Insights into Friedman stage II and III OSA patients through drug-induced sleep endoscopy

BACKGROUND: The Friedman staging is a classic system to predict outcomes of obstructive sleep apnea (OSA) surgery. Increasing stage indicates more severe upper airway (UA) obstruction and worse surgical successful rate. In previous studies, the UA obstruction between stages were usually assessed based on awake examination. Drug-induced sleep endoscopy (DISE) is a new method that can evaluate airway collapse characteristics during sleep. Therefore, we planned to compare Friedman staging and DISE findings and fulfill the knowledge gap on the correlation between awake and sedated UA examination. METHODS: Retrospective case series study that assessed patients with OSA who underwent DISE. Subjects were classified to stage II and stage III groups based on Friedman staging system. UA collapse characteristics based on velum, oropharynx, tongue base, epiglottis (VOTE) classification, including single/multiple obstruction sites, single/combined upper and lower obstruction levels, collapse degree and patterns in different sites, and surgical results among the groups were analyzed. RESULTS: A total of 175 cases were analyzed. No significant differences were found in baseline measurements between groups. Stage III patients (n=102) had a higher proportion (74.5%) with 3 or 4 obstruction sites than stage II (57.5%, n=73). Velum (V) + oropharynx (O) + tongue base (T) was the most common multi-sites combined obstruction pattern with 33% in stage II and 37% in stage III, isolated lower level obstruction was the least with 6% and 4%, respectively. No significant differences were found in obstruction sites and levels. 106 patients underwent surgeries and 33 had post-surgical sleep study, 73.7% and 63.6% response rate were found in stage II and III with no significant difference. CONCLUSIONS: Upper and lower combined obstruction was the main pattern of collapse in both, Friedman stage II and III patients. Patients with OSA and Friedman stage III had more than 2 sites of obstruction than stage II patients.