An acoustic blood pressure sensing scheme using time of flight and shear wave elastography techniques

Abstract

A novel wearable blood pressure sensor scheme is presented. The design incorporates an array of piezoelectric transducers to transmit acoustic waves through the skin, and receive reflected echoes from an arterial wall. The novelty ofthe device lies in the arrangement and operation ofthe transducers that allow for the application oftime of flight and shear wave elastography techniques to detectthe artery expansion and Young’s Modulus, respectively. The detection of these two parameters are imperative for a reliable blood pressure measurement insensitive to potential physiological changes in the body or the artery tissue. Finite element analysis was used to simulate the acoustic time of flight, shear wave propagation, and mechanical expansion of the artery wall. The device operation was experimentally validated using off-the-shelf components prior to device fabrication. The acoustic time of flight was shown to change with pressure in a decreasing linear trend. In addition, the peaks and valleys of an artificially-generated shear wave as well as the direction of wave propagation were shown to be detected. The results clearly demonstrate the capability of this design to determine the expansion and the mechanical properties of an artery. Further implementation of the device will enable the development of reliable and accurate wearable BP sensors for continuous monitoring of hypo- and hypertension-related diseases.