Determining the least time required for measuring energy expenditure in premature neonates.

OBJECTIVE: To compare O2 consumption, CO2 production, respiratory quotient and resting metabolic rate in premature neonates measured for 5 and 10 min steady-state periods and 15 and 20 min non-steady-state periods versus a 2-h measurement period. METHODS: A prospective study with neonates evaluated by indirect calorimetry. The measurements from the 5, 10, 15, and 20 min periods were taken based on the printout data from the IC monitor at an interval of 1 h before the beginning feeding and were contained in the 2-h measurement. The 5- and 10-min measurements followed the steady-state criterion. RESULTS: We evaluated 35 premature neonates appropriate for gestational age (born at 28-34 weeks' gestation). Mean age was 20 days+/-9 (median 14 days) and mean weight was 1530+/-270 g (median 1510 g). There was no statistically significant difference between mean VO2, VCO2, respiratory quotient and energy expenditure at 5, 10, 15, and 20 min and 2 h. CONCLUSIONS: The 5 and 10 min steady-state measurements or a measurement of more than 15 min without reaching steady state produce results similar to those of 2 h measurements.