Stridor is an abnormal, high-pitched, musical breathing sound. It is caused by a blockage or narrowing in the upper airways. It is more often heard during inspiration, frequently without the aid of a stethoscope.
In children stridor can be heard as a symptom of croup, a viral respiratory infection.
When a child has swallowed a foreign object and it has lodged in the upper airways, stridor sounds can be heard.
In adults, stridor breath sounds are often due to vocal cords problems. Vocal cord dysfunction can cause partial upper airways blockage resulting in stridor sounds. It occurs in 10-20% of extubated patients.
Causes of stridor are pertussis, croup, epiglottis, aspirations.
Stridor will be heard as a loud, high-pitched breath sound typically heard during inspiration. It can also occur throughout the respiratory cycle particularly as a patient's condition worsens. In children, stridor may become louder in the supine position.
The waveform of stridor sounds is not typically used in clinical practice. However it can be a useful tool for learning auscultation of lung and heart sounds.