Which description matches paradoxical chest wall motion in a flail chest?

• A. Paradoxical motion: inward on inhalation and outward on exhalation
• B. Paradoxical motion: outward on inhalation
• C. Normal chest wall motion
• D. No motion

Answer: (A)

Paradoxical chest wall motion happens when a segment of the chest wall becomes detached from the rest of the rib cage due to multiple fractures, creating a free-floating piece. That unstable segment moves opposite to the normal chest movement: during inhalation, the surrounding chest expands, but the flail segment is pulled inward by the negative pressure inside the chest, so it moves inward. During exhalation, the intrathoracic pressure becomes positive and the same segment bulges outward while the rest of the chest recoils, so it moves outward. This inward motion on inhalation and outward motion on exhalation is the hallmark of a flail chest.