A pneumothorax is the presence of air in the pleural cavity, the space between the lung and the chest wall. Normally this space contains only a thin film of fluid; when air enters it, the normal negative pressure that keeps the lung expanded is lost and the lung collapses to some degree.
Pneumothorax can be classified by cause. Primary spontaneous pneumothorax occurs without an obvious cause, most commonly in tall young men with small blebs (air sacs) on the lung surface that rupture. Secondary spontaneous pneumothorax occurs as a complication of underlying lung disease such as COPD or pneumonia. Traumatic pneumothorax is caused by chest injury, broken ribs, or procedures (including central venous catheter insertion, chest surgery, or mechanical ventilation in critical care). Tension pneumothorax is a life-threatening emergency in which air entering the pleural space cannot escape, progressively building up pressure that collapses the lung and shifts the heart and great vessels to the opposite side, impairing venous return and rapidly causing cardiac arrest.
Symptoms include sudden onset chest pain and breathlessness. Tension pneumothorax additionally causes rapid deterioration, low blood pressure, distended neck veins, and absent breath sounds on the affected side. It is treated by immediate needle decompression, followed by chest drain insertion. Small pneumothoraces may be managed conservatively with observation; larger ones or those in patients with underlying lung disease require drainage.
Pneumothorax is an important complication to exclude after central line insertion in ICU patients following cardiac arrest. A post-procedure chest X-ray is standard practice after subclavian or internal jugular central venous catheter insertion.
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