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Engineering, 2013, 5, 6-9 doi:10.4236/eng.2013.55B002 Published Online May 2013 (http://www.scirp.org/journal/eng) Study of Situation Based Environment towards Noise Reduction during ECG Acquisition Noraini Abdul Samad, Rubita Sudirman, Nasrul Humaimi Mahmood, Yoong Yee Yan INFOCOMM Research Alliance, Faculty of Electrical Engineering, Universiti Teknologi Malaysia, Johor Bahru, Johor, Malaysia Email: rubita@fke.utm.my Received 2013 ABSTRACT Even with the development of more advanced technology of ECG, there are still problems on interference to ECG sig- nals. Many attempts have been made to detect and eliminate the source of noises and artifacts from the original ECG signals. Several studies have been done to observe and study the EMI effect, however, most of them only focus on the EMI effect of mobile phone during ECG acquisition. Thus, this study is emphasized on the interference prob lem when other medical devices were being used together with the ECG device. The R-R peak distance of the ECG signal was detected by using QRS detection algorithm invented by J. Pan and W. J. Tompkins. The data from the experiment showed that even the EMI from the medical devices did not affect the physical shape of ECG, but it does affect the R-R peak distance of the ECG signal. Keywords: Electrocardiogram; Electromagnetic Interference; R-R Peak Distance 1. Introduction The increasing number of medical devices used in health care facilities [1] has guided many researchers to study about the potential problem of electromagnetic interfer- ence on medical device [2]. This study is done due to the concern towards the possibility of malfunction of life supporting system, such as electrocardiogram and elec- troencephalogram when it is being used in a close prox- imity with other medical devices. Electrocardiogram (ECG or EKG) is a simple yet painless test that used to record the electrical activity of the heart [3]. ECG device is used to detect and amplify the tiny electrical changes on the skin that caused when the heart muscle depolar- izes during each heartbeat. Those tiny electrical changes on the skin will then convert into wavy lines to be ana- lyzed by the doctor. Since ECG was able to record the electrical activity of the heart, it is being used in diagno- sis for the heart disease. Generally, the recorded ECGs and EEGs signal will always be contaminated with many types of noise and artifact. In this stu dy, the concern will be emphasized on the interference problem from other medical devices that being used together or nearby with the ECG and EEG device. It is important to ensure that there will be no interference problem occurs when it is being used together with other medical device since some equipment used in healthcare centre is designed to emit electromagnetic energy [4]. Several studies have been done to observe and study the interference effect, however, most of them only focus on the effect of mobile phone during EEG and ECG acquisition. Those types of studies always treat medical devices as the ‘victim’ and mobile phone as the ‘source’ of electromagnetic inter- ference. [5-7]. 2. Literature Review Since numerous types of Electromagnetic Interference, EMI were introduced, the effect of the EMI on the elec- tronic device performance being studied. The study in- cludes the tests of radiofrequency susceptibility on 8 types of medical devices [5] which shows that all 8 de- vices being tested is easily affected by the emitted elec- tric field at frequencies varies from 1 MHz to 2000 MHz with electric field intensity at 10 V/m. Most of the tested devices such as Fetal Monitor and Infant Incubator showed incorrect presentation of data when the electric field intensity was as low as 0.012 V/m. Based on the result of the study, the electric field intensity emitted by cellular phone or two ways radio undoubtedly can affect the performances of medical devices since the electric field of those two devices are 15 V/m and 5 V/m respec- tively. Even it is hard to foretell the occurren ce of failure causes by EMI, it is highly recommended to avoid or reduce the usage of cellular phone and two ways radio in hospital area especially the area that equipped with life supporting system and in intensive care unit since it is the most critical area. Copyright © 2013 SciRes. ENG N. A. SAMAD ET AL. 7 In order to strengthen the idea to ban the usage of cel- lular phone in hospital area, there is a study done to iden- tify the susceptibility areas in the hospital by performing immunity test on medical devices [6]. The immunity test was done by subjecting several medical devices to elec- tric field generated by cellular phone that operates in its maximum power. The result from the study shows that 80% of medical devices that being tested was affected by the radiated electric field. As many researchers only focusing on the EMI effect cause by cellular phone, few of them study on the effect of interference of medical device when it is used in close proximity to other medical devices [8]. The study in- cludes several case studies on performances degradation on apnea monitors, automatic implantable cardioverter defibrillators (AICD) and Cobalt 60 therapy system. Based on the result of each type of study, almost every author comes up with the same conclusion and recom- mendation such as the needs to establish clear policies for the usage of mobile phone in critical area in the hos- pital. They also emphasize on the safety distance be- tween medical devices and any other type electronic de- vice especially the one that emit powerful electromag- netic signal. 