Stridor

Stridor is a pathological listening finding that belongs to the so-called distance phenomena (sounds audible even from a distance, without a stethoscope). It is caused by a narrowing of the airways. We distinguish between congenital and acquired stridor. It is clinically important to distinguish inspiratory from expiratory.

Inspirational stridor makes a coarser, hoarse sound during the breath. It is caused by a narrowing of the upper respiratory tract (obstructive laryngitis, acute epiglottitis, retropharyngeal abscess). It is usually associated with inspirational shortness of breath  with prolongation of inspiration.

The expiratory stridor is a quieter, whistling or creaking sound during exhalation. It is caused by a narrowing of the lower respiratory tract (foreign body, inflammatory mucosal edema in acute bronchitis, contraction of bronchial smooth muscle in bronchial asthma). It is often accompanied by expiratory dyspnea and prolongation of expiration.

Inspirational-expiratory stridor is caused by a narrowing in the trachea area (tracheomalacia, oppression of the trachea by an abnormal vessel).

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