Purpose: Oral appliance (OA) therapy is indicated for the treatment of obstructive sleep apnea (OSA) in patients with mild-to-moderate OSA. However, since OA therapy has been reported to be effective in some patients with severe OSA, it may not be possible to determine the indications for OA therapy based on the severity alone. The purpose of this study was to determine the indications for OA therapy using endoscopy in awake patients with severe OSA.
Methods: The subjects were 36 patients (27 males and 9 females) who were given a diagnosis of severe OSA on all-night polysomnography. A nasoendoscope was inserted with each patient in the horizontal position during nasal breathing, and morphological changes in the airways of the velopharynx, oropharynx, and hypopharynx with mandibular advancement were evaluated.
Results: With mandibular advancement, the oropharynx and hypopharynx widened in all patients while the velopharynx widened in 29 patients, but did not widen in 7. The apnea hypopnea index (AHI) reduction rate after OA application was 79.8% (SD, 13.0%) in the group with velopharyngeal widening and 40.6% (SD, 27.0%) in the group without velopharyngeal widening; this difference was significant. In the group with velopharyngeal widening, evaluation of the direction of widening revealed two types: the “all-round type,” characterized by circumferential widening in the anteroposterior and/or lateral directions, and the “lateral dominant type”, characterized by 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; this difference was significant.
Conclusions: 1. With regard to the indications for OA therapy, findings in the velopharynx may be more important than those in the hypopharynx. 2. The effects of OA therapy can be expected in the presence of velopharyngeal widening, irrespective of its direction. Our results suggest that endoscopic evaluation of morphological changes in the velopharynx with mandibular advancement might play an important role in determining whether OA therapy is indicated.
