Characterization of chimeric surface submentalis EMG activity during hypopneas in obstructive sleep apnea patients

Polysomnogram (PSG) is the standard diagnostic test for the evaluation of sleep disorders. The current rules require surface (s) electromyography (EMG) of the submentalis muscle (SM) in order to document atonia during REM sleep. The sSM EMG signals reflect contracting motor units; the firing of the latter is a function of intrinsic neuromuscular characteristics of its component muscle fibers, and indeed forms the basis for the spectral properties. Here we have studied OSA patients with apnea-hypopnea index (AHI) of <5, 5-10, 30-35, and 60+, and document, for the first time, a ¿Chimeric¿ sSM EMG activity phenotype during hypopneas in Non-REM sleep. This unique pattern characteristically displays contiguous tonic-phasic segments of high activity and low activity or vice versa. We have analyzed the total duration, and other attributes of these hybrids in comparison with the normal awake and apnea/hypopnea-free sleep periods. We document an inherent heterogeneity between hypopneas, and between heterogeneous segments of the chimeras in OSA patients of varying AHI. This study emphasizes that rectified and filtered sSM EMG activity signals provide a novel, valid and useful metric in PSG evaluation which may be of clinical significance in sleep-related and other pathological conditions.