Probabilistic glycemic control decision support in icu: proof of concept using Bayesian network

Glycemic control in critically ill patients is complex in terms of patients’ response to care and treatment. The variability and the search for improved insulin therapy outcomes have led to the use of human physiology model based on per-patient metabolic condition to provide automated recommendations. One of the most promising solution for this is the STAR protocol which is based on a clinically validated ICING insulin and nutrition physiological model, however this approach does not consider demographical background such as age, weight, height and ethnicity. This article presents the extension to their personalized care solution by integrating per-patient demographical and upon admission to intensive care conditions to automate decision support for clinical staffs. In this context, a virtual study was conducted on 210 retrospectives critically ill patients’ data. To provide a ground, the integration concept is presented roughly, but the details are given in terms of a proof of concept using Bayesian Network, linking the admission background and the STAR control’s performance. The proof of concept study shows the feasibility and the clinical potential to employ the probabilistic method as a decision support towards a more personalized care. ************************************************************************************* Kawalan glisemik dalam pesakit kritikal di unit rawatan rapi adalah rumit dari segi tindak balas pesakit terhadap penjagaan dan rawatan. Sifat keberubahan individu dan pencarian hasil terapi insulin yang lebih baik telah membawa kepada penggunaan model matematik fisiologi manusia berdasarkan keadaan metabolik pesakit untuk memberikan cadangan rawatan secara individu. Salah satu penyelesaian yang paling menjanjikan harapan adalah protokol STAR yang berdasarkan kepada model fisiologi insulin-nutrisi-glukosa yang telah disahkan secara klinikal. Namun pendekatan ini tidak mengambil kira latar belakang demografi seperti umur, berat, ketinggian dan etnik. Artikel ini membentangkan lanjutan kepada penyelesaian rawatan secara peribadi mereka dengan mengintegrasikan informasi demografi pesakit dan keadaan mereka semasa dimasukkan ke dalam unit rawatan rapi untuk mengautomasikan sokongan keputusan untuk kakitangan unit. Dalam konteks ini, satu kajian ‘virtual’ dilakukan pada data 210 pesaki. Sebagai kajian kes, konsep integrasi dibentangkan secara kasar, tetapi butiran diberikan dari segi bukti konsep yang menggunakan Rangkaian Bayesian, menghubungkan latar belakang kemasukan ke unit dan prestasi kawalan STAR. Bukti kajian kes menunjukkan 71.43% dan 73.90% ketepatan dan kebolehlaksanaan unjuran masing-masing dengan dataset ujian. Dengan lebih banyak data, rangkaian Bayesian yang lebih baik dipercayai boleh dihasilkan. Walaubagaimanapun, keputusan ini menunjukkan kemungkinan rangkaian ini bertindak sebagai pengelas yang berkesan dengan menggunakan data dari unit rawatan rapi dan prestasi kawalan glisemik untuk menjadi asas sokongan keputusan bersifat probabilistik, peribadi dan automatic dalam unit rawatan rapi

Doctor of Philosophy

dissertationInverse Electrocardiography (ECG) aims to noninvasively estimate the electrophysiological activity of the heart from the voltages measured at the body surface, with promising clinical applications in diagnosis and therapy. The main challenge of this emerging technique lies in its mathematical foundation: an inverse source problem governed by partial differential equations (PDEs) which is severely ill-conditioned. Essential to the success of inverse ECG are computational methods that reliably achieve accurate inverse solutions while harnessing the ever-growing complexity and realism of the bioelectric simulation. This dissertation focuses on the formulation, optimization, and solution of the inverse ECG problem based on finite element methods, consisting of two research thrusts. The first thrust explores the optimal finite element discretization specifically oriented towards the inverse ECG problem. In contrast, most existing discretization strategies are designed for forward problems and may become inappropriate for the corresponding inverse problems. Based on a Fourier analysis of how discretization relates to ill-conditioning, this work proposes refinement strategies that optimize approximation accuracy o f the inverse ECG problem while mitigating its ill-conditioning. To fulfill these strategies, two refinement techniques are developed: one uses hybrid-shaped finite elements whereas the other adapts high-order finite elements. The second research thrust involves a new methodology for inverse ECG solutions called PDE-constrained optimization, an optimization framework that flexibly allows convex objectives and various physically-based constraints. This work features three contributions: (1) fulfilling optimization in the continuous space, (2) formulating rigorous finite element solutions, and (3) fulfilling subsequent numerical optimization by a primal-dual interiorpoint method tailored to the given optimization problem's specific algebraic structure. The efficacy o f this new method is shown by its application to localization o f cardiac ischemic disease, in which the method, under realistic settings, achieves promising solutions to a previously intractable inverse ECG problem involving the bidomain heart model. In summary, this dissertation advances the computational research of inverse ECG, making it evolve toward an image-based, patient-specific modality for biomedical research

Cost modelling of rapid manufacturing based mass customisation system for fabrication of custom foot orthoses

