ecg electrode development

1. Department of ECE , BIT
Seminar On
“Development of Novel Non-contact
Electrodes for Mobile Electrocardiogram
Monitoring System”
Presented By: Guided by:
Suraj.B.S Shailaja.V
1BI11EC107 Lecturer
BIT Dept of ECE, BIT

2. Intro
And
ECG basics
Design
Conclusion
And
Reference
Results Platform Acquisition
ImplementArchitecture
Presentation Road Map

3. INTRODUCTION`
 Electrocardiography (ECG) is one of the most widely used vital sign sensing
and health monitoring methods and provides useful diagnostic information
about the cardiovascular system.
 The conventional contact clinical ECG system employs 12 or 15 Ag-AgCl
electrodes (wet ECG), which are affixed to specific parts of the chest, arms, or
hands and legs.
 Dry Electrode consists metal plate is placed on the skin instead of wet
electrodes, so the problems of using gel are eliminated. However, it still has
direct contact with the body.
 Our proposed capacitively coupled Non-Contact Electrode consists of thin
layer of insulator is placed between the body and the metal electrode . The
electrodes can be unnoticeably applied to a cloth that can be worn by the
patient to provide ubiquitous (U) health- care ECG sensing.

4. Heart Nodes
 The contraction of any muscle is associated with electrical changes called
depolarization and these changes can be detected by electrodes attached to
the surface of the body.
 The electrical discharge for each cardiac cycle normally starts in a special area
of the right atrium called the ‘sinoatrial node’.
 There is a delay while the depolarization spreads through another special area
in the atrium, the ‘atrioventricular node’ .
 The electrical discharge travels very rapidly, down specialized conduction
tissue: first a single pathway, the ‘bundle of His’, which then divides in the
septum between the ventricles into right and left bundle branches.
 The left bundle branch itself divides into two. Within the mass of ventricular
muscle, conduction spreads somewhat more slowly, through specialized tissue
called ‘Purkinje fibres’.

5. Wiring Diagram of Heart

6. R-R gap

7. Design
 The basic concept of the proposed novel non-contact electrode is to
construct a conducting plate covered by an insulating layer to form a
parallel plate capacitor with the skin. Therefore, the non-contact electrode can
couple bio- potential signals capacitively to a bio-amplifier.
 In order to reduce the influence of the varying and high impedance of the skin-
electrode interface, an impedance converter is used to connect to the
conducting plate.
metal plate
skin
insulating layer
d1 d2
vref
r1 r2
vout

8. Architecture
 The system hardware consists of non-contact electrodes, a wireless ECG
acquisition module, and a mobile system platform.
 The proposed non-contact electrode was designed to measure ECG without
contacting the user’s skin directly. Therefore, the user can wear the non-contact
electrode to monitor real- time ECG across thin clothes.
 The proposed wireless ECG acquisition module was designed to acquire ECG
from the non-contact electrodes, and transmit it to the mobile system platform
wirelessly via Bluetooth.
 An ECG monitoring program built into the mobile system platform will
continuously monitor the user’s heart rate.
 When the abnormal heart rate is detected, the ECG monitoring program can
send an SMS message with raw ECG data to the backend healthcare server to
request emergency treatment.

9. GSM modem
GSM Network
Basic Scheme of Monitoring System
physician
non
contact
electrode
acquisition module mobile platform backend server

10. Implementation
 The circuit of non-contact electrode is placed in the opposite side of the conducting
plate.
 The gap between the PCB and the shielding layer is filled with hot melt adhesive to
hold the conducting plate.
 The shielding layer is formed by covering with aluminum foil, and plastic tape is
also used to cover the non-contact electrode to form the isolation layer.
 The electrode is topped with Velcro so it can be attached to clothing easily and
conveniently.

11. Wireless ECG Acquisition Module
 The front-end amplifier circuit, which contains a pre-amplifier and a band-pass
filter, was designed to amplify and filter ECG signals obtained from the non-
contact electrodes.
 The amplified ECG signal is digitized by a 12-bit analog-to-digital converter
(ADC), built into the microprocessor, with a sampling rate of 512 Hz.
 The microprocessor (TI MSP430) was used to control the ADC and peripheral
circuits, and send ECG data to Bluetooth module.
 The size of the wireless ECG acquisition module is about 7.5 × 3.5 cm2. It
operates at 25 mA with a 3.7-V DC power supply, and can continuously operate
over 35 hours with a commercial 1100 mAh Li-ion battery.

