Pneumothorax. X-ray of the chest of a 50 year old male patient with a pneumothorax, or collapsed lung. The right lung (left on X-ray) has collapsed due to a build-up of air (solid grey) 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.