Chronic Stridor

The most common cause for inspiratory stridor is laryngomalacia, which accounts for approximately 75% of all cases of neonatal stridor. Laryngomalacia results from the immature cartilage of the upper larynx collapsing inward during inhalation, causing airway obstruction. Vocal cord dysfunction, the second leading cause of stridor in the neonatal period, can be congenital or iatrogenic, such as from damage to the left recurrent laryngeal nerve during ligation of a patent ductus arteriosus or from direct injury to the vocal cord during endotracheal intubation. Congenital subglottic stenosis occurs when there is incomplete canalization of the subglottic airway and cricoid rings. Subglottic stenosis is most often acquired after prolonged intubation in the neonatal period, usually in the setting of extreme prematurity. Tracheomalacia results from a defect in the tracheal cartilage that causes a “floppy” airway lacking the rigidity necessary to maintain patency. Tracheomalacia is the leading cause of expiratory stridor. Tracheal stenosis can be caused by the presence of complete tracheal rings instead of the normally C-shaped rings. Stridor can also result from tracheal compression caused by vascular rings such as a double aortic arch. Other less common causes of chronic stridor include laryngeal papillomas caused by maternal human papillomavirus infection, webs, cysts, hemangiomas, and laryngeal dyskinesia.

Acute Stridor

The causes of acute stridor are primarily infectious in cause with two notable exceptions, foreign body aspiration and allergic reaction. The most common cause of acute stridor is laryngotracheobronchitis, or croup (Figure 36-2). Croup is classically caused by parainfluenza virus but can also be caused by respiratory syncytial virus, influenza, adenovirus, and Mycoplasma pneumoniae. Bacterial tracheitis, usually caused by Staphylococcus aureus, is an uncommon but life-threatening condition that occurs most frequently as a bacterial superinfection in patients who have viral croup.

Figure 36-2 Croup.

Retropharyngeal and peritonsillar abscesses are common infections that can present with acute stridor. Both infections are usually polymicrobial, including β-hemolytic streptococci; oral anaerobic bacteria; and in retropharyngeal abscess, S. aureus. Finally, epiglottitis, traditionally caused by Haemophilus influenzae type B (Hib), is now a rare cause of stridor as a result of the widespread use of the conjugated Hib vaccine.

Chronic Stridor

Laryngomalacia can present at birth but usually presents at 2 to 4 weeks of age. The inspiratory stridor of laryngomalacia is exacerbated when the infant lies supine, cries, or when feeding and is alleviated when the infant is prone.

Vocal cord paralysis can be unilateral or bilateral. Bilateral vocal cord paralysis results in aphonia and high-pitched biphasic stridor, with significant respiratory distress. Unilateral paralysis can cause inspiratory or biphasic stridor, as well as a weak or hoarse cry.

Whereas subglottic stenosis and vascular rings may likewise present with inspiratory or biphasic stridor, tracheomalacia usually presents with expiratory stridor. Tracheomalacia may present with a monophonic wheeze if the obstruction is intrathoracic.

Acute Stridor

Croup occurs most commonly in children age 6 months to 2 years and is characterized by a harsh cough described as “barky” or “seal-like.” Associated upper respiratory symptoms are common, and stridor can be mild, occurring only with crying, or in severe cases, can occur at rest with severe respiratory distress. Bacterial tracheitis is a rare complication of croup, and in addition to stridor. the child also will have high fever and a toxic appearance.

Retropharyngeal abscess usually occurs in children younger than 6 years old before the retropharyngeal lymph nodes atrophy. Patients often have a viral prodome followed by the abrupt onset of high fever, limited neck movement (especially resistance to extension), and occasionally stridor. Unilateral neck swelling may occur as the infection tracks from the retropharyngeal space, and a bulge of the posterior oropharynx may sometimes be present on physical examination. Peritonsillar abscess occurs in preadolescents and adolescents and can present with sore throat, trismus, dysphagia, a “hot potato” or muffled voice, and tender unilateral neck swelling. Asymmetric tonsils, deviation of the uvula, and a fluctuant area are present on physical examination (Figure 36-3). Stridor may be heard if tracheal compression is present. Epiglottitis classically presents with the abrupt onset of high fever, stridor, drooling, “tripod” positioning, and toxicity.

Figure 36-3 Peritonsillar abscess.

Foreign body aspiration should be suspected when stridor occurs acutely in an unobserved toddler. A history of choking or coughing preceded by eating or playing with small objects may be present. Focal wheezing or reduced breath sounds can be heard if the object is lodged in the smaller airways.

Allergic reactions, or anaphylaxis, may present with stridor or wheeze after exposure to a known food or drug allergen but should be suspected in any patient who presents with the acute onset of respiratory distress occurring within 30 minutes of food ingestion. Other signs of anaphylaxis include urticaria, gastrointestinal distress, and hypotension.

Evaluation

Although taking a thorough history is an essential part of elucidating the cause of stridor, initial rapid assessment of airway, breathing, and circulation (the ABCs) can be lifesaving. The practitioner must assess first for impending complete airway obstruction or respiratory failure; observing the patient for severity of work of breathing, intercostal and suprasternal retractions, cyanosis, perfusion, and responsiveness will guide initial management. Although a complete blood count, inflammatory markers (C-reactive protein, erythrocyte sedimentation rate), and blood culture may help guide treatment, none are essential to the initial care of patients with stridor. Arterial blood gas analysis may be helpful in assessing the degree of respiratory compromise, but the physical examination and pulse oximetry are the best tools for developing an immediate treatment plan.

Anteroposterior and lateral radiographs of the neck and chest will allow evaluation of both the upper and lower airways and may be indicated for specific diagnoses. Other imaging modalities such as contrast-enhanced computed tomography and fluoroscopy may also be used. Further imaging may be indicated for specific cases (Table 36-1).

Table 36-1 Diagnostic Approach to Stridor

CT, computed tomography; DL, direct laryngoscopy.

Management

Congenital causes of stridor often self-resolve but may necessitate surgical intervention. Laryngomalacia usually resolves spontaneously by 2 years of age. Surgical intervention such as supraglottoplasty or laryngeal reconstruction is indicated if obstruction is significant or if the patient exhibits severe failure to thrive. Similarly, unilateral vocal cord paralysis in infancy usually resolves by age 2 years with no intervention. However, in the setting of bilateral vocal cord paralysis or persistent aspiration, tracheostomy is often indicated. The presence of subglottic stenosis may necessitate tracheostomy, particularly if the patient has persistent respiratory compromise. Definitive surgical correction with laryngeal reconstruction is often needed in severe cases.

Similar to other viral processes, croup self-resolves in approximately 7 days with maximal severity of symptoms usually occurring on the third or fourth day of illness. A single dose of oral or intramuscular dexamethasone has been shown to improve symptoms and prevent return to medical care. If the stridor occurs at rest or the patient is in moderate to severe distress, racemic epinephrine can be given via nebulizer for temporary relief.

The bacterial infectious causes of stridor all require antibiotics (Table 36-2). Peritonsillar and retropharyngeal abscesses often require drainage as well because antibiotic penetration of the abscess may not be optimal. Epiglottitis is an entity that should be considered a medical emergency necessitating immediate intubation for airway protection.

Table 36-2 Treatment for Bacterial Causes of Stridor

Stridor caused by anaphylaxis requires the immediate intramuscular injection of epinephrine, which the patient can self-administer at home via EpiPen. Adjunctive treatments include antihistamines and systemic corticosteroids. If foreign body aspiration is strongly suspected or diagnosed on radiography, rigid bronchoscopy is necessary to remove the object, often from the right main stem bronchus.