RecruitingDevice studyDISE-HNS Effect StudyThe purpose of this study is to assess the site, pattern and degree of upper airway collapse before and during hypoglossal nerve stimulation (HNS) treatment using clinical standard drug-induced sleep endoscopy (DISE) and using a novel, non-invasive method predicting site of collapse from raw polysomnography (PSG) data. Furthermore, outcomes will be compared between responders and non-responders.