Design And Implementation Of Virtual Chinical ECG Monitor System

Nowadays, with the development of our country's medical treatment and sanitation career, the demand of medical instruments by hospitals of all rinks is increasingly rising. Also, the hospitals demand more functions and perfect performance implemented by the instruments. With the high speed development of modern microelectronics and microcomputer technology, it is possible that the function of clinical medical instrument is highly improved and their performance became more perfectly by use of new technology. The contemporary computer technology not only provides ideal technological methodology to the development process of the medical instruments, but also provides new conceptions to it. Now it has developed a new independent branch field of medical instrument depending on the computer technology. We call this sort of medical instruments that mainly depending on or partly depending on the hardware and software resources of general computer system as the virtual medical instruments. With the advancement of modern computer technology, the virtual medical instruments are gradually replacing the traditional medical instruments, and are becoming the mainstream in medical instrument market by their excellent performance and lower price. Even, we can anticipate that the highly automated and highly intelligent virtual medical instrument based on the computer technology may enter the families at the near future. Through the Internet, it will be possible to transmit the patient's disease data to the medical monitoring center and provide the doctors with all the patient's disease information. After the doctors made the diagnostic prescription, they can feed back to the patient with the diagnosis result via the Internet. So implements the Internet diagnosis and treatment process. This article discusses in detail a sort of virtual clinical ECG monitoring system that base on general computer system. It also discusses its entire construction and its implementation methods. Virtual clinical ECG monitoring system extends an ECG recorder and some other circuits outside the personal computer system. It uses the extended hardware to detect and sample electric physiological signal from patient's body and record them into the internal non-volatile memory. It implemented communications between the extended hardware circuit and the personal computer system through the USB bus. The most functions of the system are implemented by software system inside the ECG recorder and inside the personal computer. The total software structure of the system is separated into four parts. One is the firmware executed inside the 16 bit micro -controller of the ECG recorder to perform the ECG signal sampling and recording. The second one is the firmware executed inside the USB controller's 8 bits CPU kernel on ECG recorder circuit board. It performs the communication between the ECG recorder and personal computer. The third part is the DLL function sets used for USB operation in the personal computer. the fourth part is the Dynamic ECG Recording and Analyzing System software executed in the personal computer. The main software design tasks accomplished by the article includes: 1. Design the electric physiological signal's sampling, recording, and communicating program executed by the 16 bits micro-controller system. 2. Design USB2.0 data communication and control program executed by the 8051 CPU kernel inside the USB controller on the ECG recorder's circuit board. 3. Design the DLL function library used for communicating between the ECG recorder and personal computer system. The DLL functions perform all the communicating operations between the ECG recorder and the personal computer. It not needs the intervention of the Dynamic ECG Recording and Analyzing System software. 4. Design the Dynamic ECG Recording and Analyzing System software. This software is executed inside the general personal computer system. It includes: case management module, ECG recorder operation module, ECG analysis module, ECG waveform browse module, ECG waveform shape edit module, diagnosis report edit module, print module. This article follows the clue of the electric physiological signal's process of the virtual clinical ECG monitoring system. It discusses in detail the detection of ECG signal, the construction of the ECG signal amplifier circuit, the sampling of the ECG signal and its baseline filter and the ECG signal's buffering, storing, saving, transmitting process. The article also discusses in detail the construction and implementation of the ECG recording and analyzing system software executed in the personal computer. This ECG recording and analyzing system software includes case management, ECG signal's transmitting and storage, USB communication, ECG signal's preprocessing, ECG analysis, ECG waveform display and some other program modules. The system adopts the following technological methods for the system's hardware and software design. 