Hemothorax
Hemothorax is an accumulation of blood within the chest wall. It is often the result of blunt force or penetrating traumatic injury, which injures the pleural lining of the lungs allowing blood to build up. In these cases blood loss can be very substantial, up to 40% of total blood volume. Hemothorax can also lead to a collapsed lung where the lung deflates and is no longer capable of taking in and breathing out oxygen. Symptoms can include breathing faster than necessary, shortness of breath or pain with breathing, blue tinged skin, decreased or absent breath sounds from the lung on the affected side, and dull sounding chest when it is tapped. A simple X-ray can diagnose hemothorax. In order to treat hemothorax the blood must be drained from the chest by a procedure called a tube thoracostomy. A tube is inserted into the pleural space and fluid is allowed to drain from the chest. Recovery from this procedure is often fast, though recovery time due to the injury that caused the bleeding in the first place can vary.
Refernces: http://en.wikipedia.org/wiki/Hemothorax
http://www.emedicine.com/med/topic2915.htm