After endotracheal intubation, breath sounds are faint on the right side. What is the most likely diagnosis?

• A. Pneumothorax on the right side
• B. Hemothorax on the right side
• C. Atelectasis of the left lung
• D. Pneumothorax on the left side

Answer: (A)

Unilateral decrease in breath sounds after endotracheal intubation points to a problem on that same side. A pneumothorax occurs when air leaks into the pleural space around the ventilated lung, causing the lung to collapse and muffling or eliminating breath sounds on the affected side. So faint sounds on the right specifically indicate a right-sided pneumothorax.

The other scenarios don’t fit as neatly: a left-sided pneumothorax would cause faint sounds on the left; a hemothorax could reduce sounds but is less directly linked to the intubation event and may present with additional signs like dullness to percussion; atelectasis of the opposite lung would produce decreased sounds on that opposite side; and misplacement of the tube into the right mainstem bronchus would typically leave the right lung well-ventilated with reduced sounds on the left. Thus, the right pneumothorax best explains the finding.