FACTORS INFLUENCING CHLORIDE CONCENTRATION IN HUMAN SWEAT

Abstract

A survey of the literature revealed: complete agreement that sweat chloride (a) increases as work is prolonged, (b) varies between individuals, (c) varies in different regions of the body and (d) varies inversely as the supply of drinking water; majority agreement that sweat chloride (e) increases as the rate of sweating increases and (f) decreases during acclimatization; complete lack of agreement that sweat chloride is affected (g) by body temp., (h) by intake of salt and (i) by plasma chloride; and insufficient or no attention to (j) skin temp., (k) plasma protein and (1) the relation of sweat chloride to physical fitness for work in the heat. Expts. were conducted on men marching out of doors in the summer time and in a heated room in the winter. The present expts. confirm and extend conclusions (a), (b), (d), and (e) above. In addition they indicate that the sweat chloride increases with increasing body temps., increases with local skin temp., decreases more after ingestion of saline soln. than after an equal vol. of water and within wide limits is independent of plasma protein, plasma chloride, and physical fitness. It is suggested that 3 primary factors are concerned with the conc. of chloride in sweat. These are: the local factor of skin temp.; a central factor of which rectal temp. and rate of sweating are probably the most important indices; and the factor of individual idiosyncrasies. The general level of sweat chloride appears to be dominated by this central factor, and increases with increased rectal temp. and rate of sweating. Superimposed on this general level are fluctuations which appear to be correlated with the local skin temp. The interplay of these factors plausibly explains changes heretofore ascribed to duration of work, environmental conditions, intake of water, intake of salt, and acclimatization. Experimentally it was shown that if the rectal and skin temps. were the same, the sweat chloride was the same before and after acclimatization, as would be expected from the hypothesis above.