12. non
contact
electrode BPF
Pre amplifier
SPU
Microprocessor
ADC
Wireless
Transmission
unit

13. Mobile System Platform
 A commercial mobile phone with the Android operation system was used as the
mobile system platform in this study. An ECG monitoring program, developed
using the Eclipse IDE with Android SDK and Java Development Kit, was built into
the mobile system platform to monitor the user’s heart rate.
 In the beginning, the ECG monitoring program calls the BT API thread to locate the
Bluetooth device.
 When the wireless ECG acquisition module is found, the BT API thread will try to
create an SPP stream to connect the mobile phone with the wireless ECG
acquisition module. Then, received ECG data will be sent to BUFFER, and displayed
on the screen.
 The AGLO thread, designed by using the heart rate detection algorithm calculates
heart rate from ten-second ECG data every five seconds.
 If an abnormal state of heart rate is detected, the ECG monitoring program will call
the SMS API thread to send an SMS message to the backend healthcare server.
Figure shows the screenshot of the ECG monitoring program.

14. Monitoring Program Flow Chart

15. Results
1 . Quality of ECG
2 . Effect of Motion Artifacts
3 . Arrhythmia Detection Test

16. Quality of ECG
 Bio-potentials measured by using the proposed non- contact electrode across thin
clothes are compared with that of disposable surface electrodes.
 The experimental results show that the ECG signal measured by using the proposed non-
contact electrode across thin clothing contains a little high-frequency interference.
 The correlation of ECG signals obtained by using the proposed non-contact electrode
and the disposable surface electrode in the time domain and in the frequency domain is
about 98.43% and 97.09% respectively.
 The measurement of ECG complex for different electrodes was tested. A total of 20-trial
ECG records obtained from healthy participants were used for analysis. For the proposed
non-contact electrode, the amplitude and duration of QRS wave are 1.08 ± 0.0322 mV
and 77.4 ± 7.279 ms.
 For the disposable surface electrode, the amplitude and duration of QRS wave are 1.05 ±
0.0293 mV and 77.05 ± 5.511 ms. The experimental results show that the ECG complexes
measured by using the proposed non-contact and disposable surface electrodes are
similar.

18. Effect of Motion Artifacts
 In this experiment, a fixing waist belt was applied with different pressures to
control the tightness between the body and the non-contact electrodes. Here,
the applied pressure levels are high, middle, and low.
 the ECG signal qualities with high pressure under both static and dynamic
states provide better signal-to-noise ratio (SNR).
 Walking will also result in a change in the skin-electrode interface equivalent
capacitance and static electricity to induce more noise.
 This can be effectively reduced while a high pressure is applied to increase the
tightness between the body and the non-contact electrodes.

19. Comparison between ECG signal qualities by applying different pressures.
Static sitting posture: static state Walking: dynamic state.

20. Arrhythmia Detection Test
 True Positive : There is a R wave in ECG, and it is correctly detected as a R wave.
 False Positive : There is not a R wave in ECG, but it is wrongly detected as a R wave.
 True Negative : There is not a R wave in ECG, and it is correctly detected as not a R wave.
 False Negative :There is a R wave in ECG, but it is wrongly detected as not a R wave.
 ppv = tp/(tp + fp)
 sensitivity = tp/(tp + fn)
 accuracy = 1 – (fp + fn)/total
 The results for detecting heart rate are listed in Table I. The values of PPV, sensitivity, and
accuracy of detecting the arrhythmia patients’ heart rates by using the proposed non-
contact electrode are about 98.54%, 99.75%, and 97.37% respectively.

21. R wave Non R wave Total
R wave 2031(tp) 24(fn) 2055
Non R wave 30(fp) 5(tn) 35
Total 2061 29 2090

22. Conclusion
 The experimental results show and the correlation of signal qualities using the
non-contact electrode and conventional ECG electrode is high.
 The effect of motion artifacts on the signal quality of the non-contact electrode
was also investigated. The experimental results show applying suitable pressure
to reduce the transversal motion and lateral motion of the non-contact
electrode can effectively improve the signal quality, even while exercising.
 The experimental results show that both of the sensitivity and accuracy for
detecting arrhythmia by using the proposed non-contact electrode are high
and it can be accurately applied for monitoring abnormal heart rate.
 The above experimental results show that the proposed non-contact electrode
presents an effective way to acquire bio-potentials without contacting the skin
directly, and is practicable to be embedded in normal clothing for long-term
ECG monitoring in daily life.

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