Obstructive sleep apnoea hypopnoea syndrome (OSAHS) is a highly prevalent disease in which upper airways are collapsed during sleep, leading to serious consequences. The reference standard of clinical diagnosis, called Polysomnography (PSG), requires a full-night hospital stay connected to over 15 measuring channels requiring physical contact with sensors. The vast quantity of physiological data acquired during the PSG has to be manually scored by a qualified technologist to assess the presence or absence of the decease. The PSG is inconvenient, time consuming, expensive and unsuited for community screening. The limited PSG facilities around the world have resulted in long waiting lists and a large fraction of patients remain undiagnosed at present. There has been a flurry of recent activities in developing a portable technology to resolve this need. All the devices have at least one sensor that requires physical contact with the subject. Unattended systems have not led to sufficiently high sensitivity/specificity levels to be used in a routine home monitoring or a community screening exercise. OSAHS is a sleep respiratory disorder principally caused by functional deficiencies occurring in the upper airways during sleep. These conditions and the reduced muscle tone during sleep, cause the muscles in the upper airways to collapse partially or completely thus resulting in episodes of hypopnoea and apnoea respectively. During the process leading to collapse of upper airways, upper airways act as an acoustic filter frequently producing snoring sounds. The process of snore sound production leads us to hypothesise that snore sounds should contain information on changes occurring in the upper airways during the OSAHS. Snoring almost always accompanies the OSAHS and is universally recognised as its earliest symptom. At present, however, the quantitative analysis of snore sounds is not a practice in clinical OSAHS detection. The vast potential of snoring in the diagnosis/screening of the OSAHS remains unused. Snoring-based technology opens up opportunities for building community-screening devices that do not depend on contact instrumentation. In this thesis, we present our work towards developing a snore–based non-contact instrumentation for the diagnosis/screening of the OSAHS. The primary task in the analysis of Snore Related Sounds (SRS) would be to segment the SRS data as accurately as possible into three main classes, snoring (voiced non-silence), breathing (unvoiced non-silence) and silence. A new algorithm was developed, based on pattern recognition for the SRS segmentation. Four features derived from the SRS were considered to classify samples of the SRS into three classes. We also investigated the performance of the algorithm with three commonly-used noise reduction (NR) techniques in speech processing, Amplitude Spectral Subtraction (ASS), Power Spectral Subtraction (PSS) and Short Time Spectral Amplitude (STSA) Estimation. It was found that the noise reduction, together with a proper choice of features, could improve the classification accuracy to 96.78%. A novel model for the SRS was proposed for the response of a mixed-phase system (total airways response, TAR) to a source excitation at the input. The TAR/source model is similar to the vocal tract/source model in speech synthesis and is capable of capturing the acoustical changes brought about by the collapsing upper airways in the OSAHS. An algorithm was developed, based on the higher-order-spectra (HOS) to jointly estimate the source and the TAR, preserving the true phase characteristics of the latter. Working on a clinical database of signals, we show that the TAR is indeed a mixed phased signal and second-order statistics cannot fully characterise it. Nocturnal speech sounds can corrupt snore recordings and pose a challenge to the snore-based OSAHS diagnosis. The TAR could be shown to detect speech segments embedded in snores and derive features to diagnose the OSAHS. Finally presented is a novel technique for diagnosing the OSAHS, based solely on multi-parametric snore sound analysis. The method comprises a logistic regression model fed with a range of snore parameters derived from its features — the pitch and Total Airways Response (TAR) estimated using a Higher Order Statistics (HOS) based algorithm. The model was developed and its performance validated on a clinical database consisting of overnight snoring sounds simultaneously recorded during a hospital PSG using a high fidelity sound recording setup. The K-fold cross validation technique was used for validating the model. The validation process achieved an 89.3% sensitivity with 92.3% specificity (the area under the Receiver Operating Characteristic (ROC) curve was 0.96) in classifying the data sets into the two groups, the OSAHS (AHI >10) and the non-OSAHS. These results are superior to the existing results and unequivocally illustrate the feasibility of developing a snore-based non-contact OSAHS screening device.

