Effect of hypoxia upon temperature regulation of mice, dogs, and man.

2Mice. Mice were exposed in individual compartments of decompression chambers at temperatures constant to +0.25”C. and pressures controlled to rfr2 mm. Hg. Body temperatures were measured by copper-constantan thermocouples in the rectum. Mice, fasted 4-6 hours, were placed in the decompression chambers for 30 minutes to allow temperature equilibrium and then the pressure was reduced gradually, critical levels being reached in from 90-120 minutes. Death, as determined by the last respiration, was the endpoint, and the atmospheric pressure or equivalent altitude (3) at which this occurred was considered to be the hypoxic ceiling for the animal in question. Dogs. Dogs breathed low-oxygen gas mixtures flowing through a mask at a rate which prevented significant rebreathing. Rectal and brain temperatures were recorded using copper-constantan thermocouples. The brain thermocouple was inserted into the parietal area, several days before the hypoxic test and the leads brought out through the skin. At the time of the test, the leads were soldered to the potentiometer. Hamans. Human subjects were exposed to hypoxia by breathing gas mixtures while sitting in a cool room. A standard uniform of light underwear, socks, mitts and hood covered all parts of the body except the face. Temperatures were recorded from the rectum by thermocouple and from the skin of the forehead, arm, thigh, calf, ankle and three points on the trunk by thermocouple and/or radiation pyrometer. Subjects breathed through a face mask connected to an Q-liter closed system by a valved circuit. Carbon dioxide was absorbed with soda lime. Respiratory air flow, respiratory rate and oxygen consumption were recorded. Oxygen could be added to the system at controlled rates to maintain or change the content as desired.