Wireless ECG Monitoring System Project Report
Contents
1. 9 Figure 5 Patient unit and the wireless receiver connected to a PC 6 ececcceesseeeteeeseeeeeeesees 10 Figure 6 The base recorder of ADAS 2 4 ec secststesneasyecaicsh ant ceissaitbaastiviatensavaienereusuteniiienss 11 Figure 7 Components of the Biomedical Wireless and Ambulatory Telemetry for Crew Health eae epee etter ce teehee ac tn Serica tae re ee sacl ate he ae oR E la hse ceeds 11 Figure 8 The patient transceiver sensor unit and monitor transceiver receiver unit of the LifeSyne Wireless ECG System Uw ccuvicksducnensssa aves atedaeds amotio snann 12 Figure 10 a Indicates the final prototype of the circuit major active components include INA 126p a microcontroller MSP430 Taxes Instrument Inc the Bluetooth module numeric LCD D A converter serial port RS232 and a 3 7V battery b Indicates the final case design for the Wireless ECG system Input includes three electrodes negative positive and ground where as the outputs include RS232 and analog line out A USB port allows battery recharging The front panel also features on off switches for the device and Bluetooth as well as indicative LEDs for power and Bluetooth ccccccccsccccceeesssseeeteees 22 Figure 14 Graphical User Interface for Wireless ECG Monitoring System ceceseeseeneees 28 Figure 15 Cost of Wireless ECG Monitoring System Vs Other Currently Marketed ECG TY SENS ch Sasha As Ne te Naa aaa Sa Tae Soh ae dS a e2. 12 Frequency M P Displ Biomonitor Model SASS A APACER SE Display Size Response s Type 3 ange Numerical AT 33 Single Channel Seru EMG LED Light 0 5inchhigh 25 425 Hz EMG Bar ECG Heart Rate Numerical amp LifePAK 1 i 25x4 7 0 05 u i Temperature and BP Graphical PORE OOP LOTE 9 inches GE Marquette Eagle ECG Temperature f dia ll hical gonally BE 3000 SpO gt Graphica 0 05 100 Hz Criticare Scholar EL Heart Rate ECG BE Acie Color 0 05 100 Hz Impedance Respiration 121 x91 mm LCD Temperature SpO Schiller Cardiovit 2 AT101 3 Channel ECG ECG Graphical 7 6 x 5 7 cm 0 150 Hz PIN ECG BP ETCO Temp N ical i MiniMax 4000 cS Coa Tep Me ae 5 6 4 inches high 0 5 40 Hz SpO2 Graphical Table 1 Specifications of bedside monitors commonly used in hospitals 4 SPECIFICATIONS FOR WIRELESS BIOMONITOR SYSTEM 4 1 SPECIFICATIONS FOR WIRELESS ELECTRODE MODULE REQUIRED AND DESIRED The primary objective of this design project is to build a device capable of eliminating the need for lead wires to monitor the cardiac activity of a subject using standard bedside electrocardiographs such as General Electric s Marquette Eagle 3000 or portable biomonitors such as NASA s Ambulatory Data Acquisition System 2 This means that the system will be required to have specifications that can encompass such ECG monitoring systems 13 The integrity of the signal w
3. 2192 2195 Narayanaswamy S 2002 High Resolution EKG Indian Pacing and Electrophysiology Journal 22 51 56 Nauwer M Comi G Emerson R Fuglsang Frederiksen A Guerit J Hinrichs H Ikeda A Luccas J Rappellsburger P 1998 IFCN standards for digital recordings of clinical EEG Electroencephalography and clinical Neurophysiology 106 259 261 NASA STD 3000 Vol I Redfern M Hughes R Chaffin D 1993 High pass filtering to remove electrocardiographic interference from torso EMG recordings Journal of Clinical Biomechanics 8 44 8 Schmidt N R Mobile Sleep Diagnostic Devices for Testing Around the World Cleveland Medical Devices INC Cleveland Shubhodeep R C Harshal B N Sahambi J S 2005 Design and Development of a Novel EOG Biopotential Amplifier International Journal of bioelectromagnetism 7 271 274 32 31 32 33 34 35 The design and improvement of eye controlled interface http cs sunysb edu vislab projects eye Reports report index html Retrieved on November 13 2007 5 33 pm Though Technology Ltd 2003 FlexInfiniti Hardware Manual UltraView Telemetry www spacelab com Retrieved on December 20 2007 9 45 pm Wireless Sensor Networks for Medical Care http www eecs harvard edu mdw proj codeblue Retrieved on November 1 2007 11 45 am APPENDIX Attachments GANTT CHART OF TIMELINE TABLE OF ACTIVITIES BUDGET C AND ASSEMBLY CODE FILES FOR MICROCONTROLLER MA
4. data transmitted to the computer bedside monitors or NASA biomonitors via different interfaces Bluetooth RS232 analog line out The electrocardiograph display of the system would use a Graphical User Interface to show the name of the patient or patient ID alongside his her heart rate It will also incorporate an alarm that can be triggered in cases of abnormal heart rates below 60 bpm or above 100 bpm 5 6 USER INTERFACE MATLAB is used to further analyze the acquired ECG biopotentials on a PC by decoding the digital signal received from Bluetooth Real time ECG signals can be acquired in MATLAB using 3 different interfaces serial port RS232 wireless Bluetooth or DAQ card analog line Every time the MATLAB program is debugged two dat files are created for the patient one that stores the ECG data and another that stores the heart rate The graphical user interface GUI allows the users to identify patient ID and select bandpass filters as required GUI is also programmed to warn users if the heart rate rises above or drops to critical levels The graphical user is implemented to start or stop data acquisition without unplugging the device the corresponding dat files are updated accordingly while keeping the record of previous acquisitions Therefore the cardiac activity of a subject can be recalled by uploading previously recorded ECG data 21 D A MSP430 a Bluethooth LE b Figure 10 a I
5. ion battery that is recharged with a USB cable hence eliminating the need for connecting the device to in wall electrical outlets 25 7 DEVIATIONS FROM SPECIFICATIONS During the course of our project we have had to deviate from the originally proposed device specifications to improve performance in the system and also make it much easier to manufacture For instance it was eventually decided that the use of a separate receiver unit was redundant hence our efforts were focused on minimizing the size of the device saving more power and adding more channels to our acquisition unit which is time and cost effective Some of the features planned for the receiver unit such as a numerical LCD for heart rate display were then incorporated in the sensor unit Our modified sensor unit sends ECG data to the PC wirelessly and also incorporates the important features of the receiver unit For instance the modified sensor unit can be recharged via USB OTG and has a battery indicator Furthermore the sensor unit has optional numeric LCD display to show the instantaneous heart rate of the user Sensor unit has digital as well as analog output Digital data is transferred wirelessly or through RS232 port which directly connects to the computer and the analog data can be transfer through the leads 8 SYSTEM SET UP 8 1 HARDWARE The key hardware requirements for the ECG circuit are The circuit must be capable of operating from a supply of 2 7v t
