Browsing by Subject "Admittance"
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Item Admittance measurement for assessment of cardiac hemodynamics in clinical and research applications(2012-05) Larson, Erik Rist; Pearce, John A., 1946-The admittance method is an important tool for the indirect determination of cardiac hemodynamics in animal research and has clinical potential as a hemodynamic monitor for implantable cardioverter-defibrillators (ICDs). Animal studies use a conductance catheter to determine left-ventricular (LV) volume, but ICDs must make use of existing pacing leads to perform an admittance measurement. This work aims to further the use of the admittance method by extending its use to multi-segment conductance catheters, determining parasitic circuit element's effects on electric property measurements, using biventricular pacing leads to determine cardiac hemodynamics, and analysis of spatial sensitivity using finite element models in various configurations. Experimental results show the admittance method can be used to determine LV stroke volume with biventricular pacing leads. Modeling results show removal of the muscle component focuses the measurement's spatial sensitivity towards the left-ventricular blood pool.Item Admittance measurement for early detection of congestive heart failure(2010-05) Porterfield, John Edward; Pearce, John A., 1946-; Valvano, Jonathan W.; Yilmaz, Ali; Rylander, Henry G.; Feldman, Marc D.Impedance has been used as a tool for cardiac research since the early 1940’s. Recently there have been many advances in this field in the diagnosis of human heart failure through the measurement of pacemaker and ICD coupled impedance detection to determine the state of pulmonary edema in patients through drops in lung impedance. These new detection methods are far downstream of the initial changes in physiology, which signify heart failure risk, namely, an increased left ventricular (LV) end-diastolic volume (also known as preload). This dissertation presents the first formal validation of the complex admittance technique for more accurate blood volume measurement in vivo in mice. It aims to determine a new configuration of admittance measurement in a large scale animal model (pigs). It also aims to prove that “piggybacking” an admittance measurement system onto previously implanted AICD and bi-ventricular pacemakers is a feasible and practical measurement that will serve as an early warning system for impending heart failure through the measurement of LV preload, which appears before the currently measured drop in lung impedance using previous techniques.Item High performance wireless bio-impedance measurement system(2014-12) Le, Kelvin; Valvano, Jonathan W., 1953-Electrical and Computer EngineeringItem Wildlife rehabilitation centers: Survey of rehabilitators’ attitudes, motivations, and knowledge & study of animal admittance to the South Plains Wildlife Rehabilitation Center(2012-08) Mcgaughey, Kathleen; Perry, Gad; Wallace, Mark C.; Farmer, MichaelWildlife rehabilitation centers and wildlife rehabilitators rehabilitate and release injured, sick, displaced, and orphaned wildlife. To study the wildlife aspect of wildlife rehabilitation, mammal and herpetofauna admittance records for the South Plains Wildlife Rehabilitation Center (SPWRC) from the years of 1991-2010 were recorded and examined. These admittance data can be used to better manage similar human-wildlife interactions, offer solutions to common rehabilitation problems, and assist in successful release and survival of rehabilitated wildlife. To study the human aspect of wildlife rehabilitation, a survey was conducted of wildlife rehabilitators in Texas in order to study rehabilitators’ characteristics, knowledge and beliefs of some basic wildlife and rehabilitation issues, attitudes towards animals, reasons for rehabilitating, as well as how these things impact their desire and ability to properly educate the public about wildlife, specifically in urban areas.