A Mobile Cardiac Monitoring System

A Mobile Cardiac Monitoring System
Berney Montavon1
Department of Electrical and Computer Engineering
Cleveland State University
Cleveland, Ohio 44115
1
Email:
. This project was funded by the Cleveland State University Provost’s Office
and by the National Science Foundation under Grant No. 0826124.
Abstract:
The ability to conduct long-term, continuing electrocardiogram (ECG) monitoring is a valuable tool for
improving the quality of healthcare in the United States. Automatic detection of cardiac arrhythmias
using an inexpensive shirt provides safety to many individuals tasked with strenuous jobs, and can also be
used by heart surgery patients recovering at home. A non-invasive, mobile ECG monitoring system is
implemented using a Texas Instruments ADS1298®, a FlyPort Wi-Fi, and a PIC 18F4520. Using a
conductive polymer composite sensor (CPS) t-shirt, electrocardiogram (ECG) recordings are measured by
the ADS1298, collected and preprocessed by the PIC 18F4520, and then transmitted to a laptop computer
via any wireless network using the FlyPort Wi-Fi. The ECG data will be saved, and plotted using
MATLAB®.
Project/Problem Description:
Sudden Cardiac Death (SCD) is among the leading causes of death in the United States [1].
Abnormalities in the electrocardiogram (ECG) are used to detect potential ailments that can lead to SCD.
Early detection is key in preventing SCD, which makes the ability to monitoring a person's ECG for long
periods of time an important tool for doctors. Conventional ECG sensors require the use of a conductive
gel and the removal of the artificial layer of skin where the sensors are placed [2]. For these reasons,
sensors must be repaired and/or replaced on a continuing basis. In recent years, advances have been made
in sensor technology using carbon nanotubes (CNT) and CPSs. The structural properties of the CPS
create the ability to measure the voltage differential across the heart [3]. An athletic t-shirt development
by Cleveland Medical Polymers uses 10 CPS sensors to form the standard 12 lead ECG configuration.
Each lead represents an ECG plot measuring the voltage differential from 12 different angles to the heart.
Attached to the shirt is a DB15 connector that links to the ADS1298® board.
®
Figure 1 - The ADS1298 connects to the ECG t-shirt with an serial connection.
The SPI pins are in the J3 connector located on the lower right hand corner of the board.
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When attached to the ECG t-shirt, the ADS1298® functions as an analog to digital conversion chip. The
analog signal is measured using the CPS sensors which are attached to the ADS1298 by a DB15 serial
connector. From there, each signal is filtered and calculated using the right leg sensor as the ground.
With the current hardware configuration, the ADS1298® must be connected to a laptop that has a
Labview program which stores the data and allows the user to view the ECG on screen. There is no
practical application that would allow the wearer of the ECG shirt to be carrying a laptop, so the ability to
transmit data wirelessly is crucial to the mobile system. The purpose of this project is to increase the
mobility of the ADS1298® by eliminating the need to be connected to a computer.
Plan of Attack:
The first step undertaken in completing this project is to collect the code required to run the ADS1298
interface. The ADS1298 code was provided by Cleveland Medical Polymers and requires the use of 10
header files, 2 libraries and 1 linker file that were downloaded from the Microchip [4]. The code is
written in C. MPLAB IDE v8.83, along with the C18 compiler, is used to program the PIC. Once the
code is compiled, the ADS1298 will need to be connected to the PIC 18F4520 SPI inputs. The
connections on the ADS1298® board are seen in Figure 2.
Figure 2 - SPI breakout pins for the ADS1298 ® development board [5].
The FlyPort Wi-Fi code will be added to the MPLAB workspace after the ADS1298/PIC interface is
working properly. The FlyPort Wi-Fi is a web server module that has a 802.11 b/g/n Wi-Fi interface [6].
It can be linked to any laptop by a web based interface and it actually houses a PIC of its own that
controls the transmission process. That code that interfaces the FlyPort Wi-Fi and a Microchip PIC is
available from www.openPicus.com [6]. The FlyPort Wi-Fi module can be seen in Figure 3. The data is
transmitted to and from the FlyPort through the SPI port or any number of digital inputs and outputs.
Upon the successful connection of the FlyPort Wi-Fi, the project will conclude with the ability to receive
the ECG data that is transmitted by the FlyPort Wi-Fi from a laptop connected to a wireless network.
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Figure 3 - The FlyPort Wi-Fi operates using a PIC 24FJ256 making it an ideal
wireless transmitter for any PIC driven embedded system.
Expected Results:
The ECG t-shirt and the ADS1298® have a proven ability to capture and save ECG recordings in a noninvasive way [3]. The expected results of this project will be the ability to measure the ECG waves of a
person wearing the shirt, and then to view the ECG wave data received wirelessly on a laptop computer
using a web based interface. The data will be viewed real time with the use of MATLAB®. Much of the
work done on this project will involve the reading and learning of three different schematics. It is
expected that this project will provide a valuable background in designing and implementing of an
embedded system.
Milestones/Timeline:
March 30 - Proposal; The process of downloading header, libraries and the linker files is completed. The
ADS1298 software is successfully compiled and programmed onto the PIC.
April 6 - The ADS1298 will be connected with the PIC to send ECG data to computer using an RS-232
serial port. Indicator LEDs will blink 5 times when the PIC is receiving data properly.
April 13 - The FlyPort code is successfully compiled and all hardware will be connected by this date.
April 20 - The mobile system will be operational and ECG data will be transmitted to a laptop.
April 30 - An oral presentation of the project results will be completed along with the first copy of the
final report.
May 4 - Final report is completed.
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References:
[1] A. Miniño, S. Murphy, J. Xu, K. Kochanek, "Deaths: Final data for 2008," National Vital Statistics
Reports, National Center for Health Statistics. 2011.
[2] T. Garcia & N. Holtz, Introduction to 12-lead ECG : the art of interpretation, (Burlington, MA:
Sudbury, Jones and Bartlett, 2003).
[3] B. Montavon, M. Ergezer, P. Lozovyy, A. Venkatesan and D. Simon, “Adaptive Filtering for
Detecting Myocardial Infarction Using Noninvasive Conducting Polymer Composite Sensors ,” Imaging
and Signal Processing in Healthcare, 2012.
[4] Microchip Inc., “PIC18F4520 Datasheet,” www.microchip.com, 2007.
[5] Texas Instruments Inc, “Low-Power, 8-Channel, 24-Bit Analog Front-End for Biopotential
Measurements,” www.ti.com , 2010.
[6] FlyPORT, “OpenPicus WiFi Module,” www.openpicus.com, 2011.
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