A 10-month-old ex-preterm infant, ventilated for three weeks in the neonatal period, has persistent biphasic stridor that worsens when she cries and during intercurrent respiratory infections. She has had two episodes resembling croup. Which structure is most likely responsible for her stridor?
- A Supraglottis
- B Subglottis ✓
- C Glottis
- D Intrathoracic trachea
Correct answer: B. Subglottis
Explanation
Acquired subglottic stenosis follows prolonged or repeated intubation, particularly in premature infants whose subglottis is the narrowest part of the airway lined by tight cricoid cartilage. It classically produces biphasic stridor, worsens with agitation and infection, and mimics recurrent croup. Supraglottic lesions such as laryngomalacia give inspiratory stridor, while intrathoracic tracheomalacia gives predominantly expiratory stridor, allowing both distractors to be excluded.
Reference: Cummings Otolaryngology: Head and Neck Surgery, 7th ed.
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Written and medically reviewed by the StethoPrep medical team.