Purpose: "Microarousals" during sleep have not been analyzed systematically. We investigated the importance of 'microarousals' (lasting 1.5-3 s). Methods: Standard polysomnography including esophageal pressure (Pes) assessment was performed on ten patients (aged 54.0 ± 5.0 years) with respiratory effort-related arousal ≥5/h. We measured the number of arousals per hour (American Sleep Disorders Association (ASDA) arousal index) and the number of microarousals lasting 1.5-3 s per hour (mASDA arousal index). On the night after the baseline sleep study, we performed overnight continuous positive airway pressure (CPAP) titration. Results: mASDA arousals, characterized by lower Pes values, were observed more frequently in patients with sleep-disordered breathing. The Pes results did not differ significantly between ASDA and mASDA arousals (-15.6 ± -5.0 vs -15.0 ± -4.4 cmH2O). mASDA arousals were significantly improved by CPAP treatment (mASDA arousals, 82.6 ± 60.1 vs 6.0 ± 1.4/h). Conclusions: mASDA arousals were characterized by an increase in Pes. mASDA arousals are thus key to our understanding of clinical manifestations in patients with sleep-disordered breathing.
All Science Journal Classification (ASJC) codes