What is the most common cause of a tension pneumothorax?

A tension pneumothorax occurs when air enters the pleural space and cannot escape, leading to increased pressure within the thoracic cavity. This condition is most commonly caused by trauma to the chest. Traumatic events, such as a rib fracture, gunshot wound, or stab wound, can create a one-way valve effect, allowing air to enter the pleural cavity upon inhalation but preventing it from escaping during exhalation. This buildup of air puts pressure on the lungs and mediastinum, leading to respiratory distress and potential cardiovascular compromise.

While spontaneous rupture of the lung can lead to a pneumothorax, it is less common as a direct cause of tension pneumothorax compared to trauma. Infection and allergic reactions do not typically cause tension pneumothorax; these conditions can lead to different complications in the thoracic area but do not create the same mechanism of pressure buildup associated with trauma-induced pneumothorax. Thus, trauma remains the most prevalent cause in clinical practice.