ECONOMY-CLASS SYNDROME (DVT)

Introduction

Many of us don't bother to pay much attention to the routine pre-flight safety instructions as we take it for granted that air travel is virtually risk-free. Of course we are aware that disasters can and do occasionally happen, but most of us don't dwell on the possibility - we fully expect to arrive at our destination untroubled by the smallest mishap. The reliability of modern passenger aircraft is truly remarkable.

If we are healthy we also take for granted the reliability of our own bodies, although of course they are a lot more complicated than any flying machine. Perhaps because our bodies are so reliable, we tend to forget sometimes that they need some basic maintenance, just like any other complicated piece of engineering.

Part of this essential maintenance is getting enough water. We don't expect to die of thirst on a passenger aircraft, but some people (at present we don't know how many) get too dry and succumb to the effects of dehydration and lack of exercise shortly after a long-haul flight. This is the so-called "economy-class syndrome", the dangers of which, in certain individuals, may well outweigh the risk of anything going wrong with the aircraft. The tiny drinks doled out by the flight attendants and the many boring hours during which it is tempting to kill time by dozing in our seat conspire to make our bodies dehydrated and our blood-circulation sluggish. Some passengers who live a long distance from the airport are probably already slightly dehydrated when they take their seats on the plane. The cramped conditions in economy class can make it difficult to get up and go for a walk. Under these conditions the blood can clot more easily. If a clot forms in the deep veins of the leg (a deep vein thrombosis or DVT) it may detach and pass up to the heart and lungs. This is called a pulmonary embolism and a large one can be lethal.

Level of risk

The danger should not be overstated. Much publicity has been given to a recent report from the science and technology committee of the House of Lords, which has been looking into air travel and health. One of the points it made was that more research was needed into the possible link between flying and blood clots. We know that a DVT occurs in about 1 people out of 1000 each year, whether they travel or not. Pulmonary embolism is even less common At present it is not possible to say how many extra DVTs and embolic events occur as a result of air travel because many are symptomless and even those which result in medical problems may not be reported. It is not hard to find cases of DVT following a flight as so many people travel by air nowadays (at any one time about half a million people are in the air worldwide). How many of these are actually caused by air travel remains unknown. The House committee felt that the term "economy-class syndrome" is seriously misleading as anyone sitting for a long time is at slight risk. "Flight-related DVT" or even "traveller's thrombosis" were suggested as being more appropriate terms. The committee concluded that if there was an increased risk of DVT from flying, it was likely to be small.

Higher risk categories

Some people are more at risk of blood clots than others. These include:

• women on the contraceptive pill
• women who are pregnant or have recently given birth
• the elderly
• people who are obese
• patients with heart conditions especially heart failure
• patients on diuretics
• people with a past history or family history of thrombosis.

People with restricted mobility, perhaps because of a recent accident such as a broken leg, are also at higher than average risk.
People in these higher-risk groups should be aware of the danger of blood-clots forming on long-haul flights and take more active measures to reduce the risk.

Risk reduction

The risks can be reduced by ensuring adequate fluid intake and it is a good idea to include a bottle of water in your hand-luggage. Most adults should drink at least 2 litres a day. It is best to avoid alcoholic drinks as they have a diuretic action, which can worsen dehydration. This is also true of the caffeine in coffee and tea. For this reason it is best to stick to plain water or fruit juice. Try to get out of your seat at regular intervals - at least every hour when not sleeping - and walk up and down the aisle. You can do useful exercises in your seat, for example stretching, deep breathing and leg and foot exercises. A tablet of aspirin taken a few hours before the flight has a prolonged anti-clotting effect. However aspirin is not suitable for everyone and the small risk of serious stomach bleeding may outweigh the benefits of the anti-clotting effect for some people, particularly those with a past history of peptic ulcers.