Deep venous thrombosis, pulmonary embolism and long-distance flights.

Deep vein thrombosis resulting in lethal pulmonary thromboembolism is not-infrequently encountered in forensic cases. Predisposing factors include immobility, recent surgery, previous deep venous thromboses/pulmonary thromboembolism, indwelling central venous lines, major trauma, the oral contraceptive pill, pregnancy, congenital cardiac disease, sepsis, malignancy, systemic lupus erythematosus, renal failure and certain inherited thrombophilias. Venous thrombosis associated with air travel was reported in the early 1950's and called the "economy class syndrome", although it is now recognized that reduced movement on long distance flights is more significant than seating class. Long-distance flights of eight hours or more are associated with a two to fourfold increase in the risk of deep venous thrombosis, but only in those individuals who have underlying risk factors. With increasing numbers of flights of more than 16 h duration forensic pathologists are well placed to monitor the potential impact of extended flying on the incidence of lethal pulmonary thromboembolism.