What chest finding indicates a flail chest?

• A. Flail chest
• B. Tension pneumothorax
• C. Cardiac tamponade
• D. Rib contusion

Answer: (A)

Paradoxical chest wall motion is the hallmark of this finding. When a segment of the chest wall is free due to multiple rib fractures, that portion moves opposite to the rest of the chest during breathing—sinking inward on inspiration and bulging outward on expiration. This opposite movement, or paradoxical motion, identifies a flail chest and reflects the instability of the chest wall that disrupts normal ventilation. It often occurs with underlying lung injury like contusion and can lead to severe breathing difficulty.

Other chest injuries don’t show this paradoxical movement: tension pneumothorax typically presents with rapid distress, hyperresonance, diminished or absent breath sounds, and often tracheal deviation; cardiac tamponade shows hypotension, jugular venous distension, and muffled heart sounds; rib contusion causes focal chest wall tenderness without the characteristic paradoxical motion.