Health Professionals

Travel Health Information Sheets

Travel Related Venous Thromboembolism (Deep Vein Thrombosis)


Risk for travellers


Signs and symptoms






Venous Thromboembolism (VTE) or Deep Vein Thrombosis (DVT)  are  terms used to describe the formation of a clot, or thrombus, in one of the deep veins, usually in the lower leg. VTE can occur as a result of periods of immobility, for example following surgery, but can also occur spontaneously in otherwise healthy persons.

VTE has been known to occur following long haul air travel and was dubbed ‘economy class syndrome’; however this term is misleading as VTE has also been reported following car and train journeys. The preferred term is now travel related VTE or travellers’ thrombosis.


Risk for travellers

The risk of VTE related to long periods of immobility has been known for many years [1, 2].

Studies from the World Health Organization Research into Global Hazards of Travel (WRIGHT) project on air travel and venous thromboembolism indicates that the risk of VTE approximately doubles after a long–haul flight (>4 hours) and also with other forms of travel where travellers are seated and immobile. The absolute risk of VTE for a flight > 4 hours, in healthy individuals, is estimated to be 1 in 6,000. The risk for travellers increases with the duration of the travel and with multiple flights within a short period [3].

In addition particular risk factors for healthy young (mean age 35-40 years) travellers identified in the WRIGHT studies are:

  • obesity
  • extremes of height
  • use of oral contraceptives
  • presence of prothombotic blood abnormalities [3].

Several factors that increase the risk of VTE have been identified [4, 5]. These include:

  • history of DVT or pulmonary embolism
  • haematological hypercoaguable disorders (e.g. Factor V Leiden deficiency, thrombocythemia, antithrombin deficiency)
  • pregnancy and puerperium
  • malignancy
  • congestive cardiac failure or recent myocardial infarction
  • recent surgery of more than30 minutes duration, performed 4 weeks to 2 months ago
  • oestrogen therapy (e.g. oral contraceptive pill)
  • dehydration


The most severe complication of VTE is pulmonary embolism. This has been estimated to occur in approximately 5 cases per million flights > 12 hours [6].


The physiology of VTE involves three related factors known as Virchow’s triad. These factors are damage to the vessel wall, slowing down of the blood flow and increase in blood coagulability.

Long periods of immobility can slow the blood flow from the lower legs which can result in pooling and coagulation. A thrombus may then form which can occlude the blood vessel. Reduced blood flow can be further compounded by pressure on the popliteal vein in the back of the knee, such as that caused by an airline seat. Flights longer than eight hours have been associated with a hypercoagulable state in some travellers, particularly in those taking oral contraceptive pills and who had a genetic predisposition to venous thrombosis [7].

A pulmonary embolus caused by the thrombus dislodging from the deep veins in the leg and travelling to the lungs is a serious complication and can be life threatening [8].


Signs and symptoms

A VTE can be asymptomatic, however, some persons may develop pain in the calf accompanied by swelling and redness. The affected area is often warmer and there may also be oedema.

If the vein is completely occluded there may be cyanotic discoloration of the limb and severe oedema.

Pulmonary embolus is a serious complication and can be life threatening; sudden onset of dyspnoea is the most common clinical feature.


Once a VTE has been identified anticoagulation treatment with heparin and an oral anticoagulant such as warfarin is usually commenced. Anticoagulation therapy is usually continued for between 3-6 months, and patients are advised to wear a compression stocking on the affected limb for a period of time.


There are a number of measures that can be taken to reduce the risk of travel related VTE. All travellers intending to take long haul flights or other forms of travel where they will be seated or immobile for >4 hours should:

  • avoid dehydration and excessive consumption of alcohol
  • not wear constrictive clothing around the waist or lower extremities.
  • walk around the cabin as much as is practical at regular intervals during the flight
  • regularly flex and extend the ankles which will encourage blood flow from the lower legs
  • take regular deep breaths
  • avoid stowing hand luggage under the seat as it restricts movement


Compression stockings


Travellers at an increased risk of VTE are advised to consider the use of properly fitted below knee graduated compression stockings providing 15 to 30mmHg of pressure at the ankle, which reduce the risk of symptomatic VTE [9, 10] and also reduce swelling associated with long haul flights [11, 12]. Furthermore, it has been shown that the risk of asymptomatic VTE is reduced in travellers using compression stockings [3].  Pregnant travellers on flights >4 hours should have graduated compression stockings fitted [10, 12]. It is important for all travellers that compression stockings are correctly measured and fit properly as poorly fitted stockings could further increase the risk of VTE.

