Alternative Design #3 - Biomedical Engineering
Contents
1. Figure 5 Thermometer Circuit Values for R3 and R4 will be determined from gain equation for non inverting amplifiers R cu ed c R lt lt S The target gain for the amplifier will be based on the input current for the microprocessor The thermometer will be tested by placing the probe in a beaker of water heated to a certain temperature and comparing the resulting temperature given by the thermometer to the actual temperature of the water This will be done over a range of temperatures to determine the thermometer s actual operating range and to assure that is within the appropriate range to measure body temperature We feel an appropriate temperature range to test this would be from 10 C to 80 C It will be made sure not to test with a temperature so hot that it burns the thermometer Final testing will be done by taking group members temperature with the thermometer and comparing the reading with that taken by a commercial digital thermometer 1 2 2 Pulse Oximeter To measure blood oxygen saturation a pulse oximeter will be used Pulse oximetry uses the optical properties of blood to determine oxygen saturation Blood oxygen saturation SpOz is defined as the ratio of oxyhemoglobin HbO to the total concentration of hemoglobin in the blood Hb HbO SpO HbO Hb HbO This can be determined by measuring the difference in the light absorption spectra of oxyhemoglobin and deoxyhemoglobin 15 Assumi2. Age is the patient s age at the time of survey Numbers will not add to totals because a patient may be included in more than one category Total number of home health care patients includes manual and motorized wheelchairs Includes geri chairs lift chairs and other specialized chairs includes oxygen concentrator Figure 31 Excerpt from Table of Number of Current Home Heath Care Patients with Aides and Devices in 2000 11 30 As such it is important to have reliable technology to support home care Home care can not only save patients and insurance companies money Fig 32 but living at home can provide patients a welcome and comfortable environment in which to recover and be monitored Table 18 Cost of Inpatient Care Compared to Home Care Selected Conditions Per patient Per month Per patient Per month Per patient Per month Conditions Hospital Costs Home Care Costs Dollar Savings Low birth weight 26 190 330 25 860 Ventilator dependent adults 21 570 7 050 14 520 Oxygen dependent children 12 090 5 250 6 840 Chemotherapy for children 68 870 55 950 13 920 with cancer Congestive heart failure 1 758 1 605 153 among the elderly Intravenous antibiotic therapy for cellulitis 12 510 4 650 7 860 Osteomyelitis others Sources Casiro O G McKenzie M E McFayden L Shapiro C Seshia M M K MacDonald N Moffat M and Cheang M S Earlier Discharge with Community based Intervention for L
3. os whieh eer tse eue d dette oc onc Oe PRMIDE 12 13 Pulse Oximeter Circuit Diagram c0 oco OI EIER ed dU AR ERU ado 13 14 Pulsatile Signals Found in the Intensity of Detected Light ssseuuusuuues 14 15oBloDd Pressute CUE tas eet itineros d os ken etnenn a a es nuce t den unie Pinsent 15 16 Blood Pressure Waveform costisitor tones UE A T ECT nna cones ado ee drea 15 17 Block Diagram of Blood Pressure System 0 c cece eee cee ee eee eea eee eneeees 16 18 Thermocouple Nose C Tes cece enacsondnbee uenenum eas REP So ORUE ecigenamn nan AME U TREE 17 159 Diesgalscale d c caer ha tera vu desta estos e tA Uma D cma UR AL E LEO 18 20 Blackfin Tnmb398 o EO SOHO DM OM ds er eee T etim 19 21 EZ it Lite Evaluation Board us iso co oec vege dee waa cen OE CAR NUR TUNE 20 ZA E DTAC BErmilatlofto uode vetus rte tovto dt reti dle E vo i eoe 20 293 LCD SOCreefio n ceoadei exi eror eo EE te peo em A andes aa opa E NI Ea ia US 21 24 SpeakJet les EES 22 25 Pin Diagrami of D T8250 c ceres xeu e O eV seca Qu DOR ER A 22 26 Small speaker for Audio Outputs oo rr eo e reb o e ee Ense 23 2h Alam E49 Hp oro At nau une eer Tran Nera en Coenen A Tu AME AA dub t DNA Med 23 28 Rechargeable Batteby is cos exer e dc au rar wos Ir NE ERE EBEN AEVO ERE OM YU 24 29 EmbeddedBlue eb100 SER OEM Bluetooth Serial Module ssssus 25 30 Bruising Caused by One Use of an Automatic Blo
4. 8 vcc p i TRIGGER RESET OUTPUT 6 CONTROL THRESHOLD m Ez DISCHARGE Figure 9 Timing Circuit 10 The values of the resistors can be determined from T 7 R R C and T 7R C where T is the pulse length SOus and T is the rate 1kHz or 1ms Thus values for R1 R2 and C2 are 56kQ 3 3kQ and 22nF respectively The 10nF capacitor connected to the control will be used to eliminate any electrical noise from the timer Finally an n channel enhancement mode MOSFET connected across the each LED is used to pulse the output from them Fig 10 R1 OPAMP zi DS135C Figure 10 Circuit to Pulse the LEDs In the receiving end of the circuit is the photodetector The photodetector used in pulse oximetry probes is a photodiode The photodiode detects the light transmitted through the finger as current 15 To amplify the signal the photocurrent must be converted into a voltage with moderate output impedance This can be done by using an op amp configured for current to voltage conversion Fig 11 The photodiode provides a high junction resistance so the op amp should be a FET type with high input impedance 15 The negative input of the op amp acts as a virtual ground making the output of the op amp vo IR Thus it is common practice to make the value of R as high as tens of MQ with the value of C as 47pF 15 11 Figure 11 Current to Voltage Photodiode Conversion Circuit Because the LED l
5. a cost of 37 00 before shipping and tax Fig 15 14 SOE SO 50904 PPP 7720065 t A ax 02 2 Mradi d QNA http www dremed com catalog product info php cPath 56 121 241 242 products id 194 Figure 15 DRE Adult Single Lumen Blood Pressure Cuff The cuff will be inflated by a Sensidyne AA Series Micro Air Pump A microprocessor second to the microprocessor controlling the rest of the device will control the inflation of the cuff The sensor used to sense cuff pressure will be the NPC 1210 low pressure sensor from GE Once the pressure sensor determines that the cuff has been inflated to 160mmHg the cuff will deflate slowly at a rate of 2 3mmHg sec Deflation will occur through a release valve brand to be determined As blood begins flowing through the brachial artery again it will cause small pulsations that will be picked up by the pressure sensor in the cuff Fig 16 This waveform will be analyzed by the microprocessor to determine the systolic and diastolic pressures Vo Volts Time seconds Figure 16 Blood Pressure Waveform Picked Up by Pressure Sensor 17 Where MAP Maximum Arterial Pressure SBP Systolic Blood Pressure DBP Diastolic Blood Pressure A threshold voltage level will be set This will be done by experimentally comparing blood pressure readings from a sphygmometer or other commercial device to those Is detected by our pressure sensor Once 4 pulsations peak above the threshold level
