109 CHAPTER 6 REAL TIME IMPLEMENTATION OF GSM ENABLED SMART TELE-HEALTH CARE SYSTEM FOR REMOTE AND RURAL PATIENTS 6.1 PREAMBLE In this work, concept of telemedicine is used to monitor the cardiac patients with the help of ECG. A normal electrocardiogram with its characteristic patterns and significant points and intervals are already shown in Figure 4.3 and Table 3.1. The amplitude of a QRS complex is typically about ± 1-2mV. When the patient s cardiac level goes beyond the threshold level, this proposed system will vigilant the patient without delay by sending an alert ring to the patient as well as an alert SMS to the doctor s mobile. This proposed model is an improved version of the current patient monitoring system where uninterrupted mobility to both the doctor and patient has been provided. 6.2 PROPOSED METHODOLOGY The proposed wireless mobile tele-alert system is shown in Figure 6.1. This model consists of an ECG detection unit and heart rate sensing unit that picks up the bio signal (ECG) and then converts it into electrical signal followed by the filtering unit. Output is then fed into the programmed peripheral interface controller (PIC) 16F877 microcontroller followed by the GSM Mobile phones in the frequency range from 860 to 1900 MHz.
110 ECG Sensors ECG Detection Filtering Unit Amplifier and Conditioning Unit PIC16F877 Microcontroller Doctor s Mobile Patient s Mobile LM234 Amplifier Heart Rate Sensor Figure 6.1 Block Diagram of Proposed Cardiac Tele-Monitoring System It comprises ECG signal acquisition module that includes the ECG sensors which are used for picking up the bio-electric potentials caused by myocardium followed by an ECG amplifier. The presence of noise gives rise to the need for signal filtering by a filter section (as discussed in chapter 3) and signal conditioning unit. PIC microcontroller is considered to be the integral part of this proposed work, since it is the decision making unit based on the incoming ECG signal. Decision on the incoming noise-limited ECG signal has been done based on the amplitude of the ECG which is in the level of 1.6 millivolts and the heart rate extracted from the ECG signal. Table 6.1 shows that various interpretations of ECG wave in an elaborate manner with its normal time interval.
111 Table 6.1 Various Interpretations of ECG wave Features Description Duration RR interval P wave PR interval PR segment QRS complex The interval between successive R waves is the inverse of the heart rate. Normal resting heart rate is between 50 and 100 bpm During normal atrial depolarization, the main electrical vector is directed from the SA node towards the AV node, and spreads from the right atrium to the left atrium. The PR interval is measured from the beginning of the P wave to the beginning of the QRS complex. The PR interval reflects the time the electrical impulse takes to travel from the sinus node through the AV node and entering the ventricles. The PR segment connects the P wave and the QRS complex. This coincides with the electrical conduction from the AV node to the bundle of His to the bundle branches and then to the Purkinje Fibers. This electrical activity does not produce a contraction directly and is traveling down towards the ventricles and this shows up flat on the ECG. It reflects the rapid depolarization of the right and left ventricles. They have a large muscle mass compared to the atria and so QRS complex usually has much larger amplitude than the P-wave. 0.6 to 1.2 seconds 80 ms 120 to 200 ms 50 to 120 ms 80 to 120 ms
112 Table 6.1 (Continued) Features Description Duration ST segment T wave ST interval QT interval It connects the QRS complex and the T wave. The ST segment represents the period when the ventricles are depolarized. It is isoelectric. It represents the repolarization of the ventricles. The interval from the beginning of the QRS complex to the apex of the T wave is referred to as the absolute refractory period. The last half of the T wave is referred as relative refractory period Measured from the J point to the end of the T wave. Measured from the beginning of the QRS complex to the end of the T wave. A prolonged QT interval is a risk factor for ventricular tachyarrhythmia and sudden fatality. 80 to 120 ms 160 ms 320 ms 300 to 430 ms U wave U wave is not always visible. --- 6.2.1 ECG Sensing and Detection Unit The typical ECG wave consists of P wave, QRS complex and T wave. If the PR interval is more than 0.22 second, the AV block occurs. When the QRS complex duration is more than 0.1 second, the bundle block occurs. At first stage, transducer silver chloride (AgCl) electrode is used, which converts the bio-signal (ECG) into electrical voltage. The voltage is in the range of 1 mv to 5 mv. The signals from the three ECG electrodes (Left arm, right leg
