Flail chest is multiple adjacent rib fractures that result in a segment of the chest wall separating from the rest of the thoracic cage; it is a marker for injury to the underlying lung.
(See also Overview of Thoracic Trauma.)
A single rib may fracture in more than one place. If multiple adjacent ribs fracture in ≥ 2 places, the breaks in each rib result in a segment of chest wall that is not mechanically connected to the rest of the thoracic cage (flail segment). This flail segment moves paradoxically (ie, outward during expiration and inward during inspiration—see Figure: Flail chest.).
Patients are at high risk for respiratory complications, mainly because the large amount of force required to cause a flail chest typically causes a significant underlying pulmonary contusion. In addition, the paradoxical motion of flail chest increases the work of breathing, and chest wall pain tends to limit deep inspiration and thus maximal ventilation.
Diagnosis is clinical, ideally by observing the paradoxical motion of the flail segment during breathing. However, this motion may be difficult to see if inspiratory depth is limited by pain or obtundation due to other injuries. The paradoxical motion does not occur if the patient is mechanically ventilated, but the flail segment may be identified by its more extreme outward movement during lung inflation. Palpation can often detect crepitus of the flail segment and confirm abnormal chest wall motion.
Chest x-ray can help confirm bone fractures and usually shows underlying pulmonary contusion; x-ray does not show cartilaginous disruption.
Humidified oxygen is given. Analgesics may help improve ventilation by decreasing pain during breathing, but ventilation may need to be supported mechanically. Volume status should be closely monitored because harm can result from either hypovolemia (due to lung hypoperfusion) or hypervolemia (due to pulmonary edema).