What is the most common cause of tension pneumothorax?

Most Common Causes of Tension Pneumothorax

Iatrogenic causes, particularly mechanical ventilation and invasive procedures, are the most common causes of tension pneumothorax, with transthoracic needle aspiration (24%), subclavian vessel puncture (22%), thoracocentesis (22%), pleural biopsy (8%), and mechanical ventilation (7%) being the five leading causes. 1

Pathophysiology of Tension Pneumothorax

• Tension pneumothorax occurs when intrapleural pressure exceeds atmospheric pressure throughout the respiratory cycle, creating a one-way valve effect that draws air into the pleural space during inspiration but prevents its escape during expiration 2
• This one-way valve mechanism leads to progressive air accumulation in the pleural space, causing mediastinal shift, decreased venous return, reduced cardiac output, and hypoxemia 1
• The development of tension in a pneumothorax is not dependent on the size of the pneumothorax, and clinical presentation may correlate poorly with radiographic findings 1

Primary Causes of Tension Pneumothorax

Iatrogenic Causes (Most Common)

• Mechanical ventilation is a significant cause, particularly in ICU settings, as positive pressure ventilation can maintain and worsen air leaks 3, 4
• Invasive procedures account for the majority of cases, with transthoracic needle aspiration (24%), subclavian vessel puncture (22%), thoracocentesis (22%), and pleural biopsy (8%) being the most common 1
• The risk of pneumothorax during transthoracic needle aspiration increases with deeper lesions and in patients with underlying COPD 1

Underlying Lung Disease

• Patients with underlying lung disease are more prone to develop pneumothorax, especially when receiving positive pressure ventilation 3
• COPD patients who develop iatrogenic pneumothorax are more likely to require tube drainage 1
• Other predisposing conditions include cystic fibrosis, tuberculosis, and other chronic lung diseases 5

Spontaneous Pneumothorax

• Spontaneous pneumothoraces can develop tension physiology, though this is less common than iatrogenic causes 5
• Risk factors for spontaneous pneumothorax include smoking, family history, and underlying lung diseases 5

Clinical Presentation and Diagnosis

• The clinical presentation is striking: rapid labored respiration, cyanosis, sweating, tachycardia, and progressive respiratory distress 1
• Tension pneumothorax should be particularly suspected in patients on mechanical ventilators or non-invasive ventilation who suddenly deteriorate or develop PEA arrest 1, 2
• Diagnosis is primarily clinical, and treatment should not be delayed while waiting for radiographic confirmation 2

Management Considerations

• Immediate needle decompression with a cannula of adequate length (at least 4.5 cm) should be performed, followed by chest tube placement 1, 2
• The cannula should be inserted into the second intercostal space in the mid-clavicular line and left in place until a functioning intercostal tube is positioned 1
• Patients with tension pneumothorax, higher APACHE II scores, or PaO2/FiO2 < 200 mmHg have higher mortality rates 6

Special Considerations

• An undetected small pneumothorax without symptoms can progress to tension pneumothorax through positive pressure ventilation during general anesthesia 7
• Patients on positive pressure ventilation who develop pneumothorax should always receive tube thoracostomy as positive pressure maintains the air leak 2
• In mechanically ventilated patients with asthma, tension pneumothorax is a rare but life-threatening complication that should be considered when there is sudden deterioration 1