Collapsibility of the active pharynx, where active contraction of the upper airway muscles is evident, was previously reported to be higher in children with obstructive sleep apnea (OSA) than in those with primary snoring during sleep. Contribution of neuromuscular and anatomic factors to the increased collapsibility, however, was not estimated. We therefore evaluated collapsibility of the passive pharynx, in which upper airway muscle activities were eliminated. Our aim in the present study was to test the hypothesis that children with sleep-disordered breathing (SDB) have a structurally narrowed and a more collapsible pharynx compared with normal children. The static pressure/area relationship of the passive pharynx was endoscopically quantified in 14 children with SDB and in 13 normal children under general anesthesia with complete paralysis. The majority of children with SDB primarily closed their airways at levels of enlarged adenoids and tonsils with positive closing pressure (Pclose) (3.5+/-4.3 cm H2O), whereas half of the normal children closed their airways at the soft palate edges and the other half at the tongue bases with subatmospheric Pclose (-7.4+/-4.9 cm H2O). Cross-sectional area of the narrowest segment was significantly smaller in SDB children than in normal children. Interestingly, collapsibility of the retropalatal and retroglossal segments significantly increased in SDB children, compared with the normal subjects. We conclude that anatomic factors play a significant role in the pathogenesis of pediatric OSA and that predisposing structural abnormalities of the entire pharynx are likely to contribute to manifestation of OSA in addition to enlarged adenoids and tonsils.

Endoscopic assessment of anatomic abnormality of the pharynx in paralyzed patients with sleep-disordered breathing under general anesthesia has clinical value for the improvement of UPPP outcome.

Anatomicaland/or neuromuscular abnormalities may cause obstructive sleep apnea (OSA). We have developed a unique method to separate these two factors in order to evaluate the intrinsic mechanical properties of the pharynx. In this method, we depressed pharyngeal dilator muscle activities by providing sufficient muscle blockade under general anesthesia.During experimentally-induced apnea, airway pressure was manipulated from 20 cmH2O to velopharyngeal closing pressure while we endoscopically observed one of the pharyngeal segments. The collapsibility of the pharynx was assessed via the static pressure/area relationships of the pharynx. Employing this method, we attempted to predict the UPPP outcome. We hypothesized that the severity of sleep disordered breathing after UPPP may be related to the collapsibility of the oropharynx. Our preliminary results from 24 patients with OSA supported the hypothesis : We found a direct relationship between the collapsibility of the oropharynx and the severity of the sleep-disordered breathing. Accordingly, our endoscopic evaluation of the pharyngeal mechanics during anesthesia may be useful for the prediction of UPPP outcomes.