A patient presents to the emergency department with paradoxical chest wall movement, crepitus, hypotension, tachypnea, and tachycardia. What is the most likely diagnosis?

Flail Chest

The diagnosis is flail chest, not isolated pulmonary contusion. The combination of paradoxical chest wall movement, crepitus, hypotension (BP 90/60), tachypnea (RR 32), and tachycardia (HR 110) is pathognomonic for flail chest with underlying pulmonary contusion and impending respiratory failure 1.

Diagnostic Criteria

Paradoxical chest wall movement is the defining clinical sign of flail chest and occurs when three or more consecutive ribs are fractured in two or more places, creating a free-floating segment that moves inward during inspiration and outward during expiration 1, 2.

• Crepitus on palpation indicates subcutaneous emphysema from air leaking through fractured ribs and pleural injury 1
• The hemodynamic instability (hypotension, tachycardia, tachypnea) reflects the severity of underlying pulmonary contusion combined with pain-induced hypoventilation and potential hemorrhage 1, 3
• Flail chest occurs in only 2-4% of blunt chest trauma but carries a mortality of 10-15% 4

Why Not Isolated Pulmonary Contusion?

While pulmonary contusion is almost always present with flail chest, paradoxical chest wall movement cannot occur from contusion alone—it requires the mechanical instability of multiple segmental rib fractures 1, 5. The visible chest wall abnormality and palpable crepitus are skeletal findings, not parenchymal injury 2.

Immediate Management Algorithm

Airway and Breathing (First Priority)

• Provide high-flow oxygen immediately to maintain SpO2 >94% 3
• Do NOT routinely intubate based solely on the flail segment—obligatory mechanical ventilation in the absence of true respiratory failure increases mortality and complications 5, 3
• Consider non-invasive positive pressure ventilation (CPAP/BiPAP) as first-line respiratory support in alert patients with marginal respiratory status 3

Intubation is indicated only if:

• PaO2/FiO2 ratio <150 despite supplemental oxygen 3
• Inability to protect airway or clear secretions 1
• Progressive respiratory acidosis or exhaustion 1
• Altered mental status 1

Pain Control (Critical for Preventing Respiratory Failure)

Epidural analgesia is the preferred mode for severe flail chest because it provides superior pain control, reduces the need for mechanical ventilation, and improves pulmonary mechanics 3.

• Paravertebral nerve blocks are an acceptable alternative when epidural is contraindicated 3
• Intercostal nerve blocks can be used but require repeated administration 5
• Adequate analgesia is more important than mechanical stabilization of the paradoxical segment 5, 3

Fluid Resuscitation

Resuscitate to adequate tissue perfusion but avoid excessive fluids 1, 3.

• The underlying pulmonary contusion will worsen with fluid overload 5, 3
• Target mean arterial pressure >65 mmHg with balanced crystalloid 3
• Once resuscitated, restrict maintenance fluids and consider diuretics if signs of volume overload develop 5, 3

Chest Wall Stabilization

External stabilization with pressure dressings should be applied when the paradoxical segment is 3-5 cm or larger, as this degree of instability causes severe respiratory and circulatory dysfunction 1.

• Use local padding with multi-head chest straps for temporary stabilization 1
• Surgical fixation with titanium plates should be considered if the patient fails to wean from mechanical ventilation after 72 hours or requires thoracotomy for other injuries 2, 6, 3
• Surgical stabilization reduces ventilator days, ICU length of stay, and respiratory complications 2, 6, 3

Diagnostic Imaging

• Chest X-ray will show multiple rib fractures but may underestimate the severity 2
• CT chest with 3D reconstruction is essential to define the full extent of rib fractures, identify sternal fractures, and assess for hemothorax or pneumothorax 1, 2
• Cartilage reconstruction on CT can reveal severe flail chest missed on standard bone windows, particularly with costochondral separations 2

Common Pitfalls to Avoid

• Do not externally stabilize the chest wall by taping or binding circumferentially—this restricts chest expansion and worsens respiratory mechanics 1
• Do not use corticosteroids—they have no benefit in pulmonary contusion and may increase complications 3
• Do not delay adequate analgesia—inadequate pain control is the primary driver of respiratory failure in flail chest 4, 5, 3
• Do not assume the patient needs immediate intubation—most patients with flail chest can be managed without mechanical ventilation if pain is controlled and the underlying contusion is treated appropriately 5, 3

Monitoring and Disposition

• Admit to ICU for continuous cardiopulmonary monitoring 1
• Serial arterial blood gases to detect early respiratory decompensation 3
• Aggressive pulmonary toilet with incentive spirometry and chest physiotherapy 3
• Consider surgical consultation within 72 hours if ventilator weaning is unsuccessful 6, 3