113 and chest) have feed into the inputs of the designed instrumentation amplifier, conditioning circuit of an overall gain (A) of 1000. The signal is filtered with a frequency range from 0.15-50 Hz. The ECG derived from the surface bears frequency components up to a maximum frequency of 100 Hz, but most of the spectrum is concentrated below 40 Hz. The major difficulty in this method is that the extracted ECG is corrupted by various environmental noises because of misplacing the surface electrodes on the patient s part of the body applied with gel. In this work, ECG sensors are handled to avoid such noises which are able to mix with the ECG. ECG sensor is an electrometer capable of sensing ECG signals through insulated sensors in contact with the skin. The sensors are dry-contact, so that the gels or other contact-enhancing substances normally associated with wet-electrode ECG pads are not necessary. It also offers exciting possibilities for simplified ECG monitoring by medical professionals, this technology also makes it possible for individuals to view and collect their own detailed ECG signals on a portable device such as a smart phone. The ECG trace ideally requires two electrical signals from parts of the body on opposite sides of the heart. By mounting two sensor electrodes, these signals are easily obtained from fingers on both hands. The collected signals should be filtered, differentially amplified and digitized by circuitry case to produce the ECG signal. The complete ECG generally requires a bandwidth of 0.5 Hz to 150 Hz. The consecutive operations on the ECG signal are discussed below to make the ECG for further processing, especially for tele-monitoring system. 6.2.2 Filter Selection Even though the ECG is picked by using high technical and efficient sensors, it is impossible to have a noise free ECG signal. When the noise level is too high, it leads to the wrong estimation about the state of the heart and
114 patient s health. Thus the filter section is very important. Filters are frequency selective circuits that pass a specified band of frequencies and blocks or attenuate signals of frequency outside this band. The reason for using low pass filter with embedded microcontroller based digital tele-monitoring system for ECG 142-150 Hz pass band and all the important components of ECG lies below 150 Hz. The amplified ECG signal is passed through a low pass filter, so as to remove the noise and other high frequency signal that might picked up by the cable. The pass band of this filter is set below 150 Hz. All the important components of ECG lie below 150 Hz. In the modern ECG monitoring system, multiple filters are deployed for signal processing. In this monitor mode, the low frequency filter (also called the high-pass filter because signals above the threshold are allowed to pass) is set at either 0.5 Hz or 1 Hz and the high frequency filter (also called the low-pass filter because signals below the threshold are allowed to pass) is set at 40 Hz. This limits the artifacts for routine cardiac rhythm monitoring. The high pass filter helps to reduce wandering baseline and the low pass filter helps to reduce 50 or 60 Hz power line noise (the power line network frequency differs between 50 and 60 Hz in different countries). In diagnostic mode, the high pass filter is set at 0.05 Hz, which allows accurate ST segments to be recorded. The low pass filter is set to 40, 100, or 150 Hz. Consequently, the monitor mode ECG display is more filtered than diagnostic mode, since its pass band is narrower. 6.2.2.1 Adaptive Filter Apart from the above mentioned noises, few of them are P and T wave noise, power line interference, EMG from muscle, operating room condition. Mostly the filter option is band pass filter (BPF). But this is not suitable, if it is used for different age group people. So the adaptive filter is chosen which adapts itself according to the time and range. It does not require
