Electrocardiogram (ECG) is the test which measures the electrical activity of the heart. The heart is a muscular organ that beats in rhythm to pump the deoxygenated or oxygenated blood through the body. On the 1895, the 1st accurate recording ECG has successfully invented. ECG signal is an electrical signal that generated by heart's beating. The ECG device is invented to detect and record the ECG signal which used by doctor for taking further treatment. It is very important in clinical diagnosis of the heart disease. It provide an objective indicator for the correct analysis, diagnosis, treatment and care of heart. Due to the important value of ECG, it has a very wide range of application. Besides, there are many researches on ECG to make it more advances and keep it developed in recording, processing and diagnosis signal. Recently, Singapore has come out with an ECG mobile phone named EPI life. It can be get by purchase USD $358 in the market. The ECG device becomes more advance and keep developing, but there still have problem of interference in its signal. Normal human ECG is a non stationary, non linear and low signal to noise ration. The voltage of the ECG signal is in the range of 0.5-4mV and its frequency is 0.05-100HZ. Hence the environment, equipment or human factors are easily affecting the ECG signal. The electromagnetic interference (EMI) of ECG has widely established, but its clinical consequence still remains controversial.
1.2 Problem Statements
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Nowadays, ECG device is very developing and advance in its application. However the problem of the EMI still exists in the ECG signal. The EMI will cause the ECG device having less accuracy in producing the data. Hence, there is error in the patient's data reading. The error will lead to the delay or inappropriate treatment decision made by the doctor. It wouldn't bring too big problem to the normal people but it will cause death to the patient who are seriously injured or the patient who in emergency. So we should not take easy with this problem.
-To analyze the effect of different environment to the EMI of ECG
-To determine the effect of shielding to the EMI of ECG
In order to achieve the objectives of the project, there are several scopes should be caring on. Firstly, implementation of a portable ECG circuit is needed. Then, ECG signal data recording is taken in different place and room condition to test the EMI of ECG. There is study show that a shielding cage will affect the EMI of an ECG signal. Hence, a small shielding cage is needed for testing the EMI of ECG. The experiment is done getting the data when the ECG circuit inside and outside the shielding cage. Finally, is analysis all the data of ECG signal.
The thesis is organized into 4 Chapter. The thesis is start with an Introduction which gives a simple overview of the objective and scope of the project.
Chapter 2 will cover up the literature review part which focusing on the understanding of implement a portable ECG circuit, effect of EMI and effect of environment to the ECG signal.
Chapter 3 briefly is about the methodology of the project.
Chapter 4 will mainly discuss about the preliminary results and conclusion of the FYP1.
2.1 ECG Signal
The heart is the most vital organs within the human body. It play the role as the pump which circulates oxygenated blood and deoxgenated blood around the body in order to keep in functioning. The waste product geberated from the body will remove through the circulation. The electrical activity of the heart can be interpreted into ECG signal through the electrocardiogram recording . Its has a principle measuremnt range of 0.5 to 4mV and frequency range of 0.05 to 100 Hz . By detecting the volatge created by the heart beating, its rate can be easily use to observed and used for health purpose. Figure 2.1, a sample of single beat ECG signal produced by the heart. There are 5 identifiable features in an ECG signalwhich reperesent the different polarisation stages that make up a heart beat. The defelctions are denoted by the letters P,Q,R,S and T.
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Figure 2.1 : Sample of single beat ECG signal
The P wave represent the spread of electrical activity over the atrium and normallys is last less than 0.11 seconds . While the PR interval are in the range of 0.12 to 0.2 seconds in length, it start in the beginning of the P wave until the beginning of QRS complex. The time is depending to the electrical wave through AV nodes. The slower the electromagnetic wave go through the AV node , the prolong the time of PR interval or vice versa. Following with PR is the QRS complex which represent activation of the ventricle. It is a special conductiong bundles spread the wave of depolarization rapidly over the ventricle . Length of QRS normally is less tahn 0.10 seconds and it indicates some blockage of electrical action in the conductiong system. The The first upward in QRS is R wave while the first downward of QRS is called Q wave. R is the stage of activation of ventricle while Q represent activation of the ventricular septum and the electricity is spreading from right to left side through the septum. Q waves indicate either myocardial infarction or obstructive septal hypertrophy . ST segmnet is stage of contracting ventricle but there is no electricity flowing through. Next, T wave represent the wave when the ventricle prepare to fire again.
