Unravelling unique qualitative and quantitative characteristics of the surface submentalis EMG in OSA polysomnograms

The functional integrity of genioglossus and suprahyoid submentalis muscles plays an important role in upper airway patency. A combination of inadequate genioglossal function and UA associated anatomy and physiology underlies obstructive sleep apnoea (OSA). The gold standard for diagnosing OSA is polysomnography that provides important physiological information. Although nocturnal laryngospasm, epilepsy, or parasomnias may be missed in a one-night recording, however, surface submental EMG (sSMEMG) is invariably present in every polysomnogram. This study has assessed the polysomnographic sSMEMG, both qualitatively and quantitatively, during hypopneas in controls (AHI 5 and 10) and OSA patients with 40+ AHI. All analysed sSMEMG signals sampled at 160 HZ were digitally band-pass filtered at 10-100 HZ (notch filter at 50 HZ) for quantitation. The standard median filter with window length-9 subtracted the ECG template and eliminated the artefacts. Unlike controls, the OSA patients showed a predominantly phasic sSMEMG pattern, both qualitatively and quantitatively. This is ascribed to transformation of aerobic muscle fibers to phasic variety owing to prolonged exposure to intermittent hypoxia. We emphasize that unravelling hidden information in sSMEMG signals can be invaluable clinically.