Pulm| Pneumothorax

2.20 Pneumothorax Pulmonary system review for the USMLE Step 1 Exam Pneumothorax is a collection of air outside the lung in the pleural cavity, caused by a hole in the pleurae that allows air to infiltrate and disturb normal respiratory function. There are three categories of causes: primary spontaneous, secondary spontaneous, and trauma. Trauma, such as blunt force or penetrating wounds, is the most common cause, as well as iatrogenic causes like transthoracic needle aspiration and central venous catheterization. Spontaneous pneumothorax occurs without any trauma and can be classified as primary (no underlying lung disease) or secondary (with underlying lung disease). Smoking greatly increases the risk for spontaneous pneumothorax, especially in tall men with Marfan's syndrome or Ehlers-Danlos syndrome. Tension pneumothorax is a more emergent and dangerous type of pneumothorax, where air enters the pleural cavity but cannot exit, causing pressure to build up and compress nearby structures like the lungs, blood vessels, and heart.