A pneumothorax occurs when air enters the pleural cavity—the space between the two layers of the pleural membrane surrounding the lungs—and causes a lung to collapse, leading to chest pain and shortness of breath.
A pneumothorax may occur spontaneously—more commonly in tall, thin young men—or following a chest injury. A pneumothorax may also occur as a complication of conditions such as a chest infection, chronic obstructive pulmonary disease, cystic fibrosis, or lung cancer.
A penetrating chest injury may cause a tension pneumothorax where, with each breath, more air is drawn into the pleural cavity. This prevents blood from returning to the heart from the lungs, causing fainting and shock; a tension pneumothorax can be life-threatening.
A small pneumothorax may clear up without treatment in a few days.
A large pneumothorax or a tension pneumothorax may be treated by inserting a tube or hollow needle into the chest to allow the air to escape.