Degree Name

Master of Philosophy (Medicine)


School of Medicine


Background: Obstructive sleep apnoea (OSA) is estimated to affect up to 1 billion people in the world. Those who fail first-line continuous positive airway pressure (CPAP) therapy have salvage treatment options available. Patient assessment can incorporate multidisciplinary teams to better select therapy. Traditional parameters that define OSA severity do not always correlate with symptoms of the disease. Newly identified pathophysiological “phenotypes” of airway vulnerability, low arousal threshold, loop gain and muscle responsiveness may explain the heterogeneity of OSA for up to two-thirds of patients. Little data exists on the effectiveness of phenotyping in a real-world clinical setting for patients undergoing contemporary management paradigms.

Aims and Hypothesis: To evaluate the prevalence of the four OSA phenotypic traits and explore the clinical validity of endotyping in predicting future treatment outcomes. It is expected that non-responders to treatment will have unfavourable non-anatomical phenotypes.

Design: An observational prospective cohort study of 49 patients referred after failure of CPAP for consideration of salvage therapy was conducted. Treatments included upper airway surgery (n = 17), mandibular advancement splint (n = 7), positional therapy (n = 7), weight loss (n = 4), nerve stimulation (n = 5) and combination therapy (n = 9). Treatment “success” was defined using polysomnographic parameters and patient-reported outcome measures of sleepiness and function. Phenotypic traits were analysed according to these outcomes.

Results: Nearly all surgical patients had unfavourable loop gain (LG1 > 0.72), which improved after surgical treatment (p < .05). Patients who had decreased sleepiness (Epworth Sleepiness Scale reduction ≥ 3, total score < 10, p = .01) after any treatment had favourable traits of low loop gain, lower arousal threshold and lower muscle compensation. There may be a potential role for phenotyping in predicting expected outcomes from salvage treatment for OSA, although more prospective clinical data is required to further investigate its utility and relevance.

FoR codes (2008)

110203 Respiratory Diseases



Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.