ABSTRACT
All mammals including man exposed to increasing pressure of breathing gas mixture show disturbances at the level of the nervous system, which differ according to which gas is used. The quantity of gas dissolved within the body tissues is a function of the partial pressure of each gas making up the mixture, the partial pressure of each gas being equal to the product of the ambient pressure and the percentage of this gas in the respiratory mixture. In addition, the diluent gas should be as inert as possible for the organism and should have a narcotic potency lower than nitrogen. Three inert gases have a narcotic potency lower than that of nitrogen: hydrogen, neon and helium. Each exposition to gas pressure includes a decompression phase whose duration is a function of the value of the pressure reached, the degree of saturation of gas dissolved in the organism, and of the physical characteristics of the gases used.
