Dose-dependent effects of mandibular advancement on optimal positive airway pressure requirements in obstructive sleep apnoea.

BACKGROUND: Implementation of mandibular advancement splint (MAS) therapy as first-line treatment for obstructive sleep apnoea (OSA) is hindered by inter-individual variability of treatment outcomes and lack of robust patient selection methods. Optimal continuous positive airway pressure (CPAP) requirement provides an estimate of airway collapsibility severity, and high CPAP requirements predict MAS therapy failure in retrospective studies. Thus, understanding the effects of mandibular advancement on optimal CPAP requirements may enhance optimisation of patient selection for MAS therapy. OBJECTIVE: This study aims to determine dose-dependent effects of mandibular advancement on optimal CPAP requirements in OSA. METHODS: Prior to MAS therapy initiation, participants with OSA (apnoea-hypopnea index (AHI) > 10 events/h) underwent a research polysomnogram in which a remotely controlled mandibular positioner (RCMP) was used to determine dose-response effects of varying mandibular advancement positions (0% 'habitual bite' and 25, 50, 75 and 100% of maximum mandibular advancement, in random order) on optimal CPAP requirements. A separate polysomnography determined treatment outcome. Data are presented as mean +/- SD or median (1st-3rd quartiles). RESULTS: Seventeen participants (age = 47 +/- 9 years, body mass index = 26 kg/m(2) (23-27), apnoea-hypopnea index = 18 events/h (14-44) and minimal oxygen saturation = 84 +/- 7%) were studied. Optimal CPAP requirements were reduced with mandibular advancement in a dose-dependent manner (8.9 +/- 2.4 vs. 7.9 +/- 2.8, 6.4 +/- 1.8, 5.7 +/- 1.9 and 4.9 +/- 1.8 cmH(2)O; respectively, p < 0.0001). Compared with non-responders, responders to MAS therapy had lower AHI, lower arousal index and greater MinSaO(2) at baseline. Optimal CPAP requirements at 0% mandibular advancement (or other positions) were not different between groups. CONCLUSIONS: Increasing mandibular advancement lowers optimal CPAP requirements in a dose-dependent manner. This supports prior work indicating a beneficial effect of MAS on upper airway collapsibility.