Text

theses

Endothelial dysfunction has been proven to be an early indication of cardiovascular disease (CVD), a leading cause of death worldwide (Sorsen 1995; WHO 2017). There are three diagnostic methods for endothelial functions discussed: ultrasound Flow-Mediated Dilation (uFMD) that uses ultrasound to determine brachial artery size, Peripheral Arterial Tonometry (PAT) that uses finger pulse plethysmographs, and Cuff Flow-Mediated Dilation (cFMD) that uses pressure oscillations in a blood pressure cuff. Each of the three methods first collect a control or “resting” measurement before obtaining a vasodilation measurement of the blood vessels by occluding blood flow for 5-minutes with a blood pressure cuff. Output for uFMD and PAT testing results in a singular number, percent dilation (FMD%) and reactive hyperemia index (RHI) respectively, based on the blood vessel’s percent dilation (Sorsen 1995; Allan 2013; Whitt 2010). Each method has multiple factors that influence results such as body mass index, coronary artery disease, peripheral artery disease and a patient’s height (Van der Heijden 2017; Allan 2013; Schroeder 2000). It is proposed that a mathematical model used with cFMD can generate a smooth continuous output for analysis and help understand the effect that transmural pressure has on vessel dilation. In this thesis, a biomechanical model of the human brachial artery was programmed to represent both the resting and vasodilated conditions of the brachial artery. Data for the resting and vasodilated states of six subjects were collected using cFMD. First, the patient’s blood pressure and heart rate were observed. Next, the resting curve was obtained before a 5-minute occlusion. Lastly, the vasodilated measurements were taken. For each of the 6 subjects, the model was found to accurately represent the data collected for the resting and vasodilated states. Using the model, transmural pressure was found to influence the vessel’s percent dilation curve. Combining the model with cFMD allows for FMD to be performed without ultrasound, generates a larger SNR, and allows for analysis of percent dilation at multiple values of transmural pressure. The accuracy of the automated model has potential to generate other graphs to understand the artery’s compliance and the effects of physiological functions such as the pulse. Further research should be done to determine what transmural pressure value would be optimal in minimizing the factors that influence test results.

ETD_8725

M.S.

Includes bibliographical references

by Kristin DiStefano

doi:10.7282/T3794840

ETD graduate

The author owns the copyright to this work.