Changes in blood coagulation of arm and leg veins during a simulated long-haul flight.

Introduction: Long-haul flights are associated with an increased incidence for venous thromboembolic events. At present, markers of coagulation and fibrinolysis were only analyzed from arm veins after long distance travel. Respective data from leg veins are missing.
Materials and Methods: Here, we measured these parameters in healthy volunteers (n=12) before and after 10 h sitting in modern aircraft chairs under normobaric hypoxia (corresponding to 2400 m altitude). Blood was collected from arm and leg veins before, immediately after and 1 day after sitting in the hypoxic chamber.
Results: We did not find any evidence for a significant intravasal thrombin and fibrin formation and a changed fibrinolytic activity, neither in arm nor in leg vein blood. TAT, PAP, and PAI-1 remained unchanged, and the increases of F1+2 in arm veins and of d-dimer in leg veins were within the upper reference limits. Moreover, there was no evidence of activation of coagulation as measured by thrombelastography (ROTEM(R)) and the new Thrombin Dynamic Test at both locations. There was no evidence of arm or leg hemoconcentration.
Conclusions: In healthy volunteers, prolonged sitting in ergonomically superior aircraft seats does not induce significant changes in blood coagulation and fibrinolysis in venous blood of arm or leg. Since this study was performed under moderate hypoxia, reduction in oxygen pressure seems not to be a crucial factor for venous thrombosis at long-haul flights.