CHAPTER 3 REMOTE MONITORING OF POST-OPERATIVE PATIENTS IN A HOSPITAL ENVIRONMENT USING WIRELESS SENSOR NETWORKS

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1 87 CHAPTER 3 REMOTE MONITORING OF POST-OPERATIVE PATIENTS IN A HOSPITAL ENVIRONMENT USING WIRELESS SENSOR NETWORKS 3.1 INTRODUCTION Patients with surgical wounds experience some post-operative pain despite efforts to control this with analgesic medication; this pain impairs chest expansion, the ability to cough, and post-operative mobilization. Inadequate chest expansion and reluctance to cough can have a dramatic effect on patient recovery. The immediate postoperative period is a crucial period when numerous physiological and pharmacodynamic changes occur due to surgical trauma and anesthesia (Aziz et al 2006). The ability to monitor the recovery of post-operative patients and identify those at risk of developing complications is, therefore, clinically desirable and may result in an early intervention to prevent adverse outcomes. The purpose of monitoring postoperative patients is to provide care until patients can be safely discharged to a general ward or home in a stable condition, or be transferred to a critical care environment if further close monitoring and care are necessary (Murakami et al 2006). Patients have a generalized deterioration of organ function and loss of reserve capacity to withstand even minor stress like surgical trauma causing life-threatening complications. The disturbances in cardio-respiratory functions should be carefully monitored during the postoperative period. The condition of post-operative patients can change rapidly and therapy may need to be adjusted every few hours if optimum cardio-

2 88 respiratory function is to be maintained (Iso-Ketola et al 2008). Monitoring vital parameters like heart rate, blood pressure, body temperature, and ECG is required for immediate intervention to prevent post-operative complications (Hongliang Ren et al 2005). 3.2 ARCHITECTURE FOR REMOTE MONITORING OF POST-OPERATIVE PATIENTS USING WIREESS SENSOR NETWORKS Recent technological advances in sensors, low-power integrated circuits and wireless communications have enabled the design of low-cost, miniature, lightweight and physiological sensor nodes. These nodes, capable of sensing, processing and communicating one or more vital signs, can be seamlessly integrated into wireless personal or body networks for health monitoring. The nodes then sense vital physiological signals and report them to other nodes over flexible network architecture. Sensors are attached in the human body to monitor disorders during normal activities and help patients maintain their health even after surgery (Jovanov et al 2002). In addition, patients can benefit from continuous long-term monitoring as part of a diagnostic procedure, can achieve optimal maintenance of a chronic condition or can be supervised during recovery from an acute event or surgical procedure. The overview of the system is shown in Figure 3.1. This system consists of a front-end, a base station, and a central server. The Front-end is composed of different sensors for the recording of vital signals that are demanded by the application (ECG, Heart Rate, and Body temperature) (Bauer et al 2000).

3 89 Figure 3.1 System Overview - Remote Monitoring of Post-Operative Patients in a Hospital Environment using Wireless Sensor Networks The Patient station consists of a mote device that receives information from the sensors. Tiny sensor nodes are responsible for sensing, as well as the first stage of sensory data processing in data communication. The received signal is sent to the central server for analysis. This compact device encourages and motivates the patients in their daily routine activities. The mote attached to the central server through the USB interface board is used as a base station for the 2.4GHz wireless network. The base station is the only mote to communicate with the central server. The Central Server is the core-processing element. It receives the patient's data from the patient station via the base station for analysis. Sensor readings received at the base station are stored in a database on the central server. The database service is provided by the postresql software, which is installed on the central server. The logged data is accessed by the visualization tools in Mote-View software specifically used for wireless sensor networks.

4 HARDWARE OVERVIEW Physiological Sensors Heart rate sensor (CI-6543B) The PASCO CI-6543B Heart Rate Sensor showed in Figure 3.2 monitors the flow of blood through a part of the body, such as an ear lobe, by flashing a light through it and monitoring the change in intensity. As the heart beat forces blood through the blood vessels in the ear lobe the light transmittance through the ear lobe changes. The sensor consists of a Heart Rate Sensor amplifier box and a cable with DIN connectors for connecting to the wireless sensor node. The ear clip can be attached to a part of the body such as an earlobe, a fingertip, toe, or the web of skin between the thumb and index finger. The sensor shines an infrared light through the earlobe and measures the change in light that is transmitted. The light source is a small infrared light emitting diode. Figure 3.2 Heart Rate Sensors - CI-6543B Manufactured by PASCO Scientific, Foothills Boulevard, Roseville, California, USA ECG sensor (CI-6539A) The PASCO CI-6539A ECG (Electrocardiogram) Sensor shown in Figure 3.3 measures cardiac electrical potential wave forms (voltages

