Exposure of mice to a helium-oxygen atmosphere at pressure to 122 atmospheres.

Abstract

Forty-eight mice were subjected to saturation exposures in a He-O2 environment at pressures from 92 to 122 atm. O2 partial pressure was controlled between 160 and 380 mm Hg; CO2 was absorbed by granular soda lime. All mice remained conscious and active throughout the exposure. It became possible to decompress an entire group of mice safely even from the highest pressures employed, although in several instances early in the study technical difficulties resulted in death on decompression. Mice surviving decompression from the highest pressure lived until sacrificed several months later. Effects observed during the compression and exposure to maximum pressure phases were an altered pattern of respiration and coarse tremors. It appears that exposure of the central nervous system of mice to a pressure equivalent to 4,000 ft. of sea water is not lethal and that any narcotic effects of He are not incapacitating. It is therefore probable that the central nervous system of man can tolerate the same He pressure. However, this study in mice offers no information useful in predicting adverse effects of such pressures upon the pulmonary gas exchange of larger animals, including man.