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Upper Airway (Hypoglossal Nerve) Stimulation (UAS)

Upper airway stimulation (UAS) through the neuromuscular stimulation of the hypoglossal nerve and genioglossus muscle has emerged as an effective treatment option. This therapy utilizes an implantable device in the neck through a small incision with a stimulation electrode placed around the protrusive branches of the hypoglossal nerve and a sensor lead placed in the intercostal space in the chest to detect inspiration.

 

The patient-specific programmable device stimulates the hypoglossal nerve during timed inspiration to alleviate the airway obstruction in patients with moderate or severe OSA. UAS has been shown to affect the retroglossal and retropalatal areas be increasing the airway in an anterior-posterior direction.

By stimulating the hypoglossal nerve, the tongue base protrudes due to genioglossus muscle activation, resulting in opening of the airway in the retroglossal region as well as in the retropalatal areas (exact mechanism not entirely known); however, a concentric palatal collapse is a contraindication to UAS therapy.

Various UAS devices have been developed over the years, with the technology subsequently modified. Most recently, Inspire Medical Systems (Maple Grove, Minnesota) has obtained Food and Drug Administration approval for a UAS device, and a 5- year Stimulation Therapy for Apnea Reduction (STAR) outcome study showed improvement using validated tools in sleepiness and quality of life, with normalization of scores increasing from 33% to 78% and 15% to 67%, respectively, and showed an apnea-hypopnea index (AHI) response rate of 75% (AHI 50% reduction).