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Deep Vein Thrombosis


Long distance travel is a risk factor in the development of venous thromboembolism (VTE). The risk is not confined to air travel, increases with duration of travel and is more common in individuals with pre-existing risk factors.

Prolonged periods of immobility can lead to slow blood flow in the veins which increases the risk of developing deep vein thrombosis (DVT). Blood clots most commonly form in the lower extremities; parts of the clot may break off and travel to the lung where they can cause a pulmonary embolism (PE) which is potentially life threatening.

Although the absolute risk of developing DVT or PE after a long haul flight is very small, the risk is increased where the individual has pre-existing risk factors.

Pre-Existing Risk Factors

Those with the following conditions may be at greater risk of DVT and should be assessed by their General Practitioner prior to travel.

  • A history of DVT.
  • Malignant disease or chronic debilitating illness especially those causing mobility problems.
  • Recent surgery or deep injuries (e.g. hip fractures).
  • Pregnancy or less than 6 weeks after delivery.
  • Heart or lung disease.
  • Taking combined oral contraceptives and/or hormone replacement therapy.
  • Varicose veins.
  • Obesity.
  • Thrombophilia.

Preventive Measures

General advice

  • General advice includes: stretch and exercise the legs when possible (choose an aisle seat), keep well hydrated, avoid excess alcohol as this may encourage immobility and limit caffeine consumption as this may exacerbate dehydration.
  • Many airlines carry information on simple recommended exercises that are easy to carry out during the flight.

Aspirin therapy

  • It is now generally accepted that there is no place for aspirin in the prevention of travel related thrombosis.

Anti-embolism stockings

  • The use of anti-embolism stockings (AES) may reduce the risk of DVT.
  • Travellers should ensure that they buy the correct type and size of stocking and know how to wear them correctly.
  • There may be a small increase in the risk of superficial thrombophlebitis in those with varicose veins.
  • Travellers who require a higher lever of compression than proprietary AES provide, must have them measured and fitted by a trained individual. 
  • Incorrectly fitting AES can increase the risk of DVT.

Low molecular weight heparin

Low molecular weight heparin should be considered for those at higher risk of developing DVT (see above). This treatment is administered by injection and must be prescribed by the traveller's General Practitioner or hospital Specialist and used under their direction.

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