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Model-Based Cardiovascular Monitoring in Critical Care for Improved Diagnosis of Cardiac Dysfunction

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Model-Based Cardiovascular Monitoring in Critical Care for Improved Diagnosis of Cardiac Dysfunction MODEL-BASED CARDIOVASCULAR MONITORING IN CRITICAL CARE FOR IMPROVED DIAGNOSIS OF CARDIAC DYSFUNCTION James Alexander Michael Revie A thesis submitted for the degree of Doctor of Philosophy in Mechanical Engineering at the University of Canterbury, Christchurch, New Zealand October 2012 ACKNOWLEDGEMENTS There are many people I would like to acknowledge for helping me with my research. First I would like to thank my supervisors Geoff Chase, Thomas Desaive, and Geoff Shaw for their guidance. I am very fortunate to have such supportive and knowledgeable supervisory team. Their direction significantly helped mould my PhD and ensured I did not stray too far from the true path! I would especially like to thank my main supervisor Geoff Chase for granting the opportunity to do cardiovascular research at Canterbury. Geoff always made time to answer my questions and spent a lot of time editing my writing. I really appreciate your guidance and contributions to this work. Without your support this thesis would not have been possible. In addition, I would like to acknowledge the following people: Thomas Desaive, my co-supervisor from Belgium. Who looked after me when I did an internship at the University of Liege, provided useful improvements for my papers, and introduced me to the experimental side of cardiovascular research. Geoff Shaw, my contact in the Christchurch Hospital. Whose clinical experience and knowledge was invaluable to me understanding the physiological side of my work. Thank you for setting up and coordinating the clinical studies in the ICU. Chris Hann, a specialist in physiological modelling. His initial support, enthusiasm, and guidance on cardiovascular modelling and parameter identification methods helped set the foundation for this research. Colleagues who provided useful contributions including: David Stevenson, for providing the patient- specific driver functions for the models; Antoine Pironet, for suggestions on improving the parameter identification method; Chris Pretty, for contributions to analysing the septic shock results; and Paul Docherty for insights into structural identifiability. Mike Forrester and Rodney Elliot, for their technical assistance in acquiring data from the ICU medical devices. Students, Stefan Heldmann for his initial assistance on adapting the parameter identification to clinical measurements; Abhishek Vadnerkar on quantifying the effect of the deadspace volume on the driver function; Gregoire Coat for testing a simplified cardiopulmonary model; and Dougie Squire, for his work into analysing the aortic pressure waveform. iii | P a g e Finally, I would like to thank my lovely soon to be wife Lauren, along with my parents, sister, and friends for your friendship and support. iv | P a g e TABLE OF CONTENTS Abstract ........................................................................................................................ xxiii Chapter 1: Introduction and Motivation ......................................................................... 1 1.1 Hemodynamic Monitoring in the ICU ..................................................................................... 2 1.1.1 Data Rich, but Information Poor ..................................................................................... 3 1.1.2 One Size Fits All ............................................................................................................... 4 1.1.3 Model-Based Approaches ............................................................................................... 5 1.2 Goals of this Research ............................................................................................................. 6 1.3 Application of Research .......................................................................................................... 7 Chapter 2: Cardiovascular Physiology ............................................................................. 8 2.1 Cardiovasular System Overview .............................................................................................. 8 2.2 The Circulation ........................................................................................................................ 9 2.2.1 Arterial System .............................................................................................................. 10 2.2.2 The Capillaries ............................................................................................................... 10 2.2.3 Venous System .............................................................................................................. 11 2.3 The Heart .............................................................................................................................. 11 2.3.1 Anatomy ........................................................................................................................ 11 2.3.2 Electrical Activation ....................................................................................................... 12 2.3.3 The Cardiac Cycle .......................................................................................................... 15 2.4 Basic Concepts ...................................................................................................................... 16 2.4.1 Preload .......................................................................................................................... 18 2.4.2 Afterload ....................................................................................................................... 19 2.4.3 Contractility ................................................................................................................... 20 2.4.4 Heart Rate ..................................................................................................................... 22 2.4.5 Cardiac output ............................................................................................................... 22 2.4.6 Blood pressure .............................................................................................................. 22 2.4.7 Summary of Concepts ................................................................................................... 23 2.5 Interdependence of Preload, Afterload and Contractility .................................................... 24 2.5.1 Preload Afterload ..................................................................................................... 24 2.5.2 Afterload Preload ..................................................................................................... 24 2.5.3 Contractility Preload ................................................................................................ 25 2.5.4 Summary of Preload, Afterload and Contractility Interdependence ............................ 25 v | P a g e 2.6 Homeostasis Mechanisms..................................................................................................... 25 2.6.1 Neural Regulation ......................................................................................................... 26 2.6.2 Auto Regulatory Mechanisms ....................................................................................... 26 2.6.3 Humoral Regulation ...................................................................................................... 27 2.7 Ventricular Interaction .......................................................................................................... 28 2.7.1 Inter-Ventricular Septum .............................................................................................. 28 2.7.2 Pericardium ................................................................................................................... 29 2.8 Cardiopulmonary Interaction ................................................................................................ 30 2.8.1 Intrathoracic Pressure ................................................................................................... 31 2.8.2 Lung Volume ................................................................................................................. 31 2.9 Ventricular Arterial Coupling ................................................................................................ 33 2.10 Summary ............................................................................................................................... 33 Chapter 3: Cardiovascular System Model ...................................................................... 34 3.1 Introduction .......................................................................................................................... 34 3.2 Model Assumptions .............................................................................................................. 37 3.3 Model Development ............................................................................................................. 37 3.3.1 Passive Chamber ........................................................................................................... 37 3.3.2 Inter Chamber Flow (Non-Valvular) .............................................................................. 38 3.3.3 Heart Valve Flow ........................................................................................................... 39 3.3.4 Ventricular Chambers ................................................................................................... 40 3.3.5 Ventricular Interaction .................................................................................................
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