Tension pneumothorax can cause what potentially life-threatening shift?

• A. Mediastinal shift
• B. Cardiac tamponade
• C. Pulmonary embolism
• D. Aortic dissection

Answer: (A)

In tension pneumothorax, air enters the pleural space and is trapped under pressure. That rising intrapleural pressure on the affected side pushes the mediastinal structures, including the heart and great vessels, toward the opposite side. This mediastinal shift is life‑threatening because it compresses the remaining lung and, more critically, impedes venous return to the heart, drastically reducing cardiac output and causing shock. That displaced mediastinal position can be seen clinically as tracheal deviation and distended neck veins, and it underlies the urgent need for decompression.

The other conditions are different problems: cardiac tamponade involves fluid around the heart restricting its filling; a pulmonary embolism blocks blood flow within the pulmonary arteries; and an aortic dissection is a tear in the aorta. None of these describe a shift of the mediastinal contents caused by air under pressure in the pleural space.