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 (solid yellow area) 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.