Towards Development of a Low Cost and Portable ECG Monitoring System for Rural/Remote Areas of Bangladesh

1. DEVELOPMENT OF A COST EFFICIENT AND
PORTABLE ECG MONITORING SYSTEM FOR
RURAL/REMOTE AREAS OF BANGLADESH
Presented By,
Sayed Tanvir Alam (ID )
Md. Moin Hossain (ID )
Senior Project Supervisor:
Dr. Md. Kafiul Islam, Asst. Prof.

2. OUTLINE
Introduction
ECG Basic and its Recording
Motivation and Goal/Objectives
Challenges
Proposed System
Development
Circuit Simulation in Proteus
Hardware
 Electrode Selection
 Dual DC Voltage Regulator
 Instrumentation Amplifier
 Active Filter (Low-Pass)
 Circuit for DC Offset
Interfacing with PC
Arduino UNO + MATLAB
Software (MATLAB)
Preprocessing in MATLAB (Filtering)
QRS Complex Detection
Report Generation
Results Analysis
Effect of Filtering
QRS Complex detection
HR Detection
RR interval
Morphological values
interpretation
ECG Diagnosis Report
 Conclusion
 Future Works
References &
Acknowledgment
 Q & A
2

3. INTRODUCTION
Electrocardiography (ECG or EKG) is the process of recording the
electrical activity of the heart over a period of time using electrodes
placed on the skin. These electrodes detect the tiny electrical changes
on the skin that arise from the depolarizing and repolarizing of heart
muscle during each heartbeat.
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4. ECG SIGNAL
An ECG signal, which is as small
as 1 mV, is the heart’s electrical
signal that is extracted by an
electrocardiograph. The signal is
complex in nature. It generally is
composed of QRS complexes, P
waves and T waves.
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5. FORMATION OF ECG
SIGNAL• Electrical signal generates at the Sinoatrial
node.
• The electrical signal then travels through the
right and left atria which is recorded as P
wave.
• The electrical signal passes through
atrioventricular node which is recorded as the
flat line between the P wave and the QRS
wave.
• The electrical signal then passes through the
bundle of His and Purkinje fibers. The signal
travels then passes into the right and left
bundle branches. The signal spreads quickly
across heart's ventricles which is recorded as
the QRS wave.
• The ventricles then recover their normal
electrical state which is recorded as the T
wave.
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6. ELECTRODE
PLACEMENT
OF 12 LEAD
ECG
In a conventional 12 lead
electrocardiograph 10
electrodes are placed in
various part of the body as
shown in the figure.
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7. 12 LEADS OF
CONVENTION
AL ECG
Vertical Leads Horizontal
Leads
1. Lead I 7. V1
2. Lead II 8. V2
3. Lead III 9. V3
4. aVF 10. V4
5. aVL 11. V5
6. aVR 12. V6
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8. MOTIVATION AND OBJECTIVES
•Electrocardiographs available in the market are very expensive.
•Most hospitals and heath care centers at rural and remote
areas of Bangladesh cannot afford such expensive devices.
•Patients from these area suffer from underdiagnosing.
•A low cost portable ECG monitoring device will come in aid to
the health care of these underprivileged regions.
•As PC/Laptops are now widely available, an ECG monitoring
system that can be connected to a PC/Laptop will solve the
problem to an extent.
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9. CHALLENGES IN ECG ACQUISITION
 Very low signal amplitude (1mV – 5 mV) to detect.
 Often very noisy because of both internal & external sources
 Selection of low-cost affordable electrodes
 Available local resources
 Making it portable is not easy
 Wires connected to ECG leads or electrodes often fluctuate to
produce motion artifacts
 Subject motion is problematic in reliable ECG acquisition
 Others
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10. PROPOSED SYSTEM DESIGN
The circuit design of the whole device can be broken down in to
the following parts:
•Dual DC voltage regulator
•Instrumentation amplifier
•Active low pass filter
•Circuit to add DC offset
•Circuit to measure heart beat rate and RR interval
•Interface with PC/Laptop using Arduino
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11. DUAL DC
VOLTAGE
REGULATOR• The circuit components
require a regulated
voltages. Fluctuation in
voltage can damage the ICs
used in the system. Also,
the ICs used in the system
require a positive and a
negative voltage supply.
• 7809 provides a regulated
+9V output.
• 7909 provides a regulated
-9V output.
• Diode D1 and D2 provides
reverse bias protection to
regulators.
• Diode D3 and D4 are used
for protection against
output polarity reversal.
• Capacitors are used to filter
ripple effect.
Schematic Diagram of Dual DC Voltage Regulator
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12. DUAL DC
VOLTAGE
REGULATOR
Hardware Implementation
Simulation of the Circuit
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13. INSTRUMENT
ATION
AMPLIFIER
• Eliminates noise
interference and
extracts ECG signal.
• Takes the difference
between the two
electrodes and
amplifies it.
• Some noise also gets
amplified.
• Amplitude of input: 1
mV to 5 mV
• Gain = 1 +
49.4 𝑘Ω
47
=
1052.06
• Amplitude of output: 1
V to 5V
Schematic Diagram of Instrumentation Amplifier
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14. INSTRUMENT
ATION
AMPLIFIER
Output of Instrumentation Amplifier
Hardware Implementation of Instrumentation Amplifier
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15. ELECTRODES
Circular pad electrodes with
silicon conductor and
electrolyte contain potassium
chloride were used. These
electrodes permit electron
conduction from the skin to
the wire and to the
electrocardiogram.
Connectors of these electrodes
were made by drilling holes in
small pieces of iron sheet.
As these electrodes are
connected to the chest, these
provide a horizontal view of
the heart’s electrical activity.
Disposable Circular Pad Electrodes
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16. ACTIVE LOW
