Abstract: Introduce a wireless distributed medical monitoring system that can measure various physiological parameters such as electrocardiogram, respiratory wave, heart rate, respiration rate, body temperature, pulse rate, blood oxygen and blood pressure. The three independent OEM modules are connected to a module with control, display and wireless transceiver functions to achieve the measurement of the above parameters and information interaction with the host computer. The system designed by this solution has the advantages of small size, easy to carry, decentralized control, centralized management, short development cycle, reliable performance, easy maintenance, and easy upgrade.
The multi-parameter monitor is an important device in clinical care. This device can monitor the patient's physiological parameters such as ECG, blood pressure, blood oxygen saturation, respiration rate, pulse rate, and full temperature. At present, portable monitors with CRT or LCD display screens are commonly used in China. The instrument can display real-time data and waveforms, and the operation is relatively flexible, so it is mainly used to assist doctors in diagnosing and analyzing the patient's condition. However, due to its large size and high power consumption (connected to 220V AC or built-in current), it is not convenient for patients to carry around, and it is impossible to monitor multiple patients at the same time. The wireless distributed medical monitoring system designed in this paper makes up for the above deficiencies. The system uses three independent OEM modules to measure physiological parameters. Each module is connected to a control display module with wireless transceiver function to form an independent device. Therefore, the power consumption of each module is greatly reduced. Reduce accordingly. Patients can choose different modules to use according to different needs. The LCD display on each module can show whether the measurement signal is normal. All these modules communicate wirelessly with the host computer. The PC can register a unique serial number for each module and can access the information of each module to store, analyze, display, report to the engine, etc. It is very convenient to achieve the expansion of many modules, that is, real-time monitoring of these multiple patients.
1 System structure and working principle
The system is mainly composed of hardware and software. The hardware mainly includes PC and three independent modules, namely ECG module, blood oxygen module and blood pressure module. These three modules are composed of OEM module and control display transmission module. The ECG module is mainly used to measure parameters such as ECG, respiration rate and body temperature; the blood oxygen module is mainly used to measure parameters such as blood oxygen saturation pulse rate; the blood oxygen module is mainly used to measure parameters such as blood oxygen saturation and pulse rate; The module is used to measure blood pressure parameters. The software part is mainly the central monitoring software of the host computer, including the database part and the user interface. Figure 1 is a structural block diagram of a wireless distributed medical monitoring system.
figure 1
In Figure 1, each OEM module exchanges information with a PC through serial communication through a wireless transmission module. The data collected by each OEM module is stored on the PC after processing. The user can select any module on the central monitoring software interface to view the data or waveforms collected in real time. The software can automatically analyze the data and send out an alarm signal in time if an abnormality is found.
2 Functions and features of each module
2.1 Control display transmission module
The control display transmission module is based on the Atmega161 single-chip microcomputer, and is connected with the WGM-12864 graphic LCD module, buttons and NRF903 wireless transceiver module. Its circuit structure is shown in Figure 2.
Atmega161 is a low-power CMOS RISC 8-bit microcontroller produced by Atmel, which has 1MIPS / MHz performance, 16K bytes of FLASH, 512 bytes of EEPROM, 1K bytes of memory, 35 general-purpose I / O Port, 32 general working registers, three timers, internal and external interrupt sources, two programmable UART, SPI ports and three power saving modes that can be selected by software.
WGM-12864B module is a monochrome graphic dot matrix liquid crystal display module, the dot matrix number is 64 & TImes; 128. Its 8-bit data line is connected to the PA port of Atmega161, D / I indicates whether the signal on the data bus is dot matrix or control command word, R / W indicates that the current operation is a read or write operation, E is the enable control terminal, RST It is the reset terminal, and CS1 and CS2 are the left and right dot matrix area selection terminals. PC1, PC2, PB1, and PB0 are function selection keys, which can form a menu-based human-computer interaction interface with the LCD to control the corresponding OEM module. In the working mode, the LCD can display the relevant data information obtained from the OEM module.