115 any prior knowledge about the signal and the nature of the noise. Hence it is a optimum filter for ECG processing for tele-monitoring and tele-alert applications. 6.2.3 ECG Amplifier The front-end for the signal acquisition system is an instrumentation amplifier. The instrumentation amplifier is basically a differential amplifier that amplifies the difference between the two input signals. Hence the common mode signal is effectively eliminated. It has a very high common mode rejection ratio (CMRR) and high input impedance which is required for capturing ECG signals. Two buffer amplifiers at the input of each signal, is provided to offer very high input impedance. Its gain is set around 1000. For the implementation of this system, AD624 has been chosen. The AD624 instrumentation amplifier is a very high precision, low noise, instrumentation amplifier designed primarily to use with bio-electronics. Design of instrumentation amplifier includes IC-HA324. It is an integrated circuit (IC) having 40P-amps, Capacitor 47nF (2 Nos.), 2.2 µf (1 Nos.), 220nF (1 Nos.), 22nF (1 Nos.), Resistor 470KΩ (3 Nos.), 47KΩ (2 Nos.), 470Ω (1 Nos.), 10MΩ (2 Nos.), 18KΩ (1 Nos) and Pot 47 KΩ (1 Nos.). The signal level of ECG signals is very low. So the amplifier for processing such signal should have the following characteristics and it is listed below. Should have differential input to reject common mode noise. High input impedance and Very low output impedance. High common mode rejection ratio (CMRR) of 90-130 db. The amplifier should have simple gain adjustment. As ECG is an alternating current (a.c) signal, the response to a.c signal should be satisfactory. The circuit containing three operational amplifiers (op-amps) meets all the
116 above requirements. Op-amp A1 and A2 are connected, basically in noninverting amplifier configuration. Op-amp A3 is connected as differential amplifier. It can be easily seen that application of common mode signal at input of such amplifier will lead to zero voltage drop across XG. Therefore common mode gain is unity regardless of impedance network values. Thus the most common mode signal will be rejected by the Opamp A3, which is connected as a differential amplifier. Here op-amp in non-inverting mode has been used. Let Gain, G = 101 and for the above configuration, it is computed using the Equation (6.1). Gain = 1 + R f /R i (6.1) Where, Rf Feedback resistance and Ri Input resistance Let, Ri = 10 KΩ; Then, 101 = 1+Rf / 10KΩ ; and hence Rf = 1MΩ 6.2.3.1 Design of Summing Amplifier (6.2), Let Ra = 100 KΩ and the output voltage is given by the Equation V o = R f / R a [V RA + V LA + V LL ] (6.2) Equation (6.3). Our requirement is that, gain = 2. Equation (6.2) can be modified as Since, V o /[V RA + V LA + V LL ] = R f /R a (6.3) and Rf / Ra = 2 Rf = 2Ra = 2 x 100 KΩ and hence Rf = 200 KΩ
117 6.2.3.2 Bio Amplifier It is the combination of the instrumentation amplifier and power amplifier. The instrumentation amplifier alone is not sufficient to get the amplified QRS complex. So power amplifier is also utilized. It is an amplifier used for providing isolations and it amplifies the QRS complex alone. 6.2.4 Signal Conditioning Unit The next task is amplification of ECG signals before digitizing commonly discussed as signal conditioning, which includes analog signal filtering, demodulation, sampling, holding, etc. Amplification of signals before digitizing has done to get the highest resolution and to maximize the effective number of bits for the analog to digital conversion (ADC). Overall gain is calculated using the Equation (6.1). 6.2.5 LM234 Amplifier LM234 is a three terminal device and its operating current level varies from 1µA to 10 ma. The operating voltage level is from 0.8 V to 30 V and the regulation is 0.02% per volt. LM234 draws no reverse current and it can be used as a linear temperature sensor (Coyle, et al. 1995). Applications of LM234 are current limiter, micro-power bias network, buffer for photoconductive cell, current mode temperature sensing and constant-gain bias for bipolar stage. These circuits consist of four independent, high gain, internally frequency compensated operational amplifiers. They operate from single power supply over a wide range of voltages. Operation from split power supplies is also feasible and the low power supply current drain is independent of the magnitude of the power supply voltage.
