Study of the reproducibility of the measurement of cardiac output during exercise in pre-pubertal children by Doppler echocardiography and CO2 reinhalation

Non-invasive measurement of the cardiac output is essential in investigatio ns of healthy children. However, the data concerning the reproducibility of the measurements are very limited. The aim of this study was to assess the reproducibility of the measurement of cardiac output during exercise by Do ppler echocardiography and reinhalation of CO2 (extrapolation method). Four teen pre-pubertal children underwent two similar tests at increasingly inte nse levels of exercise. The cardiac output was measured at rest and during the last minute of each stepwise increment of exercise. The results show no difference between the cardiac outputs of the two tests, whichever method was used and at all levels of exercise. They also demonstrate a better repr oducibility of cardiac output measurement by Doppler echocardiography (coef ficient of variation : 7.5% at rest and 5.2% at maximal effort) compared wi th reinhalation of CO2 (coefficient of variation : 16.8% at rest and 11.7% at maximal effort). Both methods showed better reproducibility on exercise, resulting from smaller variations in heart rate and stroke volume on effor t than at rest. The authors conclude that Doppler echocardiography is very accurate and its simplicity makes it the method of choice in pre-pubertal children for meas uring cardiac output during exercise.