Contemplating a vacation this summer in Europe, Asia or perhaps somewhere in the southern hemisphere? If so, you should be aware of a potentially dangerous, even fatal, risk that is becoming more common now that airline seat space in economy class has been reduced almost to a form of torture. It’s called pulmonary embolism.

There is a growing incidence, particularly on long flights, of deep vein thrombosis (DVT), the formation of clots in the blood vessels of the muscles of the legs or pelvis as a result of sitting too long in a cramped position. Normally, there is little or no pain associated with a clot, and the victim will be unaware of it.

The danger comes hours or even days later, when a fragment of the clot – called an embolism – breaks loose and travels through the heart to the lungs. Blood enters the lungs through large arteries which then branch down to ever-smaller capillaries, leading finally to the alveoli, where carbon dioxide is exchanged for life-giving oxygen. Somewhere in this network, the embolism will reach a blood vessel too small for it to pass, and there it will lodge, blocking the flow.

If the embolism is large enough to cut off the body’s oxygen supply from an entire lung – or even both lungs in the case of multiple embolisms – death can result very quickly. DVT occurs in more than two million North Americans every year. Nearly 700,000 of those lead to pulmonary embolism, about 65,000 of which are fatal.

Treatment entails the use of anticoagulant and blood-thinning pharmaceuticals to thin the blood and dissolve clots, including warfarin, the common rodenticide that kills rats and mice by inducing internal bleeding. Within 10 to 14 days, clots will normally disappear, leaving the patient none the worse for wear.

But diagnosis is a formidable problem with pulmonary embolism, because the symptoms, shortness of breath and chest pain, so closely match those of other pathologies, not least heart conditions. Despite a simple and reliable blood test that will indicate the presence of a blood clot anywhere in the body, more than 90% of pulmonary embolism fatalities are undiagnosed.

So, what are the preventatives? On a long flight, don’t sit with your legs crossed, flex your toes and ankles and get up occasionally to stretch the muscles at the back of your legs by pushing hard against a wall with one foot after another flexed behind you. There’s usually space for this by the washrooms at the rear of the cabin. Drink plenty of water, avoid alcohol and – provided you have no problem with ulcers – take an aspirin a day for a week or two before departure as a blood thinner.

Finally, it’s not just airplanes that cause clots. Sitting too long in one position without stretching can have the same effect. So remember next time you’ve been immobile for hours on end, staring at your screen, even your computer can be the death of you.

©Dr. Ashely Gordon, 2007.