Environmental Engineering Reference
In-Depth Information
The majority of commentators now agree that there is a connection between air
travel and DVT, although the evidence is still largely circumstantial (Geroulakis, 2001).
However, it is difficult to compare many of the medical studies because of differences
in case selection and data presentation, and there are disagreements as to the true
frequency of air-travel-related DVT events (Hirsch and O'Donnell, 2001). This is
illustrated by recent studies that have ranged from showing no association between
air travel (for travel more than five hours' duration) and DVT (Kraaijenhagen et al,
2000), a 3.8 times increased risk of venous thromboembolic disease for travel over
four hours (Ferrarri et al, 1999), through to a 10 per cent risk of symptomless DVT
occurring in long-haul flight passengers (travel over eight hours' duration) (Scurr et
al, 2001). Thus, while a fair risk assessment of air travel and DVT has still to be per-
formed, a rough estimate of travel-associated venous thromboembolism is 0.5-3 per
10,000 general population per annum (Kesteven, 2000).
There are two key reasons for the lack of data regarding the true frequency of
DVT during long-haul flight. Firstly, many DVT events are symptomless and the
traveller may have no cause to seek any medical attention; secondly, most travel-related
venous thromboembolic disease is not recognized, as the patient can present many
days or weeks after the journey in which the clot originally appeared.
As a result of the lack of conclusive data and the increasing public concern toward
air travel and DVT, the WHO convened a meeting of international experts in March
2001 to review the existing state of evidence. It concluded that further research is nec-
essary, identifying three priorities for further research that should be undertaken as
soon as possible:
•
The first priority is to establish whether or not traveller's thrombosis is a real entity
and, in particular, is a link between DVT and air travel. This will be achieved
through a set of multicentre international epidemiological studies, including a
large prospective cohort study. If a link is to be proven, then the research would
also offer answers as to the absolute risk of DVT in air passengers and the true
scale of the problem, as well as providing clues to other causative factors.
•
The second priority is to identify independent risk factors for flight-related DVT,
both cabin related and behavioural, such as cabin air pressure, cabin oxygenation
levels, excessive use of alcohol and lack of exercise. This will demonstrate how
dangerous flying is compared to other forms of transport for the development of
traveller's thrombosis.
•
The third priority is an interventional study involving passengers prospectively
using objective diagnostic methods and examining various interventional modes
(ie in the event of a proven link, this will enable appropriate management of the
syndrome).
Preventative measures
Despite the lack of reliable and conclusive data, there is increasing concern over DVT
amongst the aviation industry, medical profession and general public. Since DVT is
still potentially fatal, there is a perceived requirement for greater recognition of the
syndrome so that preventative treatments can be adopted to promote healthy travel.
In February 2001, the International Air Transport Association (IATA) advised all
