Automated ??VO2max calibrator for open-circuit indirect calorimetry systems

Abstract

The complete calibration of indirect calorimetry systems involves simultaneous checks of gas analyzers, volume device, and software, and this requires a machine that can mimic accurately and precisely the ventilation and expired gases of an athlete. While previous calibrators have been built successfully, none have matched the ventilatory flows produced by athletes during high intensity exercise. A calibrator able to simulate high aerobic power (˙VO_2max calibrator) was fabricated and tested against conventional indirect calorimetry systems that use chain-compensated gasometers to measure expired volume (˙V_E systems) and calibrated electronic gas analyzers. The calibrator was also checked against a system that measures inspired volume (˙V_I system) with a turbine ventilometer. The pooled data from both ˙V_E and ˙V_I systems for predicted ˙VO₂ ranging from 2.9 to 7.9 L·min^-1 and ventilation ranging from 89 to 246 L·min^-1 show that the absolute accuracy (bias) of values measured by conventional indirect calorimetry systems compared with those predicted by the calibrator was excellent. The bias was < 35 mL·min^-1 for ˙VO₂ and carbon dioxide production, < 0.50 L·min^-1 for ventilation (˙V_{E BTPS}), -0.02% absolute for the percentage of expired O₂, and +0.02% absolute for the percentage of expired CO₂. Overall, the precision of the measured˙VO₂, ˙VCO₂, and ˙V_{E BTPS} was ≈1%. This˙VO_2max calibrator is a versatile device that can be used for routine calibration of most indirect calorimetry systems that assess the ventilation and aerobic power of athletes.