- Paper Report
- Open Access
Evidence for increased risk of venous thrombosis during air travel
- Joanna Lyford1
© Biomed Central Ltd 2001
- Received: 28 November 2000
- Published: 18 October 2001
- Acute hypobaric hypoxia, air travel, venous thrombosis
Healthy volunteers show increased activity of blood coagulation factors after spending just 2 h in a hypobaric chamber that simulates an aeroplane cabin at cruising altitude. According to a letter published in the Lancet which outlines a Norwegian study, the recent disputed reports of a link between venous thrombosis and air travel are 'probably clinically relevant' and deserve further investigation.
All participants had normal hemostasis before entering the chamber; however, after just two hours, concentrations of prothrombin fragments 1 and 2 and thrombin-antithrombin complex and activity of factor VIIa had increased significantly (P = 0.008, P = 0.04, and P = 0.008, respectively), whereas concentrations of factor VII antigen (P = 0.003), activity of tissue-factor-pathway inhibitor (P = 0.001) and concentrations of free antigen (P = 0.02) decreased. Concentrations of prothrombin fragments 1 and 2 increased to a maximum of 2.5-fold at 2 h, whereas concentrations of thrombin-antithrombin complex increased 8.2-fold. This increase was associated with an increase of up to 17% in factor VIIa activity, a 4.9% decrease in factor VII antigen concentrations, a 10% decrease in the activity of tissue-factor-pathway inhibitor and a 17% (14-21%) decrease in free antigen concentrations. Concentrations of D-dimer - a marker of continuing fibrinolysis - remained unchanged throughout the experiment.
Bendz and colleagues from Ulleval University Hospital, Norway, exposed 20 healthy volunteers to hypobaric pressure (76 kPa) for at least eight hours; this air pressure corresponds to the atmospheric pressure at 2400 m and is similar to the pressure in aeroplane cabins.