118 LM234 has three terminal adjustable current sources characterized by an operating current range of 10000 : 1. This facilitates the circuit to operate as a rectifier and as a source of current in a.c. applications. Zero drift can be obtained by adding an additional resistor and a diode to the external circuit. It has a very high gain and requires a low supply current which is required for increasing the amplitude level (Coyle, et al. 1995). 6.2.6 Heart Rate Sensor It uses Infrared sensors which can easily be clipped to the finger ends (or) ear lobes to detect the heartbeat. This unit is lightweight, easy to handle and extremely durable. It measures the light level transmitted through a tissue of the finger lobe and the corresponding variations in light intensities that occur as the blood volume changes in the tissue. A normal and healthy human heart beats about 72 times per minute (Elena, et al. 2002). The output of the sensing circuit is given to the microcontroller. It decides whether the heart rate is normal or abnormal. When the threshold level is in between 70 and 90, it frames a message as Normal heart rate (70 to 90 beats/min) and when the heart rate level exceeds this normal level, it frames a message as Abnormal heart rate (X1 < 70, X2 > 90 beats/min). Using microcontroller based circuit, it musters an easy way to measure and monitor heartbeat rate. The detachable Infra-Red (IR) probe is designed to get the best results in all type of pulse rate measurement applications. The pulse is also shown by light emitting diode (LED) indication. The heart rate sensor provides a simple way to study the heart s function. Unlike an ECG, which monitors the electrical signal of the heart, this sensor monitors the flow of blood through the veins (Elena, et al. 2002).
119 Figure 6.2a Ear lobe sensor Figure 6.2b Finger sensor Simple design and easy operation allows individuals to monitor the heartbeat during exercise and workouts. The device provides great safety to individuals with known heart problems. The readings of pulse meters are accurate enough when the count from the finger or ear lobe at normal body temperature. A lower heart rate can result from being a consistent exerciser, from some medications for heart or blood pressure problems, or simply because of genetic order (Elena, et al. 2002). Sensor clip consists of a small infrared LED and an infrared light sensor. The sensor measures the light level transmitted through a tissue of the ear lobe and the corresponding variations in light intensities that occur as the blood volume changes in the tissue. The clip can also be used on a fingertip or on the web of skin between thumb and index finger (Elena, et al. 2002). 6.2.7 PIC Microcontroller PIC microcontroller is considered to be the heart of this proposed work and it has an inbuilt analog to digital converter (ADC). The PIC has a set of registers that can function as a general purpose random access memory (RAM). Special control registers for hardware resources are mapped to data space. All PIC can handle the data in 8-bit chunks. The addressability unit of the code space is different as the data space. Actually the code space can be implemented as read only memory (ROM), erasable programmable read only
120 memory (EPROM) and flash ROM. Generally, external code memory is indirectly addressable because lack of external memory interface. The instructions can vary from low-end PIC to high-end PIC, with the low-end and high end PIC having instructions varying from about 35 instructions to over 80 instructions respectively (Kappiarukudil, et al. 2010). The features of the PIC micro controller are code efficiency, safety, instruction set, speed, static operation, drive capability. The advantages of PIC microcontroller include small instruction set to learn, built in oscillator with selectable speed, inexpensive microcontrollers, wide range of interfaces including universal serial bus (USB) and Ethernet. PIC16F877 Microcontroller includes 8 kilo bytes of internal flash program memory, together with a large RAM area and an internal electrically erasable programmable read only memory (EEPROM). An 8-channel 10-bit A/D converter is also included within the microcontroller, making it ideal for real-time systems and monitoring applications. All port connectors are brought out to standard headers for easy connect and disconnect. In-circuit program, download is also provided which makes the board to easily update with new code and modified as required, without the need to remove the microcontroller (Kappiarukudil, et al. 2010). 6.2.8 GSM Modem GSM modem unit provides a direct and reliable GSM connection to stationary mobile fields around the world. A subscriber identity module (SIM) card socket is located on the solder side of the module. The card can only be removed when the modem has been placed in shutdown mode. Communication to the GSM board is performed through a standard universal asynchronous receiver/transmitter (UART) channel. This onboard serial port leaves the other system serial ports free for the user. All operating systems will recognize and support this 16C550 standard UART, and therefore no special communication
121 drivers are needed to receive data from the GSM board. The address and interrupt of serial channels can be individually set with the onboard jumper fields (Kappiarukudil, et al. 2010). 6.2.9 Interfacing Microcontroller with GSM Mobile Phone A special type of commands must be needed for interfacing the microcontroller with GSM mobile phone. Here the PIC microcontroller has been used. For the interfacing purpose, Attention (AT) commands are mandatory. AT command prefix must be set at the beginning of each command line. To terminate the command line enter <CR>.Commands are usually followed by a response that includes <CR> <LF> <response> <CR> <LF>. Various AT commands are listed below. Data Commands General Commands Security Commands Network Commands 6.3 HARDWARE DESCRIPTION 6.3.1 Printed Circuit Board At present the printed circuit board (PCB) makes the manufacturing of electronic circuit as an easier one. In earlier days vast area is required to implement a small circuit to connect the leads of the components and separate connectors are needed. But PCB connects the two by copper coated lines on the PCB boards. There are two types of PCB available. They are single sided boards and double sided boards. Single-sided PCB means that wiring is available only on one side of the insulating substrate. The side which contains the circuit pattern is called the solder side whereas the other side is called the