5 91 produced by the heart as its chambers contract). Because the electrical signal produced by the heart and detected at the body s surface is so small, it is very important that the electrode patch makes good contact with the skin. Scrub the areas of skin where the patches will be attached with a paper towel to remove dead skin and oil. Figure 3.3 ECG Sensor - CI-6539A Manufactured by PASCO Scientific, Foothills Boulevard, Roseville, California, USA Body temperature sensor (CI-6505B) The low thermal mass Temperature Sensor shown in Figure 3.4 ensures a quick response and has a negligible impact on measured temperatures. This is a one-piece sensor that incorporates a stainless steel sensing element for durability. The sensor consists of a stainless steel probe, a 3-foot cable and an 8-pin connector. Temperatures can be measured in degrees of Celsius, Fahrenheit, or Kelvin. Figure 3.4 Body Temperature Sensors - CI-6505B Manufactured by PASCO Scientific, Foothills Boulevard, Roseville, California, USA.

6 Patient Station IRIS mote kit The IRIS shown in Figure 3.5 is the latest generation of Motes, which uses a 2.4 GHz Mote module, used for enabling low power, IEEE compliant integrated with an Atmega128L micro-controller (Nada Golmie et al 2004). The ATmega1281 is a low-power microcontroller, which runs MoteWorks from its internal flash memory. A single processor board (XM2110) can be configured to run your sensor application/processing and the network/radio communications stack simultaneously. The IRIS 51-pin expansion connector supports Analog Inputs, Digital I/O, SPI and UART interfaces. These interfaces make it easy to connect to a wide variety of external peripherals. All of these boards connect to the IRIS via the standard 51-pin expansion connector. Figure 3.5 IRIS Mote - Manufactured by Crossbow technology, Kit Horton Manufacturing Co., 484 Tacoma Avenue Tallmadge, Ohio Imote2 kit The Imote2 shown in Figure 3.6 is an advanced wireless sensor node platform. It is built around the low power PXA271 XScale CPU and also integrates an compliant radio. The design is modular and stackable with interface connectors for expansion boards on both the top and bottom

7 93 sides. The top connectors provide a standard set of I/O signals for basic expansion boards. The bottom connectors provide additional high-speed interfaces for application specific I/O. A battery board supplying system power can be connected to either side. Basic I/O Advanced I/O Connector LED CPU Antenna Radio USB Reset Front / Basic Back / Advanced Figure 3.6 Imote2 Kit - Manufactured by Crossbow technology, Kit Horton Manufacturing Co., 484 Tacoma Avenue Tallmadge, Ohio It integrates many I/O options making it extremely flexible in supporting different sensors, A/Ds, radios, etc. These I/O features include two Synchronous Serial Ports one of which is dedicated to the radio, 3 high speed UARTs, GPIOs, USB client and host, audio codec interfaces, a fast infrared port, PWM, a Camera Interface and a high speed bus (Mobile Scaleable Link). The Imote2 uses the CC2420 IEEE radio transceiver from Texas Instruments. The CC2420 supports a 250kb/s data rate with 16 channels in the 2.4GHz band. The Imote2 platform integrates a 2.4GHz surface mount antenna, which provides a nominal range of about 30 meters.

8 Data Acquisition Board MDA320CA The MDA320CA shown in Figure 3.7 is a general measurement platform for all mote kits. Analog sensors can be attached to different channels based on the expected precision and dynamic range. Digital sensors can be attached to the provided digital or counter channels. Mote can sample analog, digital or counter channels and can actuate them via digital outputs. Signals with a dynamic range of 0 to 2.5 V can be plugged to these channels. The analog to digital converter has 16-bit resolutions. The least significant bit value is 0.6 mv. The result of ADC can be converted to voltage knowing that Voltage = 2.5 ADC_READING / Figure 3.7 DAQ Board - MDA320 - Manufactured by Crossbow technology, Kit Horton Manufacturing Co., 484 Tacoma, Avenue Tallmadge, Ohio Channels A0 to A7 can also be used for differential analog signals. Dynamic range and conversion formulae are the same as single ended channels. Figure 3.8 describes the pin-out details of MDA320CA.

