Continuous brainstem auditory evoked potential monitoring during nocturnal sleep

Continuous monitoring of brainstem auditory evoked potentials (BAEPs) was performed simultaneously with polysomnographic recordings during nocturnal sleep in 9 normal males (mean age 25.3 +/- 2.7 years). Four-channel electroencephalography, respiration (abdominal and thoracic), rectal temperature, electrocardiography, electrooculography, chin electromyography, non-invasive blood pressure (Finapres), oxygen saturation and two channels of BAEPs were recorded by a multivariable computer system. All data except BAEPs were preprocessed, integrated over 30 s and printed on a single sheet. Sleep stages were classified visually. Latencies, interpeak latencies, amplitudes and the I/V amplitude ratio of the BAEPs were analysed in the awake state and different sleep stages. The results confirm that, as previously reported, the slight BAEP latency modifications observed during sleep are correlated to body temperature variations. The analysis of the absolute amplitudes of BAEPs showed insignificant (ANOVA) variations with sleep (e.g., mean amplitude of peak V +/- SD: wakefulness = .36 microV +/- .11, REM = .22 microV +/- .05, stage 2 = .27 microV +/- .14, stage 3 = .25 microV +/- .14, stage 4 = .26 microV +/- .11). A significant change between wakefulness and deep sleep could be found in the latencies of wave IV and V and in the amplitude ratio I/V (P < .05, ANOVA, Student-Newman-Keuls method).