Health: Long-haul flights and DVT

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Edition 26: Winter 2003/4 According to Dr Richard Dawood, Travel Africa's medical expert, his most memorable plane journey in Africa was a pilgrim's flight in 1978, between N'Djamena and Khartoum. There were no worries about the risk of deep vein thrombosis (DVT), seat pitch However, despite airlines' occasional protestations to the contrary, DVT is a risk for today's air traveller. Cramped seating and more efficient load management - so that there are fewer empty seats - are key factors, while the long journey times typical of flights from Europe to Central and Southern Africa further increase the risk. DVT occurs when blood clots form in the deep veins of the legs. A cramped sitting posture reduces the flow of blood through these veins, and additional factors such as dehydration, reduced cabin oxygen pressure, immobility and a variety of individual medical factors can combine to increase the coagulability of the blood. A clot can cause pain and swelling of the calf, often hours or days after the incident that caused it to form. This is not overly harmful in itself (though it can have long term effects on the circulation of the leg). The real concern is that the clot may detach itself from the leg veins and travel through the circulation to the lung - a condition known as pulmonary embolism (PE), which carries a high mortality. Approximately one in a hundred people with DVT die as a result of this complication. Pulmonary embolism typically occurs several days after the initial formation of a clot - which is why a causal link between flying, DVT and PE has remained obscure for so long. The airlines argue that any other form of immobility can also cause DVT, and this is true, but it is certainly no justification for complacency in the air, especially since research suggests that as many as one passenger in ten can develop tiny, symptomless clots during a long haul flight. A wide range of medical factors are known to increase the risk. These include: being over 40 years of age, overweight, very tall or very short; a previous DVT or PE; a family history of blood clots; suffering from or being treated for cancer; a history of heart failure, circulation problems or stroke; recent surgery especially to the hips or knees; any inherited clotting tendency; current or recent pregnancy; being on the Pill, HRT, or hormone treatment (including tamoxifen for breast cancer). The key preventive measures are: keeping well hydrated - ideally drinking a pint of water for every three hours in the air (tea, coffee and alcohol tend to dehydrate, so you may need extra water to compensate); standing, stretching, walking along the aircraft cabin at least once every hour; in-seat exercises; wearing compression stockings; maximising leg-room (avoid stowing luggage below the seat in front of you, and request early removal of your meal tray); travelling in the highest class you can afford; avoiding sleeping tablets in-flight unless you are able to lie flat; seeking your doctor's advice if there is any special risk. A recent ruling in the Appeal Court in July 2003 confirmed that airlines are not legally liable for DVT and its consequences, regardless of any link between DVT and flying. At issue is the wording of the Warsaw Convention, which limits airlines' liability to accidents. More needs to be done to increase our understanding of DVT, its causes and prevention. And more should be done to encourage airlines to play a greater role in its prevention. But the Appeal Court judgement makes it quite clear that responsibility for health in the air rests with passengers themselves. Further information Department of Health: www.doh.gov.uk/blood/dvt DVT Risk Calculator: www.fittofly.info

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