Much debate has arisen around a link between flying and thrombosis. Long-haul flights do expose us to prolonged periods of relative hypoxia at low pressure, combined with inactivity, but does the combination make thrombosis more likely – even if we have no risk factors?
It seems not. Toff et al (JAMA 2006;295:2251-61) simulated an 8-hour flight by placing volunteers in an oxygen chamber set to commercial aircraft conditions, then at ground settings and checked their clothing factors. It appears that lowering the environment to hyperbaric and hypoxia flight levels makes little difference to laboratory testable thrombosis propensity. If you are a Factor V Leiden positive or taking oral contraceptives, then take extra precautions, otherwise keep well hydrated, flex and extend your ankles and knees and walk around the cabin as often as you can.
