How air gets in and why the lung falls
A pneumothorax is air in the pleural space. Recall from Guide 1 that the lung is held open only by a negative intrapleural pressure. Let air in — through a hole in the lung surface or the chest wall — and that pressure rises toward zero. With nothing holding it out, the lung's own elastic recoil pulls it inward and it deflates, partly or fully.
A primary [[spontaneous-pneumothorax|spontaneous pneumothorax]] happens out of the blue, classically in a tall, thin young person when a small surface bleb ruptures. A secondary spontaneous one occurs on top of existing lung disease like COPD. Others are traumatic or iatrogenic (after a procedure). Cigarette smoking sharply raises the risk of the spontaneous kind.
Symptoms come on suddenly: sharp pleuritic chest pain on one side and breathlessness. On exam the affected side is hyper-resonant to percussion (air, not fluid) with reduced breath sounds. A chest radiograph confirms it by showing a sharp lung edge with no lung markings beyond.
Tension pneumothorax: the one-way valve
A tension pneumothorax is the dangerous version. The leak acts like a one-way valve: air enters the pleural space with each breath but cannot escape. Pressure climbs above atmospheric, the collapsed lung is crushed, and — critically — the rising pressure shoves the mediastinum and heart toward the opposite side, kinking the great veins and choking off the heart's filling.
- Recognize it: sudden breathlessness plus hypotension, distended neck veins, and tracheal deviation away from the bad side.
- Decompress immediately: insert a needle or finger to release the trapped air and convert tension into a simple, open pneumothorax.
- Then place a definitive chest tube to keep the space drained while the leak heals.
Managing the non-tension pneumothorax
Most spontaneous pneumothoraces are not under tension and are handled calmly. A small one in a comfortable patient may just be observed and given oxygen, which speeds reabsorption of the trapped air. A larger or symptomatic one is treated by removing the air — needle aspiration or a small chest tube.