Introduction
In the year 2015, Wang, Doleschel, Wunderlich, and Heinen published a paper in the Journal of Medical Systems [1]. The paper was on a wearable wireless ECG system that was based on the novel 3-Lead electrode placements. After carrying out an experiment for the 3-Lead electrode placements, it was discovered that the distance between the electrodes could further be reduced for efficiency. A smaller sized sensor node being powered by a rechargeable battery would then be developed based on the newly identified electrode positions. A dynamic method of controlling power is also automatically installed in the sensor node for control of consumed power. The performance of the device can better be evaluated, when the user is in motion, i.e., either running or walking can also help in checking the efficiency of the installed dynamic power control system. In the present paper, the methods of the study in the research are discussed along with the design criteria, the calculations used in the design, operation of the system, and drawings. Moreover, further studies for improvement in the design have been discussed.
Electrocardiogram and its efficient analysis
The electrocardiogram (ECG) helps in working on cardiac activity and mostly used for the diagnosis of cardiac illnesses. It measures and amplifies body surface potentials on the electrodes, thereby helping the system to detect any changes in cardiac activity [2]. The research on ECG monitoring system for our analysis was conducted in RWTH Aachen University, Germany. Similar researches, as discussed here, have also been conducted in several other parts of the world including Korea [3], where researchers worked on the implementation of ECG system with smartphones to help elderly people and for self-analysis, and the United States [4] as, for example, Chulsung Park performed these researches along with Pai H. Chou in the University of California [5]. They used a sensory node known as Eco for their research on wearable and ultra low power, wireless ECG system [5]. The driving force towards the research on ECG monitoring system in the United States was the increased number of cases of cardiovascular diseases resulting in increased number of mortalities, i.e. about 33% of cases of deaths in 2008 [6].
In the past century, many electrode placements had been proposed; thereby making the sequence more efficient with the passage of time due to the improvements made in electrodes and their placements. In 1908, the first limb Lead was made by Einthoven [7]. The Lead was made of three electrodes, hence was suitable enough for an ECG to get detected. A proposal of six precodial leads with six electrodes on the chest was given in 1944 [8]. In order to provide for more physical mobility, a new 12-Lead ECG was published to detect the 12-Lead signals during exercising, though the system needed ten electrodes on a person’s body. For simplicity of the Lead system, a system named EASI, was developed by Dower and it used five electrodes to identify three signals (EASI) [9]. Therefore, the 12-Lead could be redesigned to suit the three signals system. Based on the research, the novel 3-Lead electrode placement led to the establishment of the wearable wireless ECG as it only required a few modifications to make it wireless and wearable [1]. However, even after the identification of various placements, the wires were still important for connections of the electrodes to the sensor, thus the electrode placements were not suitable to satisfy the desired features of a wearable wireless ECG system that was in high demand.
Design Criteria
The explanations in the design criteria of the paper [1] are according to the novel designs because in this research, a wireless system of wearable ECG is developed on the basis of the novel 3-Lead electrode placements [10], for longer monitoring in home care. It was discovered that the separation distance between the limb electrodes could be decreased for efficiency [1], after carrying out an experiment to determine positions for the 3-Lead electrodes. According to another identified node position, a small sized node was developed to identify, amplify, and send the signals. The sensor node was being powered by a rechargeable battery as the coordinating machine received the information and sent that to the computer, then the signals were finally displayed. The amount of power getting consumed by the sensor node was controlled by a progressive method of controlling power. Appropriate method was developed to automatically control the transmission power according to the indication of the signal strength. The system gives optimal performance even during movement of the sensor [1].
The system was wireless, but more research was still required for determination of the best positions of electrodes on the chest for maximum ECG signals and sufficient information. The method is facing some challenges such as identifying a good relation between providing an appropriate link quality and the power consumption by the system for a longer period of time. For the system to be able to attract more users, it has to be comfortable to wear, has no noise, provides and maintains the quality of signals, and sends the information to the doctors at a required time [1]. From the design criteria, it would be difficult to duplicate the study in the laboratories, if we consider the practical involvement of wireless signals and identification of new positions on the body.
