Volume 45, Number 4, 2004 475 Application of the Bluetooth Technology in Telemedicine Adina AŞTILEAN, Tiberiu LEŢIA, Honoriu VĂLEAN and Camelia AVRAM Technical University of Cluj Napoca, Automation Department 15 C. Daicoviciu Str. 400020, Cluj Napoca, Romania. Abstract: The paper presents a new possibility to use the Bluetooth technology in the medical field. The proposed application checks some of the Bluetooth capabilities in order to monitor simultaneously two or more patients in the recuperate stage of a heart disease. The patients are required to work on some effort devices (such as medical bicycle, run band etc.) or to perform any others activities that require physical effort, the body parameters being measured (in the studied case were simulated two behaviors) and sent in well-established intervals. The developed application consists of two parts: the patient (client) application (with two alike but distinct functioning programs) and the monitor (server) application. The server imposes some restrictions for the patient (client program) that will act in the manner dictated by the reactions of the server to the received data. The two applications are synchronized and the user does not perceive time differences during the communication process. The implementation can be extended to allow more patients to be monitored with just one device. Keywords: Wireless Communication, Bluetooth, Telemedicine, Wearable Medical Instruments 1. INTRODUCTION 1.1. Bluetooth characteristics Bluetooth is considered the most promising technology for wireless communication in an indoor environment (10 m range). The needs that Bluetooth addresses are: the providing of mobile access to information, the providing of mobile data acquisition, the enabling use of peripherals, the enabling of new device architectures. Some of the Bluetooth most important characteristics are: non line-of-sight transmission through walls and briefcases, the including of up to 8 devices in a piconet, the omni-directionality, real-time data transfer, usually possible between 10 and 100 m. The asynchronous data channel can support asymmetric data rates up to 723.2 kb/s with a 57.6 kb/s back channel, or a symmetric channel data rate of 433.9 kb/s in both directions. By utilizing frequency hopping spread spectrum transmission techniques and packet encryption, Bluetooth ensures secure and robust communications reliability. Power consumption of wireless technology has previously prohibited battery power for truly wireless operation. Bluetooth's low power requirement reduces the cost and size of battery power for operation and the single chip design has resulted in the ability to include the technology in small instruments without necessitating large enclosure extensions. 1.2. Telemedicine The number of wireless devices in health care is expected to triple by 2005, according to a study by Technology Assessment Associates. Wireless - enabled handheld usage by U.S. physicians is likely to climb to 55% by 2005, up from the current 18% [1].
476 ACTA ELECTROTEHNICA Bluetooth is based on GFSK modulation and hopping over 79 channels, each displaced by 1 MHz at 1600 hops per second. Consequently, it is difficult to intercept Bluetooth signal, an important feature when managing sensitive data such as clinical one. Taking into account all previous considerations, medical devices and medical information management represent opportunities for Bluetooth wireless technology, contributing to the evolution of mobile telemedicine systems. There are three important categories in which BT could be implemented with success: physician personal tools, medical devices and diagnostic instrumentation and telemedicine. In the case of telemedicine applications, the patients must be able to perform auto-tests, and Bluetooth enable devices will do the rest, that is transmit the data via Internet to the personal doctor s mail or monitoring device, and so expect prescriptions and guidance without the need of occupying precious time and hospital place. It must be mentioned that sensors with incorporated Bluetooth capabilities are not yet available on the market, but wearable devices are now in a trial stage. There is only one qualified medical end-product, Ortivus Mobimed patient monitor, which uses Bluetooth specification 1.0b [5]. Some laboratories investigate non-invasive electrodes for assessing and monitoring vital parameters and for recording of BT link electrophysiological signals. A block diagram of one of the experimental device is presented in [2]. The main components are: a microcontroller, the Bluetooth module (ensuring the wireless link) and the necessary sensors modules. On the other part, wireless sensor networks networks of small devices equipped with sensors, microprocessor and wireless communication interfaces represent a technology that has gained a lot of interest lately. The broad spectrum of new and interesting applications, ranging from personal health care to environmental monitoring and military applications is proposed for such networks [3]. Many medical wearable devices were designed in order to keep under control some variables that characterize the heart activity. The data flow in a complete wireless system designed in order to obtain and interpret an is represented in Figure 1. The wireless transmission (BT link) is performed by two delimitated piconets. The first piconet is responsible with the obtaining of the signals from the sensors, replacing the usual 12 wired connected cables of the classical monitor. The data are analyzed, coded and introduced in an inference mechanism. The results are available in the abnormalities file. The wireless communication between the patients and the monitor system is performed by the second piconet, used to transmit the results and/ or the signal for a given period. BT link Patient Data Data Analysis Abnormalities file Supervisor Figure 1. Patient-Supervisor data flow. Electrode Amplifier ADC Processor RF transceiver Figure 2. Slave node architecture.