6. it back to the INA126p The feedback allows the INA126P to maintain a constant DC level at the output regardless of the change in skin contact resistance When sensor unit is fabricated four expansion connector should be made available three for electrode input and one for Rs232 output In addition no component should extend out from sensor units Computer or other monitors with Bluetooth compatibility is required to display the ECG waveform 8 2 SOFTWARE Hardware of the device requires appropriate software to digitize the resulting ECG signal at sufficiently high rate filter and transmit it via Bluetooth to the receiver unit in our case it is computer Software to program microcontroller MSP430FG439 and to apply digital filtering was written in C using IAR Embedded Workbench Kickstart edition All the essential source code files are provided in the appendix Signal must be sampled at a rate no lesser than 512Hz Since the fastest deflection in the ECG is in the 20 ms range and happens at the QRS complex It is important to capture the entire QRS complex for useful medical evaluation of the ECG waveform Having a sampling frequency of 512 Hz or sampling period of approximately 2 ms captures at least 10 samples at the QRS complex and ensures that the QRS complex is fully digitized In addition MATLAB is another software required to display the Bluetooth transmitted signal in the monitors This software is computable to read the sig
7. of good monitoring quality Moreover the Power Spectral Density PSD of this signal used here to analyze the frequency content of the signal shows that signals below 2Hz and above 30 Hz have very small magnitudes hence proving that these frquencies are nearly absent in the signal In fact as shown in figure 2b the maximal magnitude signals in the desired range of frequencies is 0 0003288 V at 2 Hz frequency marker 1 in figure 12a whereas the maximum amplitude of signal in the spectrum of frequencies considered noise to our system is 6 044e 09 V occuring at 30Hz marker 2 in figure 12b These maxima can be used to estimate the signal to noise ratio of our system using equation 1 SNR 20 log Asignai Angige SNR 20 log 0 0003288 V 6 044e 09 V SNR 94 7 dB This signal to noise ratio therefore satisfies our requirement of 65dB Hence we can confidently assert that the system satisfies its primary goal of aquiring and wirelessly transmitting clean monitoring mode quality ECG signals Figure 12 a Waveform plot of ECG signal transmitted via Bluetooth b Power Spectral Density PSD of wirelessly transmitted signals showing frequency content of those signals generated using SPTool Spectrum Viewer in MATLAB 24 6 2 TRANSMISSION As we compare ECG signals Figure 3 wireless transmitted via Blluetooth from two different distances 8 m and 12 m we can see that the effectiveness of the system in acq
8. 31 18 19 20 21 22 23 24 25 26 27 28 29 30 Delsys Inc 2004 Myomonitor I User Manual EKG Monitoring System http instruct1 cit cornell edu courses ee476 FinalProjects s2001 j1175 EE476 htm Retrieved on November 27 2007 7 30 pm Fulford Jones T R F Wei G Y Welsh M A portable low power wireless two lead EKG system Engineering in Medicine and Biology Society 2004 Volume 1 Issuel 5 Page s 2141 2144 Vol 3 IMEC realizes wireless flexible and stretchable ECG patch for comfortable cardiac monitoring http www imec be wwwinter mediacenter en ARRM2007_ECGpatch shtml Retrieved on November 11 2007 9 42 pm Kamen G Caldwell GE 1996 Physiology and interpretation of the electromyogram Journal of Clinical Neurophysiology 13 366 84 LifeSync Wireless EKG System http www lifesynccorp com products wireless system html Retrieved on November 30 2007 11 20 am Measuring the ECG signal with a mixed analog digital application specific IC integrated circuit HP Component Monitoring System technical http findarticles com p articles mi_mOHPJ is_n4_v42 ai_11398513 print Retrieved on December 2 2007 6 00 pm Montgomery K Mundt C Thonier G Tellier A Udoh U Barker V Ricks R Giovangrandi L DaviesP Cagle Y Swain J Hines J Kovacs G Lifeguard A Personal Physiological Monitor For Extreme Environments Institute of Electrical and Electronic Engineers 26
9. 40 g and have length width and thickness such that the devices dimensions are lt 8 x 12 5 x 3 cm We will strive to render this unit as small as possible weight of lt 100 g and dimensions lt 5 x 10 x 2 cm are desired goals Other required and desired design specifications include requirements for power supply battery life for continuous operation of the wireless electrode module input unit operating temperature current discharge rate maximum allowable leakage current As specified by NASA standards for portable biomonitors etc The design requirements for these specifications are listed in Table 2 14 Parameter Required Desired Remarks Most i tential Measured Parameters ECG EMG EEG as Se piopetenbialsmneasuiee by biomonitors The voltage amplitude of ECG signal is l imately 5mV th litud Signal to noise Ratio 60 dB 100 dB PESA E f aed i a of any noise present in the filtered signal is required to be lt 5 uV before gain Sensor and receiver units are not expected to be distant gt 10m from one Wireless another in a hospital setup When patient att 10m 100 m Transmission Range is mobile portable receiver will serve as continuous monitoring system for biopotentials Battery Life gt 8 Hrs gt 12 Hrs Long battery life will reduce need to continuous interrupt patient monitoring This unit is required to be lighter than the Weight lt 240 g lt 100g Patient Transceiver unit of the LifeSync Wire
10. City College of New York The City College of New York The City University of New York CUNY Biomedical Engineering Senior Design I Wireless ECG Monitoring System Project Report Coordinators Prof Marom Bikson Prof Luis Cardoso Teaching Assistant Gaurav Agarwal Sponsor National Aeronautics and Space Administration Project Team Members Mohamed Osman Ndongo Khouma Sadia Abbasi Atia Syed Mizanur Rahman Neranjan Da Silva 1 2 3 4 TABLE OF CONTENTS INTRODUCTION ccccccscssscssssssscsssvsvssssssscsssvsees Error Bookmark not defined PRIOR ARP sscecstessssscnctucscdscsicdeiatancetiecetasscuesedeesecslssssdeancussoses issceugeddstoassadbescasestoossiies 7 2 1___ The Lifeguard Crew Physiological Observation Device CPOD eue 7 De UltraView Lelemeti scstcer cde ineine aas aaa i decal aaa aS 8 2 3___The Myomonitor Wireless EMG Systemiisiv asccseestssticus teers ssciisuieesansussseulassitasss 9 2 4___Crystal Monitor 20 B sessssensessesensseersesresseersernerreerserrerrterserntrrterreereereenreenrerennnee 9 2 5___ Ambulatory Data Acquisition System sesessessessenrserrerrrerreertrsterreerenrrrrrerrernes 10 2 6___ Biomedical Wireless and Ambulatory Telemetry for Crew Health BioWatch 11 27 date syne Wireless ECG System ccscectuts secd ssa suwtectendiis sdanteweanisbalities ctbauniaadustal tusdoa saute 11 2 8__ Hospital bedside MONItOTS sssesseseenseersessnssenrserrrrsrereenenrtnrs
11. TLAB CODE FILES FOR GUI AND SYSTEM SETUP 33
