Treating obstructive sleep apnea with hypoglossal nerve stimulation

Abstract

Background: Reduced upper airway muscle activity during sleep is fundamental to obstructive sleep apnea (OSA) pathogenesis. Hypoglossal nerve stimulation (HGNS) counteracts this problem, with potential to reduce OSA severity.

Study objectives: To examine safety and efficacy of a novel HGNS system (HGNS, Apnex Medical, Inc.) in treating OSA.

Participants: Twenty-one patients, 67% male, age (mean ± SD) 53.6 ± 9.2 years, with moderate to severe OSA and unable to tolerate continuous positive airway pressure (CPAP).

Design: Each participant underwent surgical implantation of the HGNS system in a prospective single-arm interventional trial. OSA severity was defined by apnea-hypopnea index (AHI) during in-laboratory polysomnography (PSG) at baseline and 3 and 6 months post-implant. Therapy compliance was assessed by nightly hours of use. Symptoms were assessed using the Epworth Sleepiness Scale (ESS), Functional Outcomes of Sleep Questionnaire (FOSQ), Calgary Sleep Apnea Quality of Life Index (SAQLI), and the Beck Depression Inventory (BDI).

Results: HGNS was used on 89% ± 15% of nights (n = 21). On these nights, it was used for 5.8 ± 1.6 h per night. Nineteen of 21 participants had baseline and 6-month PSGs. There was a significant improvement (all P < 0.05) from baseline to 6 months in: AHI (43.1 ± 17.5 to 19.5 ± 16.7), ESS (12.1 ± 4.7 to 8.1 ± 4.4), FOSQ (14.4 ± 2.0 to 16.7 ± 2.2), SAQLI (3.2 ± 1.0 to 4.9 ± 1.3), and BDI (15.8 ± 9.0 to 9.7 ± 7.6). Two serious device-related adverse events occurred: an infection requiring device removal and a stimulation lead cuff dislodgement requiring replacement.

Conclusions: HGNS demonstrated favorable safety, efficacy, and compliance. Participants experienced a significant decrease in OSA severity and OSA-associated symptoms.

Clinical trial information: NAME: Australian Clinical Study of the Apnex Medical HGNS System to Treat Obstructive Sleep Apnea.

Registration number: NCT01186926. URL: http://clinicaltrials.gov/ct2/show/NCT01186926.

Keywords: Sleep apnea; genioglossus muscle; hypoglossal nerve stimulation; implantable neurostimulator; lung.

Figure 1

The implanted components of the hypoglossal nerve stimulating system include an implantable neurostimulator that delivers safe levels of electrical stimulation to the hypoglossal nerve via a stimulation lead having a distal cuff electrode. Stimulation is delivered synchronous with inspiration as detected by respiration sensing leads using bio-impedance.

Figure 2

Intraoperative stimulation of the hypoglossal nerve visualized using lateral fluoroscopy. The fluoroscopic imaging was undertaken to determine and verify correct electrode cuff placement (tongue protrusion/pharyngeal opening) with brief stimulation. The subject was under general anesthesia, positioned to optimize submandibular surgery (supine, head extended slightly). The endotracheal tube and connecting tubing are visible in the images.

Figure 3

Flow diagram showing the progress of all participants through the trial. PSG, laboratory-based polysomnography.

Figure 4

Apnea-hypopnea index (AHI) scores at Baseline and at 3 and 6 months following implant. (A) Boxplots of group data showing the median values indicated by the thick horizontal lines, and the 25th and 75th percentiles indicated by the upper and lower margins of the box, respectively at Baseline (n = 21), 3 months (n = 17), and 6 months (n = 19) post-implant. Error bars represent 5th and 95th percentiles. Extreme values are indicated by closed circles, *P < 0.001. (B) Line graph showing individual data (n = 21). A missing data point in any given subject was derived using the last value carried forward method and is shown as an open circle.