9 95 (a) (b) Figure 3.8 Pin Configuration and Their Functional Assignments of the MDA320CA - Manufactured by Crossbow technology, Kit Horton Manufacturing Co., 484 Tacoma Avenue Tallmadge, Ohio 44278

10 ITS400 Sensor Board The basic sensor board shown in Figure 3.9 is designed to connect to the basic connectors on the Imote2. It contains a 3d Accelerometer, an advanced temp/humidity sensor, a light sensor and 4 channels ADC. It is a pass through board to allow stacking with another sensor/communication board. Figure 3.9 ITS400 Sensor Board - Manufactured by Crossbow technology, Kit Horton Manufacturing Co., 484 Tacoma Avenue Tallmadge, Ohio The sensor board is a multi-sensor board that combines a popular set of sensors for wireless sensor network applications, including a T Micro LIS3L02DQ 12 bit ±3g accelerometer, a ±0.3 C Sensirion SHT15 temperature/humidity sensor, a TAOS TSL2651Light Sensor, a Maxim MAX Channel General Purpose ADC for quick prototyping, and a TI Tmp175 Digital Temperature Sensor with a two-wire interface USB interfacing board (MIB520) The MIB520CB shown in Figure 3.10 (a and b) provides USB connectivity to all the family of Motes for communication and in-system programming.

11 97 (a) (b) Figure 3.10 (a) MIB520 USB Interface Board (b) USB Interfacing board attached with Mote - Manufactured by Crossbow technology, Kit Horton Manufacturing Co., 484 Tacoma Avenue Tallmadge, Ohio Any node can function as a base station when mated to the MIB520CB USB interface board. It supplies power to the devices through the USB bus. The MIB520CB has a male connector which has an on-board in-system processor (ISP) an Atmega16L located at U14 to program the Motes. The Code is downloaded to the ISP through the USB port. The Motes connect to the MIB520 for UISP programming from a USB connected host PC.

12 METHODOLOGY This proposed architecture monitors a patient s physiological signals by a wireless sensor node during his recovery period after the surgery and alerts healthcare professionals about abnormal changes in the patient, which affect the sign of recovery. The main characteristics of the different elements are presented in the following sections Front-end module The front end, composed of inexpensive, lightweight and miniature sensors, can allow long-term, unobtrusive, health monitoring with instantaneous feedback to the user about the current health status and real time updates of the post operative patient's medical records to a central server through wireless mesh network nodes. For example, an electrocardiogram sensor can be used for monitoring heart activity, a Heart Rate sensor for monitoring the heartbeat and a temperature sensor for monitoring the body temperature of post-operative patients Patient station The patient station shown in Figure 3.11 is a device from Crossbow's latest generation motes, which receives information from the sensor and transmits it to the central server. The motes were designed for large-scale wireless sensor networks and, therefore, a variety of biomedical sensor boards are commercially available to integrate with the mote. The sensor node is programmed in such a way that it can be awake at a particular time period and transmits the data to the server and then returns to the sleep mode.

13 99 IRIS Device Connected to the patients Heart Rate Sensor Temperature Sensor ECG Sensor Iris mote device Figure 3.11 Patient Station Interfaced with Physiological Sensors Central Server The server, which is the core-processing element, receives the data regularly from the sensor nodes via the base station for analysis, and is shown Figure The analysis is done using the software moteview, which offers a built-in library for data acquisition, processing, analysis and display. MoteView is designed to be an interface between a user and a deployed network of wireless sensors. It also makes it easy to connect to a database to analyze and graph sensor readings. This system can also give the alert to the doctors via short message service and services. Our server uses wireless cards to attain broadband cellular internet connectivity to connect with the patient record database and make real-time patient information accessible to users through a secured web server (Khoor et al 2001; Mendoza and Tran 2002; Alaoui et al 2003; Perrig et al 2001; Nelwan et al 1977).

14 100 Central Server Base Station Figure 3.12 Central Server with Base Station 3.5 IMPLEMENTATION This section describes the implementation of the system for remote monitoring of post-operative patients in a hospital environment using wireless sensor networks Real Time Monitoring Individual wireless sensors are an important component of our system, for they provide real-time vital signals. The heart rate sensor, body temperature sensor and electrocardiogram sensor are attached to the patient's finger, armpits and chest respectively, to monitor the heart rate, body temperature and heart activities. Each patient's individual vital sign sensor continues to transmit unique, real time vital sign data to the patient base station. The base station then transmits the data to a central server. These

