How and why should we stabilize the upper airway?

This review focuses on the evidence for upper airway instability during sleep and on the methods used to correct this instability. Upper airway patency during sleep is determined by the balance between the forces tending to constrict the pharynx (i.e. negative suction force generated by the diaphragm) and those tending to dilate in the pharynx (i.e. force acting on the tongue, soft palate and pharyngeal dilator muscles). The evidence for reduction in genioglossus activity and tensor palatini activity, failure of compensatory mechanisms to maintain these activities, and increase in upper airway resistance during sleep in reviewed. Coupled with abnormal pharyngeal anatomy to start with, the above events lead to abnormal pharyngeal function and cause repetitive episodes of airway occlusion, that is, sleep apnea. It is concluded that abnormal airway function in sleep apnea is a diffuse, rather than a localized process, that may involve the entire airway from the nasopharynx to the larynx. Methods to improve abnormal pharyngeal anatomy and pharyngeal function, such as nasal continuous positive airway pressure (CPAP), oral appliances, posture, weight loss, medications, and surgery are discussed. Given the pathophysiology of sleep apnea, that is, diffuse abnormality of the upper airway, it is reasonable to expect that only those approaches that exert a beneficial effect on the entire upper airway, as opposed to the approaches that modify only a short segment of it, may be expected to be of benefit in treatment of sleep apnea.