PASS FILTER
• Removes high
frequency noise
interference.
• Cutoff Frequency:
1
2π R1R2C1C2
= 79.58 Hz
• Order of filter: 2nd
order
• Gain: Unity
• Output: Noninverted Schematic Diagram of Active Low Pass Filter
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17. ACTIVE LOW
PASS FILTER
Hardware Implementation and Output of Low Pass Filter
Simulation of Low Pass Filter with Frequency Response
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18. CIRCUIT TO
ADD DC
OFFSET
A DC offset is added to the ECG
signal so that the minimum
voltage of the signal is above 0V.
Reasons to add DC offset:
• Arduino used in the later part
can not read negative voltage.
• It was observed that adding a
DC offset eliminates baseline
wandering effect of the ECG
signal. Schematic Diagram of Circuit to Add DC Offse
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19. CIRCUIT TO
ADD DC
OFFSET
Hardware Implementation of Circuit to
Add DC Offset
Output of After DC Offset Addition
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20. CIRCUIT TO MEASURE
HEART BEAT RATE
AND RR INTERVAL
Arduino and LCD are interfaced as shown.
ECG signal is given as input to Arduino digital
pin D7.
The following algorithm is followed of make the
measurements:
• Reset Arduino timer.
• Start measuring time when the first high pulse
is detected.
• Stop measuring time after 10 high pulse is
detected.
• Convert the time measured from milliseconds
to seconds.
• Divide the total time measured by 10. This
gives the average RR interval or basically the
period of the signal.
• Calculate the reciprocal of average RR interval.
This gives the number of beats in one second
or basically the frequency of the ECG signal.
• Multiple the value obtained from the previous
step by 60. The gives us the number of beats
per minute.
• Send the value to the LCD connected to the
Arduino.
Schematic Diagram of Circuit Used to
Measure Heart Beat Rate and RR Interval
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21. CIRCUIT TO MEASURE
HEART BEAT RATE
AND RR INTERVAL
Simulation in ProteusHardware Implementation of Circuit
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22. SCHEMATIC OF THE DEVICE
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23. CIRCUIT TO PC/LAPTOP
INTERFACING USING ARDUINO
To interface the circuit with PC/Laptop, an Arduino is used.
The signal is feed into the analog input port A0 of the Arduino.
Arduino is instructed to read the analog signal.
Arduino performs ADC on the ECG signal.
Arduino is instructed to dump the data in a variable.
Arduino is instructed to initiate serial communication with serial
plotter with baud rate 115200.
Sampling frequency is 785 Hz.
ECG signal is view on PC/Laptop screen using serial plotter.
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24. CIRCUIT TO PC/LAPTOP
INTERFACING USING ARDUINO
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25. SERIAL COMMUNICATION BETWEEN
ARDUINO AND MATLAB
Serial communication is established between Arduino and MATLAB
using the same communication port and same baud rate so that data
from the Arduino can be sent to MATLAB.
Number of samples MATLAB should store is specified. Arduino sends
one sample per milliseconds. Therefore, for ECG recording of 1
minute, 60000 samples were taken.
Received data from the Arduino is dumped in an matrix array by
MATLAB.
When the specified number of samples are taken, the communication
channel is terminated and MATLAB plots the data it received from
Arduino.
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26. SERIAL COMMUNICATION BETWEEN
ARDUINO AND MATLAB
Raw ECG Data Obtained by MATLAB from Arduino
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27. FLOW OF ECG SIGNAL
ECG
Circuit
Arduino MATLAB
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28. SIGNAL PROCESSING IN MATLAB
To remove power supply and high frequency noise notch filter and
low pass filter were designed in MATLAB.
FIR filter was used to design the low pass filter of order 256 and
cutoff frequency of 80 Hz to remove high frequency signal. FIR filter
is used as they are stable, easy to implement, and have a linear phase
response.
IIR filter was used to design the notch filter of order 2 and cutoff
frequency of 50 Hz to remove interference from power line. IIR filter
was used in this case as they have better frequency response than FIR
filters with the same order of filter. An immediate attenuation in gain
is required at 50 Hz.
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29. EFFECT OF FILTERING IN MATLAB
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30. EFFECT OF NOTCH FILTERING IN
MATLAB
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31. QRS DETECTION
An open source algorithm ‘cardio24’
from ‘redxlab’ was used to detect QRS
complexes of ECG signal.
By detecting QRS complexes various
morphological values od ECG signal can
be determined.
The flowchart of the algorithm used is
provided.
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32. QRS DETECTION
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33. MORPHOLOGICAL VALUE
DETERMINATION
Once the QRST complex of ECG signal has been detected various
morphological values can be easily determined.
The ‘cardio24’ algorithm by ‘redxlab’ can determine 12
morphological values and also determine if the values are normal or
not:Maximum heart rate Average heart rate Minimum heart rate
Total number of QRS Number of irregular beats Percentage of irregular
beats
Number of episodes with
consecutive irregular beats
Average PR interval Average QRS Interval
Average QT Interval Number of P wave
absences
Number of episodes that
has more than 4
consecutive P wave
absences
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34. ECG
DIAGNOSIS
REPORT
GENERATION
The morphological values
determined by the algorithm
can be extracted and MATLAB
can be instructed to create a
text file and dump the values
on that file.
Report Generated using MATLAB34

