deep vein thrombosis
by Jenny Bryan
If you're young and healthy, your risk of getting a serious blood clot in your leg is very low – whether you are sitting at your desk or on an aeroplane 30,000 feet up. But recent research suggests that quite a few of us develop small, probably harmless clots in our veins and these come and go when we sit still for a long time.
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Vascular surgeon, John Scurr, who made headlines recently when he reported that as many as 1 in 10 people on long haul flights may get one of these small, symptomless deep vein thromboses (DVTs), urges us not to panic.
'Small DVTs are very common in people who sit for long periods, whether they are flying, in a car or at a desk. But we need bigger studies to show how serious these are,' he says.
what's a DVT?
A DVT is a blood clot in a large vein, usually in the leg. Large clots can impede blood flow, making the leg painful and swollen. If a small piece of the clot breaks off and travels to the lung it can cause a potentially fatal blockage called a pulmonary embolism. While small symptomless DVTs may be more common than previously realised, less than half are thought to be become bad enough to cause symptoms and only a few of these go on to cause a pulmonary embolism.
'It's only recently that we've had the technology to look for very small clots in the leg which is why we're finding more than we expected, but we don't yet know how important they are,' explains Mr Scurr.
Previous studies which have looked for a link between DVT and flying have shown mixed results. A study which looked at people who were admitted to a hospital near an airport in Paris suggested that recent travellers (by air or surface transport) had four times the risk of a DVT compared to those who had stayed at home. A second study showed a two-fold increase in risk. However, a third study failed to show any increased risk associated with flying or any other type of travelling.
the role of support stockings
The purpose of Mr Scurr's most recent research was to see whether wearing graduated support stockings, designed to keep the blood moving, could prevent DVTs in people flying for more than 8 hours. He found that 12 out of 116 people (approx 10%) who didn't wear the stockings developed a symptomless DVT in their calf. But none of those wearing the stockings had a DVT. Most of the people in the study had made journeys lasting 24 hours, and all were over 50.
Does this mean we should all put vanity aside and invest in support stockings? Not necessarily, says Mr Scurr.
'I don't think most people would do themselves any harm wearing stockings, but they really should talk to their GP about it first,' he explains.
Some brands of stockings haven't been clinically tested, and there's a small risk of impeding the circulation by wearing something too tight, particularly if you have varicose veins. For the technically minded, the stockings used in Mr Scurr's study provided compression of 20mm Hg at the ankles.
who's at risk?
Certain groups of people are at slightly increased risk of DVT if they travel or do anything which involves being immobile for long periods. They are older people; those who have had a previous DVT, heart or lung disease or cancer; women on a contraceptive pill that contains oestrogen (the mini-pill that contains only progesterone does not have the same effect); and those with thrombophilia (a rare condition which makes them prone to blood clots). If you are in one of those groups and are planning a long flight, particularly over eight hours, you may want to discuss steps to prevent DVT with your GP or airline.
protect yourself
Many airlines now encourage passengers to move about during flights or to do leg and arm exercises when they are in their seats. Emirates provides a special semi-inflated cushion to pummel with your feet during flights in order to work your calf muscles and improve your circulation.
Other in-flight measures to reduce your risk of DVT are:
- drink plenty of fluids
- avoid alcohol and caffeine-containing drinks before and during the flight
- keep your legs uncrossed
- wear comfortable, loose fitting clothes.
In addition to advising about support stockings, your GP can also help your decide whether to take a small amount of aspirin when travelling for long periods. Aspirin prevents blood cells from sticking together and forming clots, but about 1 in 13 people (approx. 8%) get stomach bleeds when they take it. Problems are most common in older people – the same group who are at increased risk of a DVT. So Mr Scurr advises against people suddenly taking aspirin, unless they are sure it doesn't upset them.
'I'd far rather deal with a DVT than a gastric bleed at 30,000 feet,' he says.
Research is continuing to investigate whether it is immobility, cramped conditions or the cabin pressures in today's large aircraft which affect our risk of holiday DVTs. But, for those who are wondering whether it's worth splashing out on a business or first class seat – you'll be more comfortable and eat better food, but you probably won't reduce your risk of DVT.
help and info
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organisations
Aviation Health Institute
17c Between Towns Road
Oxford OX4 3LX
Tel: 01865 715 999
E-mail: info@aviation-health.org
Investigates the effects of flying on the health of passengers, providing an independent source of reference, information and comment on aviation health issues. This website contains information on blood clots, plus an informative DVT fact file.
British Vascular Foundation
Fides House
10 Chertsey Road
Woking GU21 5AB
E-mail: bvf@care4free.net
Website: www.bvf.org.uk
Provides the vascular professional with useful information across a wide range of vascular issues. Contains information on recent trends in cardiovascular care, patient information and important links when more specialist help is required. Factsheets, including one on DVT, are available on the website.
websites
British Airways Health Services Online
www.british-airways.com/health
Contains useful information for those who are planning a flight, have a medical problem, want to know about the cabin environment and medical care in the air, and many more related topics. Health information for before, during and after your flight, including research, risks, symptoms, and specific advice on DVT.
Advice On Travel-Related Deep Vein Thrombosis
www.dh.gov.uk
Information and advice from the Department of Health on DVT, which summarises what is known about travel-related DVT in air passengers, who may be at greatest risk and how to reduce the potential risk.
TravelHealth.co.uk
www.travelhealth.co.uk/advice/dvt.htm
Health resources and information on DVT, including how to reduce the risks.
reading
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The Complete Flier's Handbook by Brian Clegg (Pan, 2002) |
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Exercises for Airplanes and Other Confined Spaces by Janet Diamond (Excalibur Publishing, 1996) |
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The Little Book of Healthy Flying by Glenda Baum (Arrow, 2001) |
Rosie's Armchair Exercises by Rosita Evans (Discovery Books, 2001) |
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(July 2001, resources updated January 2005)