122 component side. Single sided boards are mainly used in entertainment electronics where manufacturing costs have to be kept at a minimum. In the double sided PCB s, the copper layer is on both. Double sided PCB s can be made with or without plated through holes. First, the proposed circuit is drawn in one paper and it is modified or designed PCB layout on the plane copper coated board is to be drawn. Phenolic and glass epoxy are the two types of boards available. Mostly copper PCB (Glass epoxy) is used. Black colour paints are utilized to draw circuit diagram on the board. Before the required size of the plane PCB board is determined from the roughly drawn PCB layout. Using black paint the desired circuit is drawn on the board. 6.3.2 Layout Approaches The first rule is to prepare each and every PCB layout as viewed from the component side. Another main rule is not to start the designing of a layout unless absolutely clear circuit diagram is available, with a component lists. Among the components, the larger ones are placed first and the space between is filled with smaller ones. All components are placed in such a manner that de-soldering of other components is not necessary if they have to be replaced. In the designing of a PCB layout it is very important to divide the circuit into functional subunits. Each of these subunits should be realized on a defined portion of the board. In designing the interconnections which are usually done by pencil lines, actual space requirements in the art work must be considered. In addition the layout can be rather roughly sketched and will still be clear enough for art work designer. 6.3.3 Board Cleaning Cleaning of the copper surface prior to resist applications is an essential step for any type of PCB process using etches or plating resist. Insufficient cleaning is one of the reasons most often encountered for
123 difficulties in PCB fabrication although it might not always be immediately recognized. But it is quite often the reasons for poor-resist adhesion, uneven photo-resist films, pinholes, poor plating-adhesion, etc. Where cleaning has to be done with simplest means or only for a limited quantity of PCB s, manualcleaning process is mainly used. In this process, sink with running water, pumice powder, scrubbing brushes and suitable tanks are required. 6.3.4 Screen Painting This process is particularly suitable for large production schemes. However the preparation of a screen can also be economically attractive for a series of 100 PCB s or below, while photo printing is basically the non accurate method to transfer a pattern on to a board surface. With the screen printing process, one can produce PCB s with a conduction width of + 0.5 mm and a registration error of just 0.1mm on an industrial scale with a high reliability. In its basic form the screen-printing process is very simple. A screen fabric with uniform meshes and openings is stretched and fixed on a solid frame of metal or wood. The circuit pattern is photographically transferred on to the screen, leaving the meshes in the pattern open, while the meshes in the rest of the area are closed. In the actual printing step, ink forced by the moving squeegee through the open meshes on to the surface of the material to be printed. 6.3.5 Etching This can be worked out by both manual and mechanical ways by immersing the board into a solution of formic chloride and hydrochloric acid and finally cleaning the board by soap. In all subtractive PCB process, etching is one of the most important steps. The copper pattern is formed by selective removal of all the unwanted copper, which is not protected by an etch resist. This looks very simple at first glance but in practice there are factors like under
124 etching and overhand, which complicate the matter especially in the production of fine and highly precise PCB s. 6.3.6 Component Placing The actual location of components in the layout is responsible for the problems to be placed during routing of the interconnections. In a highly sensitive circuit the critical components are placed first and in such a manner as to require minimum length for the critical conductors. In less critical circuit the components are arranged exactly in the order of signal flow, this will result in a minimum overall conductor length. In a circuit where a few components have considerably more connecting points than the others, these key components have to be placed first and the remaining ones are grouped around them. The general result to be aimed at is always to get shortest possible interconnections. The bending of the axial component leads is done in a manner to ensure an optimum retention of the component of the PCB while a minimum of stress is introduced on the solder joint. 6.3.7 Drilling Drilling of component mounting holes into the PCB s is by far the most important mechanical machining operation in PCB production processes. Holes are made by drilling wherever a superior hole finish for plated through hole processes is required and where the tooling costs for a punching tool cannot be justified. Therefore drilling is applied by all the professional grade PCB manufacturers and generally in smaller PCB production plants laboratories. The importance of hole drilling in to PCB s has further gone up with electronic component miniaturization and its need smaller hole diameters and higher package density where hole punching is practically ruled out.
