Respiratory cycle-related EEG changes during sleep reflect esophageal pressures

Study Objectives: Respiratory cycle-related EEG changes (RCREC) have been demonstrated during sleep by digital analysis and hypothesized to represent subtle inspiratory microarousals that may help to explain daytime sleepiness in patients with sleep-disordered breathing. We therefore examined for the first time associations between RCREC and esophageal pressure swings (ΔPes) that reflect work of breathing. Design: Retrospective analysis Setting: Academic sleep laboratory Patients: Forty adults referred for suspected sleep disordered breathing Interventions: Polysomnography with esophageal pressure monitoring and automatic computation of ΔPes using a novel algorithm. Results: Computed ΔPes for nearly all respiratory cycles during sleep correlated well with visual scoring of selected respiratory cycle samples (Spearman rho = 0.86, P < 0.0001). The RCREC within the sigma EEG range (12.5-15.5 Hz) rather than that within other frequency ranges most often showed significant within-subject inverse correlations with ΔPes. In contrast, in between-subject comparisons, beta (15.5-30.5 Hz) and to a lesser extent theta (4.5-7.5 Hz) RCREC, rather than sigma RCREC, showed significant inverse associations with mean ΔPes. Conclusions: Variation within subjects of sigma RCREC with ΔPes supports previous evidence that RCREC within this range may reflect microarousals exacerbated by increased work of breathing. Correlation of beta and theta, but not sigma RCREC with ΔPes in between-subject comparisons is more difficult to explain but suggests that ranges other than sigma also deserve further investigation for clinical utility.