Improved detection of respiratory-related cortical EEG arousals was shown by O’Malley et al 2003 by using a single additional frontal EEG lead (Fz-A2) to the standard polysomnography. We pondered on the association between excessive daytime sleepiness (EDS), measured by the Epworth Sleepiness Scale (ESS), and cortical arousals detected by standard EEG (C3-A2) and by an additional frontal EEG lead (Fz-A2).
45 consecutive patients with symptoms of excessive daytime sleepiness and/or clinically presumed sleep-disordered breathing underwent a full overnight polysomnography with an additional frontal EEG lead (Fz-A2) using a complete computerized system (Sandman). Sleep was staged as per standard criteria (Rechtschaffen A, Kales A. 1968). EEG arousals were scored as per the report from Sleep Disorders Atlas Task Force of the American Sleep Disorders Association (1992). Daytime sleepiness was measured by ESS. Pearson correlation and Student’s T-test were used to compare data.
The population comprised 47% males, age was 50 ± 14.7 (mean ± SD), ESS was 11 ± 4.8 (mean ± SD), mean total apnea-hypopnea index (AHI) was 12.6. More arousals were detected by Fz-A2 than standard (C3-A2) EEG leads (2300 vs. 1853) and this attained statistical significance (p=0.027, 95% CI = [-18.66, -1.21]), although there was no significant difference when comparing respiratory, periodic limb movements and spontaneous arousals. There was no significant correlation between ESS and AHI, sleep efficiency, sleep stage shift, respiratory or non-respiratory arousals.
Although we found a significant difference for total EEG arousals, differently from O’Malley et al, we did not find a significant difference for the detection of respiratory-related EEG arousals between the use of standard (C3-A2) and additional frontal (Fz-A2) EEG lead.
The absence of a clear relationship between daytime sleepiness, sleep fragmentation and respiratory arousals suggest that the underlying mechanisms for daytime sleepiness in patients with obstructive sleep apnea is likely to be complex and multifactorial and needs further study.
S.K. Ramachandran, None.