Office-bound workers are now whiling away an increasing amount of the time daydreaming about their summer holiday. Already their minds are tending to wander away from the office when doing repetitive daily tasks. In their imagination they are already enjoying the freedom of being away from work and are basking in unbroken sunshine on faraway beaches.

Occasionally the thoughts of desk-bound office workers about exciting people they may meet on holiday, clothes they will wear and bars they hope to visit are interrupted by transient worries ranging from the unlikely risk of being eaten by a shark to the greater likelihood of developing food poisoning or treading on a sea urchin.

Such has been the publicity about economy-class travel that they are almost certain to also give deep-vein thrombosis (DVT) and pulmonary emboli a passing thought if their destination is some exotic spot more than four hours' flight time away from London.

In fact research has shown that the mode of travel, and even the comfort of the seats are, contrary to popular belief, less important factors in causing DVTs and pulmonary em- boli than how long travellers stay trapped in their seats with feet hanging down and the edge of the seat pressing into the backs of their thighs and calves. Five hours spent crushed into the back seat of a family car might finish off Granny, or one of her granddaughters who smokes, is overweight and on the Pill, with a pulmonary embolus almost as surely as if they had developed thrombo-embolic troubles after a long flight.

Some of the office daydreamers may never reach the airport with its queues, irritations and uncertainties, let alone the beach. Hours spent at a desk, especially if the worker is conscientious and not for ever slipping off for the odd cup of tea or chat in the cloakroom, can also induce blood clots or thromboses in the legs or pelvis and, in some cases, pulmonary emboli, clots in the lung, almost as readily as a long flight. These are the same sites in the vascular system most likely to be affected by a deep-vein thrombosis and sometimes pulmonary embolism that can follow long flights or journeys. The danger of travelling has less to do with changes in air pressure and dehydration than the number of hours spent sitting still with legs hanging down.

Research from New Zealand, published in the Journal of the Royal Society of Medicine, demonstrates that the risk from being inert at a desk doubles the chance that someone may suffer from DVT, and gives some people a greater risk of this than if they had been on a long-haul flight.

Problems arise with deep-vein thromboses because part of the clot may break off, pass through the heart and reach the lungs as a pulmonary embolism. If the embolism lodges in a vessel leading to the lungs, death of the lung tissue supplied by the blood vessel occurs. A pulmonary embolism is to the lung what a coronary thrombosis is to the heart. When a clot, whether thrombus or embolus, blocks the blood vessel taking oxygenated blood to the heart muscle or lung tissue, that part of the vital organ, once starved of oxygen and other nutrients, withers and dies.

The numbers of people and the degree of risk that they suffer if having a deep-vein thrombosis from sitting in an aircraft seat or an office chair is nothing compared with the risk to many patients who have to lie on an operating room table during some types of surgery. DVTs and pulmonary embolisms are estimated, according to a recently published Department of Health report, to account for 25,000 deaths a year in British hospitals. This is a higher death rate than the combined mor- tality in this country from breast cancer, Aids and traffic accidents, and is 25 times more than the number of patients who die annually in British hospitals from MRSA. The figure of 25,000 fatalities may well be an underestimate because many patients thought to have died from a post-operative chest infection may in reality have initially suffered from small pulmonary emboli.

If adequate precautions were taken before someone undergoes surgery associated with a high risk of DVT, many of these deaths could be prevented. Currently only four out of ten people who have an obvious risk of developing these complications during surgery receive recommended preventative treatment. Currently an injection of low-molecular-weight heparin is standard practice. Recently Pradaxa dabigatran etexilate, a new, once-daily oral anticoagulant with no more side-effects than the injections, has been introduced. Pradaxa will make it much easier for people who are elderly, having orthopaedic or pelvic (including gynaecological) surgery - or have any other co-existing medical conditions that might predispose them to thrombo-embolic troubles to have preventive treatment.

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