| Due to the ageing populations and the life style changing,the incidence of chronic diseases has a rise trend year by year.Statistics show that number of patients who were diagnosed with chronic diseases in china has reached to 260 million,and the disease has become a serious threat to health and lives of the residents in our country.Many residents and families are taking heavy financial burden caused by chronic diseases.Chronic diseases become a social problem and cannot be ignored.The chronic diseases have a variety of characteristics like long illness,poor prognosis and high incidence of complications,therefore the patients could not spend much time in the hospital for long-term treatment and monitoring,which is different from the acute deceases.Focus of works about the prevention and cure of chronic disease has change from central hospitals to community health service(CHS)centers and families.As the base part of health service and disease control organization,the construction point of CHS is gradually changed to chronic disease prevention and control.The key work of chronic disease prevention and control in CHS is providing effective intervention and prevention to the chronically ill and improve the quality of their daily life and work.In light of the community service mode,characteristics of chronic diseases,and the daily setting of patients,our research group intends to study and design a community chronic health management system(CCHMS).There are three parts in the CCHMS:health monitoring terminals,a health mobile phone and a health management server,which provide daily monitoring and disease intervention to the chronic patients,and also implement the management of chronic disease prevention and cure.As the highest incidence chronic disease and the common complication of chronic diseases such as the diabetes and hypertension,the cardiovascular(CV)disease has a higher mortality and hardly gets noticed.Thus it is important to provide the electrocardiograph(ECG)monitoring service for the chronic especially the CV patients.Therefore,the development of the portable ECG monitoring terminal,which is used to provide comfortable and acceptable ECG monitoring service to the chronic in their daily lives and achieve the remote data transfered by using wireless technology,is the main work in this study.The ECG machines was invented in 19th century and so far there are many kinds of machines like the digital ECG machine,stres test system,ECG monitor,holter and portable ECG devices.The ECG acquisition equipment has set up a file in the clinical application of more than one hundred years,and the ECG information has become the significant auxiliary diagnostic information in the diagnosis of cardiovascular and cardiac function.Along with the chronic disease incidence and an ageing population and other social status,portable ECG devices are gradually positioning in the family and the CHS,and it naturally becomes the hot spot of ECG monitoring equipment development and even the entire medical instrument research.With the concept of wearable device and the development of electronic technology,many researchers are studying on ECG monitoring equipment with the type of wear vest,which could offer more comfortable ECG detection and make some reference value for other portable ECG device designing.But these wearing devices are greatly limited because of the weather and the dressing of patients,which are not suitable for many persons with high life quality demands.Designing the ECG monitor with remote data communication using wireless communication technology and cable network technology such as GPRS,CMDA and ADSL,is also a popular direction of ECG device researches in the last few years.With the medical electronic market demand and semiconductor technology development,many ECG measurement technique and other physiological monitoring application solutions have been suggested by the semiconductor manufacturers,and single chip measurement solutions based on analog front end(AFE)is the most novel measurement technique.Many commonly used modules are integrated in AFE chip,which reduces the acquisition circuit module area and power consumption,and it is quite suitable for portable ECG equipment with battery power supply.AS the 3G network and smart phones is now gradually popularized,which provide a solid platform and foundation for stable real-time data transmission.Portable ECG devices based on the 3G network and intelligent remote communication will be research hotspot in near future.Normal heart is excited traceable cardiac atrionector,which is the wrestle since the heart is highest "headquarters".The excited signal is sent to all parts of the heart through the cardiac conduction system,which become the potential of skin surface by the body as the volume conductor,and it is collected as the ECG signal through the ECG electrode,leads and acquisition machine.As the acquisition standard,ECG lead is applied to record electrode placement and its connection with the electrocardiogram instrument.The Ag/AgCl reference electrode were used to be the monitor electrode in this research because the advantages such as electrode potential stability,good polarization effect and strong adhesion.Considering the routine and diagnosis monitoring application,the terminal will use the CM5 Lead system which is commonly used in Holter,and the Mason-Linkar