Low molecular weight heparin (LMWH)

The value of LMWH in the prevention of VTE in persons at higher risk of VTE is well established. However, its use in the prevention of travel related VTE is less clear. Most medical practitioners recommend the use of LMWH for travellers at high risk of developing VTE, for example a history of previous VTE or pulmonary embolus [6]. Pregnant travellers with additional risk factors may be advised to have LMWH whatever the duration of the flight [13, 14]. A suitable regimen of LMWH should be discussed with a haematologist, and the traveller or companion trained in its administration unless currently anticoagulated with oral medication such as warfarin.




There is good evidence that aspirin is useful in preventing arterial thrombosis, but it is not recommended for the prevention of venous thrombosis during travel. Aspirin does not reduce VTE in high risk patients [10, 15]. Furthermore a Cochrane review noted that approximately one patient in 40 taking low dose aspirin develop gastric irritation [16].

Due to insufficient evidence supporting the use of aspirin in travel related venous thrombosis, guidelines from the American College of Chest Physicians recommend against its use for VTE prevention associated with travel [5]. UK guidelines support this view and agree that aspirin should not be used for the prevention of VTE in travellers [6].



1. Ferrai E, Chevallier T, Chapelier A, Baudouy M. Travel as a risk factor for venous thromboembolic disease: a case control study. Chest 1999; 115: 440-44

2. Cannegieter SC, Doggen CJM, van Houwelingen HC, Rosendaal FR. Travel-related venous thrombosis: Results from a large population-based case control study (MEGA study). PLoS Med. 2006; 3: 1258-1265.

3. World Health Organization. WHO Research Into Global Hazards of Travel (WRIGHT) project: final report of phase I. [Accessed 29 May 2013]. Available at:


4.  Giangrande P. Thrombosis and air travel. J Travel Med. 2000; 7: 149-154.

5. American College of Chest Physicians Evidence-Based Clinical Practice Guidelines. Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: Chest. 2012; 141(2_suppl):7S 6. Watson HG, Baglin TP. Guidelines on travel-related venous thrombosis. Br J Haematol. 2011 Jan;152(1):31-4.

7. Schreijer AJM, Cannegieter SC, Meijers JCM, et al. Activation of coagulation system during air travel: a crossover study. Lancet 2006; 367:832-8

8. Parkin, L., Bell, M.L., Herbison,et al. Air travel and fatal pulmonary embolism. Thrombosis and Haemostasis 2006, 95, 807–814

9.  Hopewell S, Juszczak E, Eisinga A,et al. Compression stockings for preventing deep vein thrombosis in airline passengers. Cochrane Database Syst Rev 2006; CD004002

10. Kahn SR, Lim W, Dunn AS et al. Prevention of VTE in Nonsurgical Patients. Chest 2012;141(Suppl 2):195–226

11. Scurr JH, Machin SJ, Bailey-King S et al. Frequency and prevention of symptomless deep-vein thrombosis in long-haul flights: a randomised trial. Lancet 2001; 357: 1485-89

12. Belcaro G, Cesarone M, Shah S et al. Prevention of edema, flight microangiopathy and venous thrombosis in long flights with elastic stockings. A randomized trial. Angiology 2002; 53: 635-645

13. Royal College of Obstetricians and Gynaecologists. Air Travel and Pregnancy. Scientific Impact Paper No.1. May 2013 [Accessed 29 May 2013]. Available at:

14. Royal College of Obstetricians and Gynaecologists.Air Travel and Pregnancy- Information for you. 2011 [Accessed 29 May 2013]. Available at:

15. Cesarone MR, Belcaro G, Nicolaides AN et al. Venous thrombosis from air travel: the LONFLIT3 study- prevention with aspirin vs low molecular weight heparin (LMWH) in high-risk subjects: a randomized trial. Angiology. 2002; 53(1):1-6

16. Edwards JE, Oldman A, Smith L et al. Single dose oral aspirin for acute pain (Cochrane Review). In The Cochrane Library 2004, Chichester: John Wiley & Sons Ltd


British Medical Association Board of Science and Education. The impact of flying on passenger health: a guide for health professionals.

NICE guidelines: Venous thromboembolic diseases: the management of venous thromboembolic diseases and the role of thrombophilia testing

Last Reviewed May 2013

Last Edited December 2013