Formation of a clot in the leg veins deep inside the thigh or calf muscle. Bedridden people, particularly recovering from surgery, are particularly prone to this condition, but even passengers on long-haul flights may be affected due to sitting still and not drinking enough water. Deep vein clots (or fragments) may break off, travel with the blood stream to the lungs, where they get stuck. When this happens lung function in the affected part(s) of the lung will cease, and if a large enough part of the lungs is affected the patient will suffocate. To prevent DVT, patients at risk are often pre-treated with preventive drugs, and even after major surgery patients are encouraged to get out of bed as early and often as possible.