Introduction: During sleep, sudden drops in pulse wave amplitude are commonly observed simultaneously with microarousals. Their presence is thought to result from a vasoconstriction induced by an autonomic central nervous system activation. We sought to determine if pulse wave amplitude drops are associated with cortical activation as quantified by EEG spectral analysis.
Methods: EEG spectral analysis was performed over 5 consecutive epochs of 5 seconds before, #1+2: during #3 and after # 4+5 the pulse wave amplitude drops (>20%). A total of 1084 events, from 10 consecutive sleep polygraphic recordings were analysed. The presence or absence of visually scored EEG arousals was also determined (according to AASM criteria). EEG spectral analysis was performed over five wave lengths: (beta 17-30 Hz, alpha 8-12 Hz, theta 4-8 Hz, sigma 12-16 Hz and delta). The power density of each type of EEG wave was compared between the five epochs using
repeated measures ANOVA with a Tukey post hoc test.
Results: The global analysis of all drops in pulse wave revealed a significant increase in EEG power density of all EEG wave for the epoch #3 in comparison to the preceding (#1-2) and subsequent (#4-5) ones (p <0.001). Further analysis of pulse wave drops not associated with a visually recognized microarousal also revealed a significant increase in EEG power for all types of waves during the pulse wave drops (epochs #3; p <0.001).
Conclusion: Pulse wave amplitude drops, observed on polygraphic sleep recordings, are associated with a sudden increase in EEG power density in all wave length. This suggests that drops in pulse wave amplitude are concomitant to central nervous system activation, even in absence of microarousal.