Stridor is an abnormal, high-pitched sound produced by turbulent airflow through a partially obstructed airway at the level of the supraglottis, glottis, subglottis, or trachea.  Its tonal characteristics are extremely variable (i.e., harsh, musical, or breathy); however, when combined with the phase, volume, duration, rate of onset, and associated symptoms, the tonal characteristics of the sound may provide additional diagnostic clues. It is often heard without a stethoscope.
It occurs in 10-20% of extubated patients.Stridor may be inspiratory (most common), expiratory, or biphasic, depending on its timing in the respiratory cycle, and the three forms each suggest different causes, as follows:
  • Inspiratory stridor suggests a laryngeal obstruction
  • Expiratory stridor implies tracheobronchial obstruction
  • Biphasic stridor suggests a subglottic or glottic anomaly
  • In children, stridor may become louder in the supine position
  • Causes of stridor are pertussis, croup, epiglottis, aspirations.

Maneuver: Seated
Chestpiece Position: Chest wall
Chestpiece: Diaphragm