Flail chest is defined as what?

• A. Paradoxical motion of the chest due to multiple rib fractures
• B. Dullness to percussion
• C. Hyperresonant chest wall
• D. Increased breath sounds on affected side

Answer: (A)

Flail chest is defined by paradoxical motion of a chest wall segment caused by multiple rib fractures. When two or more adjacent ribs are fractured in multiple places, the detached segment moves in the opposite direction to the rest of the chest: it retracts inward during inspiration and protrudes outward during expiration. This abnormal movement compromises ventilation to the affected area and can worsen oxygenation, often alongside underlying lung injury such as contusion.

Dullness to percussion suggests fluid or solid tissue in the thorax, not chest-wall instability. A hyperresonant finding points toward air in the pleural space or overinflation, not the paradoxical movement that defines flail chest. Increased breath sounds on the affected side are not characteristic of this condition and don’t describe its defining feature.