0598 Hypoglossal Nerve Stimulation: Does the Ratio of Apneas to Hypopneas Matter When It Comes to Successful Outcomes?

Abstract Introduction While hypoglossal nerve stimulation (HNS) is a safe and effective treatment for moderate to severe obstructive sleep apnea (OSA) HNS is not effective in some patients despite optimal titration. This study investigates whether apnea-predominant OSA versus hypopnea-predominant OSA during pre-operative sleep study can be used to predict successful outcomes after HNS implantation. Methods This is a single-center retrospective study of consecutive patients with moderate to severe OSA who underwent implantation of HNS at an academic medical center. Apnea-predominant and hypopnea-predominant were determined by comparing the proportion of obstructive apnea and hypopnea events in pre-operative polysomnography or home sleep apnea testing if polysomnography was not conducted. Post-implantation apnea/hypopnea index (AHI) was derived from polysomnography performed 3 months or later after device activation in all subjects. The Mann-Whitney nonparametric test was used to compare the distribution of AHI reduction between apnea-predominant and hypopnea-predominant cohorts. Results Eighty-two patients treated with HNS implanted between December 2021 and July 2023 were evaluated. Sixty-two (75.6%) patients were male, with a median age of 65.5 (55.3-71) years and a median pre-implantation Body Mass Index (BMI) of 29.4 (27.5-31.5) kg/m2. Median pre-implantation AHI was 28.8 (18.5-45.9) events/hour. Before HNS implantation, 45 patients had hypopnea-predominant AHI with a median apnea-to hypopnea ratio of 0.33 (0.14-0.60) and 37 patients had apnea predominant AHI with median apnea-to-hypopnea ratio of 2.23 (1.35-4.37). There was no significant difference between the two cohorts in age or BMI. The pre-implantation AHI was higher in the apnea-predominant cohort (36 (21.2-49.6) events/hour) compared to the hypopnea-predominant cohort (23.7 (18-37) events/hour). Median AHI reduction in the hypopnea-predominant cohort was 78.3% (51.2-90.2%). Median AHI reduction in the apnea-predominant cohort was 72.3% (35.5-85.4%). There was no significant difference in the distribution of AHI reduction between the two groups after HNS (p=0.40). Conclusion There was no statistically significant difference between pre-implantation OSA which was apnea-predominant versus hypopnea-predominant in the degree of AHI reduction with HNS therapy. However, this study may be limited on the basis of comparing pre-implantation AHI as obtained on a home sleep study, as compared to post implantation AHI obtained on a diagnostic polysomnogram. Support (if any) none