PhD ThesisSolid freeform fabrication (SFF) or Additive manufacturing (AM) techniques have emerged in recent years as advanced manufacturing techniques. These techniques have demonstrated advantages particularly in situations where the demands for unique geometrical structured customer-specific products are high and the time to market is very short. Applications of these techniques in the medical sector in combination with the latest medical digital imaging technologies are growing quickly. The techniques have inherent advantages of compatibility with the output information of medical digitising techniques. Foot orthoses are medical devices used as shoe inserts in the treatment of foot disorders, injuries and diseases such as diabetes, rheumatoid arthritis, congenital defects and other foot related injuries. Currently custom foot orthoses are fabricated through manufacturing techniques which involve costly and based on lengthy trial and error manufacturing process. These techniques have limitations in terms of fabricating required geometries and incorporating complex design features in the custom-made orthoses. The novelty of this research is to explore the commercial scale application of rapid manufacturing techniques and to assess a rapid manufacturing based design and fabrication system for production of custom foot orthoses. The developed system is aimed at delivering the custom made orthoses at mass scale with improved fit, consistency, accuracy and increased product quality. The traditional design and fabrication process for production of custom foot orthoses was investigated and modelled with IDEF0 modelling methodology. The developed IDEF0 model was re-modelled and then the rapid manufacturing approach was integrated in the design and fabrication process. The main functions of foot geometry capture, orthoses design and manufacture of orthoses were modelled and evaluated individually with respect to time and cost and quality of the final product. Different well-established rapid manufacturing techniques were integrated in the current design and fabrication process. The results showed that the techniques have significant impacts on the overall design and fabrication process in terms of increased process efficiency, low lead-time, increased productivity and improved quality of the final product. An orthosis model was fabricated on an experimental basis using different well established rapid manufacturing techniques. The techniques were separately investigated and analysed in terms of orthoses fabrication cost and build time. The cost and lead-time in different techniques were modelled, analysed and evaluated for evaluation of commercial scale applications. The analysis and evaluation of the cost and lead-time modelled for different rapid manufacturing techniques showed that selective laser sintering technique is the better option for integrating the technique in fabrication of custom foot orthoses and that it has the potential to compete with conventional techniques

Développement d'outils de caractérisation de la mécanique pulmonaire en ventilation liquidienne totale

Le projet de recherche présenté consiste à la mise en place de matériel et de méthodes pour la mesure de l'impédance du système respiratoire en ventilation liquidienne totale (VLT). Ce projet a été réalisé en majeure partie en collaboration avec un étudiant à la maîtrise en physiologie, M. Dominick Bossé.Le matériel développé est un débitmètre instationnaire qui servira à mesurer le débit instantané à la trachée du patient.Le concept proposé consiste en un venturi symétrique comprenant trois prises de pression. La mesure du débit est obtenue en résolvant numériquement l'équation de Bernoulli légèrement modifiée. Un prototype a été validé expérimentalement en appliquant des débits sinusoïdaux de moyenne nulle. Les résultats ont montré que les écoulement quasi stationnaires sont mesurés précisément entre 5 ml/s et 60 ml/s et les oscillations de faible amplitude ([inférieur ou égal]10 ml/s) sont correctement mesurés pour des fréquences sous 3 Hz. De plus, une méthode pour appliquer la technique des oscillations forcées (TOF) en VLT est proposée. Elle consiste principalement à appliquer une excitation volumétrique sinusoïdale au système respiratoire, et à évaluer la fonction de transfert entre le débit délivré et la pression aux voies aériennes. Un modèle pulmonaire développé pour la ventilation gazeuse, le « five-parameter constant-phase model », est utilisé pour décrire les spectres d'impédance respiratoire observés. La méthode employée pour identifier les paramètres de ce modèle a été validée in silico sur des données générées informatiquement, et la méthode dans son ensemble a été validée in vitro sur un modèle mécanique reproduisant la dynamique pulmonaire. Les données in vivo sur 10 agneaux nouveau-nés suggèrent qu'un terme de compliance fractionnel est approprié pour décrire le comportement basse-fréquence des poumons, mais il n'a pas été possible de conclure sur la pertinence d'un terme d'inertance à ordre fractionnel. Finalement, l'étude des aspects plus physiologiques est présentée. En plus d'une description plus détaillée de la procédure expérimentale in vivo, on y observe l'influence de certains symptômes respiratoires (diminution de la compliance, augmentation de la résistance) sur l'impédance mesurée avec la TOF. Les conclusions sont que la résistance et l'inertance des voies aériennes sont grandement augmentées en VLT en comparaison de la ventilation gazeuse. La résistance et la réactance à 0.2 Hz sont sensibles à la bronchoconstriction et dilatation, autant que lors de la réduction de compliance. Ainsi, il est montré que la TOF à basse fréquence est un outil efficace pour suivre la mécanique respiratoire en VLT