Tridimensional upper airway assessment in male patients with OSA using oral advancement devices modifying their vertical dimension

Mandibular advancement devices (MADs) constitute an alternative treatment in selected patients with OSA. A mandibular advanced position has been suggested to be beneficial, whereas its combination with an increased bite-raise may increase its adverse effects. The objective of this study was to assess upper airway (UA) volume and inspiratory pressure gradient variations in a group of 17 patients with OSA. The study was performed under 3 mandibular positions: intercuspal position (P1), MAD position in closed mouth (P2), and MAD position with an increased bite-raise (P3). We conducted a 3-dimensional reconstruction of the pharynx using the finite element method via a computed tomography scan and the subsequent calculation using fluid-dynamic analysis. One hundred percent of the patients showed an increase in UA volume in both P2 and the MAD position with an increased bite-raise, P2 being the position where 76.47% of the patients showed the largest UA volume. P2/velopharynx was the position/region where the largest UA volume increase was achieved (4.73 mm³). A better gradient in P2 (mean = 0.62) in 58.82% of the patients and a better gradient in P3 (mean = 0.74) in 41.18% of patients respect P1 was observed. In 82.35% of patients, a better volume-pressure gradient match was also found. The best efficiency scores for both volume increase and better inspiratory pressure gradient were obtained in P2. This study findings suggest that in a MAD, the minimal bite opening position necessary for mandibular protrusion is more effective in increasing airway volume and inspiratory gradient compared to a larger bite-raising (15 mm).