing or respiratory distress.
Choanal atresia refers to absent patency from nasal cavity to the nasopharynx, which can be unilateral or bilateral, due to congenital membranous or bony tissue malformation. Although not common (incidence of 1 in 5,000–7,000 live births1), a high index of suspicion should be maintained for choanal atresia when a neonate or infant presents with difficulty breathing. As noted earlier, because of the close proximity of the epiglottis and soft palate in infants and with relatively anterior larynx position, passage of air for breathing must travel through the nose rather than the mouth. Therefore, with bilateral nasal obstruction, the infant will present with significant respiratory distress and cyanosis exacerbated while eating or sleeping, which can be relieved with crying (allowing passage of air from the oropharynx rather than the nasopharynx). If unilateral obstruction (Figure 2) is present, then respiratory distress may not be as apparent and the only sign may be increased nasal discharge from the affected side. Initial evaluation for nasal cavity patency would be to pass a 5-French or 6-French size catheter through each nare with visualization of the catheter through the mouth (as the catheter may coil in the nasal cavity, providing false assurance of patency). If there is continued concern, then imaging with computed tomography (CT) of the head should be performed, which would also be helpful to rule out other causes of nasal obstruction such as nasolacrimal duct cyst, encephalocele, neoplasm, or pyriform aperture stenosis.2 Investigation for other congenital anomalies should be considered in the event that the choanal atresia is a component of a syndrome such as CHARGE syndrome (coloboma, heart disease, atresia of choanae, retardation of growth/development, genital hypoplasia, and ear abnormality). Treatment requires pediatric otolaryngology surgical intervention, which is semi-urgent if unilateral obstruction is present. With bilateral obstruction and severe respiratory distress, the neonate may require intubation and stabilization of breathing prior to CT imaging and referral to specialty hospital.
Unilateral choanal atresia shown by computed tomography of the head. The arrow with dots indicates patent nasal passage and arrow with boxes demonstrates bony obstruction of patient's left nasal passage.
One of the most common congenital abnormalities of the upper airway is laryngomalacia (“soft larynx”), which is the obstruction of the supraglottic tissue. Laryngomalacia is the cause of most (60%–70%) cases of stridor in infants and children,3 and although traditionally thought to be male predominant, it has not been shown to be associated with gender in more recent investigation.4 Infants will present with stridor (high-pitched sound with inspiration) that is exacerbated with feeding or crying. With inspiration, development of intraluminal negative pressure (lower pressure in the airway as compared to external pressure) causes the supraglottic tissues to collapse. Laryngomalacia is often associated with gastroesophageal reflux and can be associated with difficulty feeding.5 Presence of feeding difficulties such as choking with feeds, poor weight gain, signs or symptoms of increased work of breathing (especially suprasternal retractions), apnea, cyanosis, and/or aspiration pneumonia is of concern and warrants aggressive management and referral to a specialist such as a pediatric pulmonologist or otolaryngologist.
Diagnosis is based on direct visualization with fiberoptic flexible laryngoscopy that can potentially be done at bedside or clinic (without sedation) (Figure 3). Other supportive testing can include swallow study (evaluate for aspiration) and polysomnography (PSG) (to evaluate severity of sleep-related obstruction to help guide urgency of management, keeping in mind that respiratory distress may often be more severe when awake or crying than during quiet sleep). Treatment will depend on the severity of the obstruction. With mild laryngomalacia, management could include close clinical follow-up to ensure adequate oral intake and growth without respiratory distress because the natural course would be to expect resolution with growth in the first year of life. For mild to moderate laryngomalacia, medical management would include starting medication for treatment of gastroesophageal reflux. For moderate to severe laryngomalacia, surgical intervention should include supraglottoplasty, which has shown to be effective for primary treatment in infants with and without comorbidities.6 In severe cases without adequate response to supraglottoplasty, tracheostomy may be necessary.
Laryngomalacia. Sleep endoscopy images with early inhalation on the left and demonstrating tubular epiglottis, short aryepiglottic folds, and poorly visualized vocal cords (often vocal cords are not visualized with laryngomalacia). On the right, arytenoid prolapse with inspiration causing obstruction.
