We propose a tonometry based solution to the problem of inexpensive, unencumbering and non- invasive measurement of blood pressure. The proposed solution will be useful in clinical as well as ambulatory blood pressure measurements. Specifically, we propose to develop a large (1cm x 5cm) two-dimensional array of pressure sensors with 0.2mm spacing (24x128 pressure-sensing elements), together with robust signal processing algorithms with a feedback controlled band-tightening mechanism in order to measure blood pressure at the wrist. The pressure sensor array together with a photoplethysmogram (PPG) sensor will be embedded in a band, and will provide signals through a multiplexed circuit designed. Signal conditioning techniques will be used to get the large amount of data in the form that can be efficiently processed on a microcontroller. The proposed two-dimensional array of pressure sensors will be built using flexible plastic and micro-fabrication techniques. The increased size of the sensor array will ensure proper contact and pressure application with arteries in the wrist for tonometric measurement of BP. The signals generated from the sensor array will be processed through advanced signal processing and optimization techniques to handle the huge amount of data and to mitigate noise. The PPG signals will be used at the wrist to improve the efficiency and accuracy of the system. The sensor array system will be embodied in the form of a band, which will be integrated in a wearable device such as smartwatch. The capabilities of the smartwatch will be used for data processing and analytics. a) Design, develop, and test a two-dimensional pressure sensor array on a polyimide flexible substrate b) Process large amount of analog data from sensor array using signal conditioning and processing techniques to generate blood pressure estimates c) Design a user friendly prototype form factor, and perform a clinical trial to validate device performance The engineering members of our multidisciplinary team have specialized in cardiac instrumentation, signal and image processing for medical applications, pressure and touch sensors, signal processing and robust optimization. The team members with clinical expertise have been engaged in blood pressure trials in US, and have been working with leading institutions in India engaged in cardiovascular research. This proposal brings together their unique expertise and experience to innovatively address this challenging problem through a joint effort.
Unmanaged hypertension is a major problem, and its management based on occasional measurement is known to be suboptimal. The ability to measure blood pressure using non- invasive techniques in an ambulatory setting has many significant benefits. We propose to research and develop a large (1cm x 5cm) two-dimensional array of pressure sensors based device together with robust signal processing algorithms with a feedback controlled to measure blood pressure at the wrist. The device will be test in a clinical trial based on the European Society of Hypertension International Protocol.