12. ac activity of astronauts or hospital patients an even narrower bandpass of 2 to 30 Hz is used to limit the possibility of getting artifacts in the waveforms during routine cardiac rhythm monitoring As mentioned above digital FIR low pass high pass amd notch filters are used to rid the ECG of unwanted signals The effectiveness of these filters can be readily verified through the real time plotting and comparison of unfiltered signals Figure 1a measured directly from the output of the INA and ignals outputed by the digital to analog converter of the microcontroller following filtering Figure 1b The two waveforms visibly differ in amplitude as the unfiltered signal is only amplified by the instrumentation amplifier while an extra gain of 200x is applied to the signal by the internal opamps of the MSP430 Furthermore we can see that the filtered ECG signal is rid of most of the artifacts that can be seen in the other signal a b Figure 11 ECG waveforms a Unfiltered ECG acquired from the acquisition circuit INA 126 b Analog output after digital filtration using MSP430 23 The system s digital filters have for goal to clean up the signal such that the required signal to noise ratio 65dB for the wirelessly transmitted signal is achieved Figure la is a plot of the waveform of an ECG signal transmitted to the computer and plotted real time using MATLAB We can see that even the wirelessly transmitted ECG is
13. all very low weight system i e patient transceiver has dimensions of 8 x 12 5 x 3 cm and weight of 240 g that allows its users more freedom of movement without jeopardizing continuity of ECG monitoring It also eliminates the need for detaching and reattaching lead wires when a patient needs to be transported 11 The absence of heavy obstructing cables also reduces the amount of noise that interferes with the signal displayed on the monitor as a waveform Patient Transceiver with rechargable battery Monitor Transceiver Patient Transceiver Figure 8 The patient transceiver sensor unit and monitor transceiver receiver unit of the LifeSync Wireless ECG System 11 3 7 HOSPITAL BEDSIDE MONITORS In addition to these biomonitors used for acquisition and processing of several different physiological parameters there exist a variety of other monitors most often used in hospitals to monitor the health status of patients One of the distinct features of these monitors is their usually bulky sizes making them bedside appliances rather than portable ones as they are sometimes marketed to be These monitors offer a range of different options for parameters measured and their specifications Table 1 below presents a sample of bedside monitors used to measure different physiological parameters The specifications must be thoroughly considered and constitute one of the basis for the minimum required specifications for the system proposed here
14. arameters notably bedside ECG monitors wireless capable computers and portable ECG monitors thus allowing a patient s vital signs to be kept track of at all times despite his her proximity to a bedside monitor This device will also be designed to be used by NASA as an adaptor for their physiological monitoring systems that make use of telemetry to acquire biopotentials This allows the continuous monitoring of the patient s vital signs despite his her proximity to a bedside monitor Together with its wireless capabilities this biomonitor system will have to meet several design specifications including NASA s technical standards for portable bioinstrumentation to ensure safety and functionality Hence this device will be battery powered double insulated and isolated from the ground to keep it from constituting an electrical hazard to the astronaut or the spacecraft The device susceptibility to electromagnetic interference will be minimized to produce more accurate signals Audio and visual alarms will be also be implemented into the device recorder receiver unit in order to warn the user when a measured parameter reaches a critical level Furthermore the extruded plastic casing will also make this device robust enough to be worn during physical activities such as exercise or research tasks This project primarily pertains to the development of a wireless monitoring system for ECG However the techniques and design concepts used in the devel
15. ast three different types of 3x UHF female 9 x UHF female interfaces are required to allow Output Leads bh ort ort analog transmission of output to Interface P P f f bedside monitor biomonitor and Serial USB USB PC simultaneously as needed Wireless Not Required Bluetooth Displa Numeral Lop Craphicaland sr vals suchas heart Spa oes Numerical LCD Perea a tear rate 17 NASA technical standards Rechargeable Rechargeable requires the use of batteries with Power Supply battery with less battery with less potential less than 30 V DC for than 30V capacity than 5V capacity bioinstrumentations NASA STD 3000 Vol I Section 6 4 3 13 L i Battery Life gt 8 Hrs gt 12 Hrs ee Pallet a T oe ie to interrupt patient monitoring Multiple options fi hargi Battery Charging Method USB OTG Solar Cells i E Ta esd increase functionality Weight of the receiver is required Weight lt 960 g lt 400 g to be less than four times 4x the weight of the sensor unit Dimensions Antenna amp wires not included lt 32x50x 12cm lt 8x12 5x3cm Receiver is required to be less than four times 4x bigger than sensor unit Values as required by NASA Max Leakage Current 0 070 mA 0 070 mA technical standards NASA STD 3000 Vol I meless T a rel A Wireless ransmission None Specified 2 4 GHz Wire ess transmission from Freq Bandwidth receiver is optional Range must include both Op
16. ch adds more weight devices and wires to the subject oo gt C gt a J 5 2 og CE z q aE CleveMed a Figure 5 Patient unit and the wireless receiver connected to a PC 6 3 4 AMBULATORY DATA ACQUISITION SYSTEM The Ambulatory Data Acquisition System ADAS is composed of the recorder base Fig 5 and the signal input module The recorder base acquires signals from twelve sensors through the signal input module These twelve sensors are EKG EEG EMG EOG EGG body position limb position heart rate blood pressure skin temperature respiration and skin conductance level After the sensors pick physiological signals they are processed displayed saved and transmitted to a HRF portable computer PC which allow the users to setup the recorder base and view the signals 8 The ADAS has a 32 bit processor It has the ability to record signals with very small amplitudes 0 125 mV and differentiated analog signals from 62 5mV to 62 5 mV Delsys Inc 2004 In order to have a continuous monitoring of the astronaut s health the astronaut has to wear the base recorder the whole time that weights approximately 1 Kg Delsys Inc 2004 Also the base recorder will be connected to the electrodes via wires that may reduce the astronaut s freedom of motion 10 a a jg i KT a Figure 6 The base recorder of ADAS 2 3 5 BIOMEDICAL WIRELESS AND AMBULATORY TELEMETRY FOR CREW HEALTH Zin Medical
