A research was done on the risks of formation of deep-vein thrombosis (DVT) and it was suggested that Low cabin air pressure and poor oxygenation in the planes contribute greatly to the formation of DVT and not only mere sitting in cramped conditions on long flights like it was previously thought.

A team of researchers from the Netherlands monitored the levels of a main clotting protein called thrombin-antithrombin (TAT) complex in 71 healthy men and women aged 20-39. They were flying with a specially chartered Boeing 757 for eight hours and their blood samples were taken prior, during and after the flight.

Later on, the same group was monitored while spending 8 long hours watching movies in the cinema as well as they regular activities on a normal day.

Blood sample showed that the levels of TAT complex increased by an average of 30% after the flight but dropped by about 2% after the cinema. The post-flight increase in levels was seen in 11 of the 71 individuals, especially those who consumed oral contraceptives and who were prone to developing DVT.

in order to reduce the chances of developing DVT on long flights, health experts advise avoiding alcohol on the flight, stretching legs and wearing the compressive stockings which improves blood circulation. There is also a drug called heparin that is effective in fighting DVT.