A metabolic cart for measurement of oxygen uptake during human exercise using inspiratory flow rate

This study evaluated an ergo-spirometry system based on mixed expired gas for gas analyses and an inspiratory based determination of flow. There were 74 paired samples of oxygen uptake (VO2) and related variables including pulmonary ventilation WE), fractional concentrations of expired CO2 and O-2 (FECO2 and FEO2, respectively), as well as CO2 output (VCO2) which were obtained from the metabolic cart and a Douglas bag system during 22 min submaximal and 58 min maximal running on a treadmill. For FECO2 and VCO2 the metabolic cart gave readings that were 2.6% and 1.8% higher and for FEO2 0.2% lower than the Douglas bag method (P<0.05). For the metabolic cart and the Douglas bag method the coefficient of variation (CV) for repeated determinations of VO2 was 1.9% and 1.8%, respectively. For VO2 and V-E, there were no significant differences between the two methods and the 95% confidence interval of the difference in VO2 was within -30 and +20 ml min(-1). The CV of the differences in VO2 between the two systems was 2.4% and it is concluded that a metabolic cart method based on inspiratory flow rate is suitable for measurement of VO2 and V-E during both submaximal and maximal exercise.