[Decompression during lowered air pressure].

A linear relationship exists between the overpressure of inert gases in the tissues which is tolerated without symptoms, and the ambient pressure in the range between 1.0 and 50.0 bar. Sixteen subjects, all residents at normal atmospheric pressure and saturated with a nitrogen pressure of 0.75 bar, were decompressed to an ambient pressure of 0.47 bar (corresponding to an altitude of 6000 m above sea level) in 15 minutes. During a 3 hours' stay at this pressure breathing air, symptoms of hypoxia developed but not arthralgias. After hyperbaric exposures in the range between 4.0 and 5.1 bar breathing air, 103 subjects were decompressed and exposed to an ambient pressure between 0.60 and 0.85 bar after surface intervals of varying duration. In 31 of the 103 subjects, the ambient pressure was more reduced than according to the tolerated linear relation. 7 of these 31 subjects reported light pain in the shoulders of knees during the 2 hours' stay at the reduced ambient pressure. These trials demonstrate that the linear relationship between the ambient pressure and the overpressure of inert gas in the tissues tolerated without symptoms is also valid at altitude.