Validation of non-invasive standing arterial stiffness measurements using ballistocardriography and photoplethysmography [electronic resource]

More than 76 million Americans have hypertension, or high blood pressure, which can shorten life by 10 15 years if left untreated. Hypertension increases the risk of developing cardiovascular diseases (CVD) such as stroke, heart attack, congestive heart failure, or kidney failure that are often debilitating and impact quality of life. Prevention is the key to minimize CVD risk and increase longevity, but accurate prognosis of a future disease is difficult. Elevated blood pressure (BP) is generally the first sign of risk, but measuring pressure alone does not provide insight to where in the body problems may exist. Therefore, other screening tests are needed to more specifically isolate the underlying cause, which would improve the selection process of prescribing medications, or diet and exercise changes. And similar to BP measurements, such hypertensive screening tests may need to be performed at home to improve accuracy, since doctor's visits often trigger physiological responses that falsely elevate and lower BP. To address these concerns this work describes the design and validation of a home based noninvasive system (a bathroom scale) to measure aortic pulse wave velocity (PWV), to assess arterial stiffness, which is a clinical risk factor for certain CV diseases. The purpose of this work was four-fold: to develop a home monitoring device with simple user operation; to develop biomechanical theories as to why forces in the aortic arch can be sensed synchronously at the feet; clinically validate the biomechanical theory; and to demonstrate potential clinical utility of standing PWV measurements for trending and prognosis. The PWV scale is comprised of two different sensing technologies, ballistocardiography and photoplethysmography, which are embedded in the scale to measure pulse arrival times in the aortic arch and the foot—simply by standing on the scale. Using this system, PWV can be routinely determined in less than 30-seconds—significantly faster than commercial systems using trained operators. To validate this PWV system, a novel biomechanical theory was developed called Central Aortic Forces (CAF) to explain how the cardiovascular forces inside the body can be synchronously sensed outside the body. The computational models accurately predicted the amplitude of forces in the aortic arch (2-3 Newtons at rest), which were empirically confirmed in a clinical study; the empirical results agreed within 10% of the theory. To demonstrate trending abilities, a longitudinal PWV study was also performed over a four month duration, with results highly correlated to the applanation methods. Finally, an age study was conducted to characterize arterial aging, which matched well (p< 0.01) in slope and intercept major clinical trials published in the literature using applanation PWV (clinical gold standard). Examples are given on how such a system may improve prognosis to detect early vascular aging in young adults, otherwise masked in standard blood pressure measurements.

Keywords: Bioengineering.
Advisor: Kovacs Gregory T. A. primary advisor. Thesis advisor
Giovangrandi Laurent advisor. Thesis advisor
Taylor Charles advisor. Thesis advisor