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Oxygen levels appear to have an effect on jet lag:
A small shift in the oxygen levels in the air could act as a "reset" button for the biological clock, according to a new study in mice. Mice in the study that were exposed to a brief dip in the levels of oxygen in the air that they were breathing adjusted more quickly to a new circadian rhythm than mice that received steady levels of oxygen, the researchers found. In other words, the dip in oxygen levels seemed to help the animals adjust to the mouse equivalent of jet lag, according to the study, which was published today (Oct. 20) in the journal Cell Metabolism [open, DOI: 10.1016/j.cmet.2016.09.014] [DX].
[...] [In] an experiment in mice, the researchers exposed the animals to either oxygen levels that remained stable at 21 percent (this is the percentage of oxygen in the air we breathe at sea level), or levels that started at 21 percent, dipped down to 16 percent for 12 hours, then rose back to 21 percent, according to the study. [...] However, the researchers noted that oxygen levels on airplanes are lower than oxygen levels on the ground. Because some people report airsickness due to these lower levels, the aviation industry is apparently investigating an increase in oxygen levels on planes to 21 percent. Given the findings of the study, however, doing so could have a negative impact on jet lag, the researchers wrote. In future experiments, the researchers would like to see if higher levels of oxygen could also shift an animal's circadian rhythm. "I believe passengers [on airplanes] might be more enthusiastic to inhale oxygen-enriched air to alleviate jet lag in contrast to low oxygen" air, Asher said in a statement.
(Score: 1, Informative) by Anonymous Coward on Sunday October 23 2016, @06:01PM
Pretty sure that oxygen (O2) is 21% of the air at any altitude where a jet can fly. Jets aren't pressurized to sea level, so the moles of O2 per lungfull are reduced. If you want constant moles of O2 per lungfull, then the % O2 has to increase as the pressure is reduced.
Ah, just remembered, I have a reference. In his wonderful memoir, "Equations of Motion", William Milliken describes test flights to 35,000 feet at Boeing, when they were developing the B-17 to fly at high altitude. The B-17 was not pressurized, and the test flight crew breathed pure O2. He reproduces a chart worked out by the Mayo Clinic, Fig 11-3, which shows that you get the same amount of O2 at sea level (from air) as you get at 33,000 feet on pure O2. Or, if you are happy breathing air at 5000 feet (~Denver), then you can fly up to about 36,000 feet on pure O2.
A major problem with concentrated O2 is that it is a huge fire promoter, a trivial smouldering fire in normal air can turn into a blaze on pure O2, like the one that killed the crew of Apollo 1 during a ground test.
(Score: 2) by darkfeline on Sunday October 23 2016, @08:24PM
Does the body's oxygen usage depend on constant moles of oxygen, or does the body require less under low pressure (up to a point, of course)?
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(Score: 0) by Anonymous Coward on Sunday October 23 2016, @10:23PM
Not sure what the latest research says about this. My reference goes back to WWII, some of the pioneering work on high altitude flight. I'm pretty sure that constant moles of oxygen is the first order effect but there are probably other factors that make a difference?