Effect of sleep stages on synchronized spontaneous otoacoustic emissions in pre-term neonates

Objectives: In infants, auditory tests are mainly performed during sleep, since they spend most of their time asleep, and because quiet is required for the duration of the recording session to obtain a precise and reliable response. The aim of this study was to investigate the effect of sleep stages on synchronized spontaneous otoacoustic emissions (sSOAEs) in pre-term neonates at the age where the sleep states begin to be well established and auditory screening can be performed in a neonatalogy unit before discharge. Methods: Synchronized SOAEs were repeatedly recorded during a polygraphic sleep recording using the Otodynamic ILO88 system in 10 pre-term neonates at 36 weeks post-conception. Results: Variations of sSOAE peak numbers occurred in each subject during the recording session. There was no clear relation between sSOAE peak number fluctuations and the different sleep stages. Conclusions: The sSOAE variations appeared to be closely related to experimental conditions, i.e. the mean background noise level. sSOAEs with the highest amplitude were always recorded; however, those with the smallest amplitude were the first to disappear from the recordings with higher background noise.