Plane conditions not likely to cause clots: study

The low oxygen and air-pressure levels during airplane flights aren't likely to lead to blood clots that can be fatal, but passengers shouldmake sure tostretch their legs, British researchers say.

"Our study provides, for the first time, a carefully controlled assessment of the effects on blood clotting of the low air pressure and low oxygen level that might be found during a long-haul flight," saidDr. William Toff, a senior lecturer in cardiology at the University of Leicester in England.

"We found no evidence that these conditions cause activation of the blood-clotting mechanism," Toff said in a release.

Deep vein thrombosis, also called DVT or traveller's thrombosis, is thought to be caused by sitting rigidly for too long.

A blood clot forms in leg veins and may travel to the lungs, heart or brain days or weeks later,possibly leadingto a heart attack or stroke.

Toff and his team designed an experiment to assess the effects of reduced air pressure and low oxygen levels similar to conditions on flights. Their study is in Wednesday's issue of the Journal of the American Medical Association.

Study clotting effects

The teamstudied 73 healthy volunteers under age 40 who sat for eight hours in a chamber with low oxygen levels. About a week later, the same group also sat for eight hours in a chamber set to normal air pressure and oxygen levels.

The volunteers gave blood before and after so researchers could look for effects on blood clotting.

There was no difference in the normal and lowpressure results, Toff's team reports in JAMA.

Toff backs the travel recommendations made by the U.K. Department of Health thatinclude:

• Wear compression stockings to improve circulation during flights.
• Stretch legs occasionally.
• Avoid alcohol.

The study participants weren't allowed to consume alcohol or narcotics, conditions that may differ on flights, Dr. Peter Bartsch of the University of Heidelberg in Germany said in an editorial accompanying the study.

He also noted that since the study included few older participants and women taking oral contraceptives, moreresearch isneeded to investigate the effects of low oxygen and pressure conditions on blood clots.