Stridor in infants: Etiologies

Advanced, Organ-Based and Clinical Sciences

Stridor in infants occurs typically secondary to the following etiologies:

1. Infectious 

a. Croup (laryngotracheobronchitis)- most commonly caused by parainfluenza virus as well as influenza and RSV.  Inflammation and swelling occurs below the level of the vocal chords. Croup presents as barking cough and breathing difficulty.  Subglottic narrowing (steeple sign) is classically on chest x-ray. 

b. Epiglottitis – Caused by Haemophilus influenza type b.  Less common due to widespread vaccination.  Epiglottitis is associated with a more toxic presentation with the patient leaning forward with an open mouth or in the exaggerated sniffing position.  Chest x-ray shows an enlarged epiglottis (thumb sign).

2. Anatomical 

a. Laryngomalacia – Most common cause. Floppy tissue above vocal chords blocks airway with inspiration. Usually appears at birth or first month of life.  Improves with age, frequently resolves by 18 to 20 months.

b. Vocal cord paralysis – Can be congenital or due to mechanical injury after neck, esophageal, or cardiac surgery.

c. Subglottic stenosis – often due to history of prolonged intubation as neonate

d. Vascular rings – Compression of airway due to artery or vein

3. Mechanical 

a. Post-extubation stridor or croup – In infants, most commonly due to use of an ETT that is too large or when the cuff is overinflated.  This results in venous congestion and edema.  Best predictor or post-extubation stridor is lack of an air leak when 30 cm H2O pressure is applied to ETT.  Presentation includes nasal flaring, audible stridor, retractions, tachypnea and decreased oxygen saturation.  Management includes humidified oxygen, racemic epinephrine, or reintubation.  Pre-treatment with steroids helps relieve edema. 

b. Foreign body obstruction – Aspiration of a foreign body such as a peanut can cause stridor.  Treatment is removal of the foreign body.


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James Dagenhart, MD