(See also Overview of Thoracic Trauma.)
A single rib may fracture in more than one place. If multiple (3 or more) 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 of flail chest 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 to patients with flail chest. 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). In select patients with flail chest (patients who cannot be weaned from the ventilator or who require thoracotomy for other reasons), operative fixation of ribs may reduce the risk of pneumonia, length of hospital stay, duration of mechanical ventilation, and death (1).
Simon B, Ebert J, Bokhari F, et al: Management of pulmonary contusion and flail chest: An Eastern Association for the Surgery of Trauma practice management guideline. J Trauma and Acute Care Surgery 73(5 Suppl 4):S351-S361, 2012. doi: 10.1097/TA.0b013e31827019fd.