Airway malacia is common, with estimated incidence of 1 to 2 per 100 infants.7 Tracheomalacia and bronchomalacia may also be found with laryngomalacia. Tracheomalacia (ie, “soft trachea”) refers to dynamic collapse of the trachea that occurs with exhalation. Congenital tracheomalacia involves impaired integrity of the cartilaginous rings, which causes pathologic narrowing of tracheal lumen, which can be associated with congenital cartilage abnormalities, congenital syndromes (ie, CHARGE, VATER [vertebrae, anus, trachea, esophagus, renal] syndrome), tracheoesophageal fistula with or without esophageal atresia, prolonged intubation, or external compression (vascular ring, pectus excavatum, teratoma, hemangioma, bronchogenic cysts). Affected infants and children may present with severe respiratory distress or may present later with chronic cough or atypical wheeze that is unresponsive or exacerbated by bronchodilators. The most common signs and symptoms of tracheomalacia are noisy breathing (eg, stridor, inspiratory noise, expiratory noise, or biphasic), increased work of breathing, gastroesophageal reflux, cough, recurrent respiratory infections, and feeding difficulties.8 Diagnosis is often confirmed around age 6 to 7 months8 and requires bronchoscopy under general anesthesia (Figure 4) and an adequately trained pediatric pulmonologist, although bronchoscopy becomes less reliable when there is external compression of the trachea. Therefore, other supportive testing should be strongly considered. This includes chest X-ray, echocardiogram, computed tomographic angiography, and magnetic resonance imaging (MRI). Treatment depends on the etiology and severity of obstruction. For external compression, surgical intervention may need to occur with greater urgency (particularly for cardiac anomalies, esophageal involvement, or masses). Mild tracheomalacia may be managed with a less aggressive approach that includes clinical monitoring as tracheomalacia usually resolves with growth. If severe, then positive airway pressure via mask (continuous positive airway pressure) or tracheostomy may be necessary to keep the airway open to prevent cardiorespiratory arrest.
Bronchomalacia. Direct visualization of the carina with bronchoscopy demonstrates anterior-posterior narrowing of both mainstem bronchi leading to altered morphology (slit-like appearance rather than the normal circular appearance).
Epiglottitis is another less common (incidence of 0.7 cases per 100,000 people immunized for Haemophilus influenzae type B9), but potentially life-threatening condition that must be recognized early. Epiglottitis refers to inflammation of the epiglottis and surrounding soft tissue most often due to infection (Streptococcus, Staphylococcus, Klebsiella; and if not vaccinated, then H. influenzae type B), but it can also be secondary to trauma or allergy. Affected children will present initially with sore throat, fever, and irritability with progression to dysphagia, sialorrhea, change in voice, and classically a posture of sitting upright while leaning forward. This condition can quickly progress to respiratory failure (particularly with agitation). Evaluation can include lateral soft tissue X-ray of the neck that may demonstrate enlarged epiglottis (“thumb” sign). Testing that requires venipuncture or examination with tongue depressor, which will exacerbate agitation, should be avoided. Management should include immediate consultation of pediatric anesthesia and pediatric otolaryngology to ensure that the patient's airway can be protected. The patient should be admitted to the pediatric intensive care unit for close airway monitoring. Further treatment after airway stabilization can include steroids, antibiotics, and intravenous fluids.
Laryngotracheobronchitis, or croup, is a common pediatric diagnosis that involves inflammation of the upper airway (larynx) and proximal lower airway (trachea and bronchi) due to infection. Most often, croup is caused by parainfluenza viral (PIV type 1) infection or other viral infection (PIV type 2 and 3), leading to a less toxic appearance than children with epiglottitis. Viruses such as influenza A and B, adenovirus, respiratory syncytial virus, and rhinovirus are among the other viruses implicated in the etiology. Children age 6 months to 6 years are most often affected and will present with signs of viral upper respiratory infection prior to abrupt onset of croup with the classic “barking” cough, change in voice, and stridor, without excessive sialorrhea.10 Typical cases due to PIV type 1 are commonly seen during the fall and winter. Supportive testing can include respiratory viral panel, soft tissue neck X-ray (classically will show “steeple sign”), and chest X-ray. Treatment is primarily supportive, initially with humidified air. With progression of respiratory distress, supplemental oxygen, inhaled and systemic steroids, nebulized racemic epinephrine, and/or heliox should be considered. Dexamethasone at a dose of 0.6 mg/kg of body weight parenterally for acute severe episode, or orally at 0.15 mg to 0.6 mg depending upon the severity, as a single dose has been recommended.10,11 Nebulized budesonide as a single dose of 2 mg has been shown to reduce the intensity of symptoms and need for hospitalization.12 If there is severe respiratory distress, the patient may require intubation.
