This site is intended for health professionals only

Deep truths about travel-related thrombosis

Liz Rosies
RGN
Author of www.travelhealth.co.uk
Bank Nurse Travel Clinic - Inter Health, London

In the last 50 years air travel has increased more than 37-fold, with more travellers venturing to long-haul destinations than ever before.(1) This increase has required health professionals to be aware of the risks involved with air travel, and more specifically the risks associated with long-haul flying.
The death of a 54-year-old doctor who had developed a deep vein thrombosis (DVT) after a 14-hour flight was reported in 1954.(2) In October 2000, newspaper headlines alerted the public to the risks of DVT when a young woman dropped dead at Heathrow after a 17-hour flight from Australia.(3) This was followed by a flood of media attention and similar reports from around the globe,(4) which set in motion an ongoing debate about just whose responsibility it is to inform passengers of the associated potential risks. Under the Warsaw Convention, airlines carry no legal responsibility to tell passengers about health risks believed to be associated with air travel.
(For more information see www.aviation-health.org)
With limited research completed in the area of travel-related DVT, there is no proven link relating DVT to air travel, but there is a wealth of anecdotal evidence. While some airlines have begun informing passengers of the potential risk of DVT,(5,6) many still claim it is the­responsibility of the passenger to be informed.
Over the last few years the media has reported numerous health scares as a consequence of air travel. The House of Lords stated that such health scares are often unsubstantiated and a better review of the facts is needed.(7) At present the first priority is air safety, with health issues often neglected in government recommendations and rulings. A meeting by the World Health Organisation concluded that "there probably exists an association between venous  thrombosis and travel in general but there is insufficient data on which to make recommendations".(8) It called for more research relating to the risks of DVT and stated that although a risk exists, it is probably only in those with pre-existing risk factors (see Table 1). It concluded that while leg exercises were useful in-flight, the committee could not endorse the use of medication until further research had been completed.

[[NIP01_table1_43]]

Physiology of DVT
The position that a passenger adopts on a plane is believed to be the primary factor in the increased risk of DVT. Cramped conditions and tight clothing add to the risk of impaired circulation, leading to a slowing down of the blood in the deep veins.(9) This can cause the development of a clot, which in turn leads to complications. During World War II there was a huge increase in death from DVT, which was believed to be due to cramped conditions and people having to adopt a similar position for many hours in the air-raid shelters.(10)
Dehydration is also believed to increase the risk of travel-related DVT. While flying at an altitude of 38,000ft, water is quickly lost through expiration and the breathing in of relatively dry recycled air.(11) Alcohol, tea and coffee can add to the dehydration problem, and the changes in pressure can lead to blood viscosity, potentially increasing the risk of DVT.(12)
The traveller suffering from DVT will often experience no symptoms. If symptoms do occur, they are likely to be a slight tingling in the lower leg along with localised tenderness or swelling and a raised skin temperature in the surrounding area. Approximately one in four patients go on to develop complications after experiencing DVT. The most serious complication is the development of an embolism, which can break off from the original clot in the deep vein and make its way to other major organs, such as the brain or the lungs. Here it can become logged and rapidly cause life-threatening difficulties.(13)

Implications for practice
In light of recent recommendations and media reports it is essential that we give patients the correct message. One of the main problems is the lack of hard research, so we are able to inform patients of potential risk only  within our current framework of recent best practice. 
The House of Lord's recommended that the public be made aware that the term "economy class syndrome" is misleading,(7) as the condition can affect anyone. It is essential that patients are aware of the risk factors and potential risk - including those business travellers who think nothing of travelling with a laptop on their knees.
Advice related to DVT should be ongoing through all aspects of general practice clinics. It is essential to seek out high-risk candidates for health promotion advice. Many long-haul travellers do not come for a consultation as they are going to developed regions and do not consider the need for travel health advice. It is therefore essential that we use websites and practice leaflets to inform travellers. Advice should also be aimed at those travelling by bus or train, because such ­circumstances can result in the same risk situation.(14) Lower air pressure, dehydration, lack of mobility and confined space can all increase DVT risk. It is our duty as travel health professionals to offer prevention advice to those patients we consider to be at risk (Table 2).

[[NIP01_table2_44]]

[[NIP01_pp_44]]

References

  1. Cossar J. Historical aspects of travel medicine. In: Lockie C, Walker E, Calvert L, et al. Travel medicine and migrant health. London: Churchill Livingstone; 2000.
  2. Homans J. Thrombosis of the deep leg veins due to prolonged sitting. N Engl J Med 1954;250:148-9.
  3. Perry K. Blood clot kills woman after flight. Guardian 2001 Oct 23.
  4. James J. Perils of passage. Time Magazine 2001 Mar 19;157:11.
  5. British Airways passenger advice related to DVT. Available from: URL: http://www.britishairways.com/health
  6. Qantas Airlines in-flight exercises. Available from: URL:http://www.qantas.com.au/flights/essentials/healthinflight.html
  7. House of Lords Report on Air Travel and Health. London; 2000. Available from: URL: http://www.parliament.uk  
  8. World Health Organisation - Press Release March 2001. Available from: URL: http://www.who.int/inf-pr-2001/en / index.html
  9. Geroulakos G. The risk of venous thromboembolism from air travel. BMJ 2001;322:188.
  10. Simpson K. Shelter deaths from pulmonary embolism. Lancet 1940;11:744.
  11. Wilson A. The problems of aircraft cabin air. J BTHA 2000;1:3-8.
  12. McIntosh I. Travel, trauma, risks and health promotion. Dinton: Quay Books; 1998.
  13. Nursing Online Education - Deep vein thrombosis. Available from: URL: http://www.nursingstandard.co.uk/archives/vol15-18/pdfs/p4754v15w18.pdf
  14. Ferrari E. Chevallier T, Chapelier A, Baudouy M. Travel as a risk factor for venous thromboembolic disease: a case control study. Chest 1999;115:440-4.
  15. Prevention of pulmonary embolism and deep vein thrombosis with low dose aspirin: Pulmonary Embolism Prevention (PEP) trial. Lancet 2000;355:1295-302.

Resources
TRAVAX database
W:www.travax.scot.nhs.co.uk
Travel Health website
Nurse-led website offering travel health advice
W:www.Travelhealth.co.uk.