Comparison of oxygen consumption, carbon dioxide production, and resting energy expenditure in premature and full-term infants.

A newly developed closed circuit water-sealed infant calorimeter has been used to measure oxygen consumption (VO2), carbon dioxide production (VCO2), respiratory quotient (RQ) and resting energy expenditure (REE) in 31 infants. There were 17 full-term and 14 premature infants. VO2 was measured volumetrically, keeping the inspired oxygen concentration constant. VCO2 was determined by infrared analysis of the mixed expired gases. Values for REE and RQ were calculated from measurements of VO2 and VCO2. All values were normalized for the infants body weight. Our findings demonstrate significant differences in VO2, VCO2, and REE associated with weight, gestational age, postnatal age, activity, feeding, and sex. In addition, VO2, VCO2, and REE were significantly higher for the premature infants. The water-sealed indirect calorimetry system: (a) is safe and noninvasive, (b) does not interfere with infant tube feeding or IV infusion, (c) permits long-term monitoring of metabolic activity, and (d) allows a more exact matching of oral and intravenous feedings to actual energy expenditure. We are finding that indirect calorimetry removes the guess work from writing daily caloric regimens, with potential advantage for the treatment of sick infants.