Pharyngeal Airway Volume as a Predictor of the Efficacy of Obstructive Sleep Apnea Treatment with a Mandibular Advancement Device
Background: The efficacy of mandibular advancement devices (MAD) in the treatment of obstructive sleep apnea (OSA) varies widely among patients, and at present it is difficult to predict success. Previous studies have shown a relationship between a gain in pharyngeal volume with MAD in situ and the success of the treatment. The aim of this study was to evaluate this change in volume of the upper airway using cone beam computed tomography (CBCT), measured at a baseline of maximum intercuspation (T0) and at maximum protusion (T1) using a George Gauge to simulate a MAD produced protusion, and investigate whether this change in volume can be used to predict success with MAD.
Methods and Findings: 10 individuals with mild/moderate OSA underwent CBCT at baseline (T0 - maximum intercuspation) and time 1 (T1 - maximum protusion using a George Gauge for bite registration). All patients then underwent polysomnography before and after MAD treatment. The total volume, total area and minimal cross section area of the pharynx were then analyzed again by CBCT. The mean of the protrusive position using a George Gauge at baseline (12.2mm ± 1.9) was similar to the maximum comfortable position achieved with MAD (11.6mm ± 2.08). MAD treatment significantly reduced the Apnea Hypopnea Index (AHI) values (11.7 ± 6.7 to 2.4 ± 3.1) (p=0.01). The retropalatal volume increased significantly between T0 and T1 (6240mm² ± 2224 to 7720mm² ± 3516) (p=0.04). Changes in volume measured by CBCT (T1-T0) were positively predictive for changes in AHI (initial-final) (p = 0.05).
Conclusion: Variations in CBCT volume of the upper airway, at baseline and using bite registration at maximum comfortable protrusion, was a predictor for a reduced apnea/hypopnea index after treatment with MAD.
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