A resident is taught to localise the level of airway obstruction from the character of stridor. A child has noise during both inspiration and expiration, continuous through the respiratory cycle. At which level is this biphasic stridor most likely produced?

• A Supraglottis, such as laryngomalacia
• B Glottis or subglottis, such as vocal cord pathology or subglottic stenosis ✓
• C Distal bronchi, such as asthma
• D Nasopharynx, such as adenoid hypertrophy

Explanation

Stridor character localises the lesion: purely inspiratory stridor suggests a supraglottic or extrathoracic lesion that collapses inward on inspiration, purely expiratory stridor suggests intrathoracic tracheobronchial disease, and biphasic stridor indicates a fixed obstruction at the glottis or subglottis where airflow is turbulent in both phases. Asthma produces wheeze rather than stridor, and adenoid hypertrophy gives snoring-type inspiratory noise without expiratory component.

Reference: Dhingra's Diseases of Ear, Nose and Throat, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.