2.2 Standard Lead of ECG
Figure 2.2: Standard Lead and Einthoven Triangle
Figure 2.2 show the standard lead and the Einthoven Triangle. The ECG device connects the common electrode at the patient's right leg while the lead selector switch connects to the proper limb or chest electrode to the differential amplifier input. The bipolar limb leads are those designated Lead I, Lead II and Lead III and the three of them often shown by a diagram called the Einthoven Triangle . However, the Lead II is more commonly used. Lead II is the connection which connects amplifier's non inverting input to the left leg (LL) and connects inverting input to the left arm (LA).
2.3 Portable ECG device
According to the World Health Organization (WHO), the one of the leading causes of death in the developed world is cardiac disease. The most common method to diagnose the cardiovascular disease (CSD) is using ECG device. Portable mean it is convenient, small size, light can easy to carry. Hence, a portable ECG device is needed to reduce the number of death due to CSD. It is not an impossible thing in the developed world as some of the engineer has successfully come out with their design of portable ECG which the prior heart attack and most common abnormal heart rhythms can easily diagnosed . The new device has enable notebook and desktop computer to support family member observing their physiological signal on the screen . The computer can display the ECG signal through National Instrument LabView. User can easily evaluate their health and record the result just by using their computer. It is very convenient to all users. Recently, Singapore has come out a mobile ECG in market which named as EPI life. EPI life is revolutionary mobile phone device that has integrated multi lead ECG and health suit function .
LabView (laboratory Virtual Instrumentation Engineering Workbench) is a graphical programming environment used for engineer to develop sophisticated measurement, test, and control system . Commonly, LabView is use to receive, display and process the data and figure out the signal. LabView helps to create flexible and scalable design and interface with the real word signals. It also can be used to analyze data for meaningful information and display the result. LabView program has three components which are block diagram, a front panel and a connector pane. When receive the data from serial port, the resource of VISA will use to process and transform the wavelet to find the characteristic points of ECG signal . Figure 2.3 show the LabView front panel which displaying the ECG signal .
Figure 2.3: LabView Front Panel
2.5 Shielding Cage
There are three types of predominant noise that commonly affect the signal which are baseline wander (BW) noise, electromyography (EMG) interference, and 50Hz power line interference . The major source of noise during recording signal is electric power system. Although differential amplifiers inside the ECG system have the function to eliminate the 50Hz noise but the range of the ECG is too small and it causes the differential amplifier unable to eliminate the 50Hz noise. In the journal title of "Electromagnetic Interference Effect from Power Line Noise in Electrocardiograph Signal using Faraday Cage", the research has successfully proved that the faraday cage in Figure 2.4 below will block the electromagnetic interference in biomedical signal such as ECG signal. The ECG device will produce the real signal without 50Hz power line noise when user taking measurement in the faraday cage. The electromagnetic waves that can penetrate through the faraday cage depend on the size of holes and the wavelength of the electromagnetic wave .
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Figure 2.4: Human Size faraday cage
2.6 Impact of environment to the EMI
Electromagnetic interference (EMI) is a function of power output and frequency of transmitting device . It will decrease the distance between transmitting and receiving devices. The signal voltage is known as very small which in milivolt range. Therefore it is very easy to be influent by the environment. The most common source of impact EMI to ECG is the cellular telephone. GSM Cellular telephone will interfere with medical equipment  . Most interference occurred with the device that displays the waveform. However, from the article of "Cellular Telephone Interference with Medical Equipment", it comes out with the statement recent technological advances have changed the EMI landscape for the better. Beside than cellular telephone, the application of auto-identification technologies such as radio frequency identification (RFID) also will case the EMI impact to the ECG signal. We can approach the RFID application in everyday life, such as price detecting machine and antitheft clips of clothing in shopping centre. RFID technology will induced EMI in medical device . The fluorescent light will add a tiny sinusoidal wave which is difficult to filter away . The temperature of the environment caused the noise to the ECG signal. For example when the user is cold, the musculature contracts, and this contraction will be taken up by the ECG electrode. Hence there is a noise in signal . The radios will also giving impact of the ECG signal as it also produces the electromagnetic waves.
