OBJECTIVEWhile the technology of the molecular sieve oxygen generation system(MSOGS) onboard was used, pilots could not breathe pure oxygen to eliminate nitrogen during a high altitude flight. There is no report whether it is a threat to altitude decompression sickness(ADS) or not in that condition. This experiment was intended to observe the effects of breathing different oxygen-rich gases of MSOGS on denitrogenation, so that we could make the medical physiological requirements for MSOGS on-board and provide experimental basis for aeromedical supply.

METHODEight healthy males were breathed oxygen-rich gases (60%,70%,80%,90%and 99.6%) in turn for 60 min, and the concentration of nitrogen, oxygen, carbon dioxide and argon at the end of expiration interval in the oxygen mask were continuously measured by a flight mass spectrometer through the oxygen mask. According to the variety of the denitrogenation rate by breathing different oxygen-rich gases, its change law was analyzed.

RESULTSThere were significant differences (P < 0.05) about denitrogenation rate in different oxygen-rich gases due to different oxygen concentration and breathing time. The denitrogenation rate of pure oxygen was higher than that of the others. It was indicated that the concentration of nitrogen in lung would decrease along with the increase in oxygen concentration of oxygen-rich gases, and the nitrogen concentration in the lung almost decreased by 50% or even more if people were breathed 60%-90% oxygen-rich gas longer than 60 s.

CONCLUSIONThe man-made respiration environment of low nitrogen can be provided by breathing oxygen-rich gases, although the denitrogenation velocity of breathing oxygen-rich gases is lower than that of breathing pure oxygen. So it can be used as a measure to eliminate and lower the nitrogen in the body to prevent from ADS.