Cabin Pressure May Add To Long-Flight Hazard

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By Keith L. Alexander
Tuesday, March 14, 2006

Recently, Mike Wood spent 17 hours flying from Lima to Sao Paulo to New York's JFK International and back home to Washington's Reagan National Airport.

During the marathon flights, Wood, a seasoned business traveler, was vigilant in making sure he kept his legs active. He stretched while in his seat and walked the aisle of the aircraft. In fact, on any flight of more than three hours, the Fredericksburg-based broker doesn't sit still long.

Wood's activity is meant to prevent potential blood clots in the legs that have been known to affect travelers on long flights. But now it seems that Wood's efforts may not be enough to avoid the sometimes-deadly condition known as DVT, or deep vein thrombosis.

A World Health Organization-commissioned study published last week in the British medical journal the Lancet found that the potentially fatal condition may be caused by the relatively low-pressure, low-oxygen environment in aircrafts.

Until recently, DVT was linked primarily to long periods spent in cramped seats without exercise.

Findings of the study are still preliminary and require additional investigation by other health agencies. But the study could have major implications for the airline industry, especially as several major U.S. carriers are increasing the number of international flights as a way to increase profit.

The study now leaves many passengers worried about what they can do to avoid DVT. "We've always known that the air quality on board flights wasn't the best, but there isn't much a passenger can do," Wood said.

DVT, dubbed "economy-class syndrome," was first linked to air travel more than 50 years ago. The condition is caused by the formation of blood clots within vessels, often in the large, deep veins in the lower legs. The clots can block the flow of blood and cause tissue damage in the legs, but can be fatal if they travel to the lungs, where they can cause a pulmonary embolism.

In 2003, NBC correspondent David Bloom developed DVT after riding in a cramped vehicle while covering the war in Iraq and died from a blood clot.

Researchers at the Leiden University Medical Center in the Netherlands and the Academic Medical Center in Amsterdam found that passengers who spent eight hours in an aircraft had a greater likelihood of suffering fatal blood clots than those who sat in a seat on the ground for a similar amount of time.

Researchers studied the blood chemistry of 71 volunteers -- age 21 to 39 -- before, during and after eight-hour flights. The same individuals were also monitored while sitting in similarly structured seats on the ground for eight hours in a theater while they watched movies. The study found that the airborne volunteers were more susceptible to blood-clotting.

Many airlines argue that there is little direct evidence to link DVT to airline travel, saying that individuals who have succumbed to the condition may have been susceptible even if they had not taken a long flight. In fact, some of the volunteers in the study actually had common thrombosis risk factors, researchers said.

Airline executives remain cautious about the study's findings. Katherine B. Andrus, the Air Transport Association's assistant general counsel and point person on various passenger health issues affecting the airlines, said in a brief e-mail statement yesterday that the group was "closely following" DVT developments and that the airlines "encourage further scientific research that will allow these risk factors to be better identified and understood."

Several airlines already urge their passengers to consult their physicians before taking long flights. American Airlines suggests that passengers stretch or walk around the cabin, wear loose clothing, and avoid alcohol and caffeine during trips. And though dehydration has always been considered a contributing factor to DVT, the study revealed that dehydration had no "known effect" on clotting.

Southwest Raises Fares: Southwest Airlines acknowledged that it raised most of its ticket prices as much as $10 each way. It's the second 2006 fare increase for the nation's biggest low-fare, low-cost carrier. In January, Southwest raised its ticket prices by up to $3 each way. Southwest spokesman Ed Stewart said the increases were to offset higher fuel costs.

United Moves at Dulles: United Airlines will move its regional jet operations, United Express, to Concourse A of Dulles International Airport by May 1 as a result of taking over gates from Independence Air, the Dulles-based low-fare carrier that folded in January.

The move comes as United prepares to increase the number of its regional flights on June 8 by adding more trips to destinations including Cincinnati and Bermuda.


© 2006 The Washington Post Company

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