EFFECT OF BATHS AT DIFFERENT TEMPERATURES ON OXYGEN EXCHANGE AND ON THE CIRCULATION

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Abstract
Cardiac output was detd. on subjects immersed in warm and cool baths, both by the acetylene method and by one previously described of calculation from blood pressure and pulse wave velocity values. The methods were found to agree except in 2 subjects in warm baths (in the summer) when the calculated values exceeded the others by over 50%. Such discrepancies disappeared in winter expts. Cold increased the peripheral resistance and raised the blood pressure; O consumption and cardiac output might be either increased or decreased. Warmth lowered peripheral resistance and increased output, with an early decrease and later increase in blood pressure. As dehydration supervened there was an increase in peripheral resistance, and this was accompanied by marked indistensibility of the large arteries, so that the pulse pressure might be increased even when the stroke vol. was diminished. The large arteries are considered to act as blood reservoirs. In the winter cardiac output was less increased on warming and the circulation failed earlier from dehydration; the discrepancies between the 2 methods in the summer are ascribed to an incapacity of the acetylene procedure to deal with the high outputs that may then develop. During incipient failure cardiac output was reduced to a basal value in spite of a large 0 intake, but the blood pressure levels were maintained or raised. Under such condition arterio-venous oxygen differences were increased in spite of the skin vasodilatation. O consumption varied with mean body temp. (estimated from skin and rectal measurements), not with rectal temp. alone.