0075 Rem Sleep Is Bimodal

• Published in: Sleep (New York, N.Y.) N.Y.), 2019-04, Vol.42 (Supplement_1), p.A31-A32
• Main Author: Thomas, Robert Joseph
• Format: Article
• Language: English
• Subjects: NREM sleep; REM sleep; Sleep apnea
• ISSN: 0161-8105; 1550-9109
• DOI: 10.1093/sleep/zsz067.074

Introduction The classic model of sleep and sleep scoring differentiates REM sleep, wake and stages of NREM which increase in depth grade. Alternate methods of sleep characterization include cyclic alternating pattern, sleep power kinetics (delta, alpha, etc), slow-oscillation density metrics, the Odds Ratio Product, network based approaches such as time delay stability, and ECG-spectrogram (cardiopulmonary coupling), the latter showing an intrinsic bimodality of NREM sleep. REM sleep has so far been considered a unitary state. Methods Fifty diagnostic or split-night polysomnograms of sleep apnea were reviewed to identify coexisting features of REM and NREM sleep, but using respiratory patterns as a key guide. Thus, periodic breathing in REM sleep, NREM EEG during REM-type sleep apnea and stabilization of NREM periodic breathing at the edges of REM sleep, before conventional REM sleep, were examples of mixed states identified. Oximetry patterns (band-like for periodic breathing, V-shaped desaturation for REM-dominant obstructive disease) were also used to identify respiratory sleep stage. These mixed states are called "unstable REM sleep". The minimum period for this state was 60 seconds. Results The subject population characteristics were 37/50 males, BMI 32.3 Kg/M2, age: 54.3 +/- 8 years. There were a total of 127 REM periods of at least 15 minutes duration, In 78/127 periods, a segment of unstable REM across EEG and respiratory domains, were noted. These occurred exclusively at the transition into REM sleep, never at the end of a REM period. In 12 periods, periodic breathing occurred within REM sleep, when REM and NREM were admixed secondary to a arousal-shift to NREM-periodic breathing-return to REM sleep sequence. Conclusion Using both conventional EEG-based scoring and the respiratory phenotype, distinctly mixed states of REM and NREM occur at the transition into REM sleep. In the case of sleep apnea, these periods can be prolonged over several minutes. It may be conceptually useful to consider REM as bimodal, in stable and unstable forms. Such bimodality can inform models of sleep regulation, and pathological states such as narcolepsy, where state boundaries are less stable. Support (If Any) None