Evaluation of a Miniature, Injectable, Wireless Stimulator to Treat Obstructive Sleep Apnea

Moderate-to-severe obstructive sleep apnea (OSA) affects a large segment of the US population and is characterized by repetitive and reversible obstruction of the upper airway during sleep. Untreated OSA is associated with increased incidence of heart attack, stroke, and motor vehicle accidents due to sleepiness. Continuous positive airway pressure is often prescribed, but most patients with OSA are nonadherent. One effective alternative is stimulation of the hypoglossal nerve (HGN) that acts to open and stiffen the airway. However, currently available HGN stimulators require major surgery to implant a pacemaker-like device and leads that connect to a cuff electrode encircling the HGN. In this study, we performed preliminary tests in rats and humans of a miniature stimulating device that, in the future, could be injected near the HGN with ultrasound guidance.

This device (1 × 9 mm) is activated wirelessly using a small wearable (3.5-cm diameter) that would be placed on the skin under the jaw in human patients. The system was effective in robustly activating the rat sciatic nerve at distances up to 2.5 cm from the wearable. Furthermore, the device delivered through injection could fully activate the rat sciatic nerve if placed at distances <4 mm from the nerve. The extent of migration of the device measured in seven rats over a one-month period was not significant for most injectables, but six of 18 did change position (mainly along the injection path). We discuss strategies for minimizing migration in the future. Lastly, we report on tests in one awake human subject, wherein wireless stimulation of the HGN caused >60% increase in airflow during inspiration.

Collectively, these initial experiments encourage future studies to determine the utility of this system in alleviating OSA in human subjects.