1. In the ECG signal detection and amplification circuit, it uses the Wilson net as the center amplifier to amplify the ECG analogue signal. This amplifier circuit successfully gained the patient's 12 channel synchronous ECG signals at a higher signal-noise rate. 2. In the implementation of the 16 bits micro-controller's monitoring program inside the ECG recorder, it adopts the ring queue data structure to build ashift-average baseline filter. The filter successfully restricts the baseline bias of the ECG signals. The program also adopts multi-interrupt sources technology and double buffering toggle mechanism to continuously store the captured ECG signals into the non-volatile FLASH memory. 3. In the ECG signal's uploading scheme, the article firstly adopts the USB 2.0 technology to implement the high speed ECG data's transmitting to and from the personal computer. It gets the highest uploading speed among the same kind of products. 4. The article implements the DLL library function sets that used in USB communication between ECG recorder and the personal computer. It thus provides a standard software interface for the PC software to easily access the ECG recorder. 5. The article adopts ODBC database technology to efficiently implement the case management module in the Dynamic ECG Recording and Analyzing System software. 6. In the process of ECG signal's preprocessing, it adopts the theory of Butterworth digital filter to successfully implement the ECG signal's 35Hz low-pass muscle electricity digital filter and 50Hz band-block working frequency digital filter. In the implementation method of the filter, it adopts ring queue data structure to save the middle result of its differential equation. So it efficiently reduces the redundant computations in the filter algorithm and highly increases the processing speed. 7. In the heart beat's characteristic points getting stage of the ECG analysis program, it adopts the self-adapted parameter identification method to identify the entire characteristic points and get the whole characteristic parameters through scanning the ECG data only one time. This superior algorithm can even complete the ECG machine's or ECG monitor's high-speed real time ECG analyzing process. 8. In the heart beat classification stage of the ECG analysis program, it adopts the production rule sets of artificial intelligence method to build classification searching tree. Based on the characteristic points and characteristic parameters, the program executes a series of judgment from root node's rough classification to leaf node's exact classification. It will eventually accomplish the heart beat classification at the leaf node of the searching tree. According to our knowledge in clinical cardiology, the classification program calculates the certitude degree of each step's judgment so that provides a numerical evidence to accomplish the heart beat classification. At the same time, the classification program also creates and maintains a dynamic heart beat shape template of each beat type to aid making calculations of the classification certitude degree. In order to establish the certitudedegree calculating formula, the article also provides a curve making program to aid us accomplish the classification program's experiment and debugging tasks. 9. In design of the identification algorithm of bigeminy and trigeminy that premature heart beat occurs in a regular manner, the identification program is designed to scan only one time the analysis result array of the single heart beat classification to gain the whole analyzing result. Through verifying and testing of the whole ECG analyzing program, the execution of the analyzing algorithm is reliable. It gets an accurate analyzing result. This ECG analyzing algorithm not only fulfils the need of the dynamic ECG recording system's concentrated analysis process, but it fulfils the need of the real time analyzing process of the 500Hz sampling rate virtual electrocardiogram machine as well. Through comparing the ECG analyzing algorithm with other famous manufacturer's same kind of products, the general result of the virtual ECG analyzing algorithm is at the front position. It really provides clinical doctors with reliable evidence in diagnosing patient's heart disease. 10. In the ECG waveform display program module provided by the Dynamic ECG Recording and Analyzing System, it is possible to show the multi-channel synchronous ECG waveforms and its analysis result on the same screen in a variety of display manner. Clinical doctors may browse the ECG waveform and its shape classification result conveniently. Besides, the Dynamic ECG Recording and Analyzing System also provides an ECG shape edit module. Within this software module, clinical doctors may easily edit and amend the classification result of each specified heart beat that they think has made a wrong classification to it. In the diagram and chart browse program module of this system, it can calculate a variety of statistical diagrams and charts for each hour's ECG analysis result. It can also output the heart rate variation(HRV) tendency chart for doctor's examination. In the report edit program module of the system, doctors can easily edit their diagnostic report on the interface. The diagnostic report and its associated ECG waveforms can be printed no papers to form a complete patient's case by use of the print software module provided by the system. The successful development of the Virtual Clinical ECG Monitor System provides a set of effective solution to the realization of the virtual clinical diagnosis instruments.