Immobility not only factor in DVT air risk -study

LONDON, Mar 11 (Reuters) Cramped conditions on aircraft can increase the odds of developing potentially fatal blood clots but researchers said yesterday, other factors may be at play too.

Low pressure and low oxygen levels in aircraft may also contribute in some people to the risk of deep vein thrombosis (DVT).

DVT, often called ''economy class syndrome,'' usually develops in the legs and can be fatal if the clot dislodges and moves to the brain or lungs.

Professor Frits Rosendaal of Leiden University Hospital in the Netherlands and his team compared concentrations of markers for blood clotting in 71 healthy people before, during and immediately after an 8-hour flight.

They also looked at the markers in the volunteers after 8 hours in the cinema and after doing daily activities.

''Activation of coagulation (clotting) occurs in some individuals after an 8-hour flight, indicating an additional mechanism to immobilisation underlying air travel related to thrombosis,'' Rosendaal said in the study.

Farrol Kahn, director of the non-profit group Aviation Health which deals with health issues linked to flying, said it was a significant study because it established a solid link between air travel and DVT.

POSSIBLE MECHANISMS Dr Suzanne Cannegieter, a co-author of the study, said the research uncovers possible mechanisms for the link between DVT and long-haul air travel.

''It was never sure if all those people had not been in an airplane but in a car for the same time, then maybe they would have had the same problems,'' she told Reuters.

''From this study it seems that is not the case. There is something extra in a plane that would increase the risk (of DVT) more than just sitting still,'' she added.

The British Air Transport Association (BATA) which represents most UK registered airlines said the research was not new.

''There are a minority of people who are predisposed to DVT.

They should get advice before they take a long flight,'' said Bob Preston of BATA.

In the study, the scientists found that concentrations of the clotting markers were higher in people after a long flight than they were after sitting in the cinema for the same time or doing daily activities, particularly in patients who had other risk factors for DVT.

Rosendaal said about 40 per cent of the people in the study had an increased risk of DVT because of a genetic mutation or were women taking oral contraceptives, which also carry a raised risk of DVT.

In a commentary on the research, Dr Hans Stricker of the Ospedale Regionale in Locarno, Switzerland described the research as adding an ''important piece of evidence to the mosaic of travel-induced thrombosis.'' He advised air travellers to avoid taking sedatives or drinking too much alcohol during flights to reduce the risk of DVT. Compressive stockings that improve blood flow could also help.

REUTERS DKS SP0948