3.1 Flow Diagram
This chapter will discuss about the progress of whole project. In order to obtain the target of the project, all the basic knowledge and information need to be understood. Thus, literature study have to be carry on at the beginning of the project. Then th estudy is continued by understanding the method and equation on develop a portable ECG circuit. The portable ECG machine will be use for collecting the data in several place. Then, there is an analysis done on the data to determine in which condition of environment will have the highest effect of EMI of the ECG signal and vice versa. Figure 3.1 show the block diagram of the project.
Figure 3.1 Block Diagram of the Project
Design portable ECG circuit using Multisim
Implement shielding Cage
Taking ECG signal at different environment with labView
Analysis the Signal
Taking ECG signal with shielding & without shielding
Figure 3.2 below show the flow chart of the work flow for FYP1 and FYP2. It starting with the literature review for the related topic. In the project, Multisim will be used to design the portable ECG circuit and the circuit will be implement in a protoboard. A shielding cage will build using some material which can cutt off the EMI such as aluminium. Then, the ECG signal will be taken in different environment such as in the lab, a free space place, hospital and in the room. Beside that, the ECG signal should be taken by considering it is inside the shielding cage or outside the shielding cage. Those are done to determine in what situation will give the most EMI effect and the least EMI effect to the ECG signal and does the shielding cage can succecssfully reduce the EMI.
Figure 3.2: Flow chart of the work
Gantt chart of the project in shown in the Table 3.1 and 3.2. The progress of the project is dividing into two parts which are FYP1 and FYP2. Basically, FYP1 is focusing on the study on the ECG signal and ECG circuit. The knowledge that gain from literature review are use to implement into the algorithm design. Besides, the designing the portable ECG circuit is a crucial task during the FYP1. At the end of phase 1, FYP1 presentation and report writing were completed.
During the FYP2, the circuit of portable ECG and the shielding cage is done. Then, is the data collecting task which involve in several place and condition. After collecting all the data that needed, the analysis process will take over for the project. Lastly is the presentation and demonstration of FYP2.
Designing ECG simulator circuit
Run ECG circuit schematic in Multisim
Presentation of proposal
Table 3.1: Gantt chart FYP1
Implement the Circuit in protoboard
Build the shielding
Collecting the signal of ECG at different environment
Analysis the signal
Presentation & demo
Table 3.2: Gantt chart FYP2
RESULT AND DISCUSSION
4.1 Preliminary Result
Figure 4.1 shows the preliminary results of the circuit design of the portable ECG circuit. This is the circuit that design using the Multisim. However, there are problem in this preliminary design which will discuss late in this chapter.
VEE and VCC will replace with 9v Battery when implement into the protoboard to make it portable
All the VEE and VCC are connect to the 9V battery
Figure 4.1: Portable ECG design
Due to the low voltage of signal ECG (range of 0.5 to 4mV), there are few equations that need to calculate the gains of the input signal. Below are the equations that use.
Equation that us to calculate the gains if main stage
Equation that use to calculate gains of Instrument Amplifier
Equation that use to calculate the overall gains
10000 X 10
Problem in the preliminary design
Through the calculation using the equation at part 4.2, suppose the overall gain is 100000. However, the value of gain get from running the design in Multisim is different with what suppose to get. There may be due to the resistance of the component and the wires itself which cause the noise in the circuit although there is a filter inside the circuit. The filter did not successfully filter all the noise.
At the end of FYP1, the preliminary portable ECG design have been designed. However the hardware Portable have not been implement. So, in the coming semester, the hardware of the portable ECG circuit and the shileding cage will be fully implement.
Next semester of FYP2, full hardware of portable ECG circuit will be implement in the protoboard. In addition, the shieding cage will also be implement. After all the hardware is done, the is needed to study LabView to get the output of ECG in laptop. Besides, study on Matlab to get the clean ECG signal also need to complete the project.
Finally, analysis the signal and come out a report to determine which environment will giving the most and least EMI effect to the ECG device. The objectives of the project is achieved successfully.