Economy class syndrome not due to pressure: study

By Michael Conlon

CHICAGO (Reuters) – Reduced air pressure and oxygen levels
do not appear to promote the formation of deadly blood clots
during long commercial flights, an ailment sometimes called
“economy class syndrome,” a report said on Tuesday.

The findings seem to bolster the widely held belief that
clots develop in otherwise healthy people mainly because they
are sitting in cramped quarters that slow blood flow,
especially in the legs, not because of cabin environment.

Travelers have been advised for several years to try to
exercise their leg and calf muscles or walk around the cabin to
prevent the development of clots that can travel to the lungs,
brain or heart.

The same problem can occur during long car or train trips.

Researchers at England’s University of Leicester said they
ruled out cabin pressure and oxygen changes as contributors to
the problem by testing 73 healthy volunteers.

They were placed in seats for eight hours in a chamber
where the air pressure and oxygen levels mimicked those
experienced during commercial air travel. They were allowed to
stand up and move about for five minutes every hour.

The same group was retested at ground-level pressure and
oxygen levels. Blood was drawn before and after each of the
tests.

The researchers said they found no significant difference
between the two tests on clot formation, on the breakdown of
small, naturally occurring clots, in the activation of
platelets — cells in the blood that clump together when
stimulated to promote clot formation — or in the action of
endothelial cells that line the interior surface of blood
vessels.

In a typical commercial flight, the cabin pressure is
equivalent to that found at 5,000 to 7,000 feet (1,500 to 2,100
metres) resulting in oxygen saturation that is about 7 percent
below normal, the study said.

The problem has been dubbed “economy-class syndrome.” But
victims have been reported throughout cabin classes over the
years, the American Heart Association says.

The association advises air travelers to drink extra water,
walk if possible during the flight and avoid alcohol.

The study, published in this week’s Journal of the American
Medical Association, was funded by the European Commission and
the UK Department of Health.