17. dy existing bedside or diagnostic ECG monitors and NASA biomonitors The aim of the wireless adapter feature is for this ECG system to eliminate the need of lead wires and cables to transmit acquired ECG signals to biomonitors and other ECG also EMG and EEG monitors This system takes the input from the patient convert it in digital form filters it convert it back to analog and the output of this converter is inputted in a class II Bluetooth module which then wirelessly transmits the data to a computer NASA biomonitors or other wireless capable bedside ECG monitors The designed Wireless ECG Monitoring System incorporates the following features Bluetooth transmission On Off switch with indicative LED Numerical LCD optional Rechargeable battery Analog output Digital output RS232 Separate switch for Bluetooth unit Battery life indicator The operating principles of the device can be summarized as follows 5 1 INPUT The input consists of three electrodes attached to a patient s chest or arms as indicated in figure 9 These electrodes detect electrical waves generated by the heart tissues such as the sinoatrial node while causing the heart to pump 5 2 ANALOG FRONT END AMPLIFICATION The acquired electrical waves are then differentiated and amplified using a traditional instrumentation amplifier like the INA126p from Texas Instruments Inc that is used here Figure 9 step 1 A fixed gain of approximately 5x is applied t
18. e monitors thus it is required to be a BNC port or similar A USB port is also required to 16 directly connect the receiver to a PC Finally in order to be attached to biomonitors with standard 3 lead ECG systems three round female UHF ports positive negative and reference will be used However in the case where the user is constantly mobile or at a considerable distance away from any bedside monitor or computer numerical measured values heart rate can be displayed on the receiver s LCD A graphical and numerical LCD is desired to allow simultaneous display of waveforms and numerical data on the receiver The receiver unit will be powered using a rechargeable battery with a voltage of lt 30 V to adhere to NASA s technical standard for battery selection This battery will be expected to power the Parameter Required Desired Justification receiver for at least 8 hrs 12 hrs desired of c ontinuous operation Most common biopotentials Measured Parameters ECG EMG EEG measured The voltage amplitude of ECG signal is approximately SmV the litude of i Signal to noise Ratio 60 dB 100 dB S S P A ae present in the filtered signal is required to be lt 5 uV before gain Wireless T eee Bluetooth transmission is a ir ransmissio ee Not required 10 to 100 m desired feature for PC wireless Range interface Cable 1xBNC output port 3xBNC output consent poris Or guna At le
19. ed for the development of our wireless ECG system will be further modified to encompass several different biopotentials such as EMG EEG and oxygen saturation in hemoglobin Hence the Wireless ECG Monitoring System is a stepping stone for the development of a Multi parameter Wireless Biomonitor REFERENCES AD instruments EOG http www adinstruments com applications research EOG Retrieved on November 27 2007 10 00 pm Ambulatory Data Acquisition System ADAS https hrf jsc nasa gov hardware adas asp Retrieved on November 22 1 33 pm BioWatch http www nasa gov centers glenn research med_topic_biowatch html Retrieved on December 2 2007 12 22 am Carsten W Kevin M Usen U ValerieB Guillaume T Arnaud T Robert R Robert B Yvonne C Nathalie C Stephen R Judith S John H Gregory K 2005 A Multiparameter Wearable Physiologic Monitoring System for Space and Terrestrial Applications Institute of Electrical and Electronic Engineers 9 382 391 Clancy E A Morin E L Merletti R 2002 Sampling noise reduction and amplitude estimation issues in surface electromyography Journal of Electromyography and Kinesiology 12 1 16 Compact Wireless Biometric Real Time Processing System ZIN MEDICAL CPOD http www nasa gov images content 57585main_lifeguard1_portal jpg Retrieved on November 17 2007 11 02 am Crystal monitor B 2 http www clevemed com pdfs Mobile_Sleep_Diagnostic_Devices 20Intl pdf
20. erating Temperature 20 to 42 C 20 to75 C expected room temperature and skin temperature Table 3 Specifications Table for Sensor Unit In addition to the aforementioned specifications some other design considerations such as safety issues ergonomics and the performance under anticipated environment are also important for both the sensor and the receiver unit Since the main users of this device are astronauts NASA safety standards will serve as foundation for the safety considerations for our device According to these standards require a maximum leakage current of 0 070 mA in bioinstruments Furthermore in order to ensure patient safety the device should be double insulated and separated from ground Hence in the worst case scenario of total device failure no electrical 18 threat will be posed to the user In addition to this the ECG Monitoring System should be resistant to electromagnetic interference and produce minimum electromagnetic interference on its own A simple user interface will make sure that a single person can operate the system without any help thus adding to the device s user friendliness and Finally our device should be robust enough to withstand and perform well under harsh spatial environments 5 PRINCIPLE OF OPERATION In this design project we fabricated a wireless ECG system This device is designed to serve both as a stand alone heart rate monitor and as a wireless adapter for the alrea
21. et oe 29 TABLES Table 1 Specifications of bedside monitors commonly used in hospitals 0 eeeeseeeeeeeteee 13 Table 2 Specifications Table for Sensor Uniit ic ccscesisciesesssecsssssaueasesadvacscatonecsevotesnsdasanenaeaassancns 16 Table 4 Specifications Table for Sensor Unit s s cs 0sacasseccssstciacasansseassardsaassaevacespansnacivaessiasdanscea 18 Table 5 Comparative Cost Table For Commonly used ECG Monitoring Systems 29 1 ABSTRACT 2 INTRODUCTION The monitoring of vital physiological signals has proven to be one of the most efficient ways for continuous and remote tracking of the health status of patients Electrocardiogram monitors are often used in many medical service centers and hospitals to diagnose and monitor a person s health status by measuring their cardiac activity An ECG is a noninvasive monitor which can be utilized to evaluate the heart electrical activity measure the rate and regularity of heartbeats the position of the chambers identify any damage to the heart and investigate the effect of drugs and devices used to regulate the heart This procedure is very useful for monitoring people with or susceptible to impairments in their cardiac activity In addition during surgical procedures the electroencephalogram EEG is measured along with his her ECG to track the consciousness level of a patient during anesthesia 7 Other physiological parameters such as oxygen saturation in hemogl
