A Mobile Wireless Electrocardiogram System for Health Care Facilities

John FarnerJason Fritts

Julian JaegerJoe Richard

Georgia Institute of Technology

School of Electrical and Computer Engineering

Project Overview

A mobile wireless EKG system that will track and store heart rhythm data, allow patients freedom of movement, and communicate with a central base station

Marketed to hospitals, nursing homes, and other health facilities to assist medical staff and increase patient care quality

Provide a reasonable alternative to conventional EKG systems at a reduced cost

Design Objectives

Safe for user Reliable EKG data under a variety of

circumstances Base station interface Easy to use mobile system Lightweight and small size Long range wireless data transfer

Two Stage Implementation

Stage 1:Measuring Potential Across the Human BodyAverage Heartbeat

Men: 70 bpm

Women: 75 bpm

Up to 200 bpm Exercising

Chest Voltage, 0.5 mV to 5.0 mV

Front End Circuitry

AD624ADPrecision Instrumentation Amplifier

Programmable gain between 1 and 1000

CMRR exceeds 110 dB when the gain is set to 1000

http://www.ortodoxism.ro/datasheets/analogdevices/AD624BD.pdf

Linear Bandpass Filter

No battery power consumption

Loss of half the signal strength during testing

Bandwidth ≈ 1 Hz – 20 Hz

Linear Bandpass Filter Bode Plot

Reducing Input Signal Noise

Before Filter After Filter

http://www.analog.com/library/analogDialogue/archives/37-11/ecg.html

Stage 2:EKG Data Acquisition

http://robot.lonningdal.net/parts/phidgets.jpghttp://f.ipc2u.ru/files/products/34462/ebox2300.jpg

A Phidgets voltage sensor gathers data from the output of the front end circuitry

An onboard ADC converts analog signal to digital values

A C# OS subproject stores the digital data for later transmission to the base station

USB

Mobile System SoftwareStart

Gather initial analog input values

Store digitally as Y0

Initialize timer

Store time as X0

Have analog inputs changed?

Has timer reached 5 sec?NO

Read system time

Store time as Xi

Read analog input

Store digitally as Yi

YES YES

Run a second timer to wait 5 min between EKG readings

Event Handling

NO

Wireless Communication

http://z.about.com/d/compnetworking/1/0/q/3/linksys_wrt54g.jpghttp://www.embeddedpc.net/Portals/6/WiFi_Option.jpg

Files shared using Windows CE filesharing on a local area network.

eBOX uses a mini PCI 802.11g WiFi card

Base station connected to a Linksys 802.11g WiFi router

802.11g WiFi Standard

Provides sufficient range (up to 38 meters)

Provides data transfer rate of 54 Mbps

Base Station GUI

Select patient from drop-down menu

Patient’s information is displayed in text boxes

Select desired heart data from list box to be graphed

Design ChoicesAdvantages Disadvantages

Amplifier- Single component

- 1K amplification

- Precision measurement

- Power consumption

- Cost

Isolation- Patient safety

- Low cost solution- Less robust design

Filtering - No battery power consumption

- Signal attenuation

Phidgets- Ease of use

- Onboard ADC- Low sensor sampling rate

eBOX- Ease of use

- Built in wireless capabilities

- Power consumption

Wi-Fi- Cost

- Ease of installation- Cell phone modem gives longer range

Project Timeline

Integration of Two Stages

October 22

Complete Wi-Fi data transmission

October 31

Final Computer Interface Software

November 7

Packaging November 28

Testing and Tweaking December 3

Final Presentation December 5

Future Work

Integration of stage 1 and stage 2 Data transfer

Connection between eBOX and base station Automated file sharing

Mobile power options: Use a 2nd voltage regulator or voltage supply Use a 5V rail voltage

Packaging for mobility

“This year an estimated 1.2 million Americans will have a new or recurrent coronary attack.”

http://www.americanheart.org/presenter.jhtml?identifier=4478