In the early 1990s claims were made that in all areas of health care, “30-40% of patients do not receive treatments of proven effectiveness”, and, “20-25% of patients have treatments that are unnecessary or potentially harmful”. Many such practices were diffused prior to the acceptance of modern evidence-based standards of clinical- and cost-effectiveness. I define disinvestment in the context of health care as the processes of withdrawing (partially or completely) resources from any existing health care practices, procedures, technologies or pharmaceuticals that are deemed to deliver little or no health gain relative to their cost, and thus are not efficient health resource allocations. Arguably disinvestment has been central to Evidence-Based Medicine(EBM) for well over a decade yet despite general advances in EBM, this topic remains relatively unexplored. This thesis examines the ongoing challenges that exist within the Australian context relating to effective disinvestment. Upper airway surgical procedures for the treatment of adult Obstructive Sleep Apnoea Syndrome (OSA) are used as a case study to contextualise these challenges. This thesis has six sections: 1. A review of the literature outlines developments in EBM broadly and provides a detailed background to OSA, including the numerous treatment options for the condition. This review examines evidence that highlights the importance of ‘highly effective treatment’ over ‘subtherapeutic treatment’ as a necessity to confer improved health outcomes in OSA. It is argued that claims of surgical success inherent in most published results of surgery effectiveness fail to assimilate contemporary evidence for clinically significant indicators of success. 2. Section two comprises the first reported meta-analysis in this area. It presents the pooled success rates of surgery according to various definitions. Specifically, when the traditional ‘surgical’ definition of success is applied the pooled success rate for Phase I (i.e. soft palate) surgical procedures is 55% (that is 45% fail). However, using a more stringent definition (endorsed by the peak international sleep medicine body), success is reduced to 13% (that is 87% fail). Similarly for Phase II (i.e. hard palate) procedures success rates decrease from 86% to 43% respectively when moving from a surgical to a medical definition of success. That various medical specialties differentially define treatment success, I argue, creates uncertainty for observers and non-clinical participants in this debate (eg policy stakeholders and patients). This represents a barrier to disinvestment decisions. 3. Results are presented from a clinical audit of surgical cases conducted as a component of this thesis. Both clinical effectiveness and procedural variability of surgery are reported. A unique methodology was utilised to capture data from multiple centres. It is the first time such a methodology has been reported to measure procedural variability alongside clinical effectiveness (inclusive of a comparative treatment arm). The observed cohort (n=94) received 41 varying combinations of surgery in an attempt to treat OSA. Results on effectiveness demonstrate an overall physiological success rate of 13% (according to the most stringent definition; phases I and II combined). This demonstration of procedural variability combined with limited effectiveness highlights clinical uncertainty in the application of surgical procedures. 4. Section four outlines how a qualitative phase of enquiry, directed at exploring the perspectives and experiences of surgery recipients, was approved by three independent research ethics review boards but was not supported by a small group of surgeons, resulting in the project being canceled. Potential consequences of this for impeding health services research (HSR) are discussed. 5. Two sets of results are reported from a qualitative phase of enquiry (semi-structured interviews) involving senior Australian health policy stakeholders. The first results are of policy stakeholders’ perspectives on the surgical meta-analysis and clinical audit studies in 2 and 3 above. The second results are from an extended series of questions relating to challenges and direction for effecting disinvestment mechanisms in Australia. Stakeholder responses highlight that Australia currently has limited formal systems in place to support disinvestment. Themes include how defining and proving inferiority of health care practices is not only conceptually difficult but also is limited by data availability and interpretation. Also, as with any policy endeavour there is the ever-present need to balance multiple interests. Stakeholders pointed to a need, and a role, for health services and policy research to build methodological capacity and decision support tools to underpin disinvestment. 6. A final discussion piece is presented that builds on all previous sections and summarises the specific challenges that exist for disinvestment, including those methodological in nature. The thesis concludes with potential solutions to address these challenges within the Australian and international context. Systematic policy approaches to disinvestment represent one measure to further improve equity, efficiency, quality of care, as well as sustainability of resource allocation. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1297655 / Thesis (Ph.D.) -- University of Adelaide, School of Population Health and Clinical Practice, 2007

Le syndrome des apnées obstructives du sommeil (SAOS) est caractérisé par des épisodes répétitifs de collapsus des voies aériennes supérieures (VAS) durant le sommeil. Au cours du SAOS les propriétés mécaniques des voies aériennes supérieures sont altérées, dans le sens d'une réduction de leur capacité à laisser passer l'air, ce qui peut être assimilé à une "charge" inspiratoire. Les apnées obstructives ne se produisent jamais à l'éveil, suggérant qu'il existe, des mécanismes protecteurs d'origine corticale, de type " compensation de charge ", liés à l'éveil. Ce travail permis de caractériser ces mécanismes chez le sujet sain et le patient SAOS. Une première étude a décrit la relation pression/débit des VAS à l'éveil afin d'approcher le phénomène de compensation de charge, avant et après un traitement modulant le contrôle neurovégétatif des VAS par la compression du ganglion ptérygopalatin. La deuxième étude a mis en évidence à l'éveil chez les patients SAOS, une activité corticale motrice liée à la respiration (présence de potentiels électroencephalographiques - PPI), dont l'origine semble liée à la dysfonction des VAS, et qui est susceptible d'expliquer l'augmentation du niveau de contrôle respiratoire central connu dans le SAOS. La troisième étude a mis en évidence un phénomène de filtrage des sensations respiratoires à l'éveil chez des patients SAOS, avec restauration des ces sensations sous orthèse d'avancée mandibulaire, permettant de relier l'amélioration des propriétés mécaniques des VAS à l'intégration centrale des sensations respiratoires. Enfin la relation pression/débit a fait l'objet de deux modélisations. / The obstructive sleep apnoea syndrome (OSAS) involves recurrent sleep-related upper airways (UA) collapse. UA mechanical properties and neural control are altered imposing a mechanical load on inspiration. UA collapse does not occur during wakefulness, hence arousal-dependent compensation. Three studies in healthy and apnoeic patients allowed characterizing it. From upper-airway pressure-flow relationships, the first study described local compensation mechanisms, before and after a neurovegetative modulation based on ptérygopalatin node compression. The second study showed a respiratory-related cortical activity that could contribute to the increased neural drive to upper airway and to inspiratory muscles that has previously been described in OSAS, and could therefore contribute to the arousal-dependent compensation of upper airway abnormalities. The third study showed a sensory gating-out process of breathing sensations in OSAS that could be reversed by mandibular advancement device, allowing linking upper-airway stability improvement to central integration of respiratory sensations. Finally, upper-airway pressure-flow relationship was approached by two models.