UBC Theses and Dissertations
Using ultrasound to measure arterial diameter for the development of a wearable blood pressure monitoring device Worthing, Richard Tyler
The goal of this thesis is to explore the potential of using ultrasound as part of a continuous and non-invasive blood pressure measurement device. Personal blood pressure measurement technology has remained relatively stagnant for decades, restricting those who take their blood pressure at home to using devices that operate with an inflatable pressure cuff. These devices are prohibitive in terms of both wearability and the ability to make measurements continuously. A device based on the methods explored in this thesis would be beneficial to anyone who requires at-home or 24-hour blood pressure monitoring without hindrance to daily activities, or blood pressure monitoring during exercise. In this thesis, a combination of ultrasound imaging and photoplethysmography are used to measure the diameter and the speed of a blood pulse traveling through the radial artery. Hemodynamic models suggest that these two metrics (arterial diameter and pulse wave velocity) are closely related to blood pressure and can be used to track changes in blood pressure at various points on the human body. To demonstrate proof of concept, two phases of a prototype device have been constructed. The first phase of the prototype makes use of an arterial phantom that simulates blood flow through an artificial artery immersed in a water bath. The purpose of the first prototype was to test the proposed method in a closed and controlled environment, using a non-destructive testing ultrasound probe for measuring the diameter of the phantom artery and pressure sensors for measuring the speed of a pressure pulse through the artery. The second phase of the prototype was built to perform measurements on human subjects. This stage used a medical ultrasound probe and photoplethysmography sensors to measure the diameter of the radial artery and local pulse wave velocity. Measurements with the phantom showed good correlation between the experimental method and absolute pressure measurement sensors. For human measurements, modelled blood pressure correlated well with values measured using a standard cuff-based blood pressure measurement device. Though the model showed good correlation with reference measurements, more work is needed on the prototype device before commercialization can be considered.
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