Coloured 3D computed tomography (CT) scan of the chest of a patient with a tension pneumothorax. This is a progressive deterioration and worsening of a simple pneumothorax, or collapsed lung. The lung at left has collapsed due to a build-up of air between the lung and chest wall. Pneumothorax can be due to trauma or lung rupture. It causes shortness of breath and pain on breathing. It is treated by inserting a tube to drain the air over a period of days, allowing the lung to re-inflate.