Association between acute hypobaric hypoxia and activation of coagulation in human beings

The risk of venous thrombosis is thought to be increased by flying. In a study of 20 healthy male volunteers who were suddenly exposed to a hypobaric environment similar to that encountered within aeroplane cabins, markers of activated coagulation transiently increased by two-fold to eight-fold. We suggest that hypobaric hypoxia, with sedentariness and dehydration, may cause this increased risk of venous thrombosis.