A pneumothorax (noo-mo-THOR-acks) is a collapsed lung. Pneumothorax occurs when air leaks into the space between your lungs and chest wall. This air pushes on the outside of your lung and makes it collapse. In most cases, only a portion of the lung collapses.
A pneumothorax can be caused by a blunt or penetrating chest injury, certain medical procedures involving your lungs, or damage from underlying lung disease. Or it may occur for no obvious reason. Symptoms usually include sudden chest pain and shortness of breath.
A small, uncomplicated pneumothorax may quickly heal on its own. When the pneumothorax is larger, doctors usually insert a flexible tube or needle between your ribs to remove the excess air.