Upper Airway Stimulation for Obstructive Sleep Apnea: Past, Present, and Future

Abstract

Obstructive sleep apnea (OSA) is an increasingly prevalent clinical problem with significant effects on both personal and public health. Continuous positive airway pressure (CPAP) has demonstrated excellent efficacy and low morbidity; long-term adherence rates approach 50%. Although traditional upper airway surgical procedures target the anatomic component of obstruction, upper airway stimulation tackles the twin goals of improving anatomic and neuromuscular pathology. After decades of trials demonstrating proof of concept of hypoglossal nerve stimulation in animal and human subjects, the results of a large multicenter, prospective trial were recently published. The trial demonstrated that hypoglossal nerve stimulation led to significant improvements in objective and subjective measurements of the severity of OSA. This novel approach is the first to combine sleep surgery techniques with a titratable medical device for the treatment of OSA. Further research is required to define optimal patient selection and device performance and to demonstrate long-term effectiveness.

Keywords: obstructive sleep apnea; sleep disordered breathing; upper airway stimulation.

Figure 1

Multilevel upper airway improvement with stimulation during drug-induced sedation endoscopy. The outlined areas demonstrate the increase in cross-sectional area of both the retropalatal and retrolingual portions of the upper airway with hypoglossal nerve stimulation.

Figure 2

Implantable hypoglossal nerve stimulation system. The hypoglossal nerve stimulation system consists of three implanted components: (1) an implantable pulse generator in a subcutaneous pocket in the right upper chest, (2) a stimulation lead with a cuff electrode placed on the medial branch of the hypoglossal nerve in the right submandibular space, and (3) a sensing lead to detect ventilatory effort placed in the intercostal space facing the pleura. (Inspire Medical Systems, Minneapolis, MN).

Figure 3

Neuroanatomy of the tongue. Sagittal illustration of the tongue showing lateral branches (l-XII) of the hypoglossal nerve supplying the retrusor muscles: styloglossus (SG) and hyoglossus (HG). The deeper medial branches (m-XII) selectively innervate the genioglossus muscle, which is the primary protrusor muscle and upper airway dilator. Ideal cuff electrode placement is distal to the lateral branching point as indicated by the rectangle. GG, genioglossus; GGh, genioglossus horizontal; GGo, genioglossus oblique; IL, inferior longitudinal; SL, superior longitudinal; T/V, transverse and vertical. (With permission, John Wiley and Sons)

Figure 4

(A) STAR trial primary outcomes data (n = 124). With upper airway stimulation therapy, median apnea-hypopnea index (AHI) and oxygen desaturation index (ODI) improved significantly from baseline to 12-mo follow-up. (B) STAR trial secondary outcomes data (n = 123). With upper airway stimulation therapy, median Epworth Sleepiness Scale (ESS) and Functional Outcomes of Sleep Questionnaire (FOSQ) improved significantly from baseline to 12-mo follow-up.

Figure 5

Titration of upper airway stimulation therapy during polysomnography (PSG). PSG snapshot showing an approximately 6-min respiratory window. The left side of the figure shows periodic airflow limitation, fluctuating respiratory effort, and associated oxygen desaturations consistent with obstructive sleep apnea. Device activation is illustrated by the vertical arrow. After the device synchronizes with ventilatory effort, immediate improvement in control of breathing and oximetry is observed.