Design Calculations
Experimental Methods
Based on the research, new electrode positions should be identified in order to reduce the distance of one electrode from another for optimal efficiency. Moreover, considering the fact that the system should be compact and wearable, there is a need to determine new electrode positions. Therefore, an experiment had to be carried out to verify the new placements that would be positioned for the three limb electrodes [1].
In the experiment, ten electrode placements were tested for the right hand, left hand and left leg. In this study, the limb placement of electrode for Mason-Likar leads, which is in use for the past few years, was utilized as a standard lead system. The right and left hand results showed that the two electrodes had to be kept on right and left sides of the middle line respectively. The present signals were dependent on the separation distance between the electrodes. The third position was accordingly chosen as the best arrangement for new right hand and left hand terminals. After that, just five positions of arrangements of the left leg terminal were tried. From the outcomes obtained, the left leg was set on the left half of the center line. In light of the exploration, the paper considers nine new arrangement positions of the left leg terminal in vertical and horizontal direction. The same way, 3-Lead signs were measured and contrasted with the standard Lead framework. Their relationship coefficients were contrasted to a point of getting the similarity. By this arrangement, the measurements of the standard Lead system and the new placement positions were then implemented and the signals were collected by a wireless ECG system [1].
The results of the experiment
According to the results obtained from the left leg electrode’s experiment, the 3-Lead placement positions were compared to the standard Lead system and their correlation coefficients were calculated. The results would obviously depend more on the horizontal direction and less on the vertical direction because the signal differences were only determined by amplitudes.
Limitation in the findings
Errors could be made in the measurements of the design due to reliance on the use of amplitudes to determine differences in arms and leg rests. Minimal attention given to vertical direction in the measurements could result in errors in the final device. Therefore, an average approximation should be done to achieve the best results [11].
Operation of the System
In spite of the elaboration concerning the ECG System, the authors have to state the specifications of the different components of the ECG system, for example, the sensor node, as well as the features of the system. The description of the mechanisms of various components of the ECG system was necessary. For example, the sensor node design, according to the authors, consisted of the analog front end that filters and amplifies the signals, and the microcontroller and RF transceiver performs the role of sampling and transmitting the signals. The authors must have to explain more about the analog front end while explaining how it takes care of the unnecessary noise produced, which could reach a 50/60 Hz electromagnetic interference [1]. This can be reduced through the use of common mode rejection ratio (CMRR) amplifier. Instead, more directions should have been given on the installation of a front circuit that includes AC-coupling circuits, instrumentation amplifiers and band pass filter may be done to avoid over voltage. According to the researchers of the study, the sensor node should always be controlled in 5.5cm by 2.5cm. It is also powered by a rechargeable battery of 600 m Ah and the charging circuit should also be fitted in the sensor node. The front end of the analog acts as the ECG system performance. A coordinator receives data from the sensor node and sends back an acknowledgement message and a request for power adjustment. The received data are then transmitted to the computer [1]. The paper requires more explanation in respect of dynamic power control of the transceiver taking in most of the power in the sensor node making the system to run successfully over a long time to monitor the signals continuously. Moreover, an explanation on how to fix the power from the receiver was also required. The additional information about the flexibility and ease of adjustment according to the strength of the signal was a good idea from the Yishan Wang, Sammy Doleschel, Ralf Wunderlich, and Stefan Heinen. On a further note, the information about the sensor node having a rechargeable battery with fifty-two hours battery life was also good [1].
The part on the GUI data acquisition, that is, development of the process to show the signals from the coordinator machine was partially explained. Here, more explanations were required on the quality rating system (QRS) patterns. Moreover, explanations are required for the identification using Hamilton Tompkins Algorithms and the rate of heart beat to be calculated for the different duration between QRS patterns. When the body is peaceful, the QRS detection, which is complex process, has a sensitivity equivalent to 97.22%, while 91.25% when the same body is in motion [1].
