A water-sealed indirect calorimeter for measurement of oxygen consumption (VO2), carbon dioxide production (VCO2), and energy expenditure in infants

Abstract

We have developed a water-sealed infant calorimeter (IC) system which uses the techniques of closed-circuit spirometry to measure oxygen consumption (VO2) in premature and full-term infants. Carbon dioxide production (VCO2) is simultaneously calculated from the effluent mixed expired CO2 and the circulating flowrate. Respiratory Quotient (RQ) and Energy Expenditure (EE) are then calculated from the primary data. Measurement of VO2, VCO2, and calculation of RQ were +/- 5.0% of predicted values determined by burning ethyl alcohol or volume extraction and CO2 infusion in our bench model. Measurement in 11 premature infants produced mean values for VO2 and VCO2 of 8.5 +/- 2.5 ml/min/kg and 8.5 +/- 2.4 ml/min/kg, respectively. This system is noninvasive, does not interfere with infant tube feedings or iv infusions, and permits safe, long-term monitoring of the infant's metabolic activity. It allows a more exact matching or oral or intravenous feedings to the actual energy expenditure of the infants, and offers potential advantages for the nutritional management of sick infants.