title: Circadian rhythm of energy expenditure and oxygen consumption.
abstract: BACKGROUND
  This study aimed to evaluate the effect of continuous and intermittent methods of enteral nutrition (EN) administration on circadian rhythm.
  
  
  METHODS
  Thirty-four individuals, aged between 52 and 80 years, were fed through a nasoenteric tube. Fifteen individuals received a continuous infusion for 24 hours/d, and 19 received an intermittent infusion in comparable quantities, every 4 hours from 8:00 to 20:00. In each patient, 4 indirect calorimetric measurements were carried out over 24 hours (A: 7:30, B: 10:30, C: 14:30, and D: 21:30) for 3 days.
  
  
  RESULTS
  Energy expenditure and oxygen consumption were significantly higher in the intermittent group than in the continuous group (1782 ± 862 vs 1478 ± 817 kcal/24 hours, P = .05; 257 125 vs 212 117 ml/min, P = .048, respectively). The intermittent group had higher levels of energy expenditure and oxygen consumption at all the measured time points compared with the continuous group. energy expenditure and oxygen consumption in both groups were significantly different throughout the day for 3 days.
  
  
  CONCLUSIONS
  There is circadian rhythm variation of energy expenditure and oxygen consumption with continuous and intermittent infusion for EN. This suggests that only one indirect daily calorimetric measurement is not able to show the patient's true needs. Energy expenditure is higher at night with both food administration methods. Moreover, energy expenditure and oxygen consumption are higher with the intermittent administration method at all times.
authors.affiliation: Laboratório de Cronobiologia Hospital de Clinicas de Porto Alegre (HCPA)/Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, Brazil.
authors.forename: Marlene
authors.initials: M
authors.lastname: Leuck
authors.forename: Rosa
authors.initials: R
authors.lastname: Levandovski
authors.forename: Ana
authors.initials: A
authors.lastname: Harb
authors.forename: Caroline
authors.initials: C
authors.lastname: Quiles
authors.forename: Maria Paz
authors.initials: MP
authors.lastname: Hidalgo
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002153:Calorimetry, Indirect; D002940:Circadian Rhythm; D002149:Energy Intake; D004734:Energy Metabolism; D004750:Enteral Nutrition / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010101:Oxygen Consumption
keywords: calorimetry; circadian rhythm; energy expenditure; enteral nutrition; oxygen consumption