Validity and reproducibility of a whole-room indirect calorimeter for the estimation of VO₂, VCO₂, and resting metabolic rate

Whole-room indirect calorimeters (WRICs) provide accurate instruments for the measurement of respiratory exchange, energy expenditure, and macronutrient oxidation. Here, we aimed to determine the validity and reproducibility of a 7500 L WRIC for the measurement of ventilation rates and resting metabolic rate (RMR). Technical validation was performed with propane combustion tests (n = 10) whereas biological reproducibility was tested in healthy subjects (13 women, 6 men, mean +/- SD age 39.6 +/- 15.3) in two 60 min measurements separated by 24 h. Subjects followed a run-in protocol prior to measurements. The coefficient of variation (CV) and intraclass correlation coefficient (ICC) were calculated for ventilation rates of O2 (VO2), CO2 (VCO2), the respiratory quotient (RQ; VCO2/VO2), and RMR. Technical validation showed good validity with CVs ranging from 0.67% for VO2 to 1.00% for energy expenditure. For biological reproducibility, CVs were 2.89% for VO2; 2.67% for VCO2; 1.95% for RQ; and 2.68% for RMR. With the exception of RQ (74%), ICCs were excellent for VO2 (94%), VCO2 (96%) and RMR (95%). Excluding participants that deviated from the run-in protocol did not alter results. In conclusion, the 7500 L WRIC is technically valid and reproducible for ventilation rates and RMR.