6. large and printed with either Braille or a universal symbol allowing patients who are vision impaired or have arthritis to successfully operate the monitor Also to accommodate vision impaired clients a text to speech function will be implemented to allow the monitor to audibly tell the patients what their current vital signs are In addition four bright LCD screens with wide viewing angles will be used to display the patients vital signs A visual and audio alarm will be installed to alert clients if their vital signs are abnormal An illustration of our design followed by a flowchart of our system operation can be seen in Figs 1 and 2 In our last two designs we purchased a pulse oximeter probe to incorporate into our vital signs monitor To save money this report includes a design for a pulse oximeter probe that we will build The respiratory belt used in the last design to measure respiratory rate has been replaced by a thermocouple a more cost effective but just as accurate solution Bluetooth wireless communication has been used in this design to transmit collected vital signs from the monitor to the client s computer This removes the USB flashdrive and the need to physically transport vital signs data to the computer which was part of previous designs We also explored an effective way to enclose the inner circuitry of our design An AutoCad drawing of our casing will be sent to Toolless Plastic Solutions who will take that file and m
7. may be especially important to have room left in our budget next semester when we begin the actual construction of our device We may need to order replacement parts or additional parts as we go and we cannot do that if we have no money left within our budget Our accessible home vital signs monitor is meant for use in the home so varying environmental conditions are not a large concern of the device However being used in the home there were a few things we needed to keep in mind as we made our design Our device will be exposed to dust sunlight food and water Though it is not meant to withstand an onslaught of any of these things it was designed to be relatively robust in these conditions No parts were used that are very sensitive to movement or other household factors that could affect their use The device will have a durable plastic casing has been designed to withstand the typical rigors of home electronic life movement animals children cleaning spills etc That being said the device is not a toy nor was it designed to be one and the user should keep in mind the device s purpose when using it There are little to no concerns over our device s effect on the environment As it is a piece of home electronics it has very little effect on the environment as a whole Offshoots of the environmental constraints laid on our device are the accessibility constraints that it needs to meet Our device was designed to be properly accessib
8. nto eal de Elmo t emet ea de aU Soh momenta yg 26 IA XT MSc ap e e a EE E EAE A CAA Ea A AA ERA EA AA AETA 26 2 Realistic Constraints aes caret ierant D TS 26 28 3o Safety ISSUCS pnn a E EE wlohe E N LEA 29 30 4 Impact of Engineering Solutions eeicee eere ront rho eran r dro rra eaae p ga 30 32 5 Life Long Learning custo Davos e Giese ia ene eae ERA EIU Ade TTA Coco ed PA Eden aan 32 33 Gi REfETENCES crue pay cue cling aan PORE vibes cat A FEES nau EA UC HEOUSNS EEE eas 33 34 Figures and Tables 1 Illustration of Vital Signs Monitors i caseles trn rta tret dex Eye mea vx o E EE awe 4 2 Flowchart of Vital Signs Monitor Operation ssssssssseee enenee ene en ones 5 3 Ofal T mperature Probes ose eret ee ae e ive bt o pet e t bed 6 4 Thermometer Linearizing Circuit aoc a eee a PERF reg en ERAN E Oe qeu SP PNE KU op OS ERRETU Gee nds 6 2 Thermateter Circuits eee ob or Diepeo eoe Ren V Rex s ad equ tA E ERA eo R data AN T 7 6 Pulse Oximeter Circuit Block DIAgtam s e E RE EE ERE EIE PEREE E Re ERE 9 Tobulse Oximeter Emper Probe oss oso de oro pila oo eoo tele rove de ser os Ra 9 8 Circuit for Constant Current LED Drivet eos er EHar rS cases Va 10 9 Timing Circuits soe e Tb e ed E eR b e ob v di ato ela e t Ln V ieee 10 10 Carcuit to Pulse dhe LEDS 2 uceoeea vetus a diae era en Pe og spe taies muto pua ed afa 11 11 Current to Voltage Photodiode Conversion Circuit eseeeeeeee 12 12 Sample a d hold Circuit
9. the voltage will be recorded and from that value the systolic pressure determined The microprocessor will continue to monitor the blood pressure readings and diastolic pressure will be taken when the voltage drops below the threshold voltage for 2 pulsations After the diastolic pressure is determined a command from the microprocessor will deflate the cuff quickly and completely Figure 17 Block Diagram of Automatic Blood Pressure Measuring System Due to the safety issues that arise with automatic blood pressure systems we have incorporated a kill switch into our design Fig 17 17 If at any time during the blood pressure measurement the user wants to stop the inflation of the cuff and rapidly deflate it they just need to press the vital signs monitor On Off button This will cut power to 16 the whole device and open the pressure release valve This method bypasses the microprocessor avoiding any software bugs that an emergency stop button might encounter As stated previously the automated blood pressure system will be calibrated experimentally This will be done through establishing a threshold voltage by which correct pressure measurements for systolic and diastolic pressures can be made Final testing of the device will be done by comparing its blood pressure readings to those of a sphygmometer In the testing the sphygmometer will be operated by a nurse or other individual who is familiar with manually measuring bl
