Browsing by Subject "Hemodynamics"

Now showing 1 - 2 of 2
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    Cerebral and peripheral hemodynamic responses to increased end-tidal carbon dioxide volumes
    (2015-03) Geijer, Justin Robert
    Though hypercapnia is a naturally occurring physiological state, it is generally accompanied by hypoxic conditions (Venkataraman et al., 2008). The convolution associated with concurrent changes in carbon dioxide and oxygen volumes offer unclear results to researchers investigating the effects of arterial gas changes (Brogan et al., 2003; Cinar et al., 2012). Researchers at the University of Toronto have developed a computer-controlled gas blender (RespirActTM, Thornhill Research, Toronto, Ontario, CA) capable of measuring and altering end-tidal gas volumes, which are indicative of arterial blood gas changes (Brogan et al., 2003; Cinar et al., 2012). Researchers have utilized this technology to investigate cerebral vascular reactivity (Kassner et al., 2010; Mandell et al., 2008; Mark et al., 2011; Prisman et al., 2008), but differing methodologies and a lack of reproducibility studies raise questions about the validity of the findings. In addition, the peripheral response to a hypercapnic, normoxic environment is not well documented. This dissertation will investigate the effects of a hypercapnic environment on the cerebral and peripheral vascular beds. We hypothesize that the vascular changes associated with a hypercapnic environment are repeatable in both the cerebral and peripheral beds. We further hypothesize that the cerebral vascular changes will occur more quickly than the peripheral changes. Lastly, we hypothesize that a comparison between hypercapnia-induced vasodilation of the brachial artery will provide a similar, but slower dilatory response than reactive hyperemia. The results of this dissertation may provide further insight into the mechanisms responsible for hypercapnia-induced vasodilation of the cerebral and peripheral blood vessels, and may provide repeatable methodologies to be utilized in future research.
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    A computational framework for simulating cardiovascular flows in patient-specific anatomies
    (2011-12) Le, Trung Bao
    The goal of the thesis is to develop a computational framework for simulating cardiovascular flows in patient-specific anatomies. The numerical method is based on the curvilinear immersed method approach and is able to simulate pulsatile flow in complex anatomical geometries, incorporates a novel, lumped-parameter kinematic model of the left ventricle wall driven by electrical excitation, and can carry out fluid-structure interaction simulations between the blood flow and implanted bi-leaflet mechanical heart valves (BMHV). The ability of the method to resolve and illuminate the physics of dynamically rich vortex phenomena is demonstrated by carrying out simulations of impulsively driven flow through inclined nozzles and comparing the computed results with experimental measurements. The method is subsequently applied to simulate: 1) vortex formation and wall shear-stress dynamics inside an intracranial aneurysm; 2) the hemodynamics of early diastolic filling in a patient-specific left ventricle (LV); and 3) and fluid-structure interaction of a BMHV implanted in the aortic position of a patient-specific LV/aorta configuration driven by electrical excitation of the LV wall motion. For all cases the computed results yield new, clinically-relevant insights into the underlying flow phenomena and underscore the potential of the numerical method as a powerful tool for carrying out high-resolution simulations in patient-specific anatomic geometries. Future work will focus on extending the fluid-structure interaction scheme to simulate soft tissues and other medical devices, such as stents, bio-prosthetic tri-leaflet and percutaneous heart valves.