Lead system which is used in routine monitoring.As the typical biological signal,ECG signal has many characteristics like low amplitude,low frequency,high impedance and randomness etc.,and it is vulnerable to external environment and interference from the human's body,such as power line interference,muscle electricity,baseline drift and other strong interferences.Therefore we should take some hardware circuits and software algorithm for interference suppression.As the ECG acquisition equipment,the sample frequency,accuracy,anti-interference performance of ECG monitoring terminal which is designed in this study,has strict requirements.Considering chronic patients ECG monitoring in daily time,this volume,power supply,energy consumption and comfort etc.of this terminal also have higher requirements.Therefore,we use the TI AFE production ADS 1298 for the core of ECG acquisition circuit,at the same time low pass filter circuit with the cut-off frequency of 100 Hz was added to the input signal channel.MSP430 microcontroller was applied for high precision ECG acquisition and data processing because of the superior performances such as ultra-low-power consumption,rich resources on chip.The 2.2 "QVGA TFT color LCD,resistive touch screen and keyboard were also adopted in the device for ECG data display,interaction and control.To realize wireless communication with mobile phone,HC-05 type Bluetooth module was used in the device for serial data transmission,which can be set up by simple configuration and control command.We used the lithium battery to supply the power because of the portable application in ECG measurement,at the same time,analog and digital power supply with low noise and stable output voltage was designed for each module power.Single star point grounding way was used to connect the digital and analog ground for reducing interference among power supply.The software system design of this portable ECG terminal is directly related to real time ECG monitoring and good user interaction.Module programming thought was applied in this study for circuit module and function modules' driver programs.And according the work status and idle status of daily monitoring,the system clock frequency and the modules work status should be adjusted by program to control the power consumption and guarantee real-time performance.The ADS 1298 chip was set on the low power mode according to related registers definition,and the sampling frequency set for 250 Hz and 500 Hz;For the convenience of system debugging,the internal test signal is configured to the 1 mV,512 ms cycle's square wave;Considering the real measurement in routine monitoring,dc detection mode was adopted to detect the lead-off status,and relevantly the programmable amplifier gain and channel configuration of WCT signal were also regulated.According to ADS 1298 communication configuration and opcode definition,we realized reading and control command of ADS 1298,and data precision adjustment on the basis of the different monitoring status.To enhance the user interaction and operability,menu interface was applied as the frame of system programs,and the function programs can be corresponding executed according the interaction of users operation and the default value.Bresenham algorithm was improved and realized under MCU environment for fast ECG drawing.ECG interference mainly includes power line interference,etc,which were cubed by the software algorithm in this study.There are much software processing algorithm to deal with the interference,such as brute-force filter,FIR filter,etc.The Matlab FDAtool toolbox was used to design low-pass FIR filter with the cut-off frequency of 33 Hz to filter the power line interference,which is created by the Kaiser Window and processed by the coefficient quantification and algorithm optimization under the MCU environment.In order to build the wireless connection between the mobile phones and the portable ECG monitoring terminal,HC-05 Bluetooth module was used in this study to achieve high speed wireless transmission,which is configured by the AT commands,and the parameters are set for 115200 baud rate and subordinate module.At the same time two different data format are designed for data transmission to strengthen the stability and robustness.In this study,portable ECG monitoring terminal was designed and used to provide the routine monitoring service for the chronic patients and the users with urgent needs.Real-time ECG data acquisition could be done by different lead system connection.ECG data processing is realized by software algorithm in embedded environment,and steady wireless data transmission is also achieved by using the Bluetooth module.However,there are some problems that should be solved and discussed in the study,such as the productization of the terminal and user's interactive optimization.At the same time the related terminals,mobile phone application and the management system server are still in development,thus terminal had not been online debugged and improved.With the perfection of portable ECG monitoring terminal development of other system modules,the Community Chronic Health Management System will be applied and spread by many patients,families and communities,which will offer effective daily health care and feasible chronic management to the patients. |
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