10. Alternative Design 3 Accessible Home Vital Signs Monitor Team 3 Robert Croce Jenna Sullivan Mike Kapinos Project For RERC National Design Competition Client Contact Dr John Enderle Director and Professor of Biomedical Engineering Program University of Connecticut Bronwell Building 260 Glenbrook Road Storrs CT 06269 2247 Phone 860 486 5521 FAX 860 486 2500 email jenderle bme uconn edu Table of Contents T IntFOGUC Ofles d s DR RE COR S XO RU ERU REOR ee ee NER DS 3 5 1 2 SUD US omisi On t du A A Met us Uus 5 26 T1 2l Thermometer os tet taal te titel ie ne tele uai s 5 8 12 2 Pulse OXITHetet sna ray Sotelo acest een EU ears condos EXEAT eon ey E SEC eS 8 14 1 2 3 Non Invasive Blood Pre3sute 0 a D RR EE SEE UNTER 14 17 12 4 Respiratory R dibus aedi worse asoataanonda stash puvaee EE EA AE eani 17 12 WEIS Gacdasasteuyn Comreranemdonmdaranned enemiaensacs cnoun EREE OE E E Ant 18 1 2 6 Mae TOPTOCSSS OT eiie RS SPESE ELEM M DIIS eke ua aes ph Me EM didus 18 20 L2 CEUDSSSISODS orc d e eor deir e Aedes adus 20 21 1 2 8 Speech ODID bis o oce de ese eta c c biete one Ca co 21 23 1 2 9 ATA cies toa Oh eem Do E NEU HA A REER gs d tu Sd Arta DR PR RR RN 23 1 2 10 Sec re E mail SVSUTI sisi esoed epa vete eoghussa b Ced ba tea tesa e bera nS 24 1 2 TP Rower SUPP Visa in Avatar RUE E Ze Yee ak eddies Edu cU ds e Pe deas 24 T2 T2 BIUCIDOLD c EA God sis D d tle ae chee tia og sedat Kat 25 26 12 15 PUSlDUttODns icc obruo
11. Term 2001 lt http www robots ox ac uk neil teaching lectures med_elec notes6 pdf gt 16 Volk Karl R Using thermistors in temperature tracking power supplies EDN August 2 2001 lt http www edn com article CA149117 html gt 17 Wattanapanitch Woradorn and Warut Suampun Portable Digital Blood Pressure Monitor Cornell University lt http www people cornell edu pages ws62 gt 18 Webster J G ed Design of Pulse Oximeters Philadelphia IOP Ltd Publishing 1997 34
12. _Descriptions 3050239 1903402849 1 1841682443833402744562989117500usb_emulator jpg Figure 22 JTAG Emulation 1 2 7 LCD Screens The digital information from the output of the microcontroller will be sent to six character LCD screens Fig 23 20 http www crystalfontz com products 16021 CFAH1602L Y YH JP_front_bl_on jpg Figure 23 LCD Screen The CFAH1602L GGH JP LCD screens are ideal for our design due to its easy to read characters ideal size and wide viewing angles It measures 122mm x 44mm with a viewing area of 99mm x 24mm and a character height of 8 06mm These LCD screens were chosen due to the fact that many of the features meet the specific needs of our clients Since the majority of our clients will be viewing the monitor from their bed it is important that the screens should be viewable from a wide variety of angles Since these screens have a wide viewing angle patients will have no problem seeing their vital signs from their bed Also the yellow backlight makes this LCD screen easy to read especially in dark or dim lighted areas Also a viewing area of 99mm x 24mm makes the screens easy to read from a distance 1 2 8 Speech Output Our vital signs monitor will contain a text to speech function which will allow the monitor to say what the vital signs are once they have been recorded This function will be useful for our client Mat who is blind and cannot see the monitor Even though his wife is around to help him s
13. annot be any voltage dropped between them Even if the hot wire accidentally touches the metal casing it will create a direct short circuit back to the voltage source through the ground wire The patients skin plays an important resistive role in protecting the body from such hazards But when the skin becomes wet or broken this resistive value drops to 1 of its original value putting the patient in serious harm if the correct electrical safety precautions are not followed correctly 1 A circuit that is not properly grounded will have the potential to cause microshock Microshock is defined as the passing of high current from one body part to another such as from arm to arm and therefore directly through the heart Such high doses of current can cause difficulty breathing and even ventricular fibrillation 1 Choosing the correct gauge wire is also an important factor to consider An electrical hazard exists when the wire is too small a gauge for the current it will carry If a wire is too small for the current it is supposed to carry the wire will heat up The heated wire could have the potential to cause a fire inside the monitor After selecting the correct wire gauge it is important to make sure that all wires are properly insulated and cleanly soldered to its respective position on the circuit board Frayed wires have the potential to interact with other wires causing the monitor to not work properly or cause a fire 29 In addi
14. anufacture a plastic casing Buttons will be customized to increase accessibility and ordered through Grayhill Co Finally in this design we have included a method to transmit the vital signs data to the healthcare professional through a secure e mail system rather than a website Figure A 10cm Alarm Handle Crystalfontz LCD Screen 12cm Viewing Area 19cm 1 gt Blood Oxygen Level Heart rate ico sse 55 BPM sna Area 2 4cm Instruments 20cm Blood Pressure Body Temperature Respiratory Rate 1201180 98 6 F 798 6 F 15 na BEI EX i c 41cm Speaker Figure B On Off Instrument Ports USB Port 20cm Figure C Power Cable 20cm 1D VG EIU 4 GLA 4U l 41cm Figure 1 Illustration of Design Power Button Pressed Device Powers On Are the transducers m O Hold connected to the patient Begin heart rate BP pulse oximetry and Button Begin blood temperature Pressed pressure readings readings Record Stop button pressed Record readings to USB flashdrive Record Stop button pressed Readings stop recorded to USB flashdrive Figure 2 Flowchart of Accessible Vital Signs Monitor Operation In the following section we discuss the subunits of our accessible home vital signs monitoring system This includes information on our apparatus for collecting vital signs how will we process this data how we will t
