What best defines tension pneumothorax?

• A. Air trapped under pressure compressing lungs/heart
• B. Air in the pleural space without pressure
• C. Blood in the pleural space causing shock and respiratory compromise
• D. Fluid in the pericardial sac compressing the heart

Answer: (A)

Tension pneumothorax is defined by air entering the pleural space and becoming trapped under positive pressure, which causes the affected lung to collapse and pushes the mediastinal structures (including the heart) toward the opposite side. This pressure impedes venous return to the heart and can rapidly lead to life-threatening a drop in cardiac output and shock. That combination of trapped air and resulting compression of lung and heart is what sets tension pneumothorax apart from other conditions.

The other scenarios don’t fit this definition: air in the pleural space without a pressure buildup describes a simple pneumothorax; blood in the pleural space is a hemothorax; and fluid in the pericardial sac compressing the heart is cardiac tamponade.