Muscles of the pharynx: structural and contractile properties.

Pharyngeal muscles are the effector organ by which the brainstem regulates pharyngeal airway size and patency during breathing. These muscles have fast contractile rates, and may be susceptible to develop fatigue when driven at the high levels required to overcome structural pharyngeal narrowing, especially under hypoxic conditions. Diseases with an increased prevalence of sleep apnea are associated with changes in pharyngeal muscle properties, and conversely diseases which primarily alter neuromuscular function have a significant prevalence of sleep apnea. However, further studies are needed to define the precise role of pharyngeal muscle fatigue, and of changes in pharyngeal muscle properties with disease, in the pathophysiology of obstructive sleep apnea.