In tension pneumothorax, which radiographic or physiologic change is typical?

• A. Mediastinal shift toward the affected side
• B. Mediastinal shift away from the affected side
• C. Left axis deviation
• D. No change on radiograph

Answer: (B)

In tension pneumothorax, air builds up under high pressure in the pleural space, pushing the mediastinal structures away from the affected side. This shift of the mediastinum (and often the trachea) to the opposite side reflects the space-occupying force of the trapped air and the resulting compression of the opposite lung. The pressure also decreases venous return to the heart, leading to hypotension and tachycardia. So the typical radiographic or physiologic change is mediastinal shift away from the side with the pneumothorax.