Tension Pneumothorax

Overview

A tension pneumothorax is a life-threatening emergency that requires immediate action. In a tension pneumothorax, injured pleural tissue leads to the formation of a one-way valve. This allows air to enter the pleural space during inspiration, but it cannot escape during expiration, leading to an increase in intrathoracic pressure. Obstructive circulatory shock follows, where the heart, lungs, and major blood vessels are compressed, leading to haemodynamic compromise.

Risk factors are similar to that of a pneumothorax, along with blunt or penetrating chest trauma (such as knife stabbings).

Presentation

Features of a pneumothorax and signs of haemodynamic instability should ring alarm bells for a tension pneumothorax. Patients have features of a pneumothorax along with:

• Tracheal deviation away from the affected side – due to increasing intrathoracic pressure as more air enters
• Signs of respiratory distress:
  • Hypotension – due to cardiac outflow obstruction
  • Tachycardia – due to the heart trying to compensate for outflow obstruction
• Altered levels of consciousness
• Sweating

Differential Diagnoses

Pneumothorax

• There is no tracheal deviation
• There are signs of haemodynamic compromise

Cardiac tamponade

• There is no tracheal deviation
• Beck’s triad is present:
  • Heart sounds are ‘muffled’ or reduced in volume
  • Hypotension
  • Elevated jugular venous pressure (JVP)

Pulmonary embolism

• There may be venous thromboembolism risk factors present (e.g. prolonged immobility, pregnancy, recent surgery)
• Examination may show a swollen calf
• There is no tracheal deviation

Investigations

• Clinical diagnosis – do not wait for imaging and treat immediately

Diagnosis

Diagnosis is clinical. Decompression may lead to a ‘hiss’ of air which can confirm the diagnosis.

Management

All patients

• 1^st-line: immediate decompression + high flow oxygen– insert a large-bore cannula through the second intercostal space in the mid-clavicular line:
  • A ‘hiss’ of air arising can confirm the diagnosis
• Insert chest drain immediately after decompression and admit to hospital:
  • This is inserted into the ‘triangle of safety’ – mid-axillary line of the 5^th intercostal space