Automated VO2max calibrator for open-circuit indirect calorimetry systems

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 ((V) over dot O-2max calibrator) was fabricated and tested against conventional indirect calorimetry systems that use chain-compensated gasometers to measure expired volume ((V) over dot (E) systems) and calibrated electronic gas analyzers. The calibrator was also checked against a system that measures inspired volume ((V) over dot (I) system) with a turbine ventilometer. The pooled data from both (V) over dot (E) and (V) over dot (I) systems for predicted (V) over dot O-2 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 (V) over dot O-2 and carbon dioxide production, < 0.50 L.min(-1) for ventilation ((V) over dot (E BTPS)), -0.02% absolute for the percentage of expired O-2, and +0.02% absolute for the percentage of expired CO2. Overall, the precision of the measured (V) over dot O-2, (V) over dot CO2, and (V) over dot (E BTPS) was similar to 1%. This (V) over dot (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.