Noninvasive aortic pressure derivation from peripheral arterial sites: a comparative study

In the United States approximately 73 million people 20 and older, i.e. 1 in every 3 person, suffer from high blood pressure. Hypertensive subjects have significantly increased stiffness in their arteries, making it harder for blood to flow through. Anti-hypertensive drugs such as beta blockers and calcium channel blockers are used for their treatment with the aim to lower blood pressure through reducing vascular stiffness or increasing arterial compliance. The efficacy of the drugs’ effects on each patient cannot be accurately determined by the commonly used blood pressure cuff, which provides just systolic and diastolic pressures. In order to accurately diagnose certain severe cases of cardiovascular disorders, invasive and costly catheterization is performed. This thesis develops a model-based noninvasive diagnostic technique for personalized treatment. The methodology utilizes noninvasively measured peripheral artery pulse waveforms as an input to a transfer function in order to compute central aortic pressure waveforms. This is because aortic pressure cannot be obtained directly by noninvasive means and large vessel compliance or stiffness is critical in determining proper function and treatment of hypertensive patients. A cardiovascular system model allows critical parameters, such as large artery compliance and blood pressure augmentation index, to be readily computed. Many research groups have attempted to produce the aortic waveform noninvasively, while some have succeeded, most of the existent models have flaws which limit the accuracy of the synthesized waveforms. Therapeutic drug efficacy can be easily monitored at regular intervals through this new model-based noninvasive hypertension evaluation system. This project also evaluates the preferred site for noninvasive blood pressure measurements such as radial artery, carotid artery and femoral artery through comparison of their respective transfer functions. Evaluating the physiological advantages of the various peripheral arterial sites for noninvasive blood pressure measurements, radial arterial sites seems to be ideal as it provides best stability during tonometry due to its anatomical advantage of bone packing in the area and increased accessibility compared to other sites such as carotid and femoral. The scope of the thesis limits direct comparison of noninvasively derived with directly invasively measured aortic pressure waveform. Future testing of this step will allow the eventual system to have many advantages, in that it is noninvasive, accurate and low-cost, and affords personalized care for hypertensive patients.M.S.Includes bibliographical referencesby Priya Moha