Metabolic rate at rest and during sleep in a thermoneutral environment

This study characterised the pattern of oxygen consumption (V̇o 2) in healthy infants and children asleep and awake (at rest) in a thermoneutral environment. Measurement of respiratory gas exchange (V̇o 2 and V̇co2) 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 V̇o2 and age in the two groups and children aged 2 years or less had the highest values. The value of V̇o2 was significantly higher in the awake subjects (12·5-15·0 ml/min/kg compared with 7middot;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 V̇o 2 of resting and sleeping subjects up to the age of 9·5 years.