What condition involves the collection of air in the pleural space?

The condition that involves the collection of air in the pleural space is pneumothorax. This occurs when air leaks into the pleural cavity, which is the space between the lungs and the chest wall. The presence of air in this cavity can cause the lung on that side to collapse partially or completely, leading to respiratory distress. Recognizing pneumothorax is crucial, as it requires immediate medical attention to restore proper pressure in the pleural space and allow the lung to re-expand.

In contrast, pleural effusion refers to the accumulation of fluid in the pleural space, hydrothorax specifically denotes the presence of serous fluid, often due to heart failure or other causes, while emphysema is a progressive lung disease that involves the destruction of the alveoli but does not specifically refer to the presence of air in the pleural space.