Eunjeh Hyun, Seungwoo Noh, Chiyul Yoon, Hee Chan Kim Patch Type Integrated Sensor System for Measuring Electrical and Mechanical Cardiac Activities Nice to meet you, My name is Eunjeh Hyun. I’m from Republic of KOREA and on master’s course in Seoul National University. I’m studying about u-healthcare device and BioMEMS under professor hee chan kim as academic advisor. Today I’m going to talk to you our research result about patch type integrated sensor system for measuring electrical and mechanical cardiac activities Eunjeh Hyun, Seungwoo Noh, Chiyul Yoon, Hee Chan Kim Interdisciplinary Program, Bioengineering Major, Graduate School, Seoul National University

Introduction u-Healthcare service system Cardiovascular monitoring New healthcare service paradigm using Information-Communication Technologies Requires special devices to monitor health-related parameters out of hospital Interest in EASY-TO-USE sensors for Continuous and Unobtrusive monitoring Cardiovascular monitoring Of primary importance in u-Health service Early detection/ management of cardiovascular diseases - Through contin New healthcare service paradigm using Information-Communication Technologies has been emerged because aging of the population, prevalence of chronic diseases, and the growth on healthcare spending have lead to transformation of paradigm from hospital-centered healthcare service to a ubiquitous-healthcare service. Therefore, it requires special devices to monitor health-related parameters out of hospital. Many researchers have been interested in EASY-TO-USE sensors for Continuous and Unobtrusive monitoring. Especially, cardiovascular monitoring is of primary importance in ubiquitous-healthcare service. Early detection and management of cardiovascular disease through continuous physiologic monitoring of cardiac activities are more and more important.

Previous researches Sensors installed on the objects Unobtrusive measurement of physiological parameters Installed on everyday-objects Car seats, chairs, bathroom-scales Not feasible for continuous monitor Wearable sensors Over-the-clothes, textile-sensors, chest or wrist bands Separate sensors to measure each physiological parameter Discomfort to the subject In previous researches, healthcare sensors and devices were developed focused on continuous and Unobtrusive monitoring of physiological parameters. First image shows that sensors installed on car seat can measure electrocardiogram. This type of sensors have an advantage of unobtrusive measurement of physiological parameters,. However it is not feasible for continuous monitoring because the sensor can measure the signal only when they are used. Another sensor type, wearable sensors including over-the-clothes, textile-sensors, and chest or wrist bands, is usually the array of sensors integrated on clothes separately to measure each physiological parameter such as electrocardiogram, photoplethysmogram, body temperature, et cetera. This type of sensors can enhance user compliance, however it is still discomfort in long-term use Ford’s car seat for ECG measurement (TOP) Proceedings of the 9th ACM SenSys Conference on Embedded Networked Sensor Systems, Nov 2011 (Bottom)

Methods BE-patch A film-based sensor for simultaneous measurements of Ballistic & Electrical signal of human Thin, flexible and attachable to skin Can be applicable to ECG, BCG, CPF, and BP monitoring Unified sensor platform BCG Sensor Circuits Power ECG Electrodes Circuits Power Sensor Circuits Power Act Sensor Circuits Power Electrode Circuits Power BP We developed a film-based sensor for simultaneous measurements of ballistic and electrical signals of human The proposed sensor, named BE-patch from ballistic and electrical signals, is a unified sensor platform composed of electrode, circuit, and power. The sensor is thin, flexible, and attachable to skin for measuring physiological signals. And It can be applicable to electrocardiogram, ballistocardiogram, cardiopulmonary fitness , and Blood pressure monitoring Actigraph : monitoring human rest/activity cycles BCG : Ballistocardiogrph ECG : Electrocardiograph Acti : Actigraph BP : Blood-pressure

Methods EMFi sensor A ferroelectret film Permanently charged air-voids inside Displacement in charges from external pressure result in current Metal plating on both sides for the signal pick-up Commonly used for the vibration measurements, especially for BCG in physiological measurements G. S. Neugschwandtner et al, Applied Physics Letter (2000) EMFIT® (Emfit Ltd, FINLAND) We used commercial available ElectroMechanical Film as base material for fabrication. EMFi is a ferroelectret film composed of thin plastic layers and charged air-voids inside. It has quasi-piezoelectric property. When the external pressure is applied on the surface, displacement in charges inside result in electric current. Therefore, usually metal is plated on both sides for the signal pick-up. The EMFi has been commonly used for the vibration measurements, especially for BCG in physiological measurements