Design Drawing
ECG checking framework span of a sensor hub have to be kept up at 5.5 cm by 2.5 cm. The simple front end and the connectors to nodes ought to be set beneath the sensor hub while the rechargeable battery and charging port have to be put on top of the sensor hub for simple charging. Transceiver and the antennae should be implanted below the battery. The maximum distance that should be left between the sensor node and coordinator is forty meters (in the presence of obstacles) [12] to allow efficient communication between them, so that the system can fulfill its application at home. The current is usually measured, when the sensor node in not connected to the coordinator machine [1]. During this time, the sensor node usually consumes lot of energy, i.e. about 5 mA current, as it goes into sleeping mode then wakes up after every one second to search for connection with the coordinator [1]. The sensor node saves much power even when not in connection with the coordinator because of the power mode control it possess, besides, having a 52-hour battery life. Even with compact size and light weight of the whole system, it establishes a stable communication between the node of the sensor, coordinating machine, as well as GUI. The best performance of the system would be determined when the person wearing the device is in motion, such as walking and running [1].
The following is a drawing of the sensor nod and the coordinator machine.
Automated control system of Transmission Power
The performance of the automatic transmission and power control is best evaluated when a person is taking the measurement while the body is moving. Distance is one of the major factors affecting the transmission of power. For instance, the person wearing the sensor node may walk some meters from the coordinator machine and comes back at different speeds. Therefore, the changes of the rate of signal strengths recorded will automatically adjust the transmission power. When a person is walking, about 20% power is saved in 45 seconds, while 30% power is saved when the person is at rest, thereby enabling power level and rate of signal strength to be kept stable [1].
With the automatic control system, the power can be very low in the ECG system, when the user is sleeping or motionless. In addition, power changes as a result of differences in steps in levels, which are low, are usually higher than at higher levels due to the difference in steps and the ground levels. The adjustment steps in lower levels are usually large as compared to adjustments in high levels; hence the rapid power changes could be decreased by reducing the sizes of steps [1].
The following is an image of a wearable wireless ECG system:
Design and further study
Despite the potential advantages associated with the use of a wearable and wireless ECG system, it faces challenges before using it on a large scale. For example, it would face technological challenges regarding the limited availability of the modern batteries that would be used by the system [1]. Personal issues such a person’s beliefs and thoughts, and his medical concerns associated with the use of the system for home care may hinder the full adaption of the device. The user may have to undergo a check up after using the device as, for example, irritation can develop on the skin. Findings of a similar study in America are closely related to the paper’s findings [4, 5] as both researches were aimed at developing a wearable wireless device. This has greatly confirmed the research’s accuracy due to the similarity of findings that would be used towards the development of the device. However, the efficiency of the ECG system should be monitored closely in order to check for areas of failure, which in turn will provide recommendations and ideas for further studies on how to improve the device performance.
Conclusion
The design of the wearable wireless ECG is more flexible compared to the novel placement of electrodes as a person can also connect the electrodes with a sensor node completely wirelessly. The research introduces a wearable wireless ECG that can be applied in long term home care. The idea originated from the novel three electrode placement, whereby research showed the increase in efficiency of the electrode placement by reducing the distances between electrodes. Based on the hypothesis of the research, an experiment had to be carried out to confirm the study, because the experiment results in the development of a small sized ECG system, which was compact and wearable. Several developments and changes in the electrode placement have helped in improving the qualities of electrode placement, thereby making the system more efficient.
The use of ECGs is an invasive and inexpensive way of diagnosing heart attack at an early phase. There was an increasing demand for wearable wireless ECGs that would keep monitoring the user’s health for a long term as they keep on doing their normal activities such as walking. It also helps to avoid frequent visits to the hospital through communication of information to hospitals and doctors. However, the system has limitations in the experimental methods used for analysis as the difference in the results of the right hand, left hand and left leg compared to the standard Lead placements could only be determined through amplitude. That means that the method focuses more on the horizontal measurements than vertical measurements.
Finally, one of the ways of reducing health costs in health services by ensuring quality of care is through provision of systems that monitor an individual’s health as they continue engaging in their normal activities. A wearable and wireless ECG is one of the systems that will help in reducing the frequent visits to the hospital aside from offering an accurate diagnosis that will enable people to detect symptoms of heart attacks at an early stage. The proposed design of an ECG monitoring system is favorable to implement because of its flexibility, low costs and ability to apply for home care. However, Yishan Wang, Sammy Doleschel, and Ralf Wunderlich failed to mention that ECG system is too technical, and the study method cannot easily be used by many other researchers. Moreover, the authors can improve the presentation of their study by using some other more efficient methods such as live demonstration.
Bibliography
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