Prediction of Mandibular Advancements Splint Therapy Outcome in Obstructive Sleep Apnoea

Obstructive sleep apnoea (OSA) is typically managed by mechanical stabilization of the upper airway (UA) via provision of continuous positive airway pressure (CPAP) therapy, which is not preferred by many OSA patients. Mandibular advancement splint (MAS) therapy is the leading alternative therapy for OSA and is highly preferred by patients. However, MAS efficacy is suboptimal for some OSA patients. Hence, robust methods for predicting MAS therapy outcome is required. This thesis utilised novel methodological approaches to provide an understanding of the relationship between MAS therapy outcome and key pathophysiological, anatomical and clinical measurements related to OSA. Several findings were noted. MAS reduced UA collapsibility (critical pharyngeal collapsing pressure) and optimal CPAP requirements in a dose-dependent manner. No improvement in genioglossus muscle function was noted with MAS. We also noted higher levels of UA collapsibility, but not optimal CPAP requirement, at habitual mandibular position in non-responders to MAS therapy, compared with responders. Estimation of the pathophysiological causes of OSA from diagnostic polysomnography via an automated algorithm showed that favourable MAS therapy outcome was related to moderate UA collapsibility, poor UA muscle function, respiratory control system stability, less arousability from sleep and weak ventilatory response to arousal. Finally, we found that dimensions of anterior neck space and facial height, measured via photogrammetric assessment of facial surface landmarks, may be informative of OSA responses to MAS therapy. These findings support the notion that MAS therapy resolves OSA via anatomical amelioration of pharyngeal narrowing in those with abnormal pharyngeal anatomy and with a minimal contribution from non-anatomical factors. This also highlights the importance of phenotypic mechanisms causing OSA in determining outcomes of MAS therapy and providing targeted and personalized therapy for OSA