22. from certain motions e AN e Figure 3 UltraView Telemetry 22 3 3 THE MYOMONITOR WIRELESS EMG SYSTEM This is another device used to specifically monitor muscle activity using a wireless EMG sensor The device is composed of two units with the first one consisting of the wireless EMG sensor module Fig 3 which acquires the signals from the input module connected to the EMG electrodes via lead wires and transmits them to the second unit the Myomonitor Datalogger This second unit is used for the display and storage of measured data 6 The Myomonitor detects EMG signals optimally at the skin surface thus reducing the introduction of noise and artifacts in the EMG signals Figure 4 The Myomonitor wireless EMG module connected to the input module 7 3 4 CRYSTAL MONITOR 20 B This device is designed primarily to monitor patients for any sleep disorder breathing SDB The patient unit is a small hand held device worn or carried by the patient Fig 4 This unit contains channels for up to ten sensing modules EKG EEG chin and leg EMG pulse Oxymeter airflow snore thoracic and abdominal effort and body position sensors It transmits the data wirelessly to a receiver that displays and stores the data on a PC Schmidt The patient unit does not have any external antenna which decreases its size An SD memory card is used to store patient s data It functions as a mediator between the receiver and the sensors whi
23. hile it is wirelessly transmitted to the receiver or relayed to an electrocardiograph via input cables is a very important aspect of this system It is important that a physician or astronaut using continuous ECG monitoring be able to objectively notice variations in a subject health status based on the trends of the waveform of the signal Moreover a distorted signal can cause erroneous medical diagnostic or inaccuracy of measured values e g heart rate For this reason the wireless biomonitoring system must have a signal to noise ratio SNR deemed acceptable for ECG signals and possibly for other types of signals Since the voltage amplitude of non amplified ECG can be approximated to 5mV 12 we require that the maximum amplitude of any noise present in the filtered signal to be 5 uV or less gain is not incorporated here Hence the required SNR for the sensor node is given as SNR 20 log Asignat Anoise 65 dB Equation I SNR 20 log 5000 uV 5 uV 60 dB In order to optimize the performance of the signal acquisition system the desired SNR will be set at 100 dB This will allow our system to also accommodate the needs of other biopotentials as far as the strength of the desired signals compared to the undesired ones The dimensions and weight requirements of our proposed system should demonstrate added value on the dimensions and weight of the LifeSync Wireless ECG System As such our sensor node is required to weight less than 2
24. iopotentials are being measured First of all most of these systems receive power from an electrical outlet and are heavy enough to require wheeling to be displaced making casual movements or urgent transportation of patients from one location to another very difficult 24 thus resulting in patients being mostly confined to their beds while in a hospital Moreover besides limiting the freedom of mobility of the subjects the wires used to connect electrodes and the recorder often constitute a source of noise to the acquisition system 4 And although such stationary conditions might be acceptable in the case of a bed ridden patient it cannot be used for astronauts who are required to constantly move by their activities during space flights The alternative commercially available biomonitoring devices which can be used under severe non stationary conditions such as athletic scientific studies are very limited and prove to be costly These devices are also usually uncomfortable due to their heavy weight vigorous structure and network of lead cables running from subject to monitor The goal of our project is to design and fabricate a wireless biomonitor to help eliminate the restrictions caused by lead wires in conventional systems used in hospitals or by NASA by permitting the acquisition and wireless transmission of a signal from sensor to recorder In hospitals our device would readily be adaptable to any system used to monitor physiological p
25. less ECG System Dimensions antenna wires amp electrodes not included lt 8x 12 5 x 3 cm lt 5x 10x2 cm This unit is required to have dimensions less than the patient transceiver unit of the LifeSync Wireless ECG System NASA technical standards requires the Rech l Paver Sinai Battery with less aoe ce use of batteries with potential less than pea a than 30V capacity a oes acit 30 V DC for bioinstrumentations NASA Pac Y STD 3000 Vol I Section 6 4 3 13 Max Leakage Values as required by NASA technical 0 070 mA lt 0 070 mA Current Si standards NASA STD 3000 Vol I Range must include both expected room Operating temperature and skin temperature Also 20 to 42 20 to 75 Temperature S i RTS takes into account burn hazard NASA STD 3000 Vol I Wirel ss Depends on wireless transmission Transmission Freq None Specified method used e g Bluetooth 2 4 GHz 15 Bandwidth None Specified Length of Electrode Electrode wires can have different lengths but the longest one should be lt 1 lt 0 20 Wires j i9 shorter than the average distance from the left to the right forearms Electrode patches should be fully Electrode U E ue eit a gt 8 Hrs gt 12 Hrs functional for as long as or more the continuous power source can last Reusable Reusable electrodes will optimize device Electrode Reusability Not Required electrodes cost effectivene
26. nal from the serial port and soundcard of the computer In order to avoid any possible destruction caused by other wireless device around area of use this device should be paired with desired display monitor Transmission of each data packet should occur regularly and no more frequently than once every 0 5 second A graphical user interface GUI is created using this software which will allow the user to choose desired filter for the signal and acquire the patents history through the patient id system A block diagram of the GUI is shown below in figure 27 ECG WAVEFROM OF PATIENT Sadia CCNY BME Wireless Biomonitor 30 Apr 2008 Heart Rate Bpm 79 Figure 14 Graphical User Interface for Wireless ECG Monitoring System 9 COST ANALYSIS AND MAINTENANCE 9 1 DESIGN AND FABRICATION COST OF PROTOTYPE The main focus of this project was to manufacture a cost effective and portable biomonitor which would be used on astronauts to measure their physiological parameters throughout their perilous and long journey to outer space The project was fully funded by the sponsors National Aeronautics and Space Administration NASA and a total amount of 2000 was allocated for the duration of the project Deviating from the initial objective of creating a lightweight and cost effective Biomonitor that functioned both efficiently and accurately in comparison to the biomonitors available out in the market the NASA biomonitor team was successful in c
