Collapsed lung is also called as pneumothorax. It occurs when air escapes from the lung. The escaped air fills the space of lungs between the chest wall and lungs. This air exerts pressure on the lung, so it cannot expand as much as it normally does when you take a breath. Collapsed lung is caused due to injury of lung. A blunt or penetrating chest injury causes lung disease. Symptoms include shortness of breath, fast heart rate, chest pain and cough. The disease is caused due to injuries which include knife wound to chest, gun shot, rib facture and certain medical procedures. In some cases, a collapsed lung is caused by air blisters that break open, sending air into the space around the lung. Lung diseases can also increases the chance of getting a collapsed lung. Physical examination alone is difficult for diagnosis of pneumothorax. Chest X ray, CT scan, ultrasound are also used for the diagnosis of a pneumothorax. When pneumothorax is large, needle or tube is used to remove excess air.