Thoracic Trauma — Recognition of Flail Chest
A 45-year-old man is brought in after a high-speed car crash in which his chest struck the steering wheel. Blood pressure is 92/60 mm Hg and pulse 118 beats/min. A segment of the right anterolateral chest wall moves inward on inspiration and outward on expiration, with crepitus over several ribs. The trachea is midline and breath sounds are present bilaterally. Which injury explains the abnormal chest wall movement?
- A.Pulmonary contusion
- B.Blunt cardiac injury
- C.Tension pneumothorax
- D.Flail chestCorrect
Explanation
Paradoxical movement of a chest wall segment, drawn in during inspiration and pushed out during expiration, is the defining sign of flail chest. It occurs when three or more adjacent ribs are each fractured in two or more places, so the segment loses continuity with the rest of the thoracic cage and follows pleural pressure rather than muscle action. The movement itself rarely causes the hypoxia; the underlying pulmonary contusion and pain-limited ventilation do, which is why treatment centres on oxygen, strong analgesia including regional blocks, careful fluids, and ventilation if gas exchange fails. Pulmonary contusion almost always accompanies a flail segment but does not produce paradoxical motion. Tension pneumothorax causes hypotension with tracheal deviation and absent breath sounds, both absent here. Blunt cardiac injury may explain hypotension or arrhythmia, and warrants an ECG and troponin in any steering-wheel impact, but it does not alter chest wall mechanics. Hypotension in this man still requires a search for haemorrhage in the chest, abdomen and pelvis. Surgical rib fixation is increasingly used for selected flail segments.
Why each option
- A.
- Contusion usually lies beneath a flail segment and causes hypoxia, but it does not produce paradoxical movement of the chest wall.
- B.
- Cardiac injury can cause hypotension or arrhythmia after steering-wheel impact, yet it leaves chest wall mechanics unchanged and needs ECG screening.
- C.
- Tension pneumothorax gives tracheal deviation and absent breath sounds on the affected side, neither of which is present in this patient.
- D.
- Correct. A segment moving inward on inspiration with multiple rib crepitus reflects ribs fractured in two places, defining a flail chest.
Reference: American College of Surgeons ATLS Student Course Manual, 10th edition (2018); EAST Practice Management Guideline: Management of pulmonary contusion and flail chest (2012)
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