15. be that we will use with our device we will need a red LED a NIR LED and a photodiode The LEDs will be placed opposite the photodiode within a casing that can be clipped to a finger Fig 7 LEDs Probe casing Finger Photodiode Figure 7 Finger Probe Diagram One LED will work at a red wavelength 660nm and the other at a near infrared NIR wavelength 910nm Also in the probe is a photodetector that will detect the light transmitted through the finger The red LED used in the probe will have been manufactured to give high intensity output and the NIR LED will have been designed to be pulsed so that its peak power can be increased without increasing its average power By pulsing both light sources only one photodiode is needed to detect the light transmitted through the finger 15 To transmit light the LEDs need to be driven by a constant current source This can be done by a non inverting op amp combined with a FET Fig 8 In this circuit the current driving the LED is given by ILep Vin 1 5V R because LEDs usually need 1 5V to turn on 12V TU e Figure 8 Circuit for Constant Current LED Driver To control the pulsing of the LEDs timing circuits need to be used For this we will use 555 timer circuits Fig 9 The 555 timers will supply 50ys pulses to the LEDs atarate of 1 kHz This is well above the maximum frequency in the arterial pulse which is never more than a few Hz Vcc R1
16. by doctors anywhere 5 Life Long Learning During the research of this design we were introduced to new and challenging engineering applications In updating our processing technique we learned about the Blackfin and digital signal processing Although we have already learned about FIR and IIR filters thus far in our engineering curriculum we were now able to apply these concepts to a real life situation Through researching digital signal processing we were able to compare it to traditional microcontroller design and see the differences Digital signal processing is not only substantially faster it also eliminates additional hardware associated with analog circuits Although analog circuits are cheap and easy to assemble software based DSPs provide flexibility in modification and maintenance We learned to integrate microcontroller based data gathering with digital signal processing to achieve a cheaper more efficient way of data analysis Also the text to speech function in our design was a new and exciting function to learn about Since none of us have ever worked with such a unique and advanced tool it made the research enjoyable and informative There are many devices out there used for speech synthesis but we needed to find the one that would be compatible with the microcontroller we selected as well as capable of converting the text output from the microcontroller to sound Most algorithms associated with speech chips cannot convert E
17. count the pulses to determine heart rate beats per minute which will be displayed on an LCD screen The microprocessor will be programmed calibrated to count the peaks of the signal for 10 seconds Multiplying this by 6 will give the heart rate in beats per minute This function will be tested by comparing the heart rate given by the pulse oximeter to that of a group member taken manually 1 2 3 Non Invasive Blood Pressure Blood pressure will be automatically measured through the oscillometric method 14 This is done by wrapping a blood pressure cuff around the upper arm and inflating it until the pressure around the arm due to the cuff collapses or occludes the brachial artery The cuff is then slowly deflated As the cuff deflates blood starts pumping through the brachial artery causing minute vibrations of 5 to 1 mmHg in the cuff 3 The pressure at which these vibrations start is the systolic pressure and the pressure at which they stop is the diastolic pressure 4 The block diagram in Fig 17 illustrates how this method will be used to measure blood pressure in the accessible vital signs monitoring system Each system in the flow chart is described in more detail in the following paragraphs When the blood pressure Start button on the vital signs monitor is pressed the blood pressure cuff will be inflated to about 40mmHg above normal 160mmHg The blood pressure cuff used will be a DRE Adult single lumen cuff from DREMed com at
18. d pressure and temperature cost closer to 5000 Ifa patient s health insurance will not cover this cost than it becomes a large out of pocket expense for them or they may not be able to afford the device at all This is detrimental to their health and recovery By designing a monitor that s expected cost is 700 a third of the cost of the cheapest monitors currently available we will be able to alleviate some of this financial stress and provide more comprehensive health care and monitoring to more people Globally this design may translate into an affordable piece of medical equipment for undeveloped countries With its two button user interface detachable transducers and simple design it may be useful in countries with a low level of technology Our device is designed for home use but in countries and areas with poor healthcare systems and little to no medical equipment it would be useful in a hospital or emergency room Because it is lightweight and has a rechargeable battery and because vital signs are saved onto a USB flashdrive our accessible vital signs monitoring system is an excellent option for remotely monitoring patients in areas where there are few trained medical personnel A layperson with no medical training could use our device to visit a patient who does not have access to a hospital or doctor and record their vitals signs on a USB flashdrive These measurements could then be uploaded to the secure website and accessed
19. d to generate the voltage that sets the value of the LED currents 15 The complete schematic Fig 13 of the pulse oximeter shows how each of the different circuits previously described will be integrated into a whole 12 Figure 13 Pulse Oximeter Circuit Diagram Calibration of the pulse oximeter will be done through the lookup table stored on the microprocessor Due to the scattering effects of blood Beer s Law does not apply for a pulse oximetry system 18 Therefore the blood oxygen saturation equations explained previously are good for theory but not for practice As such pulse oximeters are usually calibrated by comparing the oximeter R value SpO gt ratio to the oxygen saturation ratio obtained from in vivo samples using human test subjects Manufacturers of pulse oximeters do this and determine calibration curves or lookup tables for their devices The pulse oximeter will be calibrated tested through a pulse oximeter simulator a device designed to test the accuracy of pulse oximeters We plan to find a simulator to use at a local hospital or the UConn Health Center 13 Heart Rate Pulse oximetry will also be used to determine heart rate There are pulsatile signals detected in the intensity of the detected light by the photodiode Fig 14 14 03 38 2 14 03 43 2 20 02 23 7 20 02 28 7 Figure 14 Pulsatile Signals Found in the Intensity of Detected Light 15 One pulse is one cardiac cycle The microprocessor will
