Pneumothorax (plural pneumothoraces) is a collection of air or gas in the pleural cavity of the chest between the lung and the chest wall. It may occur spontaneously in people without chronic lung conditions ("primary") as well as in those with lung disease ("secondary"), and many pneumothoraces occur after physical trauma to the chest, blast injury, or as a complication of medical treatment. The symptoms of a pneumothorax are determined by the size of the air leak and the speed by which it occurs; they may include chest pain in most cases and shortness of breath in many...