Volume 45, Number 4, 2004 477 buffer Inference mechanism Reference bit pattern Obtained bit pattern Abnormality file (Time of occurrence) Sinus Arrhythmia.. Complete heart block...... Nodal tachycardia Nodal escape. Atrial fibrillation Figure 3. Interpretation. The slave mode architecture is given in Figure 2. To collect the data the smart sensors are wireless connected to a central node, in a master-slave configuration. Each sensor, placed on the patient s body, transmits an analog signal corresponding to the read biopotential. In order to be recognized by the baseband processor, the amplified signal is passed through an analog to digital converter. Finally the microcontroller, using the adequate packet format, sends the packets via the RF transceiver to the master node [7]. The master node comprises of the interface to the PC, which is responsible for communicating directly with each particular slave. The obtained information will be displayed through a graphic user interface. A similar structure was used in 2002, to obtain an experimental device in the laboratories of the Queensland University, Australia. The subsystem designed in order to interpret the resulted [8] is another important part of the application. The corresponding block diagram is given in Figure 3. simultaneously two or more patients in the recuperate stage of a heart disease/failure. The generic architecture presented in Figure 4 is considered to integrate the Bluetooth technology in a telemedicine system that allows the interpretation of cardiac rhythm disorders. A master-slave configuration, Figure 5a, that can be extended as in Figure 5 b or 5 c, [4], is used. Figure 4. The application architecture. 2. THE ARCHITECTURE OF THE APPLICATION The proposed application checks some of the Bluetooth capabilities in order to monitor a b c Figure 5. Master-slave configurations.
478 ACTA ELECTROTEHNICA The patients are required to work on some effort devices (such as medical bicycle, run band etc.) or to perform any others activities that require physical effort, the body parameters being measured (in the studied case were simulated two behaviors) and sent in well-established intervals. These intervals can be modified by the doctor from the monitoring device. Two important objectives have to be considered: to create the possibility to monitor more patients simultaneously and to leave maximum freedom to the patient. Taking into account this last goal, the application constitutes only a part of a more complex system that will include wearable sensors, based on the Bluetooth technology. Thus, the main advantage of the presented application consists of the offered possibility to supervise simultaneously the heart activity of many patients. The operational area must be from 5 meters to 10 meters (a circle with radius of maximum 10 meters), but it should be operational in small crowded areas too. Because the necessary smart sensor node, having as possible structure the connected components presented in Figure 6, is not available yet on the market [3], a set of data representing the patients evolution characteristics during the recuperate stage is given. It replaces the data that will be sent in the real case by each patient to be processed by the server in order to take a decision. It was assumed that a possible short Sensor1 Sensor 2 Micro controller RS 232 Bluetooth device Figure 6. Smart sensor. transmission delay will not put in danger the patients life. 3. IMPLEMENTATION ASPECTS The developed application consists of two parts: The patient (client) application (with two alike but distinct functioning programs); The monitor (server) application. The behavior (pulse values and ) of two monitored patients is simulated, only one monitor being required. The implementation can be extended to allow more patients to be monitored with just one device. The two applications must interact according with specified times and transmitted messages. All time related issues were established in a way that the application keeps its functionality and respects the previous specified time intervals. The simulation does not treat any kind of interferences that can occur within the interactions of other wireless devices. Some of these aspects were studied in [6]. The server monitor application translates the data received by the patients into charts that illustrate the dynamic behavior. The interface allows the user (monitoring personnel) to perform a sequence of actions that are recognizable for the client. So the user (physician) is able to stop, to exit, to view charts representing pulse and (electrocardiogram) of each patient, and this action should not interfere with the program of other patient. The server imposes some restrictions for the patient (client program) that will act in the manner dictated by the reactions of the server to the received data [3]. The two applications are synchronized and the user does not perceive time differences in the communication process. Test duration for each patient is 3 min and can be modified by setting the time interval. The client application is set to transmit data at each 1 sec (at each second a value for and a value for pulse are transmitted to server). In
