To compensate for this loss, the heart has to work harder, leading to an increased heart rate.
The research was led by scientists at the German Aerospace Centers Institute of Aerospace Medicine.
So they wanted to know if a combination of alcohol and long-haul flying would make the problem even worse.
A flight attendant serving passengers a drink during a flight from Dessau, Germany on July 17 2003.Image: Roland Weihrauch (AP)
The team recruited healthy volunteers between the ages 18 to 40 for their experiment.
A level below 90% isconsidered lowand could merit medical attention.
Those sleeping in the altitude chamber fared worse, especially after drinking.
The teams findings,publishedin the journal Thorax, are based on a small sample size.
So its not clear yet whether the same pattern would be true for those drinking and sleeping while sitting.
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