Obstructive Sleep Apnea

Neuroprosthesis for the Treatment of Obstructive Sleep Apnea

Principal Investigator: Dominique Durand, Ph.D.

Project Description: Obstructive sleep apnea (OSA) is the recurrent occlusion of the upper airways during sleep. Most OSA patients are unaware of their condition, but almost all have excessive daytime sleepiness.

Four percent of men and 2% of women, aged 30 - 60 are reported to have undiagnosed sleep apnea (Young et al., 1993), and 1-4% of a male population in Sweden (Gislason et al., 1988), and 9% of the Australian population suffer from this sleep disorder (Bearpark, 1993).

The prevalence of sleep-disordered breathing in a sample of 2,202 subjects was at least 3.6% in Australia (Olson et al., 1995). In most severe cases, the obstructions occur as often as 40-60 times per hour, last more than 15 seconds, and associated with dramatic reductions in the arterial oxygen saturation (more than 4%). Most common complications are excessive daytime sleepiness, restless sleep, morning headache, job-related accidents, impaired short-term memory, polycythemia (an abnormal increase in red blood cells), hypertension, right-sided congestive heart failure, and decreased libido. Personality disorder and other psychological problems may further complicate the situation in the long run.

The development of occlusions in this disorder has been related to the prolapse of the tongue and its surrounding structure into the pharynx. Tongue prolapse, in turn, has been attributed to diminished neuromuscular activity in the upper airway dilating muscles. This suggests that one should be able to compensate for the lost activity and preserve the upper airway patency during sleep by electrical activation of the tongue muscles.

The hypoglossal nerve is the main motor nerve to the intrinsic and extrinsic muscles of the tongue. The mechanics of the tongue muscles are able to open the pharynx during voluntary control of the tongue. Our current research efforts are focused on finding the muscles and their appropriate coordinated pattern or patterns of activation that would provide the desired tongue movement for pharyngeal dilation. We are developing a novel multi-contact electrode, as opposed to an electrode with a single stimulation contact, placed on the main trunk of the hypoglossal nerve to obtain selective activation of tongue muscles.