Mechanical Properties, Anatomy, and Control of the Upper Airway

Abstract

The physiology of the upper airway is fundamental to current and trending therapy for obstructive sleep apnea and neurostimulation in particular. Proper functioning of the upper airway will promote sleep health by supporting the requisite airflow without snoring or significant flow limitation. Dysfunction produces snoring, obstructive hypopneas, and the metabolic sequelae of sleep disordered breathing. How a particular section of the upper airway (e.g., velopharynx, oropharynx, or hypopharynx) remains open while it is suspended from the skull base, maxilla, and mandible is the result of anatomy and neuromuscular control. The genioglossus muscle, originally designed for bringing food into the mouth and swallowing, along with multiple other muscles, participates in the maintenance of patency of the muscular pharynx during wakefulness and sleep. If the genioglossus were the only muscle important for airway stability, then hypoglossal nerve stimulation would likely be universally rather than selectively effective; instead, its effectiveness is predicted by velopharyngeal functions, which in terms of sleep health are poorly described. Literature clearly indicates a fundamental role for muscles other than the genioglossus in maintaining airway diameter, shape, and wall stiffness. Models that incorporate a more complete neuromechanical coupling of these components are necessary to understand a stable airway during sleep and helpful for decisions in management of obstructive sleep apnea.