15 101 wireless sensor nodes provide a powerful platform for experimentation with both digital and analog sensors. The central server output shown in Figure 3.13 represents the number of patients who are being monitored and the database for all the postoperative patients under normal conditions. The Chart tab provides the ability to generate graphs of a sensor reading against time for a set of patients. Three different sensor types can be selected for plotting at a time. A different plot color will be used for each patient; a legend is displayed on the right side of the window. The x-axis on the graph shows the date and time. The y-axis on the graph shows data in engineering units for the sensor readings. With all the peripheral devices turned on, the heart rate, body temperature, and electrocardiogram are reported every second to the central server. The moteview installed in the central server automatically records and analyses the patient's real time vital signs Sending SMS and The central server has been programmed with a threshold-based algorithm, which attempts to identify the physiological parameter values that are potentially harmful or indicative of immediate danger to the patients. The algorithm detects the upper and lower threshold values from the sensors output. When an anomaly is detected in the patient's vital sign, the moteview software application generates an alert in the central server and also to physicians and emergency departments through SMS and services. If

16 102 the patient has a previously entered medical record, information from that record is used in the alert detection algorithm. Table 3.1 shows a partial list of physiological conditions that cause alerts. Figure 3.14 shows the alert window in the central server when an anomaly event is detected. The alert manager allows users to define alert conditions based on any sensor data of any sensor node. An alert is a user programmable event that gets triggered when the sensor data exceeds the predefined threshold. An alert is composed of several pieces: alert ID, node name, sensor name, alert condition, alert threshold, alert action, send an , alert interval and alert duration. Figures 3.15 and 3.16 show the screen shots of automatically generated alerts to physicians and emergency department personnel through and SMS services. Table 3.1 Alert detection parameter for monitoring post-operative patients in hospital Heart rate change ΔHR/5 min > 19% Bradycardia Tachycardia HR < 60 Bpm HR > 100 Bpm Body temperature BT > 99 F, BT < 90 F

17 103 Figure 3.13 Central Server Monitor s Screen under Normal Conditions

18 104 Figure 3.14 Central Server Monitor s Screen under Abnormal Conditions

19 105 Figure 3.15 Generation of Alerts through to Physicians and Emergency Department

20 106 Figure 3.16 Generation of Alerts through SMS for Physicians and Emergency Department

21 WEB Based Information Portal We present a real-time remote patient monitoring service through World Wide Web (WWW), which allows physicians to monitor their patient in remote sites using popular Web browser. The web browser provides access to the patient s records and clinical data. The purpose of the system is the provision of extended monitoring for patients in some particular cases, with improved health delivery and reduced health expenditure. The web based monitoring is defined as follows: the client application provided visualization, archiving, transmission, and contact facilities to the remote user (i.e., the patient). The server, which is located at the physician s end takes care of the incoming data, and organizes patient sessions. The client application has been designed and developed using VB Script in Asp page, and the server application developed using MoteView and PostgreSQL database. The patient database has been implemented in MS Access. It consists of tables that store patient information, medications and doctor s information and clinical measurements. The client s application is mainly to measure the patient s heart rate, temperature in real time. The user is able to add new patient, save patient details and login based on patient name and password. While the server is running, the client (patient) can start a session from anywhere in the Internet by accessing the server s connection port and providing a proper log in name and password. The entire system web site is written in ASP Steps involved in Implementation The following are the steps involved in collecting physiological signals from sensors and viewed in the web browser for monitoring.

22 108 Connecting the base station (MIB520 gateway) with USB interface of the computer. Open the MOTE VIEW software. Program the sensor mote. Connect the physiological sensors with the MDA300 sensor Board. The data s are stored in the PostgreSQL database. Using ODBC connectivity the data s are retrieved in the ASP page Database storage in PostgreSQL In the PostgreSQL the data s are stored in the table format. The following are steps involved in viewing the table. To open the PostgreSQL command prompt. File->PostgreSQL->template-1 In the command Prompt then change the template directory into task #template-1 \c task tele Where task is the database name and tele is the user name. To display the tables in the command prompt # task \d To view the corresponding tables in the database # task select * from mda300_results; Using ODBC Connectivity retrieving data into Webpage The following are the steps involved in ODBC connectivity, Select Start -> Settings -> tools->data Source. Control Panel -> Administrative

23 109 In the Data Source -> User DSN tab select ADD -> PostgreSQL. Now the postgresql driver window is opened. Fill the following details in it Server localhost Database task Username tel. Password- tiny Then Click the Save button. Now the Driver is created. Using the ASP code we are establishing connection and data s are viewed in the webpage. In our implementation, we are able to connect two disparate systems, that is, the patient record database and the web portal, through the use of well-defined web services. The web-based information portal is an effective emergency response information system to support the need for multiple parties to share the information about patients' status and locations. Our web-based information portal allows different types of user to access patient information in real time. When a users logs in, the information displayed to that particular user is managed by group-level permissions. The portal has three groups of users: 1. Caretakers of the Patients who need to send queries to the doctors and view the doctor's replies and message. Figures 3.17 and 3.18 show the screen shots of a patient s login and his physiological information that can be accessed by the caretakers through secured web services. Here the caretakers can login for the patients through the patient s login, to view the patient s physiological information to closely monitor post-operative patients.

