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

Abstract.

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 (V_E), fractional concentrations of expired CO₂ and O₂ (F _ECO₂ and F _EO₂, respectively), as well as CO₂ output (VCO₂) which were obtained from the metabolic cart and a Douglas bag system during 22 min submaximal and 5–8 min maximal running on a treadmill. For F _ECO₂ and VCO₂ the metabolic cart gave readings that were 2.6% and 1.8% higher and for F _EO₂ 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.