DVT affects 1 in 10 passengers

[SaturnV]

The results of a study to be published in "Lancet" indicate that DVT occurs in 10 percent of passengers on long-duration flights. Most of those afflicted show no clinical signs. The results are both surprising and controversial.

See the following news item:
http://news.bbc.co.uk/hi/english/health/newsid_1322000/1322107.stm

[GotTheTshirt]

Is there sometning with DVT that I am missing ?
I have a relative, and there are many other people, that spends every waking hour in a wheel chair. why do they not suffer from DVT ?

[wooof]

Yeh, and milk (colesterol) was bad for you, now good for you, dito: alcohol, apples (pestercides), eggs blah blah blah.
Just some scientist trying to get some work published me thinks.

[Devils Advocate]

............ and what I still can't get my head around is why is it that so few flight-crew seem to be afflicted with it, inspite of spending a veritable lifetime sitting immobile on our arses ! .... and certainly so when compared to the few short hours your average pax is exposed to this (apparent) risk, i.e. surely if the title of the thread is true then surely 1 in 10 pilots should be similarly effected ?

[SaturnV]

The following was excerpted from "Lancet" (probably the most prestigious British medical journal).

The study involved 89 male and 142 female passengers. Passengers were included if they were over 50 years of age and intended to travel economy class with two sectors of at least 8 hours duration within 6 weeks.

Of the passengers involved in the study, 115 were given elastic compression stockings to wear; 116 wore their usual stockings or hose.
The average age was 62, none were younger than 56. 12 of the 116 passengers wearing the 'usual' developed symptomless DVT in the calf (five men, seven women). None of the passengers who wore class-I compression stockings developed DVT.

The study invsetigators made an interesting reference to another study which simulated long-haul flights in a hypobaric chamber and detected substantially increased plasma markers of thrombosis in volunteers exposed to reduced ambient pressure.

This might suggest that reduced ambient pressure combined with cramped and largely immobile in-flight seating conditions could jointly contribute to the occurence of DVT.

The doctors who ran the stockings study also voiced the following qualification as all the participants in the study were volunteers who knew they were participating: "We accept that our method of recruitment was not ideal, although we did exclude individuals at highest risk. We were concerned that because of their interest in the problem some of the volunteers may have taken steps to reduce the occurrence of venous thrombosis--ie, by being active during the flight and drinking more fluids. We could not assess the effect that participation in the study had on the behaviour of volunteers while aboard the aircraft. These factors would have applied equally to both our study groups. Whether leg exercises, walking, or drinking water prevent thrombotic events after airline travel remains to be established."

Lancet also published a commentary on the study, somewhat critical of the study methods. In particular, the study investigators were criticized for not eliminating possible bias by the ultrasound technicians looking for clots.

The commentary concluded by saying that "what
is needed are rigorously designed and adequately powered studies to resolve the issue, as agreed at a meeting of scientists and the airline industry organised by WHO on March 12-13. Until more definitive information becomes available, however, it is reasonable to continue to recommend simple measures for long-distance travellers, such as regular isometric muscle contraction and adequate hydration. More aggressive measures might be considered for high-risk patients (such as those with previous VTE or thrombophilia), but these patients should be handled on a case-by-case basis. It would be premature to legislate that airlines change the seating configuration or introduce other costly prophylactic procedures until there is more information on the extent of the problem and on the effectiveness of much simpler preventive measures."

Clearly, many more studies are needed. But given the serious and sometimes fatal consequences of symptomatic DVT, a study that indicates a high incidence of symptomless DVT among a particular cohort of the flying public should raise concerns about how many seats to pack into a long-haul tube and how to go about getting people to stretch their legs without clogging the aisles or bumping their heads in unexpected rough air.