24 Medical specialists, often located at distant facilities, may be called on to give treatment instructions to the medics at the scene. They login to view the real-time medical data of the patients being treated. Figures 3.19, 3.20 and 3.21 show the screen shots of a doctor s login details, list of doctors and their corresponding details of their patients respectively. Here, the medical specialists can login through the doctor s login to view their respective patient s real time health status and alert the caretakers near the patients. 3. Emergency personnel have full rights to access all data in the system. Emergency department personnel login to the portal to retrieve information about the patients who are being transported to their hospital. 3.6 RESULTS AND DISCUSSION The proposed system was tested using an ECG simulator for ECG signals and varying DC voltage source for heart rate, and body temperature in abnormal conditions. In normal conditions, the proposed system was tested using volunteers. The results show that the proposed system is capable of continuously monitoring / logging patients daily activities. Table 3.2 gives the comparison of functional capability of proposed techniques with the other techniques reported in the literature. In general, the Bluetooth, and Wi-Fi are intended for WPAN (about 10m) and WLAN (about 100m) communication respectively, while proposed Wireless Sensor Networks is oriented to WPAN (about 250m). Bluetooth uses frequency hopping (FHSS) with 79 channels and 1 MHz bandwidth and Wi-Fi uses DSSS (802.11), complementary code keying (CCK, b), or OFDM modulation (802.11a/g) with 14 RF channels and 22 MHz bandwidth

25 111 Figure 3.17 Monitoring Through Secured Web Server Patient s Login

26 112 Figure 3.18 Monitoring Through Secured Web Server Details of Patient

27 113 Figure 3.19 Monitoring Through Secured Web Server Doctors Login

28 114 Figure 3.20 Monitoring Through Secured Web Server List of Doctors

29 115 Figure 3.21 Monitoring through Secured Web Server Dr. Aravind s Patients details

30 116 Table 3.2 Comparison of Functional Capability of Proposed Technique with Existing Techniques for Monitoring of Post-operative Patients at Hospital Parameters Using Bluetooth (Khoor et al 2001) Using Wi-Fi (Tejero- Calado et al 2005 ) Range 5-6m 100m 250 m Data Rate 57.6kbps 11 Mbps 250kbps Channels bandwidth Alert Through Alert SMS and through 79 channels with 1 MHz 14 channels with 22 MHz No No Yes No No Yes Analysis Off-line On-line On-line Using WSN (Proposed in this thesis) 16 channels with 2 MHz while the proposed Wireless Sensor Networks uses direct sequence spread spectrum (DSSS) with 16 channels and 2 MHz bandwidth.. Bluetooth and Wireless Sensor Networks are intended for portable products, short ranges and limited battery power. Bluetooth transceivers are designed as low power consumption devices but there are technologies as Wireless sensor networks which are designed to be ultra low power consumption technology. The proposed technique is found to be better in most of the cases. In the case of data rate, 250Kbps is sufficient to communicate the information as we are using data aggregation techniques explained in Chapter 4.

31 117 The proposed system has additional advantages of alerting caretakers at nearby the patients, physicians, and emergency department personnel s in hospitals through and short message service when anomaly is detected when compared to the earlier system.this system facilitates communication among patients, medical professionals in local hospitals and specialists available for consultation from distant places through a secured web server. The most valued features of this system are to prevent the patient from re-hospitalisation and to avoid possible critical events, thus reducing global healthcare cost 3.7 SUMMARY OF CONTRIBUTIONS In this chapter the great potential of the proposed system in addressing problems in today's emergency response system, especially those recovering from surgery, is well demonstrated. Key activities that could be improved using the proposed technology are continuous patient monitoring, patient record generation, and remote review and alerts over and Short Message Service (SMS) to medical specialists in hospitals and caretakers nearby, when an anomaly is detected. This system implements the concepts of `care at the point of need' in cooperative environments to provide continuity of patient care through the simple and secured web, and ensures the privacy and confidentiality of the patients.