Open Pneumothorax

Open pneumothorax is a chest wall defect that lets air move between the pleural space and the atmosphere. When the defect is over two thirds of the tracheal diameter (about 3 cm), air flows through the wound in preference to the trachea, giving a sucking chest wound and failure of ventilation.

Epidemiology. It results from penetrating chest trauma such as gunshot, stab or blast wounds and from large chest wall avulsion.

Pathophysiology. On inspiration, air is drawn through the defect and the lung collapses. The ipsilateral lung cannot ventilate, and the mediastinum can swing toward the opposite side. If air is trapped by a flap, tension pneumothorax develops. Hypoxia and hypercapnia follow.

Presentation is breathlessness, chest pain, a sucking sound and bubbling blood through the wound, reduced chest movement, tachypnoea and hypoxia. Hypotension suggests tension physiology or associated bleeding. Check the back, axillae and abdomen for further wounds.

Red flags.

• Hypotension, distended neck veins or tracheal shift.
• Wound over the cardiac box or bleeding.
• Associated abdominal or great vessel injury.

Diagnosis is clinical. Use extended ultrasound examination and chest radiograph to show pneumothorax, haemothorax, foreign body and mediastinal shift. CT when stable.

Differential diagnosis. Simple closed pneumothorax and traumatic diaphragmatic injury.

Immediate. High flow oxygen. Cover the wound with a sterile occlusive dressing taped on three sides to form a one way valve, or use a commercial vented chest seal. A fully sealed dressing risks converting the injury to tension pneumothorax. If tension signs appear, lift the dressing and decompress.

Chest drain. Insert a drain (28 to 32 Fr) through a separate site, never through the wound, then complete the dressing to seal the defect.

Resuscitation. IV access, blood products for shock (1 red cell unit to 1 plasma to 1 platelet pool), and tranexamic acid 1 g IV over 10 minutes then 1 g over 8 hours.

Analgesia. Fentanyl 25 to 50 microgram IV every 5 to 10 minutes titrated, or ketamine 0.1 to 0.3 mg/kg IV. Regional block when stable.

Antibiotic. Cefazolin 2 g IV (3 g if weight is over 120 kg), repeated every 4 hours during surgery.

Definitive care. Surgical debridement and closure of the defect in theatre, with primary closure or flap and mesh for large defects. Intubate for respiratory failure, using positive pressure only after a drain is in place.

Monitoring. Respiratory rate, saturation, drain output, air leak and haemodynamics.

Referral and escalation. Trauma surgery and anaesthesia at once, and thoracic surgery for large defects or ongoing air leak.

Special groups. In children, use proportionately smaller drains and dressings and take care with warmth. In pregnancy, give the same treatment with obstetric input.