35. TARGET REPORT
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36. CONCLUSION
The ECG monitoring system developed is very cheap (around 1500
BDT) and will come in aid of people living in the rural and remote
areas of Bangladesh.
The system only requires a PC/Laptop as processing terminal which
are now even available in these rural or remote areas.
The ECG signal obtained after analog and digital filtering is of
satisfyingly good quality.
The morphological values and the report generated by the algorithm
can help doctors make diagnosis more easily.
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37. FUTURE WORK
 Eliminate the need of an Arduino to
interface with PC/Laptop.
 Interfacing a graphical LCD and eliminate
the need of a PC/Laptop for real-time
monitoring.
 Develop a smartphone application and
interface the circuit with it so that real-time
analysis can be perform using a smartphone.
 Convert the circuit into PCB and Use two 9V
batteries as overall power supply.
 Packaging of the whole system
 Generating professional ECG Diagnosis
Report (After consultation with clinicians )
37ECG Traces on Graphical LCD
ECG Traces on Smartphone Apps

38. REFERENCES AND
ACKNOWLEDGMENT
Key References:
Acknowledgment and Thanks:
1. IUB for Senior Project
Funding
2. Dehan Rahman from EEE,
IUT for helping with PC
interfacing and report
generation
3. R&D Officers, Lab
Technical Officer,
Technician and
Housekeeper.
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39. THANK YOU
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