Determination of the basal metabolic rate of humans with a whole-body calorimeter

Claim 1

A whole-body calorimeter for use in obtaining data for calculating the basal metabolic rate of a human subject, comprising, means presenting a chamber for enclosing the subject to be measured, a base on which the subject can recline in said chamber, an inlet for admitting ambient air into said chamber, an air outlet, said chamber being substantially sealed except for said inlet and outlet, means for establishing a constant, known flow of ambient external air through said chamber from said inlet to said outlet, said flow being discharged to atmosphere, means for measuring the temperature of air external to said chamber, the temperature of air entering said chamber by said inlet, and the temperature of air leaving said chamber by said outlet, means for measuring the relative humidity of air in said chamber, and a heat source comprising an electric heater of known heat output within said chamber for heating air in said chamber at a known energy input rate when no subject is present, in order to calibrate heat losses through the walls of said chamber from said heat source when no subject is present in the chamber, said heat source being inactive when the subject is present in said chamber.

Claim 11

A method of measuring the basal metabolic rate of a human, comprising A. providing an openable, sealable chamber sized to accommodate a human subject in a resting position therein; B. calibrating the calorimeter, without a subject in the chamber, by the steps comprising: 1. establishing a flow of atmospheric air through said chamber from an inlet thereof to an outlet from which said air is discharged to atmosphere; 2. supplying heat into said chamber at a known rate from a steady heat source in said chamber, 3. measuring the inlet air temperature, the ambient air temperature, the outlet air temperature as a function of time, the relative humidity in the chamber, and the rate of flow of air through said chamber; 4. calculating the heat capacity of the air discharged from the outlet; and 5. from the data obtained in step B3 and the rate at which heat is supplied by said heat source, calculating calibration constants of the chamber, comprising the rate at which heat is lost from the calorimeter surface to its surroundings and the total heat capacity of said calorimeter; C. de-energizing said heat source; D. positioning the subject in a resting position within said chamber, and again establishing a flow of air from said inlet through the chamber to the outlet; E. with said subject in said chamber and air flowing through said chamber, measuring the inlet air temperature, the ambient air temperature, the outlet air temperature as a function of time, the change of relative humidity of air in the chamber with time over the test period, F. calculating the rate at which heat is generated by the subject in the chamber in accordance with the heat transport equation, rate of heat generation by the subject within the calorimeter=rate of energy accumulation within calorimeter-rate of energy supplied to calorimeter by inlet air stream+rate of energy removed from calorimeter through outlet air stream+rate of heat lost through the calorimeter walls, wherein the rates summed in such calculation are calculated from the calibration constants determined in step B5, the heat capacity of air discharged from the outlet with the subject in the chamber, and the measurements obtained in step E, G. calculating the rate of latent heat absorption by evaporation, and H. calculating the basal metabolic rate of the subject by adding the rate at which heat is generated by the subject in chamber, as calculated in step F, and the rate of latent heat absorption by evaporation as calculated in step G.

Claim 12

A method of measuring the basal metabolic rate of a human, comprising A. providing an openable, sealable chamber sized to accommodate a human subject in a resting position therein; B. calibrating the calorimeter, without a subject in the chamber, by the steps comprising: 1. establishing a flow of atmospheric air through said chamber from an inlet thereof to an outlet from which said air is discharged to atmosphere; 2. supplying heat into said chamber at a known rate from a steady heat source in said chamber, 3. measuring the inlet air temperature, the ambient air temperature, the outlet air temperature as a function of time, the relative humidity in the chamber, and the rate of flow of air through said chamber; 4. calculating the heat capacity of the air discharged from the outlet; and 5. from the data obtained in step B3 and the rate at which heat is supplied by said heat source, calculating calibration constants of the chamber, comprising the rate at which heat is lost from the calorimeter surface to its surroundings and the total heat capacity of said calorimeter; C. de-energizing said heat source; D. positioning the subject in a resting position within said chamber, and again establishing a flow of air from said inlet through the chamber to the outlet; E. with said subject in said chamber and air flowing through said chamber, measuring the inlet air temperature, the ambient air temperature, the outlet air temperature as a function of time, the change of relative humidity of air in the chamber with time over the test period, F. calculating the rate at which heat is generated by the subject in the chamber in accordance with the heat transport equation, rate of heat generation by the subject within the calorimeter=rate of energy accumulation within calorimeter-rate of energy supplied to calorimeter by inlet air stream+rate of energy removed from calorimeter through outlet air stream+rate of heat lost through the calorimeter walls, wherein the rates summed in such calculation are calculated from the calibration constants determined in step B5, the heat capacity of air discharged from the outlet with the subject in the chamber, and the measurements obtained in step E, G. calculating the rate of latent heat absorption by evaporation, and H. calculating the basal metabolic rate of the subject by adding the rate at which heat is generated by the subject in chamber, as calculated in step F, and the rate of latent heat absorption by evaporation as calculated in step G.