125 6.3.8 Soldering Soldering is a process for the joining of the metal parts with the aid of a molten metal (solder), where the melting temperature is situated below that of the material joined and whereby the surface of the parts are wettered, without then becoming molten. 6.4 RESULTS AND DISCUSSION Real time implementation of this proposed work is shown below in Figure 6.3 where the presence of red color glow in LED indicates the abnormality detection and the alert SMS will be sent with the help of serial communication port which links the PIC Microcontroller unit with the GSM Mobile phone. This module has been validated with the help of medical practitioners and doctors. The system shown in Figure 6.3 is significantly smaller than 6.5 cm in size and is precisely fit in a shirt pocket. Figure 6.3 Real Time Implementation of Tele-Alert System
126 The reliability of the system is proved through the fault tolerance limit of this system which has found to be around ± 4%. It is inferred that the cost for designing this model is very low when compared to the existing patient monitoring system. It has already been discussed that after the detection of abnormality in patient s ECG, an alert SMS will be sent to the doctor s mobile through the GSM technology. SMS has been received by the patient and doctor is shown in Figure 6.4 and 6.5 respectively and also a self-alarm has provided to the cardiac patient. Figure 6.4 Abnormal ECG Detection in patient s end using GSM Mobile phone Figure 6.5 Abnormal ECG Detection to Doctor s Mobile phone
127 Each and every patient is provided with a patient identification number (ID) and the patient ID should be forwarded to the doctor s mobile phone through the SMS services. Also the name of the patient must be stored in the doctor s handset. Hence the confusion may be avoided and the format of the SMS displayed in the doctor s mobile phone is given below. Patient s name and patient s ID Heart rate : Numerical value ECG level in millivolts. : Normal or Abnormal along with ECG amplitude If both the heart rate and ECG are abnormal, then a statement Abnormality Detected in your ECG readings and First Order Medical Attention is required will be displayed as in Figure 6.5 and 6.6. Automatically status of the myocardium is to be detected by the microcontroller and action has been taken through the mobile phones depends on the status of the heart (in terms of heart rate and ECG) is listed in Table 6.2. Table 6.2 Different operations of this system based on the cardiac status S.No. Status Action 1 Normal Idle 2 Urgency (Abnormal HR alone) SMS 3 Critical (Abnormal in both HR and ECG) Alert Ring
128 Table 6.3 demonstrates the processing time requirement for the proposed system using different randomly selected ECG files on three different mobile phones using 10 randomly selected ECG entries from MIT-BIH arrhythmia database. The amplitude based technique (ABT) performs very simple comparison where the ranges of sample ECG points falling beyond an amplitude threshold are determined to be a QRS complex candidate. Table 6.3 Performance Comparison of three different Mobile Handsets S. NO. MIT-BIH DB ENTRY Amplitude Based Technique (milliseconds) Nokia N91 Nokia C2 Siemens C75 1. 100 5 0.8 4 2. 102 5 0.8 4 3. 105 5 0.8 4 4. 114 5 0.8 4 5. 117 6 0.8 5 6. 201 5 0.8 3 7. 213 6 0.8 3 8. 219 5 0.8 3 9. 222 5 0.8 4 10. 228 6 0.8 5 Table 6.4 shows the test results for different telecom companies (Service Providers). Different telecom SIM cards are used to perform this test. It can be seen from the results that the time required for short messages can be transmitted from patient s mobile to doctor s mobile within few seconds. The processing time of urban, sub-urban and remote (rural) processor is also included in the test results. Performances are compared for three different mobile phones (Nokia C2-01, Nokia C2-03 and Nokia C2-06). All the three
