Which statement best describes the basic mechanism of a spontaneous pneumothorax?

• A. A hole in the lung without injury that allows air to enter the pleural space
• B. Fluid around the heart
• C. Buildup of mucus in the bronchial tubes
• D. Air enters the pleural space without injury

Answer: (A)

A spontaneous pneumothorax occurs when air leaks into the pleural space because part of the lung surface ruptures, usually from a small bleb or blister that bursts without any chest injury. This rupture creates a hole in the lung, allowing air to escape into the pleural space—the gap between the lung and chest wall. When air collects there, the pressure balance changes and the lung cannot stay fully expanded, leading to partial or complete collapse of the lung on the affected side. This is why the statement describing a hole in the lung that lets air into the pleural space best captures the mechanism. The other options point to different problems (fluid around the heart, mucus buildup in the airways) or are too vague about the source of the air entering the pleural space.