Obstructive Sleep Apnea
Physiologic hyperplasia of the adenoid tissue and tonsils in children often occurs between the ages of 2 and 7 years. Although this airway crowding can also result in sleep disordered breathing, which refers to the spectrum of affected breathing from primary snoring to upper airway resistance and OSA. OSA has an estimated prevalence of 1% to 4% in children.13 Presentation depends on parental report of snoring during sleep, mouth breathing, witnessed apnea with or without gasping or choking episodes, restless sleep, secondary nocturnal enuresis, and daytime behavior problems such as irritability and inattention/hyperactivity. In older children, there may be difficulty in getting up in the morning, daytime somnolence, and poor performance in school. Evaluation should initially include physical examination of the airway. The ability to visualize the posterior pharynx can be documented with either the Friedman tongue position assessment or with the Mallampati airway classification (from class I [complete visualization of soft palate] to class IV [soft palate is not visible at all]); both have shown an association of OSA severity based on PSG data.14 The most reliable inter- and intraobserver scale is the assessment of palatine tonsils and degree of airway crowding (Brodsky grading scale) that is scored from 1 to 4.15 As adenoid hypertrophy cannot be directly visualized on physical examination, endoscopy per otolaryngology and lateral soft tissue neck imaging (Figure 5) should be performed. The gold standard for evaluation of OSA is PSG. Standard pediatric PSG should include monitoring of carbon dioxide values in addition to oxygen saturation. The severity scale for pediatric OSA varies from adult criteria such that fewer respiratory events (apnea hypopnea index [AHI]) are expected and interpretation includes consideration of deviation from normal of both oxygen saturation and carbon dioxide values. In brief, an AHI score 1 to 5 per hour is considered mild, 5 to 10 per hour is moderate, and AHI >10 per hour is severe. First-line management should be surgical intervention with adenoidectomy and/or tonsillectomy, with the literature demonstrating improvement in PSG findings, signs/symptoms of sleep disordered breathing, quality of life measures, and behaviors.16,17 Therefore, referral to pediatric otolaryngology is advised if evidence for OSA is found on PSG. Adenotonsillectomy has a low mortality rate and complications are primarily respiratory or hemorrhage but can also include pain and dehydration.18
Adenoid hypertrophy. Lateral neck X-ray demonstrating adenoid hypertrophy (outlined by red line) causing narrowing of the adjacent airway in the nasopharynx.
Vocal Cord Dysfunction
Paradoxical movement of the vocal cords (adduction during inspiration and possibly expiration) is referred to as vocal cord dysfunction. The prevalence of vocal cord dysfunction (VCD) is not established; although one pediatric study found a prevalence of 27% in pediatric patients presenting with exercise-induced asthma19 and up to 40% in patients with asthma who fail to respond to aggressive therapy.20 Affected patients will present with intermittent shortness of breath, stridor, and wheezing with normal oxygen saturation. It is of note that breathing difficulty predominantly occurs with “breathing in,” and some patients do report tightness in the throat, throat closure, or even upper chest tightness. Therefore, the patient is often misdiagnosed with asthma and will report poor response to bronchodilators, although asthma has been found to be a concomitant diagnosis in patients with vocal cord dysfunction.21 Triggers can include exercise, direct irritant, or strong emotion. In some patients, VCD is triggered by exercise effort, referred to as exercise-induced VCD, or may be provoked by underlying psychological symptoms of anxiety or depression, referred to as a spontaneous VCD.20 Evaluation can include direct visualization of the vocal cords to demonstrate paradoxical movement, which is not easily captured due to the intermittent nature of events and because of the associated discomfort/anxiety of evaluation during an acute episode. Other supportive testing should include pulmonary function tests with flow volume loop demonstrating an inspiratory curve that is flattened or truncated. It is especially true for exercise-induced VCD. Most treatments have not been clearly established but can include speech therapy (teaching patient techniques for relaxing the throat and decreasing cough), psychotherapy (relaxation techniques), biofeedback, control of gastroesophageal reflux, heliox for acute exacerbation, and continuous positive airway pressure therapy.22 There are reports of using an inhaled anticholinergic agent (ipratropium bromide) before exercise and a single-dose, long-acting anticholinergic agent (tiotropium) as a daily preventive therapy with apparent positive effect for patients experiencing frequent spontaneous VCD symptoms.23,24
Subglottic stenosis is a narrowing of the space below the true vocal cords and lower margin of cricoid cartilage, and it may be congenital. It is often associated with other congenital head and neck abnormalities and syndromes such as trisomy 21 or can be acquired secondary to prolonged intubation, difficult or traumatic intubation, or the use of an oversized endotracheal tube. Typical presentation is biphasic stridor due to fixed upper airway obstruction or breathing difficulty that is persistent in severe cases or present intermittently during upper respiratory infections in mild cases. Patients with mild subglottic stenosis may also present with recurrent croup. The diagnosis is confirmed by flexible or rigid laryngoscopy. Patients with severe subglottic stenosis may present with signs and symptoms of severe obstruction, biphasic stridor, and respiratory insufficiency. Tracheostomy may be indicated in severe cases such as severe bronchopulmonary dysplasia, chronic respiratory failure, and ventilator dependence with failure to wean off the ventilator. The pediatric otolaryngologist may also consider serial tracheal dilation among other methods that are beyond the scope of this review.25 Anterior cricoid split may be an alternate to tracheostomy in infants with severe subglottic stenosis.26