27. ndicates the final prototype of the circuit major active components include INA 126p a microcontroller MSP430 Taxes Instrument Inc the Bluetooth module numeric LCD D A converter serial port RS232 and a 3 7V battery b Indicates the final case design for the Wireless ECG system Input includes three electrodes negative positive and ground where as the outputs include RS232 and analog line out A USB port allows battery recharging The front panel also features on off switches for the device and Bluetooth as well as indicative LEDs for power and Bluetooth 6 SYSTEM PERFORMANCE EVALUATION Different aspects of the device must be evaluated for performance and concurrence with the aforementioned system specifications The most significant device performance considerations 22 are filtering transmission weight and dimensions battery performance and durability user friendliness as well as cost effectiveness The cost analysis of the device will be done further in this report 6 1 FILTERING The most common settings for modern ECG systems for filtering are monitor mode and diagnostic mode For the monitor mode the bandpass for allowed frequencies ranges from 0 5 or 1 Hz to 40 Hz www wikipedia org Filters in diagnostic mode Eg systems have a broader bandpass to avoid filtering out vital parts of the signal that could be used to diagnose cardiac abnormalities Since the main purpose of our system is to simply monitor the cardi
28. o 3 7V The circuit will be powered by a 3 7V Li ion battery Circuit also contains rechargeable circuit which will allow user to recharge the battery through mini USB port Bluetooth circuit will share power from the sensor circuit which will minimize the size of device by avoiding having two batteries one for each parts Cardiac tissue is not capable of generating signals which are grater then Smv in magnitude As a result circuit must provide adequate amplification of signals which are in range of 5 0mv to 5 0mv Signal acquired from the electrode passes through an instrumentation amplifier INA126p to amplify the signal in a factor of 5 The ECG signal at the output of INA126p is further amplified by on of the three integrated operational amplifier in the MSP430FG439 This operational amplifier contain 1Mohm feedback resistor in parallel with a 4 7nF capacitor which provides a high frequency roll off at about 250 Hz and serves as an anti aliasing filter Because of the large amplification factor the output is sensitive to the variation in electrode to skin contact resistance This result in a variation of the de content of the amplified 26 differential signal and manifests itself as a drift in the baseline of the ECG which often causes wavy traces on EKG signal This issue is managed by using an analog integrator scheme designed with OA1 in MSP430FG439 The integrator integrates the dc content of the 5X amplified ECG and feeds
29. o the signal using the INA The 19 signal will be further amplified to render it usable for heart rate detection during signal processing as the electrical waves derived from the electrodes have a typical peak to peak amplitude of ImV or less 5 3 SIGNAL PROCESSING The differentiated and amplified signal is conditioned using a microcontroller MSP430FG439 from Taxes Instruments Inc The basic functions of the microcontroller are to further amplify digitize and filter the acquired ECG signal The MSP430 digitizes the electrical waves using a 12 bit microprocessor The resulting signal is then filtered to eliminate noise and artifacts The microcontroller incorporates a 17 taps highpass FIR filter with a 2 Hz cutoff a 17 taps lowpass FIR filter with a 30 Hz cutoff and bandstop FIR filter to cut out the s60 Hz AC line Clean signals are then used to calculate the corresponding heart rate of the patient MSP430 is programmed using C and Assembly programming languages to calculate the heart rate and display it on a numeric LCD 5 4 TRANSMISSION To add further value and increase applications the designed system incorporates three different modes of signal transmission Figure 9 step 3 The digitally processed signal output of MSP430 can directly be transferred to the monitoring computer using a serial port interface RS232 however a voltage level shift is required to do so The digital signal is converted back to its analog e
30. obin electromyography and blood pressure similarly provide vital information about the health of a given person when continuously monitored One of the invariable risks associated with space missions are the threats posed by the very harsh spatial environments to the physical and mental health of the astronauts Being exposed to these types of environment for long periods of time has adverse impact on cardiac muscular and neurological functions on astronauts 3 example of reduced gravity high temperatures planet dust particles solar rays etc Fortunately the continuous monitoring of physiological parameters such as electrocardiography electromyography electroencephalography oxygen saturation in hemoglobin and variability of cardiac frequency may provide crucial information for a rapid diagnosis of medical conditions in astronauts preventing the growth of any health condition to proportions susceptible to cause mission failure or even death of a crew member To provide a means to continuously monitor several physiological parameters using just one device a variety of multi parameter monitors or biomonitor systems have been introduced in the past few years with many of them currently used by hospitals researchers and NASA Although these devices are commonly used to detect process and record several physiological signals simultaneously the conventional telemetry system they employ limits the freedom of movement of the subjects whose b
31. of ECG systems that are used The first one is the standard ECG which generally involves twelve or fifteen leads that are connected to the patient s chest arms and right legs through electrodes The device records the ECG signal for almost thirty seconds Eu Possible ailments can be discovered from reading the ECG signal However due to the short time for sampling sporadic abnormalities which mostly occur in the intensive care unit ICU patients may not be discovered In order to address the problem mentioned above continuous electrocardiogram telemetry is used by many hospitals to monitor patients in the ICU This device has three electrodes that acquire ECG signal for an extended period and then the signal is displayed on a screen or printed on an ECG graph paper The Wireless ECG Monitoring System proposed here falls in this second category of ECG devices as it will be used to monitor the cardiac activity of subjects Many ECG machines both standard and continuous are marketed as portable but are not necessarily small and lightweight In addition most such appliances receive power from an electrical outlet and are sufficiently heavy that they must be mounted on a cart and wheeled from one location to the next Wireless devices have the potential to significantly improve this situation by reducing the weight and size of such devices and eliminating the need for power or lead cables The purpose of this project is to design a working pr
