title: Circadian variation on oxygen consumption in preterm infants.
abstract: OBJECTIVE
  We investigated the diurnal variation in oxygen consumption to determine the optimal time periods of calorimetry in preterm infants.
  
  
  METHODS
  Oxygen consumption (VO(2)) was measured continuously for 24 h using indirect calorimetry. Twenty-two premature infants with gestational age of 27-31 (31+/-1.7) weeks were enrolled in the study. Heart rate, respiratory rate, oxygen saturation, skin and rectal temperature and physical activity were monitored continuously.
  
  
  RESULTS
  The averaged values of VO(2) showed a significant pattern (P<0.0001) of circadian rhythm with a peak in the afternoon and a nadir during the night with significantly differences between the mean VO(2) values. A circadian variation of VO(2) was found in more than 80% of preterm infants and was unrelated to gestational age, physical activity or environmental stress. The infants spent 90.4% of their time sleeping.
  
  
  CONCLUSIONS
  These findings indicate the possible existence of an endogenous circadian rhythm of VO(2) in preterm infants beginning shortly after birth. Day-night variations of VO(2) should be considered when VO(2) values are extrapolated from short measurement periods to prevent overestimation of values.
authors.affiliation: Department of Pediatrics, University Hospital of Muenster, Muenster, Germany. Jacqueline.Bauer@ukmuenster.de
authors.forename: Jacqueline
authors.initials: J
authors.lastname: Bauer
authors.forename: Andreas
authors.initials: A
authors.lastname: Janecke
authors.forename: Joachim
authors.initials: J
authors.lastname: Gerss
authors.forename: Katja
authors.initials: K
authors.lastname: Masjosthusmann
authors.forename: Claudius
authors.initials: C
authors.lastname: Werner
authors.forename: Georg
authors.initials: G
authors.lastname: Hoffmann
mesh_terms: D002153:Calorimetry, Indirect; D002940:Circadian Rhythm; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000378:metabolism*; D010101:Oxygen Consumption