Purpose: In treatment for obstructive sleep apnea (OSA), oral appliance (OA) therapy is indicated in patients with mild-moderate OSA. However, since patients with severe OSA in whom OA therapy was effective have also been reported, it may not be possible to determine indications for OA therapy based on the severity alone. The purpose of this study was to determine indications for OA therapy using endoscopy during wakefulness in patients with severe OSA.
Methods: The subjects consisted of 36 patients (27 males and 9 females) diagnosed with severe OSA using all-night polysomnography. In each patient, a nasoendoscope was inserted in a horizontal position during nasal breathing, and morphological changes in the airway of the velopharynx and oro-hypopharynx with mandibular advancement were evaluated.
Results: With mandibular advancement, the oro-hypopharynx was widened in all patients while the velopharynx was widened in 29 patients, but not in 7. The apnea hypopnea index (AHI) reduction rate after OA application was 79.8% (SD, 13.0%) in the group with and 40.6% (SD, 27.0%) in the group without velopharyngeal widening, being significantly different between the two groups. In the group showing velopharyngeal widening, evaluation of the direction of widening revealed two types: the "all-round type", which is circumferential widening in the anteroposterior-lateral directions, and the "lateral dominant type", which is widening mainly in the lateral direction. The AHI reduction rate was 80.1% (SD, 15.0%) for the all-round type and 79.3% (SD, 10.6%) for the lateral dominant type showing no significant difference.
Discussion: (1) Concerning indications for OA therapy, findings in the velopharynx rather than those in the hypopharynx may be important. (2) The effects of OA therapy can be expected in the presence of velopharyngeal widening irrespective of its direction. Thus, to determine whether OA therapy is indicated, endoscopic evaluation of morphological changes in the velopharynx with mandibular advancement may be important.