Materials and methods Electrode configuration Screen-printed silver Nonconductive gap The front(skin) side ECG electrodes Electrode configuration Four electrodes for the electrical signal pick-up Two electrodes for the mechancial signal pick-up Shares the ground electrode ground electrode The back(circuit) side BCG electrode 90 mm 50 mm Screen-printed silver paste EMFi film BCG electrode ECG electrodes & ground electrode Components layer Skin Cross-sectional diagram The sensor was fabricated as a layered structure of ElectroMechanical Film with screen-printed electrodes and a flexible electronic circuit. We segmented one conductive layered for simultaneous measuring of electrocardiogram as well as ballistocardiogram by screen printing conductive silver paste on to the EMFi film. For the ECG measurement, the potential difference between two ECG electrodes located in the front side was recorded with reference to the ground electrode. And for the BCG measurement, the electric current produced with reference to the ground electrode was recorded. The pattern of the top layer was determined to ensure maximum distance for the ECG lead while providing fine signal quality for both the ECG and BCG.

Methods Circuit block-diagram The front(skin) side Signal conditioning ECG electrodes ground electrode Micro Controller Unit A/D converter Comm I/O Filter & amplifier Bluetooth module The front(skin) side Connecting hole BCG electrode A flexible circuit was integrated as a top layer for conditioning ECG and BCG waveforms. The each electrodes were connected with circuit separately via connecting holes filled with silver paste. An instrumentation amplifier and a charge amplifier were utilized for amplification, respectively. And a micro controller unit digitalized the analog signals and Bluetooth module transmitted the data to a remote monitoring computer Filter & ampilfier Remote monitoring PC The back (body) side

- Quality of raw signals Results - Quality of raw signals J peak R peak Conformal contact to the skin (chest) Typical morphologies of the ECG and BCG were confirmed R peaks in the ECG J peaks of the BCG First image shows the whole sensor system which is thin and flexible. Next image shows the sensor system was attached to the subject’s chest acquiring fine BCG and ECG simultaneously. The acquired signals shows that R peak of ECG and J peak of the BCG were clearly confirmed.

Results - Blood pressure estimation BP estimation using dissimilar heart signals Pulse propagates FAST under HIGH BP Pulse propagates SLOW under LOW BP ECG provides the timing of pulse onset Valsalva maneuver To induce a BP changes We Investigated the feasibility of continuous blood pressure monitoring using our developed sensor. Blood Pressure can be estimated by the time delay for a pulse pressure waveform to propagate between two points in the arterial tree. Pulse propagates fast under high pressure, and slow under low pressure. RJ interval, which is time delay from R peak of ECG to the J peak of BCG, has been also known to have a negative relationship with BP. On this principle, we estimated blood pressure from RJ interval and validate estimated blood pressure with reference blood pressure. Subjects performed the Valsalva maneuver to induce a BP change. Normal physiological response to the Valsalva maneuver are a rapid blood pressure increase when the strain is applied and a slow stabilization to normal blood pressure when the strain is released. reference systolic blood pressure, was obtained simultaneously by the FINOMETER, commercial device for continuous arterial pressure from finger.

Results - Blood pressure estimation Negative relationships Between the RJ interval and the SBP Estimation performance Intraclass correlation coefficient (ICC) of 0.95 (p<0.01) Meets both guidelines from AAMI & BHS standard for medical usage As a result, negative relationships between the RJ interval and the reference BP were found in all subjects. RJ intervals during the stabilization were associated with the Systolic Blood Pressure by linear regression. And the systolic blood pressure was estimated by the regression equation. The estimated SBP showed excellent agreement with the reference SBP And this result comply with the recommended guidelines from the Association for the AAMI in the United States and the BHS Featured article,  Electronics Letters, issue 3, vol 50 SBP : Systolic blood pressure AAMI : Association for the Advancement of Medical Instrumentation (U.S. standards) BHS : British Hypertension Society

Discussion Performance of BE-patch Limitations Application Simultaneous measurement of BCG & ECG with little discomfort Reduces hardware complexity and power consumption Showed a BP-estimation application Limitations Susceptible to the motion artifacts Clinical efficacy has yet been fully tested Application Energy expenditure monitoring Cardiopulmonary fitness monitoring Proposed sensor can successfully measure fine electrocardiogram and ballistocardiogram simultaneously. It reduces hardware complexity and power consumption and showed a BP-estimation application. However susceptibility to the motion artefact is weakness. However, motion artefact is the problem to overcome, which resides in almost every wearable healthcare sensor The sensor needs to be validated on more subjects and its long-term efficacy should be tested. to gain more general acceptance on the usage in practice We are now about to try another application. Because proposed sensor can measure vibration of body, We are investigating the feasibility of energy expenditure monitoring and cardiopulmonary fitness monitoring.

Thank you!