Volume 45, Number 4, 2004 479 both cases data is stored initially in local buffers from which are transmitted or taken. The server receives almost instantly the data and after a process of comparing, places it on the dynamic charts. A counter holds the number of times in which the limit values are exceeded and according to the initial specification the application is stopped; otherwise an analysis messages will appear for the patient. The demonstration of the simulation is made visible. In a future system the client application will be embedded in the corresponding medical device. As simulation devices were used two computers with Bluetooth capabilities: Desktop Athlon 950MHz processor 256 Mb DDRAM with a MSI 6869 main board with MSI Bluetooth Transceiving Module (Transceiving Module, Dipole Antenna, Cable for pin connection) (manufactured by Cambridge Silicon Radio ver373 USB type); Laptop Sony Vaio Intel Pentium 550MHz processor 128Mb SDRAM with Belkin PCMCIA Bluetooth dongle (manufactured by Cambridge Silicon Radio ver115 PCMCIA type). The server application is run on the desktop and two client applications can be run simultaneously on the laptop. The server and client class diagrams are given in Figure 7, respective 8. The serial communication is implemented using a set of open source classes. These classes are available as a serial communication library that allows several operations and communication protocols using the serial ports. The CSerial class can open a connection to a listening server and to perform several operations on this connection. The most important operations are the data sending to the listening server and the data reading from server. In order to be able to accept data from server, the CSerialEx class must be used. This class enhances the CSerial class with server like abilities. Objects of this class can be very easy turned into listening mode or standard mode. The two states/modes of serial CSerial CSerialEx ServerListener ActiveSkin MainDialog CDialog Figure 7. Server Class Diagram. ActiveSkin MainDialogDlg CDialog CSerial CSerialEx Figure 8. Client Class Diagram. VSChart connections coexist because of optimization and performance raisons. Serial communication wraps the Bluetooth protocol. Communication s speed on serial port is limited by hardware components. When the server is started, it can receive client connections. The server application reads from the configuration file the ports on which it starts listening. A server listener is created for every port the server reads from the configuration file. Then, the server can accept connections from several clients. If no connections are incoming the server remains in the idle status that does not uses system resources. When the server is started, it can receive client connections. Starting the client applications does not initialize the connection and the test. This is made by clicking the start button, which calls the method StartTest. This method tries to connect to the server and if succeeded announces the server that a new client is available, by sending a START
480 ACTA ELECTROTEHNICA command to the server. If the server is offline, or the port on which the client tries to connect is busy, the connection and the test fail, and the client/patient are notified of the occurred failure. If the client receives a confirmation consisting in an OK message from the server, the client starts sending data to server, when the timer events occur. When there is no more data to send to the client, this sends a STOP command and the server closes the connection. During the period of a test, both client and server can terminate the test by pressing the stop button. If one stops the test the other is notified by a STOP command. When a test is finished (either normally or forced) the server can display charts using all the data received from the client. During the test, the server displays only the last 15 entries received from the client. 4. EXPERIMENTAL RESULTS The main functional characteristics of the proposed application were tested and evaluated. The server monitor interface, with Patients 1 and 2 running and the of patient 1 are presented in Figure 9, respective 10. It must be mentioned that, taking into account the previous considerations, the chart illustrates a given set of data transmitted during the simulation test and not the real data corresponding to an. 5. CONCLUSIONS A new possibility to use the Bluetooth technology in the medical domain was proposed. The approach combines features of auto-testing and distance surveillance systems in order to guide simultaneously the activity of more patients in the recuperate stage of a heart disease/failure. The experiments prove the possibility to transmit the necessary amount of information in the case of two monitored patients, without observable delays. The operational area must be of 5 meters to 10 meters, but it should be operational in small crowded areas too. In order to leave maximum freedom to the patient, sensors with incorporated Bluetooth capabilities have to be used. Taking into account the advantages and the accelerated development of the Bluetooth technology, the present study can constitute the basis for a future successful application. 6. REFERENCES 1. Sapal Tachakra, X.H. Wang, R. S.H. Istepanian and Y.H. Song, Mobile e-health: The Unwired Evolution of Telemedicine, Telemedicine Journal and e-health Volume 9, Number 3, 2003, Mary Figure 9. The Server Monitor Interface.
Volume 45, Number 4, 2004 481 Figure 10. of Patient 1. Ann Liebert, Inc. 2. A. Tura, M. Badanai, D. Longo, L. Quareni, Measurement in Biomedicine. Measurement Science Review, Volume 3, Section 2, 2003. 3. Srdjan Krco, Bluetooth Based Wireless Sensor Networks Implementation Issues and Solutions, Applied Research Lab, Ericsson Ireland. 4. John Johnson, The Next Wave of Wireless: Exploring Bluetooth, Leading Edge Forum Bluetooth, April 2001. 5. Baniel Beaumont, Bluetooth brings mobility to healthcare, Planet Wireless June 2002. 6. Magnus Berggren, Wireless communication in telemedicine using Bluetooth and IEEE 802.11b, Department of Computer Systems, Uppsala University, November 2001, ISSN 1404-3203 http://www.it.uu.se. 7. Haroon Mustafa Khan, Wireless, University of Queensland, Thesis 2002. 8. Y.S. Rao, Nayan Savla, a.o., Remote Monitoring of Heart Abnormalities, IEEE Computer Society International Design Competition 2002.