32. opment of this system can be used for the development of a multi parameter ECG EEG EMG oxygen saturation etc wireless biomonitor system 3 BACKGROUND Electrocardiography is a medical diagnostic procedure used to record the electrical activity of the heart and display it as a waveform An _ electrocardiogram ECG is obtained by measuring electrical potential between various points of the body using an instrumentation amplifier linked to the body via leads attached to electrodes electrical contacts Electrodes are placed on different sides of the heart to measure the activity of various parts of the heart muscle and the voltage between pairs of these electrodes is what is returned as ECG in the form of a graph A typical ECG tracing of a normal heartbeat or cardiac cycle consists of a P wave a QRS complex and a T wave Figure 1 The baseline voltage of the electrocardiogram is known as the isoelectric line Typically the isoelectric line is measured as the portion of the tracing following the T wave and preceding the next P wave The waveform and the relationship between the different sections composing it can be used to determine heart rate as well as distinguish various cardiac arrhythmias including tachycardia abnormally high cardiac rhythm gt 100 bpm bradycardia an abnormally slow cardiac rhythm lt 60 bpm OT laturval Figure 1 Representative Schematic of Normal ECG wavefom Currently there are two different types
33. ototype of an ECG that acquires the electrocardiograph from astronauts or patients and sends it wirelessly via Bluetooth to a receiver unit such as computers and hospital monitors This device will save time and effort for the nurses who are constantly following the patients conditions and help them to operate more efficiently At the same time the goal of this project is to minimize the cost of the device so hospitals can afford one for every patient especially the ones that are in the ICU In the next section previous ECG devices are introduced as well as their shortcomings 3 PRIOR ART 3 1 THE LIFEGUARD CREW PHYSIOLOGICAL OBSERVATION DEVICE CPOD One of the biomonitors that is used for monitoring astronauts health is Crew Physiological Observation Device CPOD which is composed of 3 units Fig 1 Unit 1 is a small wearable computer which is the central unit This unit analyzes the physiological signals acquired from unit 2 the external sensors Unit 2 is composed of an ECG respiration blood oxygenation SpOz2 and blood pressure sensor All physiological signals are sent wirelessly using Bluetooth from unitl to unit 3 Tablet PC Unit 3 is used to display the physiological signals and store them Unit 3 doesn t only serve as a receiver but it also calculates heart rate and breath rate from the received signals Another feature in unit 3 is that the received and calculated data can be stored on a removable media 5 Des
34. pite the device can be connected to Accutracker II 5 its blood pressure sensor has high motion sensitivity Because signals from the sensors are transmitted to the wearable computer via lead wires the latter can easily constitute an obstacle during motion or can be accidentally disconnected at any time Moreover weak wire connections may cause artifacts or signal acquisition failure Event a 5 64 32 Bution ai Sp02 Sensor ECG Respiration Monin Xpod Sensor Patch 3911 Nexan x Speaker Status and Parameter Cispley esm u ana Glood Pressure Monvor Accutracker i Sa Suntech Ski probe ar amperi ft y ONW OFF Built in Wireless Swifter Transceiver Blueioatn ov 9TEMH2 Tablet PC Figure 2 The Lifeguard Crew Physiological Observation Device CPOD and components 5 3 2 ULTRAVIEW TELEMETRY The UltraView Telemetry unit Fig 2 monitors the physiological signals of heart and SpO through a multi parameter patient worn transmitter The signals are transmitted wirelessly and displayed on any Spacelab monitor 21 One of the advantages of this device is that it allows the monitoring of more than one person at the same time However the UltraView Telemetry lacks other crucial sensors that are vital for monitoring astronauts health such as EEG and EMG Moreover the devices sensors also are connected to multi parameter patient worn transmitter via wires which may obstruct its users
35. quivalent using a D A converter to be wirelessly transmitted to a PC using a class II Bluetooth module To make the system readily adoptable by the bedside hospital monitors traditional telemetry method is also incorporated in the design Thus an analog line out allows to directly transmit data from the device to the PC using a DAQ card Step 3 Transmission using Class IT Bluetooth traditional telemetry options include serial port RS232 and g0gloo line uj Digital Line Out RS232 FA Analog Line Out Processor Acquisition Circuit 12 bit Analog Output N Digital Signal Processing using POFO TI Inc amplificatiRihium E MDARNRAIndicating LED Dalumar pares Step 4 Signal is further analyzed plotted and recorded using MATLAB Step 1 Analog Signal Acquisition and Amplification Figure 9 Block diagram highlights the major principles of operations Step 1 includes the analog acquisition of the ECG biopotential which is differentiated and amplified The output of the instrumentation amplifier INA 126 is then used as an input for the microcontroller MSP430 which digitizes the signal using 12 bit microprocessor The digital signal is filtered and transmitted to PCs via serial port RS232 after a level shift A D A converts the filtered signal back to analog which is then wirelessly transmitted using a class II Bluetooth module 5 5 OUTPUT The output from this system is the
36. reating a lightweight wireless ECG unit 28 that can be used as a substitute to the popular biomonitor for approximately 1 061 11 refer to excel sheet close to half of the projected price DEVICE AVERAGE COSTS 1 Biomedical Wireless and Ambulatory Telemetry 3 500 2 The LifeSync Wireless ECG system 4 000 3 Ambulatory Data Acquisition System 3 000 4 Crystal monitor 1 850 5 LifeGuard CPOD 1 200 6 CCNY NASA Wireless ECG Monitor 1 062 Table 4 Comparative Cost Table For Commonly used ECG Monitoring Systems Projected Average Cost 4 500 4 000 3 500 3 000 2 500 2 000 1 500 1 000 500 0 Cost Device m Projected Average Cost Figure 15 Cost of Wireless ECG Monitoring System Vs Other Currently Marketed ECG Systems 29 9 2 BULK PRODUCTION COST ANALYSIS Several orders were placed over the period of the project from different venders clearly shown in the Excel sheet Due to the ambiguity of the project at hand several components were ordered multiple times and others were replaced due to defects this is reflected in a much higher total expenditure than anticipated The Bluetooth evaluation kit from DIGIKEY was noted to be the most expensive component in the device This can be significantly reduced by replacing Bluetooth with technologies such as ZigBee AM FM Transmission Given the miniature nature of the de
