A 5-year-old presents with a 2-month history of noisy breathing that occurs predominantly during expiration, accompanied by a monophonic wheeze. Flexible endoscopy through the nose and pharynx is normal. The most likely site of obstruction is:

• A Supraglottic larynx
• B Trachea or bronchus ✓
• C Subglottis
• D Glottis

Explanation

Expiratory stridor localises to intrathoracic airways, the trachea and bronchi, where positive intrathoracic pressure during expiration dynamically collapses a compliant narrowed segment. Supraglottic lesions such as laryngomalacia produce inspiratory stridor, glottic and subglottic lesions produce biphasic stridor, and a normal flexible nasendoscopy further supports a lesion beyond the larynx. A monophonic wheeze suggests fixed large airway narrowing rather than variable small airway disease.

Reference: Scott-Brown's Essential Otorhinolaryngology, 2nd ed.

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Written and medically reviewed by the StethoPrep medical team.