20. d vision impairment who need to have their vital signs monitored This device will allow those individuals the ability to go home to recuperate while still being effectively monitored by their health care provider This is especially important in cases where home health care would be a treatment option for someone without visual or hearing impairments but not for someone with them Home health care is a growing industry Approximately 7 6 million individuals receive home care in the United States The Center for Disease Control reported that in the United States in 2000 317 600 individuals in home care were using medical devices Fig 31 Medical Total with medical devices 2 2 2 2 ee 317 600 15 900 31 700 58 300 74 300 84 800 52 600 Blood glucose monitor llis 132 500 11 800 19 200 38 600 37 300 25 000 Enteral feeding ee eee 30 700 s s Intravenous therapy 6 ee een 52 300 2 17 100 M Dxypori caos nere ER RR RESET RR 114 600 R 18 200 25 700 43 400 19 900 Other respiratory therapy s saas 00 20000 45 300 15 000 Other kia 2 eee 187 500 11 600 23 600 33 100 28 200 58 600 32 400 Figure does not meet standard of reliability or precision because the sample size is less than 30 if shown without an estimate If shown with an estimate the sample size is between 30 and 59 or the sample size is greater than 59 but has a relative standard error of 30 percent or more Quantity zero
21. e buttons require a proper size whole to be drilled in the area where the buttons will be place The buttons will then be snapped into the whole Once the button is snapped into the whole it has wings which will then open causing the button to not be removed The only visible problem with this product is that the button may be too small and also that we are not yet aware of the price We are awaiting a price quote from the Gray Hill Company It may tend to be a little pricey because we have the option to customize the details of the button The main factors we tend to look at when determining what button option we will be using are the price and size of the buttons Our buttons are basically going to act like a switch either turning the power on or off The start button will be connected to the beginning of the circuit There will be a switch in the circuit that will either be open if the circuit is not working or closed if power is wanted to be given to the entire circuit When the start button is pressed the switch on the circuit will close allowing for the power supply to be sent to and power the rest of the circuit When the patient feels the process is complete they will be able to press the stop button which will allow for the circuit to open disallowing any power to get through to the circuit 1 2 14 Casing In order to safely enclose the internal circuitry of our design a plastic enclosure needs to be manufactured We will use the company Toolle
22. er month 1 2 11 Power Supply When designing this project we found it rather important to include two different types of power The device will mainly be run from an external power source by using a power cord It will also be equipped with rechargeable backup batteries in case of a power failure Fig 28 For the power supply we plan on using a very generic universal power cord which will plug into the back of our device and then also plug into the wall This cord will only fit into the socket designated for it on the device to prevent any accidental power surge or electrocution For the backup power supply we determined the best way would be to use nickel cadmium rechargeable batteries Although lead acid batteries can sometimes produce more voltage nickel cadmium batteries are safer and will recharge a lot quicker The need for a backup battery is so the patient can take signs even if the power is gone Also if power is lost that means the alarm will also be shut off causing the patient to possibly miss a time This could be life threatening to some patients so we felt it was very important to include a backup supply Figure 28 Image of Rechargeable Battery 24 1 2 12 Bluetooth To increase accessibility we will transmit the data collected by the vital signs monitor to the client s computer wirelessly using Bluetooth We will purchase the EmbeddedBlue eb100 SER OEM Bluetooth Serial Module from A7 Engineering for 40 to integrate int
23. hat it should be explosion proof It should not spark or create flames to prevent explosion used in the presence of pure oxygen Most components of our design are relatively benign provided that basic electrical safety is followed but a major point of health and safety constraint was the design and incorporation of the automatic blood pressure measuring device 27 Self inflating blood pressure cuffs can cause injury if not properly calibrated and used Fig 30 Figure 30 Bruising Caused by One Use of an Automatic Blood Pressure Cuff 14 Bruising can result if the cuff inflates too much Pain and circulation cutoff can occur if the cuff does not deflate and at the extreme this could lead to tissue death Our accessible vitals signs monitoring system has really no political constraints but it does have social and privacy constraints Part of our system includes the transmission of vitals signs of the internet to a health care provider To protect patient privacy and abide by the Health Insurance Portability and Accountability Act HIPAA the transmission of vital signs will be done via a secure password protected website This will protect our clients personal information while still giving them flexibility in the transmission of their vital signs to their physicians or HMOs This is an important and valid constraint in our device design The internet provides rapid transfer of information but it is filled with predators and opportu