37. rernertenreerreneenrrerrenres 12 SPECIFICATIONS FOR WIRELESS BIOMONITOR SYSTEM 0000 13 3 1___ Specifications for Wireless Electrode Module Required and Desired 13 3 2___ Specifications for the Receiver Unit Required and Desired eeeseeeees 16 DESIGN CONCEPTS seniri a enes soia 18 4 1__General Design Concept assrsreerreenrenrennnen Error Bookmark not defined 4 2 Specific Concepts nonin teas Error Bookmark not defined 4 2L CCONCEDE 0 pictadocatieaddeiac iid ten adia ae Error Bookmark not defined L 22 CONCEDE 2 ridetan a aeaa i viva Error Bookmark not defined 42 3 Concept 3 ven siteriaaslstiv cdeints tiiin Error Bookmark not defined 4 2 4___ Wireless transmission options ooon Error Bookmark not defined DESIGN SELECTION 0ccccsssssssssssssssvsssssssssvcees Error Bookmark not defined BUDGE DA EAT T E T E ES 20 REFERENCES iiss cccsccsstsisccctsctsccsesasscssosessccsosescsecteesscses Error Bookmark not defined LIST OF ILLUSTRATIONS FIGURES Figure 1 Representative Schematic of Normal ECG wavefom cesccsesseeeeeeceteceseeneeeeeeeeees 6 Figure 2 The Lifeguard Crew Physiological Observation Device CPOD and components 5 8 Figure 3 UltraView Telemetry 22 sac coes sts acc pane at sseadtun gu dose clegaedudevuded aevaenas ca deaeeueguneaat auaeseactantes 8 Figure 4 The Myomonitor wireless EMG module connected to the input module 7
38. s Biomedical Wireless and Ambulatory telemetry for Crew Health BioWatch is a light weight 155 to 190g depending on number of channels in use device used to monitor the health status of a subject It can measure EKG EMG EEG EOG blood pressure blood glucose heart rate joint angle oxygen level in blood temperature and acceleration Data acquired by BioWatch is transmitted wirelessly to a PC 9 The BioWatch also uses lead wires to connect electrodes thus the device has to be worn by the subject at all times during physiological monitoring Figure 7 Components of the Biomedical Wireless and Ambulatory Telemetry for Crew Health 2 3 6 LIFESYNC WIRELESS ECG SYSTEM The LifeSyne Wireless ECG System is an innovative method for monitoring a patients ECG without the attachment of any data cable between the electrodes and the monitor This device Fig 9 is composed of a patient transceiver which acquires the biopotential via leads attached to 3 or 12 electrodes placed on the subject s skin This unit is usually worn on the arm Once the 11 signals are acquired they are amplified and wirelessly transmitted using a Bluetooth module embedded in this first nit to a secondary unit the monitor transceiver The monitor transceiver is connected via input cables to a conventional monitor which then processes the signal as usual numerical display of heart rate graphical display of waveform etc 12 The two units together make up for a sm
39. ss Table 2 Specifications Table for Sensor Unit 4 1 SPECIFICATIONS FOR THE RECEIVER UNIT REQUIRED AND DESIRED The basic concept of this project is to make a portable wireless device that causes the minimum discomfort to the patient astronaut and allows maximum mobility The receiver unit will be designed to be portable and considerably lighter than most of the commercial devices In particular the weight of this unit is required to be less than 960 g less than 4 times the weight of the sensor node It is also required to have dimensions less than 32 x 50 x 12 cm The desired values for weight and size of the receiver are respectively lt 400g and 8 x 12 5 x 3 cm One of the principal features of the receiver unit is the flexibility it offers as a device which can be used as a portable biomonitor system or as a wireless adapter that links a wireless sensor unit to other physiological monitoring systems such as bedside monitors other biomonitors or even a computer If the user is stationary and is close to a monitor the signal transmitted by the sensor can be transferred physically to the monitor via output ports Because they are at least three different types of monitors biomonitor standard ECG monitor PC which can be used to process the transmitted signal and display its waveform the receiver should be equipped with at least three different types of output ports The first output port will accommodate standard bedsid
40. uiring and transmitting clean signals is not jeopardized even at a distance above 10 m Thus the transmission performance of our device satisfies well our required specifications Naturally we can only expect the device to effectively transmit monitoring quality signals within a reasonable range above the treshold of 10m By contrast we can also see that the signal sent to the computer via conventional telemetry RS232 or USB port of the latter is also well filtered However the waveform displayed through telemetry contains some artifacts resulting mainly from undersampling of the signal Figure 13c a b c Figure 13 Plots of filtered ECG signal digitally transmitted to PC via Bluetooth from a 8 m and b 12m c is the plot of an ECG waveform transmitted to PC via digital telemetry RS232 port 6 3 WEIGHT AND DIMENSIONS The Wireless ECG Monitoring System designed in this project satisfies very well our projected size and weight requirements In fact our unit surpasses the dimensions of the LifeSync system with dimensions 2 5 X 1 75 X 0 75 and a weight of 0 5 Ib This adds to the device s user friendliness by making it easier to carry and handle It also reduces the chances of injury related to falling of device 6 4 BATTERY In addition to its small size lightweight and easiness to carry its built in power unit lasts over 8hrs This power unit consists of a 3 7 V lithium
41. vice and its long lasting battery capacity the Bluetooth was utilized despite its high price 9 3 MAINTENANCE Having little maintenance requirements can be seen as one of the key benefits of this device The device can be recharged via the mini usb eliminating the need for any additional battery usage in the future 10 CONCLUSION The Wireless ECG Monitoring System effectively acquires and wirelessly transmits diagnostic quality ECG signals to a monitoring unit PC bedside monitor even at ranges over 10 m Signals are digitally process with the MSP430FG439 Texas Instruments Inc without compromising their quality Fig 3a and 3b The device also features a numeric LCD for heart rate and thus can be used as a stand alone heart rate monitor For improved user friendliness and adaptability to other applications two output ports were added a digital port for serial transmission and an analog one for analog acquisition of ECG signals Not only is the device small 2 5 X 1 75 X 0 75 lightweight 1 2 lbs and easy to carry its built in power unit lasts over 8hrs This power unit consists of a 3 7V lithium ion battery that 30 11 12 13 14 15 16 17 is recharged with a USB cable hence eliminating the need for connecting the device to in wall electrical outlets This project primarily pertained to the development of a wireless monitoring system for ECG However the concepts techniques and design approach us
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