CBC In Depth
The perils of travellers' thrombosis
CBC News Online | Jan. 11, 2006

It has been called "economy-class syndrome," but that's a misnomer as even people who fly first-class have been killed by it. A better name is "travellers' thrombosis," although the correct name is deep-vein thrombosis or DVT.

It's caused by sitting rigidly for too long – usually on lengthy intercontinental flights – so that a blood clot forms and makes a lethal journey to the lungs or heart. It was first noted more than 50 years ago in London, when people crowded into air-raid shelters to escape bomb attacks during the Second World War.

It became front-page news in September 2000 after the death of Emma Christoffersen, a 28-year-old Briton who died after returning to London from Australia, where she had attended the Olympic Games. Christoffersen collapsed at Heathrow airport following the 19,000-kilometre, 20-hour trip. She died before she reached hospital. She had developed a clot in her leg on the Qantas flight; the clot dislodged and made its way to her heart.

Estimates of the number of deaths from travellers' thrombosis vary widely. A conservative estimate is about 100 a year, though David Derbyshire, medical writer for The Daily Telegraph, says that doctors who carried out a study at Ashford Hospital in Surrey believe more than 2,000 people a year die from the condition in Britain. What made Christoffersen's case more noteworthy was that she was young, in good health and about to be married.

Travellers' thrombosis is regarded as such a new condition that it has not properly been tracked and many deaths may not be recorded as caused by long-haul flights. The Science and Technology Committee of Britain's House of Lords issued a report demanding that the air travel industry do "urgent" research into deep-vein thrombosis among fliers. (The committee also recommended an end to the phrase "economy-class syndrome" on the basis that it is not accurate.)

Blood clots, thrombosis and embolisms are not new, but there appears to be a sharp increase in their occurrence among long-haul air travellers during the past 10 years. Many speculate one of the contributing factors is the decrease in legroom on passenger planes.

To cite an example, British Airways has decreased the distance between seats from 91 centimetres to 79. Seats on Qantas flights are about 81 cm apart. For Air Canada, the seats are spaced about 83 cm apart. The distance between seats is not identical even on the same plane. Exit and bulkhead seats have much more legroom, making them safer for potential travellers' thrombosis victims.

A hospital study in England found that at least 30 people died in a three-year period in the late 1990s of massive blood clots after arriving at Heathrow airport on long-haul flights. An Australian surgeon has been quoted as saying 400 people a year landing at Sydney airport suffer blood clots.

The condition is not always fatal. A story in The New York Times in October 2000 estimated that five million Americans a year experience a blood-clotting thrombosis caused by prolonged immobility. The story said this results in some 800,000 hospitalizations a year. DuPont Pharmaceuticals Co. has responded to the situation by selling the blood-thinning drug Innopehn, designed to prevent and treat the condition.

Remedies suggested include taking Aspirin as a blood-thinner before long flights, maintaining liquids (but avoiding alcoholic beverages), wearing knee-length elastic stockings and getting up from the seat at regular intervals. Critics have also drawn attention to increasingly smaller, cramped seating arrangements in economy sections, especially on charter flights.

The problem has more to do with immobility than with cramped conditions on planes. Travellers' thrombosis has been known to affect passengers in buses, trains, cars, trucks – even theatres. Deadly blood clots also tend to be more of a risk to the elderly, smokers, pregnant women, diabetics, cancer patients and overweight people.

The risk is exacerbated when these people are confined in a cramped, immobile position for long periods. Something as innocent as a kick in the leg a week before a flight can add to the risk of an in-flight blood clot.

The World Health Organization launched a major study in the summer of 2005 aimed at determining how best to prevent travellers' thrombosis. It involves 30,000 travellers on long flights.

The study's participants will be divided into three groups. One third will be asked to use a special machine that keeps the calf muscles stimulated. A second group will be given special exercises to keep the blood flowing. The last group will do nothing. They will be monitored for eight weeks.

It's believed the risk of developing travellers' thrombosis is about one in 1,000 for people on long-haul flights. Results of the study are expected by the end of 2006.

Deep Vein Thrombosis FAQ:
What is Deep Vein Thrombosis?

Deep vein thrombosis is the formation of a blood clot in a deep vein, usually in the calf or the thigh.

What is the cause?

If the vein becomes narrowed or blocked, a blood clot can form at that point. The problem is not only poor circulation from sitting too long in cramped conditions. (Patients confined to bed as a result of a heart condition may also suffer from deep vein thrombosis.) It can also be caused by injury to the vein, or be a side effect of radiation therapy or surgery, or during pregnancy.

What are symptoms of DVT?

  • Pain or soreness in the joint
  • Tenderness and redness in the area
  • Fever
  • Rapid heartbeat
  • Sudden unexpected cough
  • Pain and swelling in the "path" (the area drained by the vein) that is blocked
  • The vein feels hard, like a cord
Some people do not display symptoms if the thromobosis forms in an area other than the leg or arm.

Note: for travellers, the symptoms may not appear immediately. They could occur sometime after the traveller leaves the aircraft, bus or other vehicle.

Danger signs

Deep vein thrombosis can develop into pulmonary thrombosis where the clot breaks away from the vein and travels to the lungs. Danger signs include:

  • Chest pain
  • Coughing up blood
  • New symptoms of pain or swelling which could indicate that treatment is not working
If you have symptoms of Deep Vein Thrombosis, you should call your doctor immediately. If you have the symptoms plus chest pain or coughing up blood call 911.

How to do doctors diagnose deep vein thrombosis?

  • Ultrasound
  • X-ray
  • Tests for blood clots
How is Deep Vein Thrombosis treated?

Preventing the clot from travelling to other parts of the body is the most important part of the treatment. Doctors may prescribe anticoagulant or anti-platelet medication or in some cases, medication called thrombolytics that dissolve blood clots.

Do not rub the affected area, that may dislodge the clot. Keep the limb elevated.

If deep vein thrombosis is detected early, treatment is usually successful. If untreated, the condition can be fatal.

In some cases, deep vein thrombosis becomes a chronic condition, where patients continue to have pain and swelling of the leg because the thrombosis has damaged the blood valves in that vein. The pain and swelling then decrease the activity of the patient.


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Regulate medical care for air passengers: report (May 31, 2004)

Low-dose blood thinner reduces clot risk: study (Feb. 24, 2003)

'Economy class syndrome' risk remote (Dec. 9, 2003)

British man wins court case over cramped air travel (Jan. 24, 2002)

British aviation report calls for more leg room (Sept. 19, 2001)

Airlines agree to study economy class syndrome (March 13, 2001)

Lawsuits lined up over cramped airline seating (Dec. 12, 2000)

Obese passengers need second, free seat: government agency (Dec. 10, 2000)

Economy class seat kills British woman (Oct. 23, 2000)

'Flying Economy causes blood clots' (Aug. 3, 1999)

Thrombosis Interest Group of Canada

Thrombosis: Heart and Stroke Foundation of Canada

Deep vein thrombosis British United Provident Association

Health Aviation Institute

Heathrow airport

Sydney airport

Qantas Airways

British Airways

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