The assumption has always been that deep vein thrombosis (DVT) only occurs on long-haul flights. But a recent study showing that 17 per cent of flight-related DVT arose during short flights puts paid to that assumption.
According to early Italian evidence published in The Independent, during a relatively short flight to Rome, 4.3 per cent of the 568 passengers developed clots, detected by ultrasound, two of whom went on to suffer a pulmonary embolism. Furthermore, the blood clots develop in the first two to three hours, and grow larger and more dangerous over time.
DVT refers to a blood clot, or throm-bus, in one of the deep veins of the legs (a vein near an artery), usually caused by inactivity. This is life-threatening if the clot breaks off from the wall of the vein and travels through the blood-stream ('embolizes') to end up in the brain, lungs, heart or other organs, where it can cause severe damage.
Researchers in the New Zealand Air Traveller's Thrombosis study looking at 878 air travellers who frequently flew for more than 10 hours at a stretch discovered four passengers with pul-monary embolisms and five with DVT, despite the use of aspirin or com-pression stockings. However, eight of the nine had a risk factor for clotting (Lancet, 2003; 362: 2039-44).
Also, new evidence from Norway suggests that in everyone, including healthy people, the clotting activity of blood temporarily increases while in an airplane by up to 30 per cent (Lancet, 2006; 367: 832-8).
Although aspirin is the conventional preventative of choice for traveller's thrombosis, a study found that 17,000 people would have to be treated in order to prevent a single case of DVT (Medscape Gen Med, 2002; 4: 4).
Happily, besides keeping your feet moving (with a variety of exercises, such as flexing the foot and calf muscles, while seated, for two minutes every half an hour), a number of alternative meas-ures will ensure that you land in the peak of health.
Contrary to expectations, a Japanese study found that those who drank one cup of water each hour during a nine-hour flight increased the thickness of their blood. However, those who drank an electrolyte fluid (such as a sports drink) showed no such increases in blood viscosity (JAMA, 2002; 287: 844-5).
Also, although travellers are exhort-ed to avoid wine because of its dehy-drating qualities, the resveratrol found in red wine can reduce blood-platelet stickiness (Thromb Res, 2002; 107: 141-5). Resveratrol pills are available for those who don't drink.
Take anti-clotting nutriceuticals
The best of these is said to be Pycno-genol, a grapeseed extract that can strengthen capillaries and enhance blood flow. This is a registered, trade-marked product created by a French company, and originally derived from the bark of the French maritime pineree. A superantioxidant, it is a stan-dardized mixture of catechins and oligomeric proanthocyanidin complex-es (OPCs)-both of which have been touted as a mild blood-thinner.
French studies have shown that 100 mg/day of proanthocyanidin bolsters capillaries (Bordeaux Med, 1980; 13: 903-7), and 150 mg/day can reduce symptoms of chronic venous insufficiency (Ther Rev Med, 1981; 27-28 Sept: 1793-802).
Nattokinase, an enzyme found in the Japanese fermented soybean foodstuff natto, has been shown to directly break down clots, a process called fibrino-lysis. However, these studies, done in animals, may not apply to humans (Biol Pharmaceut Bull, 1995; 18: 1194-6).
A product called Flite Tabs, containing pinokinase, a proprietary blend of both Pycnogenol and natto-kinase, was recently put to the test among 200 high-risk volunteers, who were given either the active treatment or a placebo before a long-haul flight. Ultrasound scans done before and after the flights showed that those taking the supplement not only suffered no DVTs, but had a statistically significant decrease in DVT. In con-trast, among the controls, five people had developed DVT, and two had suffered superficial thromboses (Angiol-ogy, 2003; 54: T1-3).
Garlic, ginkgo biloba, garlic, flaxseed and even tomato also thin the blood.