Mechanisms of nasal obstruction in sleep.

Pathophysiological aspects of the nasal and pharyngeal airways are discussed with particular reference to breathing disorders in sleep. Hypotonus of dilator muscles in sleep permits the pharynx to comply with inspiratory pressures. If airflow resistances are increased by nasal disease, complete inspiratory obstructive closure of the pharynx and apnea can result from nasal breathing in sleeping subjects. Recumbency increases resistive swelling of inflamed nasal mucosa. Furthermore in patients with normal mucosa and unilateral nasal obstruction, contralateral recumbency induces contralateral obstruction which increases resistance to nasal breathing; and in either dorsal or lateral recumbency the congestive phase of the spontaneous nasal cycle acts in a similar way. Examples of breathing disorders in sleep and impaired quality of sleep in patients with obstructive mucosal disease and both bilateral and unilateral structural abnormalities are cited.