Physiologic Mechanisms of Response to Hypoglossal Nerve Stimulation

Study Objectives To evaluate the relationship between physiologic mechanisms under drug-induced sleep endoscopy (DISE) and polysomnographic response to hypoglossal nerve stimulation (HGNS). Materials and Methods In an NIH-funded interventional trial, thirty subjects with HGNS devices underwent DISE with pneumotachometer, pharyngeal manometry, and positive airway pressure titration. On the previous night, subjects underwent a split-night polysomnogram (first portion without HGNS and second at a single clinically-determined voltage) in the supine position. Responder status was determined by a 50% reduction in supine apnea-hypopnea index (AHI). Groups (responders vs. nonresponders) were compared using the Wilcoxon Rank Sum Test, and Spearman’s rho was used to assess correlations between physiologic mechanisms under DISE and polysomnographic response. Results Patients (n = 30) were generally older (64.3 ± 8.9 years), female (56.7%), and overweight (BMI 28.1 ± 3.1 kg/m2) with severe OSA (supine AHI 47.7 ± 25.4 events/hour). Among 14 responders and 16 nonresponders, there was no statistical difference in baseline collapsibility (PhOP, 5.9 ± 2.4 vs 7.2 ± 3.7 cmH2O, p = 0.39) or baseline inspiratory epiglottic pressure (Pepi,-17.2 ± 9.0 vs -18.6 ± 12.8 cmH2O, p = 0.99). Improvements in collapsibility (rho = 0.70, p = 0.0001) and inspiratory epiglottic pressure (rho = -0.70, p = 0.0001) with HGNS were strongly associated with reduction in supine AHI. Conclusions In this small interventional study, decreases in collapsibility and effort during DISE are markers of clinical response to HGNS therapy. Our novel findings demonstrate responses to acute physiologic interventions during DISE translate to natural sleep outcomes.