Deep Vein Thrombosis

What is deep vein thrombosis?

Deep vein thrombosis (DVT) is the formation of a blood clot in the deep venous system. It may occur in any situation where there is prolonged pooling of blood in the deep veins of the legs. For travellers, it is often seen in those who have sat still too long in long-haul airline flights and has often been mistakenly called Economy Class Syndrome. In fact, research has shown that DVT can occur as a result of prolonged immobility during long-distance travel by car, bus, train or air (in business class too). If the formed blood clot become detached and travel with the bloodstream to become lodged in the lungs, it will cause a pulmonary embolus (PE). A PE large enough to block a major pulmonary vessel can be fatal.

The risk of developing DVT when travelling is very small unless one or more of the following risk factors exist:-

  • Previous DVT or PE

  • History of DVT or PE in a close family member

  • Use of oral contraceptives or hormone replacement

  • Pregnancy

  • Recent surgery to tummy or legs

  • Cancer

  • Inherited blood-clotting abnormalities

Some researches suggest old age, smoking, obesity and varicose veins also increase the risk.

What are the symptoms of DVT?

Any symptoms. Larger clots may cause symptoms, such as soreness, pain and swelling of the leg. PE is also commonly silent, but can cause chest pain, breathlessness and occasionally coughing up of blood. In severe case, the large clot can cause sudden death. Most episodes of serious DVT or PE occur during or immediately after flight while the passenger is still in the airport, but they may occur many hours or even days later.

How to prevent DVT?

Travellers with one or more above risk factors should seek advice from their doctors or travel medicine practitioners before taking a flight of 3 or more hours.

For the majority who do not possess above risk factors, the advices are:-

  • Whenever possible and at least hourly, travellers should get up and walk around the cabin as preventing blood pooling is the most important measure for DVT. The walking will make leg muscles contract and keep blood flowing through the veins. Alternatively, they can do some foot exercises while seating. Most airlines have video show to inform passengers on how to do the exercises during long-haul flight.

  • Wearing comfortable, loose-fitting clothing that is not tight at the knees or waist and compression stockings may be useful, but the latter need to be of the correct size to be effective.

  • Drink enough water and avoid alcohol and coffee to prevent dehydration and thickening of blood.

  • Do not to use aspirin just to prevent DVT, as there is lack of clear evidence of its benefit.

What is the treatment of DVT?

Anticoagulant therapy is effective for DVT. Travellers who develop any symptoms or signs of DVT, during or immediately after a flight or within the next 4 weeks, should seek medical attention at once for treatment.


Last revision date: 10 October 2012