Influence of aircraft chair quality on blood coagulation and leg edema formation during a simulated long-haul flight

Introduction World wide approximately 1.5 billion passengers travel by aircrafts yearly. In the past years there have been increasing reports suggesting a causal link between longhaul flights and thromboembolic events. It has been postulated that besides sitting in a cramped position DVT may be triggered by aircraft-specific factors. Whether these aircraft-specific factors (moderate hypoxia, low humidity) may in fact induce hemostatic changes thus triggering DVT is discussed controversially. Recently, we measured parameters of hemostasis in 20 passengers during and after a return flight from Vienna to Washington (ref. 1). A hypercoagulable state was found as evidenced by thrombelastographic measurements, by an increased activity of clotting factors FVII and FVIII and suppressed fibrinolysis. There was no evidence of a pronounced thrombin and fibrin formation. At present it is controversially discussed whether these findings are aircraft-specific or the consequences of sitting in a cramped position. In order to clarify this issue we performed a long distance bus travel (10 hrs) using the same protocol as in the ECS-study. Similar to long-haul flights we could demonstrate a certain activation of the coagulation system even after a long-distance bus travel in healthy subjects (ref. 2). Leg edema, as a sign of venous stasis is a well-known problem among passengers during and after long haul flights. Until now no investigations have been made on the development of leg edema and fluid shifts under real flightand bus-travel conditions. Plethysmographic measurements were carried out using an optoelectronic scanner system (Perometer) in order to evaluate edema formation in the leg during the ECSand the BUS-study. In both studies leg volume increased between 100 and 150 ml per leg (ref.3). However, at present there are no studies available which investigated the contribution of the seat quality on measured changes of coagulation and leg volume during prolonged sitting in a cramped position. Therefore, the study “SEAT2003” was performed in order to measure changes in coagulation and edema formation during and after 10 hrs sitting.