3. Methodology The measurement was taken in the situation where dif- ferent types of medical devices operated during ECG data acquisition within 1 meter range of distance. KL- 75001 Electrocardiogram Module was used to take ECG signal from a healthy subject (a female, aged 20 years old) and with the assistance of oscilloscope to display the signal. As a precaution, the subject was ensured to be in a good health condition and not taking any medication before the experiment. The acquired signal was saved in .txt format for further observation and investigation through Matlab. The signal was compared with the ref- erence signal (free from noise) in term of the wave pat- tern and RR Peak Distance. Data analysis was done to emphasize that EMI from other medical devices when being used in the same area with the ECG does affect the ECG data. There are 8 types of medical device that being tested during the ex- periment (one at a time). The duration of experiment for each type of medical device is 10 second. Table 1 and Figure 1 below shows the list of medical device and the block diagram of the experiment respectively. 4. Result and Discussion Several testing had been conducted to observe the ECG signal patterns. All data from those testing were obtained. From those data, analysis was made to clearly state the comparison between the reference signal and the ac- quired signal. Table 2 showed the signal acquired from the experi- ment. Physically, there is no obvious alteration towards the wave shape. The shape of the ECG signal is still maintained. The noise is hardly compared or extracted from the ECG signal. Unlike the electric field intensity that radiated from cellular phone or two ways radio, electric field intensity emitted by medical devices is definitely low. Even the signal does contain several type of noise; it does not alter the amplitude of PQRS of the ECG. Table 1. Types of medical device that being tested during the experiment. Figure 1. QRS Detection algorithm [9]. Copyright © 2013 SciRes. ENG N. A. SAMAD ET AL. 8 Table 2. Signal acquired from experiment. Medical Device Signal produce Reference signal Wacom Tablet Electro- glottograph Non Invasive Blood Pressure Cuff Electro muscle stimulator Ultrasound Thera- peutic Device Infusion Pump Analyzer Electro- encephalogram Micro spirometer Table 3. R-R peak signal of each device. Medical device R Peak Signal Reference Wacom Tablet Electro- glottograph Electro muscle stimu- lator Ultrasound Non Invasive Blood Pressure Cuff Infusion Pump Electro- encephalogram Micro spirometer Since the reference signal and the test signal are hard to differentiate in term of physical shape, the average of Copyright © 2013 SciRes. ENG N. A. SAMAD ET AL. 9 R-R peak distance of each signal were compared. In or- der to calculate the R-R peak of the ECG, th e QRS com- plex detection was done by using Pan & Tompkins algo- rithm. The detection of R-R peak is important during ECG signal analysis as its can be used to show th e condi- tion of the heart, calculation of heart rate and even can be used to define various heart defectiveness [10-11]. As stated previously in introduction section, even the electric field intensity emitted by medical devices is low; it does affect the ECG signal. This phenomenon is proved by the graph of R-R peak distance of each tested medical device shown in Table 3. The detection of R-R peak was done based on the Pan & Tompkins’s algorithm as shown in Figure 1. As the R-R distance of the test signal and the reference signal was compared, it shows that the space between each R peak is not evenly spaced and its include 6 of 8 (75%) tested medical devices such as ultrasound, infusion pump, Wacom tablet, EEG, and blood pressur e cuff. 5. Conclusions Different approaches in analyzing ECG signal should be done to get better observation on the effect of EMI to- wards the signal. As described in [3], the author calcu- lated the peak to peak value of noise embedded in the signal and many other authors that observed any changes in device function, including failure, distortion of dis- played informatio n, erroneou s readout or activation of an alarm. However, some types of analysis may be unable to detect the effect of EMI on ECG signal. Thus for this study, analysis was done by observing the RR peak dis- tance in order to strengthen the fact that EMI from other medical device can definitely affect the ECG signal data. Even all medical devices are certified with their own electromagnetic compatibility standard, some of them still being affected by the EMI within or lower than the standard value [5]. In spite of the simplicity of the analy- sis, the result however emphasized the need of separating the easily susceptible medical device from the other medical device for better performance. Several precau- tions must be taken in order to avoid any harmful effect caused by device malfunction due to EMI. 6. Acknowledgements The author would like to express our appreciation to Ministry of Higher Education (MoHE), MyBrain15 and Universiti Teknologi Malaysia for supporting and fund- ing this project under vote Q.J130000.2623.09J28 . REFERENCES [1] M. Lin and E. Peper, “Keep Cell Phones and PDAs Away from EMG Sensors And the Human Body to Prevent Electromagnetic Interference Artifacts and Cancer,” Bio- feedback, Vol. 37, No. 3, 2009, pp. 114-116. doi:10.5298/1081-5937-37.3.114 [2] A. Escobar and H. Cadavid, “Electromagnetic Field En- vironment in a Typical Hospital,” ANDESCON 2010, pp. 1-4, 2010. [3] W. Y. Wong, R. Sudirman, N. H. Mahmood, S. Z. Tu- mari and N. 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