A 2-year-old is brought to the emergency department after witnessed aspiration of a peanut. Chest X-ray shows hyperinflation of the right lung. Which mechanism explains this radiographic finding?
- A Complete obstruction of the right main bronchus causing lobar collapse
- B Reflex bronchospasm triggered by chemical irritation from peanut oil
- C Partial obstruction acting as a ball-valve, allowing air entry but impeding expiration ✓
- D Mediastinal shift due to tension pneumothorax
Correct answer: C. Partial obstruction acting as a ball-valve, allowing air entry but impeding expiration
Explanation
Foreign body impaction in the right main bronchus (most common in children due to more vertical orientation) causes partial obstruction with a ball-valve mechanism — the bronchus widens slightly during inspiration allowing air entry, but narrows during expiration trapping air, producing obstructive emphysema (hyperinflation) of the ipsilateral lung. Complete obstruction would cause collapse/atelectasis, not hyperinflation. Chemical irritation may cause bronchospasm but not unilateral hyperinflation.
Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.