CHAPTER 75 ■ STRIDOR ERIC C HOPPA, HOLLY E PERRY INTRODUCTION 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 lifethreatening symptom This chapter presents the causes of stridor and provides the emergency clinician 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 anatomic 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, usually with a fixed obstruction, 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 75.1 ) 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 75.2 ) Life-threatening causes of stridor must be considered early during the evaluation process ( Table 75.3 )