General Discussion

Stridor is defined as turbulent airflow through a narrowed segment of airway or air passages. The word stridor is derived from the Latin “stidere” or “stridulus” signifying to whistle, creak, or make a harsh noise.

Stridor is not a disease; rather, it is a symptom of underlying airway or soft tissue pathology. Although a relatively common finding in pediatric populations, patients presenting with stridor require a prompt and careful evaluation. The patient’s age, history, and physical examination findings will provide clues to the underlying cause of stridor.

The most common cause of congenitally acquired stridor is laryngomalacia. Occurring most often in children younger than 2 years of age, laryngomalacia is due to delayed maturation of the structures supporting the airway. The most common cause of acquired stridor is croup, caused by parainfluenza virus. Croup accounts for 80% to 90% of stridor seen in children aged 1 to 4 years. Often croup is accompanied by a characteristic barking or harsh-sounding cough.

Anatomically, stridor is a phenomenon caused by narrowing of the upper airway. The upper airway may be divided into supraglottic, glottic and subglottic, and intrathoracic areas. These anatomic distinctions are essential in targeting the possible causes of stridor (Figure 42-1). The supraglottic area includes the nasopharynx, epiglottis, larynx, aryepiglottic folds, and false vocal cords. The glottic and subglottic area extends from the vocal cords to the extrathoracic portion of the trachea.

Figure 42-1 Algorithm, based on clinical findings, for evaluating stridor in children.

(Adapted with permission from Handler SD. Stridor. In: Fleisher GR, Ludwig S, eds. Textbook of Pediatric Emergency Medicine. Baltimore: Williams & Wilkins; 1993:474–478.)

Stridor heard on inspiration signals airway obstruction in the supraglottic area. Obstruction in the intrathoracic cavity usually results in stridor that is more pronounced during exhalation. Biphasic stridor is the product of obstruction at the glottic or subglottic area, although obstruction in this area may result in inspiratory stridor alone.

Epiglottits, retropharyngeal abcess, and diphtheria infections are among the common causes of inspiratory stridor. Biphasic stidor is most commonly associated with croup, laryngomalacia, or vocal cord paralysis. Stridor that originates from the thorax is most commonly associated with foreign body ingestion.

If a bacterial cause is suspected, rapid and decisive action must be taken.

A patient with an infection of the soft tissue spaces of the neck often will appear toxic and may lie supine with the neck extended in an effort to maintain airway patency. Drooling and the use of the accessory muscles of the neck and abdomen are signs of airway compromise. This patient may require endotracheal intubation or tracheotomy to protect the airway.

Causes of Stridor

Supraglottic area

Glottic and Subglottic Area

• Bacterial tracheitis

• External compression of the trachea

Anomalous left common carotid artery

Gastroesophageal reflux disease (GERD)

Lymphadenopathy

Lymphoma

Mediastinal cyst

Right aortic arch with left ligamentum arteriosum

• Tracheomalacia

• Vocal cord paralysis

Intrathoracic

• External compression of the trachea

Aberrant subclavian artery

Anomalous innominate artery

Anomalous left pulmonary artery

Double aortic arch

Lymphadenopathy

Lymphoma

Right aortic arch with left ligamentum arteriosum

Teratoma

• Foreign body

Key Historical Features

Age at time of onset (in neonates up to age 6 weeks), congenital abnormalities such as micrognathia, macroglossia, choanal atresia, vocal cord paralysis, laryngeal web, and vascular ring are most likely. Laryngomalacia is the most common cause of chronic stridor in children younger than 2 years. In children aged 1 to 4 years, foreign-body-aspiration and infectious etiologies such as croup and epiglottitis are the most likely causes.

Key Physical Findings

Suggested Work-up

The most important step in the evaluation of a child with stridor is to determine the degree of airway compromise and the potential for respiratory failure. Prompt airway visualization is essential if epiglottitis or bacterial tracheitis is suspected as the cause of stridor in an acutely ill child. In such cases, airway visualization should be performed by clinicians experienced in managing pediatric airways in a facility equipped with appropriate resuscitation equipment. If the patient does not have a stable airway or needs a thorough evaluation, rigid laryngoscopy, bronchoscopy, or both should be performed in the operating room with anesthesia, sedation, and continuous monitoring.

Additional Work-up