Venous thromboembolism (VTE) is the process of clot formation in the veins. While it can occur anywhere in the system, it is usually in the vessels of the leg that deep vein thrombosis (DVT) occurs (Blann and Yip 2006). It has been estimated that 25,000 people in the UK die from preventable, hospital-acquired VTE every year (House of Commons Health Committee, 2005). This includes patients admitted to hospital for both medical care and surgery.