Hypoglossal nerve stimulation adherence monitoring: emerging from the shadows of continuous positive airway pressure

Hypoglossal nerve stimulation (HGNS) is a relatively novel treatment for positive airway pressure (PAP) intolerant moderate–severe obstruction sleep apnea (OSA) patients. HGNS specifically addresses a deficient physiologic reflex contributing to OSA, namely, inadequate pharyngeal dilator muscle response. In 2014, the HGNS device manufactured by Inspire Medical Systems (Minneapolis, MN) was FDA-approved following the publication of the pivotal Stimulation Therapy for Apnea Reduction (STAR) trial [1]. The trial results from the 124 patients demonstrated a reduction in the apnea–hypopnea index (AHI) from 32.0 to 15.3 events/h. Given that the residual AHI with HGNS remains significantly higher than with PAP therapy [2], superlative adherence is required to achieve comparable levels of mean disease alleviation [3]. In recent years, Inspire Medical has developed a cloud-based monitoring platform which offers provider-facing objective adherence measures in both graphical and tabular formats.

In this journal of SLEEP, Soose et al. [4] utilized adherence data from the Inspire cloud-based monitoring system to examine the first 90 days of adherence after therapy activation. Using over 2000 HGNS patients, the authors performed a cluster analysis which identified six distinct groups of therapy usage. Fifty-seven percent of patients were in Cluster 1 with roughly 7.2 h per night, 28% in Cluster 2 with roughly 6.4 h per night, and 15% in Cluster 3 with roughly 5.8 h per night. Each cluster was stratified into two subgroups based on the timing of therapy (time of day, variability), number of therapy pauses, or frequency of missing days. The authors identified clinical interventions to mitigate suboptimal adherence for each cluster. One surmises that both sleep hygiene and insomnia-related concerns predated the HGNS implantation, underscoring the importance of a thorough sleep history prior to surgical intervention. In this way, the sleep physician can work to optimize these aspects prior to this OSA surgical intervention or even consider alternatives to surgery for Cluster 3. As this study represents a novel approach to HGNS adherence management, the authors acknowledge the important limitation of not having clinical, demographic, and socioeconomic factors in this initial data set. These patient-level factors have elucidated nonadherence risk factors in both continuous positive airway pressure (CPAP) and mandibular advancement device cluster analyses and will likely be illustrative for future HGNS studies [5, 6].

HGNS has made several significant advances since its FDA approval in 2014. The latest version of the implantable pulse generator is both physically smaller and MRI conditional. The surgical approach has been modified from a 3- to 2-incision approach [7]. Future expected modifications of HGNS technology include measurement of AHI (à la rAHI from PAP downloads) and sleep detection algorithms to guide appropriate therapy levels through the night. Most notably, however, the advent of adherence monitoring in the form of this cloud-based platform has positioned this therapy squarely alongside that of CPAP for the sleep clinician. The additional features of phone-based applications and bluetooth remote connectivity will further promote patient engagement. In essence, the well-established methods of PAP adherence have facilitated the rapid maturation of HGNS technology as it actively shapes the future of PAP alternative treatments.

Funding

Dr. Dedhia receives research funding from the National Institutes of Health (NHLBI R01HL144859), Inspire Medical, and Nyxoah Medical related to hypoglossal nerve stimulation therapy.

Disclosure Statement

None declared.