Upper-airway obstruction and stridor

Overview & Definition

A three-year-old who was well yesterday now barks like a seal, and every breath in makes a harsh crowing noise you can hear across the room. That sound is stridor, and it is the single most useful clue in the whole of paediatric airway medicine: it tells you the obstruction sits in the large upper airway, and its timing in the breath tells you roughly where. Upper-airway obstruction is any narrowing from the nose to the large intrathoracic airways that impedes the movement of air, and stridor is the harsh, monophonic sound turbulent flow makes as it squeezes past that narrowing. [1]

Stridor is a sign, not a diagnosis, and the whole skill lies in reading it. Inspiratory stridor points to an obstruction above or at the larynx, where the extrathoracic airway collapses inward on the negative pressure of inspiration. Expiratory stridor points below the thoracic inlet, where positive intrathoracic pressure narrows the airway in expiration. Biphasic stridor — heard on both phases — points to a fixed narrowing at or just below the vocal cords, classically the subglottis. Naming the phase, the time course and the child's overall stability is worth more than any single investigation. [1]

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