Upper airway physiology and respiratory phenotyping to understand and improve mandibular advancement treatment outcomes in people with obstructive sleep apnoea

Abstract

Oral appliances are a common alternative to CPAP for obstructive sleep apnoea (OSA) therapy. However, efficacy varies and current methods to predict favourable treatment responses are inadequate. This thesis aims to advance knowledge on the effect of oral appliance therapy on upper airway physiology and identify physiological characteristics to help predict which patients are most likely to respond favourably to oral appliance therapy.

Study 1 examines the role of body posture and mandibular advancement on nasal resistance in people with OSA. Efficacy of a novel titanium-based oral appliance with an in-built oral airway was also quantified. Awake nasal resistance increased systematically from seated, to supine, to lateral but was not altered by acute mandibular advancement. Unlike conventional devices, the novel oral appliance had similar therapeutic efficacy in people with high and low nasal resistance.

Study 2 used a detailed physiological approach to carefully quantify therapeutic CPAP requirements during combination therapy with CPAP and an oral appliance in the clinically relevant group of non-responders to oral appliance therapy alone. CPAP requirements reduced by ~40% with combination therapy.

Study 3 prospectively explored potential differences in the 4 pathophysiological traits that contribute to OSA between responders and non-responders to oral appliance therapy using gold standard respiratory phenotyping methodology and validated algorithm-based estimates. Efficacy of a next generation nylon-based novel oral appliance with a built-in oral airway was also assessed as was awake nasal resistance. Oral appliance therapy reduced OSA severity by ~40%. OSA severity reduced by >50% in half of the participants in both people with and without high nasal resistance. Responders to therapy tended to have a less collapsible upper airway and better pharyngeal muscle compensation at baseline when these traits were estimated via polysomnography but not when measured directly in this prospectively recruited cohort, none of whom had major anatomical compromise at baseline (Pcrit all <2cmH2O).

These findings provide new insight into the effects of a novel oral appliance on upper airway physiology and therapeutic efficacy and the potential for combination therapy for those with an incomplete therapeutic response to monotherapy with an oral appliance and the potential for estimates of OSA pathophysiological traits to help predict a favourable treatment response.