A remote medical monitoring system based on wireless sensor networks

Introduction

Medical monitoring equipment can be divided into two categories. One is a special instrument used by professional doctors or professional technicians in hospitals to monitor the physiological indicators of patients; the other is a remote medical monitoring system used by patients or their families to monitor patients at home or outdoors under the guidance of doctors, and the obtained physiological indicators will be transmitted to relevant doctors in a timely manner. At present, the monitoring methods used in hospitals mostly use fixed medical monitors, and the connecting equipment connects the sensor probe between the patient and the monitoring equipment for signal transmission. Complex equipment and numerous connections will cause psychological pressure and tension on patients, which may affect the patient's physical condition, making the data obtained from the diagnosis have a certain gap with the actual situation, causing inconvenience to both patients and medical staff, and may affect the correct diagnosis of the disease.

In order to enable people who often need to measure physiological indicators (such as chronic patients or elderly patients, etc.) to measure certain routine indicators at home while exercising at will, the international attention to telemedicine is increasing. This paper designs a new network monitoring device and system, the purpose of which is to use high-frequency wireless multi-channel data transmission to transmit information between medical sensors and monitoring control instruments, reduce the connection between monitoring equipment and medical sensors, so that the monitored person can have more free space for activities, and obtain more accurate measurement indicators while exempting the patient from the hard work of running between home and hospital. At the same time, a wireless monitoring network is established in the hospital ward, and many tests can be completed on the bed, which can greatly facilitate patients' medical treatment and enhance the hospital's modern information management and work efficiency. In addition, the remote monitoring system can also be expanded so that patients far away from hospitals and other medical institutions can also receive necessary medical monitoring at any time, and get consultation and guidance from remote doctors when necessary, such as rural areas in my country where there is a shortage of doctors and medicines.

System Structure

This paper proposes a remote medical monitoring system based on wireless sensor network technology, and proposes a new scalable multi-level network architecture and implementation method, that is, a micro-monitoring network composed of monitoring base station equipment and wireless dedicated sensor nodes. The central controller on the sensor node controls the vital indicator sensors to be monitored to collect data, and sends the data to the monitoring base station equipment through wireless communication. The base station device transmits the data to the connected PC or other network devices. The data can be transmitted to the remote medical monitoring center through the In2ternet network, and professional medical personnel conduct statistical observations on the data and provide necessary consulting services to realize remote medical care.

FIG1 is a diagram of the architecture of the remote medical monitoring system, which includes a monitoring base station device and a series of medical sensor nodes of a medical monitoring network.

In the system designed in this paper, medical sensor nodes are used to measure various human physiological indicators, such as body temperature, blood pressure, pulse, blood sugar, blood oxygen, etc. The sensors can also dynamically monitor the status of certain medical equipment or the treatment process. The data information obtained is transmitted to the medical monitoring base station device through wireless communication. We design this type of home base station or ward base station as a handheld device. The base station device can save and process the received sensor data information and display the data on the LCD screen of the device. It can also choose to use a variety of methods for remote data transmission communication as needed, such as connecting to the remote network through the RS2232 interface connected to the PC, through GSM short messages or through modem access to remote Ethernet. The information transmitted to the remote end will be counted and analyzed by professional medical personnel in the remote monitoring center or hospital management center, and timely feedback, advice and suggestions will be given to patients.

Medical sensor nodes can be set up according to different needs, so the system has great flexibility and scalability. At the same time, connecting the system to the Internet network can form a larger community medical monitoring network, hospital network, and even the entire city and national medical monitoring network, as shown in Figure 2.

Figure 3 shows the block diagram of the medical monitoring base station device designed in this paper. The main function of this system is to collect and display the data information obtained from the test, and to store and forward the data information appropriately on the network. Therefore, the monitoring base station device in this system is designed as a handheld device. At the same time, the monitoring base station device can communicate with multiple sensor nodes in the system to complete functions such as data collection and display. During use, the monitoring base station device sends a control command to the sensor node through a wireless channel to start the sensor node. After receiving the command, the sensor node performs the corresponding data collection action to collect human physiological index data. After the collection is completed, the data is returned to the monitoring base station through wireless communication, and the monitoring base station performs further display, storage and other operations. If necessary, the monitoring base station device can transmit data to the remote server through the network.

Medical monitoring base station equipment mainly includes: processor, memory, human-computer interaction module, communication module interface and other parts. The main processor of medical monitoring equipment adopts TI's MSP430 series low-power processor, which has the characteristics of ultra-low power consumption, high processing speed and rich interfaces, and is very suitable for embedded devices that require ultra-low power consumption and high speed. The human-computer interaction interface includes two parts: a keyboard for users to input commands and an LCD display screen for displaying data results and operation processes.

In order to enhance the applicability and compatibility of the system, a variety of communication module interfaces are designed on the monitoring base station equipment, including RS-232 interface, modem interface module, GSM short message interface module and radio frequency interface module. The radio frequency interface module is used for short-range communication with the wireless sensor nodes in the system, and other communication interfaces are used for communication with the host server. For example, if there is no Internet access at home, the user can use the modem module to access the telephone line for dialing and transmit the data to the server. If there is no other connection method outdoors, the user can use the GSM short message method to transmit the data to the server.

