Pneumothorax

A pneumothorax (pneumo- + thorax; plural pneumothoraces) is an abnormal collection of air or gas in the pleural space that causes an uncoupling of the lung from the chest wall. Like pleural effusion (liquid buildup in that space), pneumothorax may interfere with normal breathing. It is often called collapsed lung, although that term may also refer to atelectasis. One or both lungs may be affected.