Metabolic rate and O2 consumption in newborns during different states of vigilance.

In 135 asymptomatic newborn infants, 1--53 days of age, body weight 1,820--4,120 g, indirect calometry was performed. According to the state of wakefulness the infants showed during the testing procedure, they were divided into four groups of vigilance (V1--V4). Metabolic rate and oxygen consumption showed similar results between groups V1, V2 and V3 (deep sleep; REM sleep; wakefulness with no muscular activity). V4 infants (with muscular activity) had a higher metabolic rate and O2 consumption. Correlation between metabolic rate and body surface area is similar in V2 and V3 but shows a steeper slope in the V1 group. It is speculated that central regulatory mechanisms may account for this difference.