Abstract
In a previous study 1 one of us derived a multiple prediction formula for estimating basal metabolic rate from pulse rate and pulse pressure. Recent interest in the clinical usefulness of this formula made it advisable to reinvestigate this problem and attempt to increase its reliability if it is to be applied clinically. Pulse rate and pulse pressure changes which were found to parallel variations in basal metabolic rate were interpreted as indicative of accompanying alterations in blood flow. The subsequent development of methods for measuring blood flow, and their applications in myxedema and thyrotoxicosis, have demonstrated that heat production, and minute volume closely parallel each other. Simultaneous determinations of blood pressure show that minute volume can be roughly estimated clinically by determining the pulse rate and blood pressure. We first assumed that minute volume varied directly with the product of the pulse rate and the pulse pressure. However, resting minute volume must also vary with the individual's size, so this factor was introduced by multiplying the pulse rate-pulse pressure product by surface area. Combining the above equations, we obtain:
Total heat production = K · Pulse Pressure · Pulse Rate · Surface Area.
Dividing both sides of the equation by surface area gives:
Calories per sq. m. per hour = K · Pulse Rate · Pulse Pressure.
The next step was to ascertain whether or not observations on patients would fit this equation. When the data were assembled, it became evident that the products of pulse rate and pulse pressure were in general higher, and the heat production lower, in women than in men. The derivation of separate formulae for the 2 sexes was therefore essential. Observations were recorded on 416 women and 321 men. A correlation table was prepared for each sex and the equations for the regression lines were determined in the usual way. The simplified final equations are:
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