Spontaneous Pneumothorax

A spontaneous pneumothorax occurs when air enters the pleural space without trauma. The pleural space normally maintains negative pressure, which holds the lung expanded against the chest wall. Once air enters that sealed space, the pressure gradient is lost and the lung recoils inward—much as a suction cup releases when air slips beneath its edge. Primary spontaneous pneumothorax (PSP) occurs in a person without clinically apparent lung disease. It is classically associated with rupture of small apical subpleural blebs and is more common in tall, thin young males. Secondary spontaneous pneumothorax (SSP) occurs in the setting of diseased lung, most often COPD, but also severe asthma, cystic fibrosis, interstitial lung disease, or Pneumocystis pneumonia. The distinction changes the risk calculation. A small PSP may cause sharp pain but little physiologic compromise because the remaining lung is healthy. The same-sized pneumothorax in a person with severe emphysema can cause profound hypoxemia or hypercapnia because there is little respiratory reserve to lose. Tobacco smoking is the dominant modifiable risk factor for both first episodes and recurrence. Cannabis smoking also increases risk. Smoking...