Unassisted Blood Pressure Monitoring Using Arterial Tonometry and Photoplethysmography

Our goal is to develop and test a pressure sensing and vasculature imaging surface device that is capable of measure a subject’s point of contact blood pressure. In our design, the user places his/her hand on the surface, hold it there for a few heartbeats, and the device outputs the subject’s blood pressure to a clinically acceptable accuracy. Integration and development of several different technologies is needed for the creation of such a device, requiring a multi-disciplinary team. The engineering members of our design team have specialized in instrumentation, signal and image processing for medical applications, pressure and touch sensors, photonics, machine learning 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. This proposal brings together their unique expertise to innovatively address this challenging problem. In the proposed approach, the subject’s hand is pressed against the surface resulting in an uncontrolled pressure application and imprecise information of pressure location. The device consists of an array of pressure sensors interspersed with low cost visible-light and infrared miniature sources and cameras. The pressure sensors give information on the applied pressure, while the multispectral imaging is used to map a subject’s vasculature. This map is processed together with pressure data to suppress misleading noise and accurately estimate a subject’s blood pressure. The measurements are processed through advanced machine learning and optimization techniques to account for noise and vessels hidden by the pressure sensors to generate robust output. Noise is further mitigated through a differential electrocardiogram, generated by having the subject place both hands on the surface. To improve the performance of the design, a cost function will be minimized over the parameters of interest (e.g. cost, accuracy, time of acquisition, etc.) to obtain a cost and signal effective arrangement of pressure sensors and cameras. Specifically we will: a) Design and develop a pressure sensor array that can reliably measure the blood pressure on the palm of the hand. Design and develop a vascular imaging system using miniature cameras. b) Develop and test a cost effective integrated system arrangement combining pressure information and vasculature images to determine point of contact systolic and diastolic blood pressure. c) Perform a clinical trial to validate the performance of our blood pressure measuring device. The novel proposed system combining pressure sensing and optics in an optimal way provides a unique opportunity to develop a cost effective non-cuff based blood pressure measurement system that can be used in uncontrolled environments. The development of the proposed system is possible due to the combined expertise of research experts in the desired aims of the proposal.