129 models are popular and regularly used because of their affordable price in India. Table 6.4 Test Results of Time required for SMS with different Service Providers and Different mobile handsets for Urban, Suburban and Rural areas Time required for SMS Type of Service Providers Variety of Mobile Phones Urban (in Seconds) Sub Urban Rural Area Area Area Government Service Provider - 1 (Proposed System) Non Government Service Provider - 2 (Proposed System) Nokia C2-01 10-15 9-13 5-7 Nokia C2-03 10-15 9-13 5 7.5 Nokia C2-06 9.8-13 7 9.8 4.9 6.1 Nokia C2-01 22-25 20-24 15.6-17 Nokia C2-03 22-25 20 23.3 15.6-17 Nokia C2-06 21.4-23 18.5 21.8 13 15.4 Non Government Service Provider (Existing System) Nokia C2-01 25-30 22-24 20-21 Nokia C2-03 25-30 22-24 20-21 Nokia C2-06 22.2-24 21-23 19-20 The enhanced features of this proposed system are listed in Table 6.5 and also it is compared with other existing monitoring system.
130 Table 6.5 Deviations of Proposed System from Existing monitoring System S.No Existing System Proposed System 1. Web based system i.e internet based. For example, To send the information websites like, www.way2sms.com was used. No need for such internet facility (web). Only mobile devices and its communication network are needed for this system. 2. Centralized server is required Centralized server is not required 3. 4. 5. It has performed a feature matching operation for any incoming ECG and made classification for sending information to doctors. Common to all age group people which may increase false alarm rate. Using MMS, it sends the abnormal ECG wave to the patients as well as to doctors. An illiterate person doesn t know what is ECG, QRS complex and when it will be abnormal. They can simply watch the wave alone. Feature matching of ECG produces high false alarm rate, since the amplitude and time interval of the wave is varied depend upon the mode used like avr, avl., etc. This system is based on the amplitude level and time interval. But age tuner is present for changing the threshold limit, since HR is not a constant value. Here the decision making job can be done by the microcontroller and sends a selfalarm (ring) to the patient as well as alert SMS to the doctors.
131 Table 6.5 (Continued) S.No Existing System Proposed System 6. For ECG extraction, 12 lead system was used. Surface electrode with 3 lead configurations is used for extracting the ECG. 7. Bluetooth technology was used. GSM technology is used because of its more coverage. 8. Applicable to only literate people It is applicable to all levels of people. (Both literate and illiterate) 9. Power consumption : 40.8 W Power consumption : 31.6 W 10. False alarm rate : above + 10 % False alarm rate : around + 4% 11. More than 45cm and circuit weighs 60 grams. Compact in size (6.5cm) and the entire system can be accommodated within the shirt packet. 6.5 CONCLUSION This chapter discusses the real time implementation of ECG based cardiac tele-monitoring system for remote and rural environment. The main objective of this chapter is to reduce the false alarm rate of ECG based cardiac tele-monitoring system. It can be seen from the results that the time required for short messages can be transmitted from patient s mobile to doctor s mobile within few seconds, as tabulated in Table 6.4. The processing time of urban, sub-urban and remote (rural) processor is also included in the test results.
132 i. Design and development of ECG based cardiac tele-monitoring system in real time has been achieved with compact in size about 6.5 cm. Hence the entire system can be accommodated within the shirt packet. ii. Demonstration on the processing time requirement for the proposed system using different randomly selected ECG files on three different mobile phones using 10 randomly selected ECG entries from MIT-BIH Arrhythmia database has been done. iii. Reliability of the system is proved through the fault tolerance limit of this system which has found to be around ± 4%. iv. Validation has been done with the help of doctors and medical practitioners in the remote areas.