Sleep states and neonatal pulse oximetry

Pulse oximetry is a quick, easy, noninvasive method widely used for monitoring oxygen saturation (SaO2) in the neonatal period. The greatest recognized problem with SaO2 readings measured from the oximeter is artifact, arising from an inability to record accurately during movement. The aim of this study was to determine the proportion of pulse oximeter readings affected by movement artifact during sleep in term and preterm infants.

Polygraphic recordings were obtained from 11 term and 6 preterm infants at postconceptional ages (SD) of 39.8 (0.8) and 39.3 (1.5) weeks respectively. The polygraphic and computer recordings were divided into epochs of 30 seconds duration and identified as active sleep (AS), quiet sleep (QS), indeterminate sleep (IS), or wakefulness (AW), using electrophysiological parameters and behavioral observations. Movement artifact was identified by visual examination of polygraphic computer recordings using strict criteria. Signal containing artifact was removed from recordings and the percentage of artifact time present per recording calculated.

Signal artifact was present in recordings of all infants studied, comprising an average state time of 19% during quiet sleep, 49% of active sleep, 49% of indeterminate sleep and 91% of wakefulness. A significant difference in the proportion of artifact present in recordings of term and preterm was observed only during quiet sleep.

Movement artifact during pulse oximetry recordings is dependent on behavioral state, and overall affects up to 50% of recorded traces. A reliable and more accurate noninvasive method of recording oxygen saturation is thus needed, for use in both neonatal nurseries and in sleep studies, to aid in accurate clinical decision-making.