What is a tension pneumothorax?

Tension Pneumothorax: A Life-Threatening Emergency

A tension pneumothorax is a life-threatening emergency characterized by air accumulation in the pleural space under pressure, creating a one-way valve effect that prevents air escape during expiration, leading to progressive respiratory distress, decreased cardiac output, and potentially fatal cardiovascular collapse if not promptly treated with decompression. 1

Pathophysiology and Mechanism

Tension pneumothorax occurs when:

• Intrapleural pressure exceeds atmospheric pressure throughout both inspiration and expiration
• A one-way valve mechanism allows air to enter the pleural space during inspiration but prevents its escape during expiration
• Progressive air accumulation causes:
  • Mediastinal shift
  • Impaired venous return
  • Reduced cardiac output
  • Hypoxemia 1

Clinical Presentation

The clinical presentation is often dramatic and includes:

• Respiratory symptoms:

  • Rapid, labored breathing
  • Progressive respiratory distress
  • Cyanosis
  • Decreased or absent breath sounds on affected side

• Cardiovascular symptoms:

  • Tachycardia
  • Hypotension
  • Sweating
  • Shock in severe cases

• Other findings:

  • Chest pain/tightness
  • Distended neck veins (JVD)
  • Tracheal deviation away from affected side
  • Subcutaneous emphysema 1, 2

Important Clinical Considerations

1. Radiographic correlation may be poor:

   • The development of tension is not dependent on pneumothorax size
   • Clinical presentation may correlate poorly with chest radiographic findings 1

2. High-risk settings:

   • Mechanical ventilation
   • Non-invasive positive pressure ventilation
   • Recent procedures (subclavian venous catheterization, transthoracic needle aspiration)
   • Trauma patients 1, 2

3. Often missed in ICU settings:

   • Particularly suspect in ventilated patients who suddenly deteriorate
   • Can present as electromechanical dissociation (EMD) arrest 1

Emergency Management

Immediate intervention is required:

1. Administer high-concentration oxygen 1

2. Perform needle decompression:

   • Insert a cannula of adequate length (at least 4.5 cm recommended) into the second intercostal space in the mid-clavicular line
   • For right-sided tension pneumothorax, either the 5th intercostal space along the midaxillary line or the 2nd intercostal space along the midclavicular line may be appropriate
   • For left-sided cases, the 2nd midclavicular line is safer due to potential cardiac injury risk 1, 3

3. Leave the cannula in place until a functioning intercostal tube can be positioned 1

4. Insert a chest tube after initial decompression to provide definitive management 1

Pitfalls and Caveats

• Needle length matters: Studies show a 32.84% failure rate for needle penetration into the pleural cavity, with failure rates decreasing by 7.76% per cm of increased needle length 3

• Chest wall thickness variations: The 5th anterior axillary line and 5th midaxillary line have less chest wall thickness than the 2nd midclavicular line, but may have higher injury rates 3

• Asymptomatic pneumothorax risk: An undetected small pneumothorax without symptoms can progress to tension pneumothorax through positive pressure ventilation during general anesthesia 2

• Open chest wounds: If a dressing is placed on an open chest wound, monitor for worsening breathing/symptoms and loosen or remove the dressing if breathing worsens to prevent tension pneumothorax 1

• Spontaneous tension pneumothorax: Though rare in spontaneously breathing patients, large and rapidly expanding pneumothoraces may require urgent intervention even if not technically meeting all criteria for tension 4, 5

By recognizing the clinical signs and providing prompt decompression, healthcare providers can prevent the potentially fatal consequences of tension pneumothorax.