[Sleep organization in normal premature newborn infants. Polygraphic study].

Polygraphic recordings including EEG, eye movements (REMs) and limb movements (recorded by piezo-electric crystals), chin EMG and respiratory rate, were performed in 23 normal neonates of 31 to 38 weeks conceptional age (CA). The concordance between various parameters characteristic for sleep states was analysed. For all infants, it was possible to define periods (greater than 7 min) of active (AS) and quiet sleep (QS) according to EEG and REM criteria. Mean duration of the 1st sleep cycle (including both AS and QS) lasted 57 to 65 min; no significant difference regarding CA was observed. According to EEG and REM criteria, AS accounted for 47 to 52% of each sleep cycle; QS rose from 27% at 31-34 wCA to 33% at 35-36 wCA (P less than 0.05); indeterminate sleep (IS) decreased from 32% at 31-34 wCA to 10% at 35-36 wCA (P less than 0.01). At all ages studied, the observed duration of AS was not modified when other criteria were considered in addition to EEG and REMs. On the contrary, the observed duration of QS was frequently shortened and scattered with interruptions (indeterminate sleep) when respiration and body motility were considered; but the tonic EMG remained for 80% of QS. The concordance between different criteria characteristic for QS was not better at 37-38 wCA compared to 31-34 wCA.