Flexible Piezoelectric Array for Cardiovascular MonitoringDuring Cardiac Arrest

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Project Summary In situations of out of hospital cardiac arrest, it is critical to quickly detect the performance of adequate cardiopulmonary resuscitation (CPR) through clinically acceptable pulse rate and blood pressure (BP). However, the detection of adequate CPR can be difficult for someone not trained in first aid. Currently the standard for measuring BP noninvasively is using cuff-based oscillometeric approaches. Attempts at developing these into wearable devices for automated and continuous measurements have proven difficult and so researchers have looked at other methods. However, these methods have not met the criteria for flexibility, accuracy, and low power consumption. This project aims to develop a flexible patch for accurate detection of pulse rate and blood pressure superficially through the radial, brachial, carotid, and/or femoral arteries. Piezoelectric polymers, are inherently flexible and have been used in many applications for pressure sensing, offering great potential for use as a patch-like sensor for monitoring of cardiovascular function. However, in the standard form, the material is not sensitive enough to accurately detect blood pressure. In our lab we have developed a core-shell nanofiber structure of conductive and piezoelectric nanofibers, respectively. The core-shell nanostructure shows a 4.5 times improvement in pressure sensitivity when compared to standard piezoelectric nanofibers and a nearly 40 times improvement when compared to piezoelectric polymer thin films. This improvement in pressure sensitivity should allow for a wearable device composed of these materials to exceed the necessary 35 dB signal to noise ratio required for the accurate detection of pulse wave velocity, a cardiovascular parameter used to determine blood pressure. Coupled with inkjet printing patterning techniques of conductive polymers developed in our lab, we propose to fabricate a novel core-shell nanofiber piezoelectric array in a wearable patch form for cardiovascular monitoring. In order to test this piezoelectric array and develop data-driven algorithms for the detection of blood pressure, testing will occur on a controllable simulated cardiovascular system capable of replicating a human’s diastolic and systolic blood pressures, pulse rates, and arterial mechanical properties. The blood pressure attainable by the simulated system falls within the AAMI standard benchmark for accuracy and precision for noninvasive blood pressure monitoring of 5 ± 8 mmHg. We will train various regression models using the data generated from this system to relate the detected pulse wave velocities to blood pressure and we will compare the outcomes to commonly used correlation equations. We propose that the fabrication methods we will develop, when coupled together with data-driven algorithms, will allow for the development of a low- power, flexible patch, capable of detecting pulse rate and blood pressure, giving feedback on the adequacy of CPR.