STRIDOR

ERIC C. HOPPA, MD AND HOLLY E. PERRY, MD

Stridor, although a relatively common occurrence, can be frightening to both children and parents. The presence of stridor necessitates a complete and careful evaluation to determine the cause of this worrisome and occasionally life-threatening symptom. This chapter presents the causes of stridor and provides the emergency practitioner with guidelines for initial evaluation and management.

PATHOPHYSIOLOGY

Stridor is a respiratory sound caused by turbulent airflow through a partially obstructed upper airway. Stridor can be inspiratory, expiratory, or biphasic depending on the level of airway obstruction. Inspiratory stridor occurs with obstruction of the extrathoracic trachea, biphasic stridor when the obstruction is at the level of the glottis or subglottis, and expiratory stridor when only the intrathoracic trachea is involved. The pitch of the stridor also varies with the location of the obstruction. Laryngeal and subglottic obstructions are associated with high-pitched stridor. In contrast, obstruction of the nares and nasopharynx results in a lower-pitched snoring or snorting sound called stertor. Because the passage of saliva and the flow of air are impeded in pharyngeal obstruction, these patients often have a gurgling quality of breathing. The relative length of inspiratory and expiratory phases may be helpful in localizing the airway obstruction. Laryngeal obstruction results in an increased inspiratory phase, whereas expiration tends to be prolonged in bronchial obstruction. Both inspiratory and expiratory phases are increased in patients with tracheal obstruction.

DIFFERENTIAL DIAGNOSIS

Stridor may occur in a wide variety of disease processes affecting the large airways from the level of the nares to the bronchi, but most often arises with disorders of the larynx and trachea (Table 70.1). For the purposes of differential diagnosis, it is helpful to categorize the common causes of stridor as acute or chronic in onset and to further divide acute onset into febrile and afebrile causes (Table 70.2). Life-threatening causes of stridor must be considered early during the evaluation process (Table 70.3).

Stridor with Acute Onset in the Febrile Child

Laryngotracheitis (croup) is by far the most common cause of stridor in the febrile child. Other diagnoses that should be considered include bacterial tracheitis, epiglottitis, and much less commonly retropharyngeal abscess or laryngeal diphtheria in the unimmunized child (see Chapter 102 Infectious Disease Emergencies). Though less common than croup, these diseases have a greater potential for life-threatening airway compromise.

Croup most commonly affects children between 7 and 36 months of age with peak incidence around 2 years of age but can be seen throughout childhood. Croup typically begins with symptoms of an upper respiratory tract infection and fever, usually ranging from 38° to 39°C (100.4° to 102.2°F). Within 12 to 48 hours, a barky, “seal-like” cough and inspiratory stridor are noted. The stridor is worsened when the child is agitated and often improves with nebulized racemic epinephrine. Supraclavicular and subcostal retractions may be present. Most children appear mildly to moderately ill, though the loud breathing and respiratory distress can be very alarming to family members.

Bacterial tracheitis has a varied presentation but can resemble croup. Patients tend to be older, appear more toxic, and may not improve as much as expected with nebulized racemic epinephrine. Dysphagia is common, and drooling may be present. The verbal child may complain of anterior neck pain or a painful cough.

Epiglottitis is an infection of the supraglottic structures. Historically, epiglottitis was most commonly caused by Haemophilus influenzae type B. Other causative pathogens include Staphylococcus aureus, Streptococcus pneumoniae, β-hemolytic streptococci, and viral agents (parainfluenza, HSV 1, and varicella). Noninfectious causes can include direct trauma and thermal injury. The incidence of epiglottis due to H. influenzae has plummeted to as low as 0.02 per 100,000 in Western countries following the introduction of the conjugate vaccine. Sporadic cases are seen in unimmunized children or vaccine failures. Patients with H. influenzae epiglottitis typically appear toxic with fever and drooling. Respiratory distress and a tripod stance (upright position, neck extended, and mouth open) are characteristic symptoms. Sudden airway compromise may occur and can be precipitated by the manipulation of the oropharynx.

In contrast, epiglottitis caused by pathogens other than H. influenzae has a more insidious onset, is more common in older children and adults, and is almost universally associated with dysphagia or sore throat. Importantly, the risk of airway compromise is less in this population. However, any child with suspected epiglottitis should be managed as if he or she has disease caused by H. influenzae with risk of imminent airway compromise.

A retropharyngeal abscess is an infrequent cause of stridor. Patients more commonly present with fever, limitation of neck movement, agitation, or lethargy. Physical examination may reveal midline fullness of the oropharynx.