Oxygen consumption and CO2 production of low-birth-weight infants in two sleep states.

The influence of sleep states on the metabolic rate and on the respiratory quotient (RQ) of low-birth-weight infants during continuous feeding was analyzed. Gestational age at birth varied between 29 and 35 weeks, postnatal age between 2 and 56 days and body weight between 0.81 and 2.11 kg. The mean oxygen consumption and carbon dioxide production were 10% higher, while the rise in SD was about 3-fold during REM sleep compared with NREM sleep. The RQ, however, was equal in both states. The sequence of the two sleep states did not have any influence on the analyzed parameters. Averaged over all the measurements, no statistically significant linear trend in oxygen consumption as a function of time could be found. However, small non-zero trends could be found, the direction of which appeared to depend on the sequence of the states.