15 THE CALCULATION OF ENERGY EXPENDITURE (EE) FROM CO₂-PRO-DUCTION. (VCO₂) IN PRETERM INFANTS (PI) IS IMPROVED BY ESTIMATING RESPIRATORY QUOTIENT (RQ) FROM NUTRITIONAL INTAKE (FOOD QUOTIENT FQ)

Abstract

In studies of EE with doubly labelled water or with respiratory gas exchange analysis during high FiO2 only VCO2 can be measured and EE is calculated from VCO2 and an estimated RQ. For PI a fixed RQ of 0.87 has previously been used. Does using FQ, an estimate of individual RQ from nutritional intake, improve the accuracy of the EE calculation?

METHODS. We did 32 measurements of VCO2 and VO2 in 17 PI (BW 1450±365 g, GA 30±2wks) breathing room air with a DELTATRAC II. FQ was calculated from intake on the same day (FQ = p*0.81 + f*0.71 +c*1; p,f,c: protein, fat, carbohydrate intake, factors: RQs of nutrients).

RESULTS. EE from VCO2 and FQ agreed well with EE from VO2 and VCO2 (Fig). Median error was 0.13% (range -0.4 to 0.7%), which was considerably less than the error from a fixed RQ-estimate of 0.87 (median -0.3 % (range -5.9 to 9.5%). The error was not influenced by the amount of weight gain (p = 0.809) or by the amount of energy intake in excess of EE (p = 0.345).

CONCLUSION. EE in preterm infants can be precisely calculated from VCO2 and FQ even when they grow or are in positive energy balance.

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