24. he is also vision impaired The output text from each pin on the microcontroller will need to be converted to sound To do this we will use the Magnevation SpeakJet IC Fig 24 It is an 18 pin IC which uses a mathematical sound algorithm to control an internal five channel sound synthesizer to produce sound The SpeakJet can be controlled by a single I O line from the Blackfin 12 Since this microchip requires phonetics and not text the TTS256 Text to Code IC will have to be used in conjunction with the SpeakJet The TTS256 is an 8 bit microprocessor programmed with letter to sound rules This built in algorithm allows for the automatic real time translation of English ASCII characters into allophone addresses compatible with the Magnevation SpeakJet Speech Synthesizer IC This IC is Compatible with Basic Stamp OOPic Pic and any processor with a serial port like our microchip 12 We will use pin 5 TX to output the phonetics from the SpeakJet and pin 18 RX to receive the data from the Blackfin Fig 25 The pin diagram of the TTS256 is shown below The final sound will be sent from the Voice Output pin 18 of the SpeakJet using 5V and a speaker Since the SpeakJet is preconfigured with 72 speech elements 43 sound effects and 12 DTMF touch tones we will also use the SpeakJet to produce an alarm when the vital signs are out of range range to be determined This chip will be tested 21 experimentally by providing to it a series of i
25. ic Measurements New Jersey Prentice Hall Inc 1983 6 Design and Engineering Toolless Plastic Solutions 2006 lt http www toolless com gt 7 Getting Started with Blackfin Processors Analog Devices 2006 lt http www analog com gt 33 8 Lineared NTC Thermistor eCircuit Center 2002 lt http www ecircuitcenter com Circuits therm_ckt1 therm_ckt1 htm gt 9 Northrop Robert B Noninvasive Instrumentation and Measurements in Medical Diagnosis New York CRC Press 2002 10 Northrop Robert B Class notes BME 255 University of Connecticut Oct 17 2006 11 Number of current home health care patients by type of aids devices used sex and race United States 2000 Current Home Care Patients Feb 2004 http www cdc gov nchs data nhhesd curhomecare00 pdf 12 SpeakJet User s Manual Magnivation 2004 lt http www speechchips com downloads speakjetusermanual pdf gt 13 Safe Circuit Design All About Electric Circuits 2003 lt http 72 14 209 104 search q cache HY M2hyPm4rcJ www allaboutcircuits com vol_1 chpt_3 8 html circuit designtsafety amp hl en amp gl us amp ct clnk amp cd 1 gt 14 Townsend Neil Non Invasive Blood Pressure Medical Electronics Michaelmas Term 2001 lt http www robots ox ac uk neil teaching lectures med_ elec notes7 pdf gt 15 Townsend Neil Pulse Oximetry Medical Electronics Michaelmas
26. ight is pulsed sample and hold circuits are needed to reconstitute the waveforms at each of the two wavelengths The timing circuits that were used to control the red and NIR LED drivers also are used to provide the control pulses for their corresponding sample and hold circuits 15 A simple sample and hold circuit can be created from a FET switch capacitor and op amp Fig 12 1 M2N680 C3 d in Ex 70 Figure 12 Sample and hold Circuit Once the signal goes through the sample and hold circuit it is sent through a band pass filter with cutoff frequencies 5Hz and 5Hz to eliminate high frequency noise and the d c offset Then it is amplified resistor values to be determined and sent through an A D converter and the microprocessor to be analyzed A lookup table stored in the microprocessor will be used to calculate SpO values This signal is also sent through a low pass filter f 1Hz to extract the d c value of the transmitted signal which is then sent to an automatic gain control circuit The gain control circuit adjusts the light intensity from the LEDs so that the d c level always remains at the same value whatever the thickness of the patient s skin tissue etc This circuit is implemented by feeding the d c signal to one input of a differential amplifier The other input to the amplifier is a constant reference voltage The output of the differential amplifier the voltage difference between the two inputs is use
27. iquids be kept off of and way from the monitor regardless of how good the casing Also it is important for the casing to be made of a non conductive material such as plastic so that if the hot side of the power system touches the side of a casing there is no danger to the user of the monitor The inner part of the monitor should be designed so that neither the hot or neutral part of the power cord touches the casing but if the hot wire does accidentally touch the casing then this could be dangerous If the casing is conductive and the hot wire touches the side of the case then the case will be made electrically common to the wire and touching the case will be just as hazardous as touching the wire bare In addition it is always important for an electrical design to have a solid connection to earth ground A power system with no secure connection to earth ground could pose a safety hazard There is no way to guarantee how much or how little voltage will exist between any point in the circuit and earth ground By grounding one side of the power system s voltage source at least one point in the circuit can be assured to present no shock hazard One way to ensure proper ground is to use a three prong plug The third prong on the power cord provides a direct electrical connection from the appliance case to earth ground making the two points electrically common with each other If they re electrically common then there c
28. larm light v F Y Y http img alibaba com photo 50538513 Alarm Lights Warning Lights jpg Figure 27 Alarm Light 23 1 2 10 Secure E mail System In the first couple designs the way we decided to send data was through a secure website that was password protected After looking at a few different options we decided that another good idea to send data is through a secure e mail system By doing this it would send information directly to the host making it very tough for someone to hack into it We decided the best way to accomplish a secure e mail system is through a website http www certifiedmail com This website provides the software necessary to protect e mail using transparent encryption It provides easy to use software that the recipient of the e mail does not need to download in order for complete security to occur There are some advantages to having a secure e mail system to send data this way For starters there is no password required and information is automatically secured every time with the Certified Mail software Also it is possible to send information from anyplace with an internet hookup It is also made possible to track the e mail to determine that the e mail was received and who opened it The Certified Mail software is also very easy to use and rather inexpensive All it requires is a one time download and just clicking the send certified button every time after that The whole Certified Mail System costs only 10 p
