Oxygen uptake in infants and children: a simple method for measurement.

Abstract

We have measured oxygen consumption continuously in children of any age by drawing room air through a hood placed over the child9s head. The oxygen concentration of mixed expired gas was measured with a new paramagnetic oxygen analyzer (Servomex OA 150). By in vitro tests the system was accurate to within 4.2% (standard deviation) of known oxygen uptakes calculated by burning ethyl alcohol. There was also good correlation between oxygen consumptions measured sequentially by this method and by conventional collection of expired air in a Douglas bag. When oxygen uptake is stable a sample of mixed expired gas can be withdrawn for analysis of carbon dioxide concentration by the Scholander technique. This allows calculation of carbon dioxide production and respiratory exchange ratio. In 22 children under 3 years of age the oxygen consumption at cardiac catheterization was 162 ± 34 ml/min/sq m or 8.8 ± 1.6 ml/min/kg (mean and standard devialion). The wide variability indicates the importance of measuring oxygen consumption rather than using tables of average values. The system is portable, inexpensive, stable and very easy to use.