What term refers to air trapped in the pleural space?

• A. Hemothorax
• B. Pleural effusion
• C. Atelectasis
• D. Pneumothorax

Answer: (D)

Air in the pleural space is called pneumothorax. The pleural space normally has a tiny amount of fluid and negative pressure that keep the lung expanded against the chest wall. When air leaks into that space, this negative pressure is lost and the lung may collapse partially or completely, producing sudden chest pain and shortness of breath. This is different from a hemothorax (blood in the pleural space) and a pleural effusion (fluid in the pleural space). Atelectasis refers to collapse of lung tissue itself, not air between the lung and chest wall. On exam you might hear decreased or absent breath sounds on the affected side and a hyperresonant sound when tapping the chest; imaging typically shows a pleural line with lung markings beyond it. In a tension pneumothorax, the pressure buildup can compress the heart and great vessels, requiring urgent intervention.