29. le so that it will be of use to our clients and meet their needs Audio and visual output along with Braille and raised universal symbols were used to make the device user friendly to anyone with vision or hearing impairment Also the simple user interface of the device allows it to be used by individuals of all ages and technological savvy This leads into sustainability Our device was designed with its ability for future and continued use in mind Not only must the device be designed so that it can last and function properly for years but it also needs to use up to date parts and technology so that it does not become outmoded An example of this was the selection of the rechargeable battery for our device In many vital signs monitors being used rechargeable lead batteries power the device However lead materials are currently being phased out of medical devices so we chose to use a nickel cadmium rechargeable battery in our design This is one step that was taken to ensure that our device will still be acceptable for use years from now Because this is a medical device and will have direct contact with our clients client patient safety was an important constraint in our design process All circuits and power sources must be properly grounded to prevent accidental electrocution and safety measures had to be put in place to prevent an injury use of the device might cause Since this is a medical monitoring device one of its safety constraints is t
30. ly for home use However because of this we do advise that users ensure they are within a 10 m radius of their computer when using their vital signs monitor Another way in which Bluetooth limits interference is through frequency hopping This also helps ensure the security of the data being transmitted Bluetooth transmitters use 79 randomly chosen frequencies and hop between them 1 600 times per second Our Bluetooth communications system will be calibrated through UART communication with any extra equipment necessary provided by the BME 252 lab It will be programmed to set up a network with the Bluetooth USB dongle when it detects it The Bluetooth system will be tested by acquiring vitals signs from the monitor and sending them to a computer in the design lab to which the USB dongle is installed The 25 vital signs monitor will be placed at different ranges within 10 meters to determine signal strength at different ranges and the optimum range for data transmission 1 2 13 Pushbuttons One important feature of our design is the buttons that involved We need to have our buttons customizable so we can include a universal sign and Braille so they can be used by individuals with vision impairment A company that offers customizable buttons is Grayhill The model button from Grayhill that fits our project the best is a rectangular button that is about 15 by 20 millimeters These buttons are very easy to secure by a short simple process Th
31. n evaluation board and an emulator Before the processor is even programmed VisualDSP software will be used to simulate the behavior of the DSP chip Using this software we will be able to build edit and debug our DSP program before we even have the actual processor which is done solely on the computer After the simulation is complete evaluation of the simulation is performed using the EZ KIT Lite evaluation system to determine the specific Blackfin processor that fits our needs This board Fig 21 connects up to the computer via a cable allowing us to run our simulation program After the evaluation process the JTAG emulation board Fig 22 will be used to serially scan the I O status of each pin on the device as well as control internal operations of the device This hardware connects our PC to the actual process target board via a USB cable Table 1 Blackfin Specifications Blackfin Specifications Clock Speed MHz 350MHz MMACS MAX 700 RAM Memory Kbytes 308 External Memory Bus 32bit Parallel Periph Interface No PCI Yes USB Device Yes UARTS Timers Yes Watchdog Timer RTC Yes Core Voltage V 1 0 1 6 Core Voltage No Regulation 260 Figure 20 Blackfin Image iiid PBGA 19 http www analog com images Product_Descriptions 60475542243306341558700011339bf535_hardware jpg Figure 21 EZ Kit Lite Evaluation Board Sint tiainnt iei http www analog com images Product
32. ng A D converted and processed by the microprocessor As mentioned previously this circuit will be calibrated experimentally Voltage output from the thermocouple will be measured for inspiration and expiration most likely from being tested on group members From these measurements voltage thresholds will be set for inspiration and expiration Experiments will also be done to determine the optimum time period for measurement Testing will be done by comparing the readings from our respiratory rate monitor to those taken by the Biopac respiratory belt from the Biopac software used in the ENGR 166 lab 17 1 2 5 Weight Weight is an important vital sign to monitor In addition to ensuring proper eating habits weight is used to determine medication doses We will include weight monitoring into our vital signs monitor by buying a digital scale that exists on the market and connecting it to our device The scale that will be used is the Homedics SC 200 Digital Scale Fig 19 L DIGITAL SCALE Figure 19 Homedics SC 200 Digital Scale This scale was chosen because it fits quite well with our project We figured with our clients we will have to build handles onto the scale so people will be able to hold on and not fall The reason for this is that some of our clients are elderly and might not be able to stand steady on their own Also since this scale already has a main waist high base it should not be difficult to connect handle
33. ng that the transmission of light through the arterial bed in the finger is only influenced by the concentrations of Hb and HbO and their absorption coefficients at two measurement wavelengths red and near infrared then the light intensity will follow the Beer Lambert Law Thus for an artery of length Z through which light of intensity In passes Jl 0 AC a 4C 1 I Tins I 1 10 at wavelength Az at wavelength A and where I and L are the intensities of the light passing through the artery at each wavelength Cois the concentration of HbO Cris the concentration of Hb a is the absorption coefficient of HbO2 at wavelength An and Qm is the absorption coefficient of R BUE le od I then blood oxygen saturation can be calculated from QR B a C SpO _ m Cy tC a TAn JR a ay Circuit Design The block diagram of the pulse oximeter below shows an overview of the circuits that are involved and will be included in the vital signs monitoring device Fig 6 Sample and Bandpass filter Amplifier hold circuit Current to Sample and hold circuit LCD Bandpass filter Amplifier Photodiode detector AEN e NIR LED driver Red LED driver Timing circuit Timing circuit circuit circuit Automatic gain Automatic gain control circuit control circuit Low pass filter Low pass filter Figure 6 Pulse Oximeter Circuit Block Diagram To build the finger pro
