22 Circadian Variation in Oxygen Consumption in Preterm Infants

Abstract

Aims: This study investigated the diurnal variation on oxygen consumption to determine the optimal time periods to obtain measurements representative of a 24-h measurement period in preterm infants.Methods: Oxygen consumption (VO2) and carbon dioxide production (VCO2) were measured continuously over 24 hours using indirect calorimetry. Twenty-two very low birth-weight preterm infants with gestational age of 27 to 31 weeks were enrolled in the study. None of the selected infants were intubated, treated with CPAP or supplemental oxygen at the time of study. All infants were free of malformations and of major current clinical problems. Heart rate, respiratory rate, oxygen saturation, skin and rectal temperatures, and physical activity were monitored continuously.Results: The averaged values of VO2 showed a circadian rhythm with a peak in the afternoon and a minimum during the night. There was no physical activity or environmental stress effect.Conclusions: These finding indicating the possible existence of an endogenous circadian rhythm of VO2 in preterm infants beginning early after birth with a slight synchronization to the daylight cycles. Circadian rhythms of VO2 should be considered when VO2 values were extrapolated from short measurements periods.