When the server in the hospital or community medical center receives the data information sent by the monitoring base station device, it can store the data and make necessary analysis, and the doctor can make corresponding judgments and processing based on the data. For medical monitoring equipment used at home, users can also connect the equipment to the PC at home through the RS-232 interface as needed. In this way, the data of the monitoring base station device can be transferred to the computer for more flexible management. Family members can judge the physical condition of the monitored person based on the data. At the same time, the data can also be transferred to the main server for analysis and management by professional medical personnel. Figure 4 shows a hardware photo of the monitoring base station device developed in this work.

The monitoring base station equipment is powered by batteries under normal working conditions. Therefore, special attention is paid to the management and control of low power consumption during the design process. When not working, the system will enter low power consumption and sleep state to save system energy.

Design of monitoring sensor node

The main function of medical wireless sensor nodes is to collect human physiological index data, or dynamically monitor the status of certain medical equipment or the treatment process, and transmit the data to the monitoring base station equipment through radio frequency communication. As shown in Figure 5, the medical sensor node mainly consists of 4 parts: processor part, data storage part, sensor module and RF radio frequency communication part. The processor part adopts TI's MSP430 series microcontroller according to the needs of low power consumption and processing power. The memory part is mainly used to store temporary data collected by the sensor. After the processor transmits the data, the sensor node does not store a large amount of data. In the system designed in this paper, the medical sensor module mainly realizes the following functions, including blood oxygen, pulse, blood pressure and blood sugar measurement. Among them, blood oxygen and pulse measurement integrates the BCI blood oxygen pulse measurement module produced by Shanghai Berry Company; blood pressure measurement integrates the blood pressure measurement module produced by Taiwan TaiDoc Company, and blood sugar measurement integrates the blood sugar measurement module produced by TaiDoc Company.

Figure 6 shows the hardware circuit photos of these three modules. Among them, Figure 6 (a) is a blood sugar measurement node, Figure 6 (b) is a blood pressure measurement node, and Figure 6 (c) is a blood oxygen and pulse measurement node. In the design of this system, the wireless node has reserved a rich interface for sensor expansion. If other types of physiological index data are required, such as body temperature, electrocardiogram and other data, you only need to connect the corresponding sensor to the reserved interface to form a new wireless sensor node. By developing the corresponding embedded control and processing software, you can directly add the node to the wireless sensor network.

Wireless communication design

Medical monitoring equipment used in hospitals has very high requirements for electromagnetic radiation. For the equipment, the electromagnetic waves radiated should not interfere with the normal operation of other equipment, and at the same time, it should have a certain anti-interference ability and not be interfered by the electromagnetic waves radiated by other equipment. Therefore, this aspect must be considered in the design of medical equipment in hospitals or home medical equipment using wireless communication.

In this system, the radio frequency communication used is the globally open and free 214GHz ISM band, and the communication standard adopted is the 802.15.4/Zigbee standard, which is specifically designed for short-distance high-speed data transmission and has high data error correction and anti-interference capabilities. In addition, the system controls the working intensity of the wireless signal so that under normal conditions, the signal strength can meet the needs of communication without excessive waste, which saves system energy on the one hand and reduces the interference of the wireless communication process to other devices on the other hand.

The RF communication device designed in this system uses a RF communication module with CC2420 chip as the core. This chip is produced by Chipcon Corporation of the United States and is a low-power wireless transceiver chip, which is particularly suitable for working in low-power, low-voltage wireless communication devices. This chip works in the free 2.4GHz ISM band, and the RF transceiver complies with the IEEE802.15.4/Zigbee standard, which can meet the needs of RF communication in this system.

Experimental verification

This system has achieved preliminary results in the comprehensive test process. The sensor collects data and sends the data to the monitoring base station device through the wireless channel; the monitoring base station device displays the data on the LCD screen and transmits the data to the computer through the RS2232 interface; the computer displays the data in the form of curves and graphs in the software based on the obtained data. In practical applications, the health status of the monitored person can be analyzed based on these curves and data. If in an outdoor environment, the measured data can be sent to the server for management and analysis using GSM short messages. Figures 7 and 8 illustrate the monitoring of the blood oxygen status of the monitored person and the display of the data on the monitoring base station device and on the computer.

Summary and Outlook

This paper introduces a scalable remote medical monitoring system based on wireless sensor networks. The system establishes a wireless sensor network in the environment of home or hospital ward. Through this network, sensor nodes collect human physiological index information, or dynamically monitor the operation of medical instruments and the treatment process, and transmit the information to the monitoring base station equipment and server computer. The sensor network system can be connected to the remote monitoring center in different ways through the monitoring base station equipment. The system has high flexibility and scalability and can be widely used in the environment of community telemedicine and hospital ward monitoring. Through the Internet network, a remote medical information network can be built, which is not only conducive to patients in developed areas to obtain health care services, but also conducive to patients in poor areas to obtain necessary medical services. In future work, the software and hardware of the system will be further developed to improve stability and practicality. At the same time, the upper management software will be customized and developed according to special needs, and the medical monitoring management platform software will be improved.