CORONADO, CALIF. – Some patients with treatment-refractory obstructive sleep apnea may be candidates for upper airway stimulation, though those with complete concentric palatal collapse may not respond, according to Dr. Marion Boyd Gillespie.
“There’s been sound research showing that patients with obstructive sleep apnea have reduced neural tone, so it may not be due to fat in the tongue; some of it may have to do with reduced neural tone,” Dr. Gillespie, who directs the snoring clinics at the Medical University of South Carolina, Charleston, said at the Triological Society’s Combined Sections Meeting. “During these apneic events, there’s a reduction in the neural tone of the genioglossus muscle, which is the main dilator of the upper airway. With upper airway stimulation, we’re trying to account for that loss of neural tone by providing more neural impulse to these muscle groups that perform the dilator functions.”
In 2014 the Food and Drug Administration cleared an upper airway stimulation system manufactured by Inspire Medical Systems, a pacemakerlike device that’s implanted in the subclavicular space. The system features a stimulator lead that attaches to the right hypoglossal nerve and a sensing lead that goes between the external and internal intercostal muscles to detect breathing. “That allows the device to know when in the phase of respiration to fire,” said Dr. Gillespie, professor of otolaryngology–head and neck surgery at the university. “The sensing lead detects the respiratory wave, and the stimulatory lead starts stimulation at the end of expiration, because that’s when the airway is in its most collapsible state. It continues about two-thirds of the way through the inspiratory cycle to keep the airway open.”
Titration of the device is very similar to continuous positive airway pressure, he continued. Once implanted, the patient “will go back to the sleep lab where a tech who’s trained in the device will ramp up stimulation until observed apneas and hypopneas are adequately reduced. You would think that isolated stimulation of the hypoglossal nerve would only open up the airway at the level of the tongue. However, our initial investigation showed that there is dilation at the velopharynx as well,” Dr. Gillespie said. By moving the tongue out of the posterior airway, “you’re moving the dorsum of the tongue away from the velopharynx. You’re also getting active traction on the palatoglossal fold,” he added.