Comparison of calculated with measured oxygen consumption in children undergoing cardiac catheterization

Our objective was to compare calculated (LaFarge) with measured oxygen consumption (VO(2)) using the AS/3 TM Compact Airway Module M-CAiOVX (Datex-Ohmeda, Helsinki, Finland; AS/3 TM) in children without cardiac shunts in a prospective, observational study. VO(2) was determined at the end of the routine diagnostic and/or interventional catheterization. VO(2 )was calculated according to the formula of LaFarge and Miettinen for each child and compared with the measured VO(2). Data were compared using simple regression and Bland Altman analysis. Fifty-two children aged from 0.5 to 16 years (median, 6.9 years) and weighing 3.4 to 59.4 kg (median, 22.9 kg) were investigated. Calculated VO(2 )values ranged from 59.0 to 230.8 ml/min, and measured VO(2) values from 62.7 to 282.2 ml/min. Comparison of calculated versus measured VO(2) values revealed a significant correlation (r = 0.90, p < 0.0001). Bias and precision were 8.9 and 48.3 ml/min, respectively (95% limits of agreement: -39.4 to 57.2 ml/min). Comparison of calculated VO(2) in children older than 3 years (n = 41), as restricted to the formula, with measured VO(2), revealed a slightly reduced correlation (r = 0.86, p < 0.0001). Bias and precision were 10.0 and 52.5 ml/min, respectively (95% limits of agreement: -42.4 to 62.5 ml/min). We conclude that calculation of VO(2) by the LaFarge formula does not provide reliable values compared to measured values. In clinical routine, measured rather than calculated VO(2) values should be used for the estimation of cardiac output and related variables.