The NRF903 module is a wireless transceiver module. NRF903 is a monolithic wireless receiving / transmitting integrated chip launched by NORDIC. It adopts Bluetooth (Bluetooth) core technology design, including a three-pin high-frequency transmission, high-frequency reception, PLL synthesis, I / Q in a 32-pin chip Modulation, I / Q demodulation, multi-channel switching, asynchronous communication interface, etc., its programming interfaces CFG_CLK (configuration register clock), CFG_DATA (configuration register data), CS (configuration register chip select) and Atmega161's SPI port PB7 (SCK ), PB5 (MOSI), PB4 (SS) are connected, and programming parameters such as operating frequency, channel, output power and output clock frequency can be programmed. Set CS to high level, the 14-bit control word from the microcontroller, at the rising edge of each CFG_CLK programming mode clock signal, write the logic value on the CFG_DATA terminal to the configuration register, the programming information is loaded, and the parameter setting is completed. STBY and PWR_DWN are connected to PD6 and PD5 of Atmega161 respectively, and can be set to standby or power-down mode. The data interface DATA is connected to a UART1 port of Atmega161 for receiving and sending data. The TXEN pin is connected to PD7 to control data transmission and reception.
figure 2
2.2 ECG OEM module
The ECG OEM module adopts the BT007 seven-channel ECG board of Beijing Maxtron Electronic Co., Ltd. BT007 can automatically measure the parameters of human body such as electrocardiogram, respiratory wave, heart rate, respiration, body temperature, etc. It has the following characteristics: synchronous seven-channel electrocardiogram, four-level programmable gain, three-level filtering (diagnostic, monitoring, surgical) , Pace pulse suppression function, lead off alarm, heart rate range 20 ~ 250BPM, anti-defibrillation and electrocautery interference, impedance breathing, respiration rate range 5 ~ 99BPM; dual body temperature measurement, measuring range 0 ~ 50 ℃, display The accuracy is 0.1 ℃, and the measurement accuracy is 0.2 ℃. The communication interface with the user and the UART serial communication method, there are two kinds of internal communication protocols: synchronous three-channel ECG protocol and synchronous seven-channel ECG protocol, which can be selected by jumpers. The characteristics of the synchronous three-channel ECG protocol are: 19200 baud rate, 8-bit data, 1 start bit, one stop bit, no parity bit; the characteristics of the synchronous seven-channel ECG protocol are: 28800 baud rate, 8-bit data, 1 start bit, 1 stop bit, no parity bit. The control word can be sent to the module through the MCU to control the ECG gain, filtering method, etc .; the data transmitted by the ECG board to the MCU is a group of 1 byte data header plus several bytes of data, which are sent in groups, in which the data The header is 251 to 254, and the digital byte is 0 to 250. MCU can store, analyze, display and transmit these data to PC in real time.
2.3 Blood Oxygen OEM Module
The blood oxygen OEM module adopts the DIGISAT pulse blood oxygen module of Beijing Maxtron Electronic Co., Ltd. The module communicates with the MCU through the UART port of TTL level. It can provide the following data: arterial oxygen saturation, pulse rate, volume scan, bar graph, signal strength and status information. Its communication protocol is compatible with BCI communication protocol, the data transmission baud rate is 4800bps, the transmission format is: 8-bit data + parity transmission baud rate is 4800bps, the transmission format is: 8-bit data + parity bit + 1 stop Bit. Every second, 60 data packets are sent to the MCU, and each data packet is 5 bytes.
2.4 Blood Pressure OEM Module
The blood pressure OEM module adopts the BTN602 noninvasive blood pressure measurement module of Beijing Maichuang Tongyuan Electronic Instrument Co., Ltd. The module also communicates with UCM through the TTL level UART port. After receiving an external command, it completes the corresponding operation and returns the system status and corresponding data. The data format is: start bit + 8 data bits + 1 stop bit, no parity bit, baud rate is 4800bps.
image 3
3 Design of software system-central monitoring software
The software is designed using VC language. Under the premise of combining with the hospital's previous management system, in accordance with the principle of unified norms, the organic integration of the new and old systems has been achieved, fully ensuring the independent reliability of the original system, and achieving the modularization and reconfiguration of the software structure. The system first requires the administrator to manually enter the hospitalized patient information into the computer system, where the key information is stored in the central database server; then sort, count, and classify the key data in the database. Copy the data to the database of the monitoring center of each department according to the category. When the monitoring needs are started, the patient will be monitored and recorded. The alarm level of the patient's monitoring data can be adjusted according to the monitoring needs. When inquiring, the key data and images can be displayed separately, and the key data of the query can be remarked, the images can be annotated, and the key data and image files can also be printed out in batches. Its software system structure is shown in Figure 3.
The security control of the system is mainly guaranteed from three aspects: the security of the database, the security of the image file, and the security of the user authority. The SQL Server, a database server built on NT Server, requires users and database operators to log in for authentication. Only users who log in with the database user's account and password can manage and maintain the database, and users have different levels of permissions for different tables. The file server uses port-controlled access to ensure the security of the file server.
The system software uses the wireless transceiver module to collect data from low-end modules by polling. If the system times out when querying patient information, it skips the query of this module and enters the query of other modules. The software will record the number of query failures. After the number of failures exceeds a certain threshold, the system will issue an alarm signal.
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