Flail chest pathophysiology

(A) Flail chest occurs when multiple rib fractures result in a loss of stability of the chest wall. The loss of continuity with the remainder of the rib cage causes the flail segment to move paradoxically.
(B) Pressure within the chest is negative during inspiration, causing the flail segment to retract.
(C) With expiration, intrathoracic pressure becomes positive and the flail segment bulges.