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Neuromuscular Mechanisms of Upper Airway Patency
Walter T. McNicholas, M.D.
The pathophysiology of obstructive sleep apnoea (OSAS) is principally based on an
imbalance of the collapsing forces of the upper airway (UA) during inspiration and the
counteracting dilating forces of the UA dilating muscles. A narrowed UA is very common
among OSAS patients, which is usually due in an adult to non-specific factors such as fat
deposition in the neck, or abnormal bony morphology of the UA. Functional impairment
of the UA dilating muscles is particularly important in the development of OSA, and
patients have a reduction in both tonic and phasic contraction of these muscles during
sleep when compared to normals. A variety of defective respiratory control mechanisms
are found in OSA, including impaired chemical drive, defective inspiratory load
responses, and abnormal UA protective reflexes. These defects may play an important
role in the abnormal UA muscle responses found among patients with OSA. Local UA
reflexes mediated by surface receptors sensitive to intrapharyngeal pressure changes
appear to be important in this respect. A better understanding of the integrated
pathophysiology of OSAS should help both in the choice of optimum therapy for each
individual patient, and also in the development of new therapeutic techniques. (Sleep and
Hypnosis 2000;5:241-247)
| Keywords: sleep apnoea, upper airway, neuromuscular, reflexes, respiratory control |
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