Flail Chest

Flail chest is a life threatening chest wall injury in which three or more adjacent ribs are fractured in two or more places (or the sternum is detached with costal fractures), creating a segment that moves independently of the thorax. It occurs in about 5 to 10% of those with blunt chest injury, and in a larger share of those with severe trauma (road traffic crashes, falls from height, crush injuries).

The main problem is not the paradoxical movement but the underlying pulmonary contusion, pain related hypoventilation, atelectasis and poor cough. Mortality is about 10 to 20% overall and higher in the elderly and those with comorbidity or associated injuries.

Pathophysiology. The unstable segment is sucked in on inspiration and pushed out on expiration, wasting tidal volume and increasing the work of breathing. Underlying lung contusion causes intrapulmonary shunt and hypoxaemia, while pain reduces cough and breathing, leading to sputum retention, atelectasis and pneumonia. The injury is worst on days 2 to 3 as contusion evolves.

Severe chest pain, tachypnoea, shallow breathing, bruising, crepitus and chest wall tenderness. Paradoxical movement may be masked at first by muscle spasm and appears as the patient tires or after intubation is removed. Hypoxaemia, subcutaneous emphysema and signs of pneumothorax or haemothorax may be present. Associated injuries are common (head, abdomen, spine, great vessels).

Respiratory rate over 35, falling oxygen saturation, exhaustion, hypotension or a rising arterial carbon dioxide needs urgent airway and ventilatory assessment.

• Clinical diagnosis by observing paradoxical chest wall movement and palpating crepitus, with the trauma primary survey.
• Chest radiograph: multiple rib fractures, and associated pneumothorax, haemothorax or contusion, but it underestimates fractures.
• CT chest: shows the number and displacement of fractures, lung contusion volume, haemothorax, aortic and diaphragmatic injury. Used to plan surgical fixation.
• Arterial blood gas for hypoxaemia and hypercapnia, repeated at intervals, and lactate.
• Extended focused ultrasound (eFAST) for pneumothorax, haemothorax and haemopericardium.
• Electrocardiogram and troponin for myocardial contusion, and screening for abdominal and spinal injury.

• Airway and oxygen: high flow oxygen with target saturation of 94 to 98%. Early high flow nasal oxygen or non-invasive ventilation (continuous positive airway pressure 5 to 10 cmH2O) can avoid intubation in cooperative patients.
• Analgesia is the cornerstone: multimodal, with paracetamol 1 g every 6 hours, ibuprofen 400 mg every 8 hours with food (if renal function and bleeding risk allow), and regional anaesthesia. Options are thoracic epidural (preferred if no contraindication), paravertebral block, erector spinae plane or serratus anterior plane block with catheter, and intercostal block. Add low dose ketamine (0.1 to 0.3 mg/kg bolus or 0.1 to 0.2 mg/kg per hour infusion), lidocaine patch, and opioid when needed with caution for respiratory depression.
• Chest physiotherapy, incentive spirometry, cough assistance and early mobilisation to prevent atelectasis and pneumonia.
• Intubation and mechanical ventilation for: respiratory failure (PaO2 under 8 kPa on oxygen, rising PaCO2, respiratory rate over 35), exhaustion, severe associated injury (head injury, shock), or need for surgery. Use lung protective settings (tidal volume 6 mL/kg ideal body weight), with positive end expiratory pressure 5 to 10 cmH2O and early weaning.
• Fluid management: avoid fluid overload, aiming for euvolaemia, since contusion worsens with excess fluid.
• Drain pneumothorax or haemothorax with a chest drain (28 to 32 French for haemothorax) before positive pressure ventilation.
• Surgical stabilisation of rib fractures (plates and screws, within 48 to 72 hours): considered for flail chest with ventilator dependence, severe pain not controlled with regional block, severe displacement, failure to wean, or when thoracotomy is done for another cause. It reduces ventilator days, pneumonia and tracheostomy in selected patients.
• Prophylaxis: venous thromboembolism prophylaxis with enoxaparin 40 mg daily (when bleeding is controlled), and stress ulcer prophylaxis if ventilated.

Complications and prognosis. Pneumonia (a third), respiratory failure, prolonged ventilation, tracheostomy, empyema, chronic pain (a quarter to half at 6 months), chest wall deformity and reduced lung function. Elderly patients, those with more than 6 rib fractures, and pulmonary contusion have the worst outcomes.

Monitoring. Respiratory rate, saturation, pain scores and blood gases at least every 4 hours early, daily chest radiograph, and follow up at 6 weeks, 3 months and 6 months for pain and function.

Referral and escalation. Refer to the trauma team and intensive care on admission, to thoracic surgery for fixation, and to the pain service for regional analgesia.