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 (VO2max calibrator) was fabricated and tested against conventional indirect calorimetry systems that use chain-compensated gasometers to measure expired volume (VE systems) and calibrated electronic gas analyzers. The calibrator was also checked against a system that measures inspired volume (VI system) with a turbine ventilometer. The pooled data from both VE and VI systems for predicted VO2 ranging from 2.9 to 7.9 L.min-1 and ventilation ranging from 89 to 246 L.min-1 how 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 ventilator (VE 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 VE BTPS was approximately 1%. This VO2max 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.

Historical Development of Nutrient and Calorimetry and Expired Gas Analysis Indirect Calorimetry

“…Furthermore, the Douglas bag method is not a suitable criterion method for breath-by-breath EGAIC. This problem has been recognized, and researchers have developed mechanical calibration systems from which numerous EGAIC validation studies have been completed [13,16]). …”

“…These tests are usually conducted to (a) the maximal oxygen consumptions (VO2max), (b) an increase in the ventilator equivalent for oxygen (ventilation threshold, VT), (c) assessment of aerobic power, (d) the rate of change in VO2 for a given increase in exercise intensity (VO2 kinetics), (e) detection of cardiovascular and pulmonary diseases [2,7,20,13,29,32].…”

Assessment of Accuracy of the Vacu-Med 17053 Calibrator for Ventilation, Oxygen Uptake (V̇O2), and Carbon Dioxide Production (V̇CO2)

“…Some calibrators are accurate, but all have limitations, including delivery of calibration gas without correction for pulmonary air saturation, over-reliance on complex equations, and failing to prove accuracy of pulmonary ventilation in conjunction with V O 2 and V CO 2 . [12][13][14][15] None of the available calibrators has been found to be as accurate or reliable as the Douglas-bag method. A recently released calibrator (model 17053, Vacu-Med, Ventura, California) was designed to work with various metabolic monitors, but the manufacturer has not provided accuracy and reliability data, nor has the 17053 been validated in independent academic research.…”

“…In previous studies of mechanical calibrators, none of the instruments were validated for pulmonary ventilation, V O 2 , and V CO 2 against the accepted standard method: Douglas bag. [12][13][14][15] The 17053 calibrator's method differs from the Douglas-bag method in that it serves as the source of gas, and the clinician can calculate and alter pulmonary ventilation, V O 2 , and V CO 2 output with the calibrator. We compared the 17053 calibrator to the Douglas-bag method.…”

The Complex Reality of VO2 Kinetics to Steady State: Reassessment of the Models Used to Quantify and Interpret VO2 Kinetics, Steady State, and Time to Steady State

“…Despite the Douglas bag method often being used as a criterion method in prior EGAIC validation research (Wilmore & Costill, 1974;Wilmore et al, 1976;Proctor & Beck, 1996;Gore et al, 1997;Carter & Jeukendrup, 2002), such a method is based on time averaged expired air collection and subsequent gas mixing across multiple breaths. Consequently, the Douglas bag method is not suitable for validation of new methods for breath-by-breath EGAIC.…”