EVALUATION OF AN AUTOMATED METABOLIC CART COMPARED TO DOUGLAS BAG MEASUREMENT OF VO2

Abstract

1494 To assess the accuracy and reliability of an automated metabolic cart (MC), 19 male subjects (age 18-47) participated in a progressive cycle ergometer protocol. The MC measured inspired volume and gas concentrations from expired air via a mixing chamber. The air from the mixing chamber was then collected in the Douglas Bags (DB), which served as the standard for comparison. VO2, Ve, FeO2, and FeCO2 values were measured at rest, while cycling at 100 and 150 W, and while cycling at a workload close to maximum capability. On a separate occasion, seven subjects repeated the protocol, and values from the two trials were compared to assess the reliability of the DB and MC measurements. Data were analyzed by simple regression and 4 × 2 repeated measures ANOVA (4 workloads × 2 measurement systems). Averaged across the four workloads, the MC underestimated the DB VO2 values by a mean of −87 ml/min. Mean relative error was −3.3%, while total error was ±136 ml/min. There were no statistically significant differences between the MC and DB values for any of the four parameters, though values for VO2 approached significance (p=0.0528). By workload, the mean relative error for VO2 at the peak workload (−6.5%) was noticeably larger than at rest (−0.6%), 100 W (−3.0%), or 150 W (−3.3%). VO2 for the MC demonstrated high repeatability, with an absolute error (64 ml/min, 3.2%) slightly greater than that of the DB measurements (55 ml/min, 2.5%). It is concluded that the MC evaluated in this study is a suitable instrument for measuring oxygen consumption.