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Measurement of Respiratory Air Temperatures and Calculation of Respiratory Heat Loss When Working at Various Ambient Temperatures

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Heat loss due to respiration can represent a sizable portion of the bodys total heat loss. The temperature and humidity of expired air are important in determining the respiratory heat loss since this heat loss depends upon, among other things, the difference between the inspired and expired air temperatures and the change in the absolute humidity of the respired air. The purpose of this investigation was to establish the temperature and humidity of the expired air of subjects working at various metabolic rates at ambient temperatures between -40 C and 20 C in order to calculate the heat loss from the body due to respiration. Measurements of the respired air temperature and water vapour content were made for five subjects while they either stood or walked on a treadmill. The results indicated that the maximum respired air temperature varied slightly with the ambient air temperature but changes in metabolic rate, respiration rate and breathing frequency had no apparent effect on the expired air temperature under the conditions studied. The relative humidity of the respired air was found to be close to saturation in the extreme-cold environments. Heat loss due to respiration was calculated and the influence of various physiological and environmental variables on the respiratory heat loss is discussed. Keywords Heat loss Body temperature. Canada.

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  • Anatomy and Physiology

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