Metabolic rate at rest and during sleep in a thermoneutral environment.

This study characterised the pattern of oxygen consumption (VO2) in healthy infants and children asleep and awake (at rest) in a thermoneutral environment. Measurement of respiratory gas exchange (VO2 and VCO2) was made using an open circuit flow through system of indirect calorimetry with a specially designed facemask for the collection of exhaled breath. Fifty two healthy subjects aged 4.5 months to 12.8 years were studied for 15-20 minutes; 18 during sleep and 34 at rest (awake). There was a curvilinear relation between VO2 and age in the two groups and children aged 2 years or less had the highest values. The value of VO2 was significantly higher in the awake subjects (12.5-15.0 ml/min/kg compared with 7.5-9.0 ml/min/kg in sleeping children). Comparison of the regression lines after log transformation of these data showed a significant difference in VO2 of resting and sleeping subjects up to the age of 9.5 years.