Caloric Requirement of Man in Cold Climates: Theoretical Considerations

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Abstract
Basic equations are given for estimating the heat necessary to warm and humidify the inspired air at various air temps., and for the fraction of the total energy metabolism involved in this process. These equations are: [image] Where U = heat to warm inspired air, Cal./hr.; M = energy metabolism, Cal.; d = density of air corrected to 0[degree]C, g./l.; i = fraction of air breathed absorbed as O2; C = heat value of 1 1. of O2 at 0[degree]C; cp = specific heat of air at constant pressure, Cal./g./[degree]C; tp = temp. to which air is raised in the body, [degree]C; ta = air temp., [degree]C; P = percentage of energy metabolism to warm inspired air; m = insensible heat lost during respiration, Cal./hr.; r = latent heat of vaporization of water at lung temp.; Ai = absolute humidity of the inspired air, g. water/100 g. dry air; Ae = absolute humidity of the expired air, g. water/100 g. dry air; and F = percentage of energy metabolism as insensible heat during respiration. Using these basic equations, assumptions are made for the parameters, and estimations of the actual energy and percentages of metabolism (under the conditions of the assumptions) are tabulated and plotted. From the equations and estimations of the heat necessary to warm and humidify the inspired air, tables and graphs are prepared showing the increase in caloric requirement (food intake) of man which might be expected (in cold climates) at various air temps. Hypothetical equations and calculations are given for the ratio of survival time without to with conservation of the heat necessary to warm and humidify inspired air.

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