Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 96-105). Also available in electronic version. Access restricted to campus users.

Thesis (D.PT.)--Sage Colleges, 2009. / "May 2009." "A Capstone project for PTY 768 presented to the Faculty of the Department of Physical Therapy Sage Graduate School in partial fulfillment of the requirements for the degree of Doctor of Physical Therapy." Includes bibliographical references.

Thesis (Ph.D.)--University of Rhode Island, 2005. / Includes bibliographical references (leaves 90-95).

This thesis is concerned with the role of 'central command' in cardiorespiratory control during exercise and the peripheral autonomic modulation of cardiac excitability. Chapter One reviews the background to the work in the thesis. The cardiorespiratory and autonomic changes occurring during exercise and the ways in which they are brought about are discussed. This is followed by a review of some pathological changes in autonomic activity and the ways in which they might be arrhythmogenic. Chapter Two details the experimental techniques used in the thesis and discusses their theoretical background. Chapter Three studies the cardiorespiratory responses to imagination of exercise under hypnosis. This results in hyperventilation, hypocapnia and an increase in heart rate. In contrast, no cardiorespiratory changes are seen when the same protocol is repeated in the awake state. The response to imagined exercise under hypnosis is not affected by maintaining isocapnia. A powerful drive to breathe arising from higher centres, that is independent of peripheral muscular feedback, is elicited when 'exercise' is imagined under hypnosis. Chapter Four investigates the neural correlates of imagined exercise under hypnosis using positron emission tomography to see if they are the same as those classically implicated in 'central command' during exercise. Activation of 'motor' areas occurs, including the supplementary motor area, primary motor cortex for breathing, premotor area, thalamus, basal ganglia and cerebellum. The insular cortex, right dorsolateral prefrontal cortex and posterior parietal cortices are also activated. These activations are similar to those previously reported during actual exercise, but occur in the absence of peripheral feedback that accompanies actual exercise and may therefore reflect 'central command'. Chapter Five studies the responses to altered perception of work rate during actual exercise using hypnotic suggestions. If exercising hypnotised subjects are told that the work rate has increased (when it hasn't), they hyperventilate, become hypocapnic and heart rate increases, suggesting a partial uncoupling of 'central command' from peripheral feedback. Chapter Six investigates the cardiovascular effects of electrical stimulation of the thalamus and midbrain in awake man to determine the role of subcortical areas in cardiovascular control. High-frequency stimulation of the thalamus, subthalamic nucleus and substantia nigra results in increases in heart rate and blood pressure, whereas stimulation of the globus pallidus has no effect. In patients with implanted stimulating electrodes, chronic high-frequency electrical stimulation does not affect baroreflex sensitivity, heart rate variability or blood pressure variability. Chapter Seven characterises the cardiac electrophysiological consequences of sympathetic imbalance using multi-electrode array mapping techniques in the pig heart in vivo. A novel potential arrythmogenic mechanism of noradrenaline is also investigated in two in vitro preparations. Chapter Eight presents a brief summary of the findings in the thesis and discusses future research directions.

Thesis (Ph.D.) - University of Glasgow, 2008. / PhD. theses submitted to the Department of Mechanical Engineering, Faculty of Engineering, University of Glasgow. Edited version of thesis available, uncleared 3rd party copyright material removed. Includes bibliographical references. Print version also available.

Thesis (M. Med. Sc.)--University of Hong Kong, 2005.

Firefighters are responsible for protecting citizens as well as the infrastructure of cities across the United States. In order to safely protect and perform on-duty tasks, firefighters must be capable of performing physiologically demanding skills. Emerging evidence has led to heightened concern for firefighters’ increased obesity levels and decreased physical activity (PA). Formal exercise and PA research specific to firefighters is lacking. More specifically, there is a lack of literature using accelerometers to objectively measure PA. There is more evidence, however, to demonstrate firefighters have a high prevalence of obesity surpassing the general population. Not only are firefighters overweight and inactive, but also they are not aerobically fit to adequately perform their job-specific tasks. Purpose: To examine the relationship of PA and obesity to cardiorespiratory fitness (CRF). Methods: Firefighters (n=29) wore an accelerometer for eight consecutive on- and off-duty days. The accelerometer was worn on the right hip and tracked sedentary activity, light physical activity (LPA), moderate physical activity (MPA), vigorous physical activity (VPA), and moderate-to-vigorous physical activity (MPVA). Additionally, each participant completed a stage-graded exercise test with submaximal square-wave verification bout to determine maximal oxygen uptake (VO2max). A stepwise linear regression model was conducted using physical activity intensity, body mass index (BMI), and waist circumference (WC) as predictor variables for CRF. Results: According to the World Health Organization BMI categorization, none were normal weight, 20 were overweight, and 9 were obese. Firefighters spent roughly 61% of their waking hours in sedentary activity, 35.4% in LPA, and only 3.6% in MVPA. The two linear regression models were used to investigate whether PA intensity, step count, physical activity rating scale, BMI, or WC were more predictive of VO2max. VPA was predictive of VO2max (F(1,27) = 7.89, R2 = 0.23, p <0.01). Additionally, when BMI and WC were added, only WC was predictive of VO2max (F(1,27) = 11.76, R2 = 0.30, p<0.01). Conclusion: It is imperative fire departments emphasize the importance of cultivating an environment where improved health and wellness is essential for firefighters to adequately perform their physiologically demanding tasks.

Evidence-based medicine is at the heart of current medical practice where clinical decisions are driven by research data. However, most current therapy recommendations follow generalized protocols and guidelines that are based on epidemiological (population) studies and thus not suited for the individual patient's demands. Patient-tailored therapies are considered, hence, an unmet clinical need. We believe that mathematical models of the physiology can attend to such a clinical need, because they can be tuned to the individual patient. Such models provide a sound mathematical framework for personalized clinical decisions. In particular, physiological models in medicine can serve the following two purposes: 1) They can be an efficient tool to quantify cardiopulmonary dynamics, conduct virtual clinical/physiological experiments, and investigate the effects of specific treatments. 2) Model-based estimation techniques can assess physiological parameters or variables, which are otherwise impractical or dangerous to measure; they can effectively tune a generic model to become patient-specific, able to mimic the behavior of a particular patient. In this thesis, we propose a series of modifications to a previously developed cardiopulmonary model (CP Model) in order to better replicate heart-lung interaction phenomena that are typically observed under mechanical ventilation, hence allowing for a more accurate analysis of ventilation-induced changes in cardiac function. The response of this modified model is validated with experimental data collected during mechanical ventilation conditions. Further, as an industrial application of mathematical models, we present a patient emulator system that comprises the modified CP Model, a physical ventilator, and a piston-cylinder arrangement that serves as an electrical-to-hydraulic transducer. The modified CP Model then serves as the virtual patient that is being ventilated, where disease conditions can be instilled. Such a system is designed to offer a well-controlled experimental environment for ventilator manufacturers to efficaciously test and compare ventilation modalities and therapies, thereby enhancing their verification and validation manufacturing processes. Finally, we develop a model-based approach to estimate (noninvasively) the function of the cardiovascular system, in terms of cardiac performance (i.e., cardiac output) and the dynamics of the systemic arterial tree (i.e., time constant). With this technique, we envision to provide continuous and real-time bedside monitoring of changes in cardiovascular function, such as those induced by changes in ventilator settings.

Access to abstract is permanently restricted to Ball State communtiy only. / Access to thesis permanently restricted to Ball State community only / School of Physical Education, Sport, and Exercise Science

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