Upper airway patency and nocturnal desaturation in habitual snoring and obstructive sleep apnea: pathogenesis of sleep-related breathing disorders.

Sixty patients, 53 men and 7 women, referred for excessive snoring or suspected sleep apnea syndrome were analyzed by polysomnography, Mueller maneuver, cephalometric roentgenography, and pulmonary function testing, to evaluate the contribution of static and dynamic upper airway obstruction in the pathogenesis of sleep-related breathing disorders and OSAS. Desaturation index and maximal desaturation were used in the analysis as indicators of severity of sleep-related breathing disorders. Body Mass Index, increased collapsibility at the base of the tongue by the Mueller maneuver, increased distance between hyoid and mandibular plane, and increased soft palate diameters by cephalometry as well as a decreased peak inspiratory flow by pulmonary function testing were found to be related to increased oxygen desaturation parameters. In a multivariate analysis the significant obstruction parameters could explain only 37% of the variability of maximum desaturation and 31% of the variability of desaturation index, 63 and 69%, respectively, must therefore be explained by other mechanisms. We conclude that instability of respiratory and muscular control, possibly enhanced by sleep-phase-related changes, is more important in the pathogenesis of sleep-related breathing disorders than pure anatomic narrowing of the airway.