Medical officials from 16 major airlines and international experts began two days of talks Monday to examine links between deadly deep vein thrombosis (DVT) and air travel.

The closed-door talks follow a number of reported deaths in recent months that have increased concern among travelers that clots may form in the lower limbs due to immobility and poor blood circulation while passengers fly in cramped seats.

If the clot travels to the lungs, heart or brain, it can block vessels and prove fatal.

So-called "economy class syndrome" has sparked a spate of litigation in Britain and Australia and a threat of class action suits against airlines.

"This meeting is very important in the sense that it's the first time that airlines of the world have got together under the auspices of the WHO to talk about a problem that has been booming in the last year or so.

In October, Briton Emma Christoffersen, 28, died after collapsing in the arrival hall of London's Heathrow airport after returning from Australia, a 12,000-mile trip.

But the jury is still out as research mounts into the link between air travel and DVT. Some airlines have begun showing videos about DVT to instruct passengers on ways to decrease the risk through in-seat exercises to increase circulation.

Risk factors for DVT include

• age
• obesity
• smoking
• pregnancy or taking hormone replacement pills
• history of thrombosis or recent surgery
  

Australian scientists plan to conduct the world's biggest study of patients suffering DVT to examine the link with travel.

The European Commission also said last month it was funding the largest-ever study into the effects of flying on passenger health. The aim is to devise a minimum standard for all commercial aircraft in Europe.

Three carriers -- British Airways, SAS and KLM -- are taking part in the three-year study into cabin air pressure, humidity, temperature, and blood oxygen levels of passengers and crew.

Both the International Civil Aviation Organization (ICAO) and International Air Transport Association (IATA) are attending the Geneva talks organized by WHO's cardiovascular disease unit.

IATA, which has 274 member airlines, said last month there was "no conclusive medical evidence" of a link.

But it urged airlines to warn travelers of the DVT risk when reservations are made and recommended in-flight precautions to passengers.

Passengers should drink enough fluids to avoid dehydration, wear loose-fitting clothing, avoid smoking and alcoholic drinks, and do exercises while seated, it said.

World Health Organization Geneva, Switzerland March 12, 2001