34. nglish text straight to audio which is why we integrated the TTS256 Text to Code microcontroller to convert text to phonetics which is compatible with the SpeakJet Through designing the thermometer for the accessible vital signs monitor we have learned about the Steinhart Hart equation and the properties of thermistors It is important to realize that thermistors behave nonlinearly and to understand what effects this has on designing a thermometer In order to use the thermistor output it must be linearized This can be done over a small temperature range but any readings outside the 32 temperature range will be increasingly inaccurate the farther away they are This means that one should only use an oral thermometer to measure oral body temperature not air temperature or a cold beverage We learned about the optical properties of blood and the Beer Lambert law to design a pulse oximeter circuit Also from the pulse oximeter we saw the application of transistors to switching and timing Research into an automated blood pressure measurement system highlighted the importance of control systems in medical devices Even for something as seemingly benign as an automatic blood pressure cuff system safety precautions have to be taken to ensure that a patient is not harmed through the use of the device This design also required us to learn about pressure sensors pressure release valves and air pumps Blood pressure waveforms were studied and the
35. nists who like to access the private information of others It is important for us to protect our clients when they are contacting their physicians so that their medical information does not end up all over the World Wide Web By paying heed to these constraints and working with them not around them our accessible home vital signs monitoring system has been designed with the best interests of our clients and society at heart This ensures that we have designed an economically feasible device affordable for our clients Our device is appropriately designed for the environment which it will be used in and with careful part selection it will sustain and continue to be appropriate for the home monitoring of vital signs 28 3 Safety Issues Safety plays a crucial role when designing a product especially one that contains electrical components Because our design will be comprised mainly of electrical components we strive to effectively enclose the inner circuit of our final design with a durable non conductive completely enclosed casing The casing of our final design will show no wires circuit boards or any part of the inner circuitry Loose wires will have the potential to not only cause the device to operate ineffectively but could also be hazardous to the patient Any moisture from the air or water accidentally spilled near the device could cause a spark and start a small fire It is for this reason that it will be recommended that all l
36. nputs to confirm that it is giving the correct outputs http www speechchips com images SpeakJetIC jpg Figure 24 SpeakJet IC 4 TX TTS256 on oO Pp OH J_BUF_FULL RX http www speechchips com images tts256 gif Figure 25 Pin Diagram of TTS256 To play these computer generated sounds a speaker from Futurelec Fig 26 will be purchased and attached to the microcontroller This speaker was chosen due to its small size and affordable price This speaker will be used to play the data output from the 22 microprocessor as well as sound an alarm when the patients vital signs become irregular http www futurlec com Pictures Sm_Speaker jpg Figure 26 Small Speaker for Audio Output Features Small Size Power rating 0 5W Impedance 8 ohm Dimensions 50mm Diameter 16mm High 28mm base diameter 1 2 9 Alarm To assist our clients we will install an alarm system to alert them when their vital signs have become irregular or dangerous On top of the monitor will sit a light that will flash when these signs become abnormal A light we have chosen is shown below Fig 27 In addition an alarm sound generated by the SpeakJet will also serve as an alert The majority of the alarm design will be done by programming the microprocessor We will have a set of defined limits for each vital sign and if these signs fall out of range a signal from the microcontroller will be sent to the SpeakJet and a
37. o our vital signs monitor to provide Bluetooth connectivity Fig 29 This module contains all the components of the Bluetooth stack on the board so that no additional host processor code is needed The interface between our host processor and the eb100 SER radio will be done through UART communication When a connection is made to another Bluetooth device the link will appear as a cabled serial connection which eliminates the need for any special wireless protocol knowledge Assuming that our clients computers are not Bluetooth ready a USB Bluetooth dongle will be purchased usually at 10 20 to provide connectivity on the PC end These USB dongles are easy to use and come with software to install on the PC to allow Bluetooth connectivity Bluetooth communicates data via low power radio waves on the 2 4 GHz frequency This is the ISM frequency band It has been internationally agreed upon to be used only for industrial scientific and medical devices ISM Many devices make use of the ISM band but Bluetooth has precautions in place to prevent interference with these other systems making it and ideal technology for our use One way in which Bluetooth prevents interference is by only sending out very weak signals of about 1 milliwatt This limits Bluetooth s range to about 10m although advances in the technology have made it possible for transmission ranges up to 100m This is an acceptable range considering that our device is meant on
38. od Pressure Cuff 28 31 Table of Current Home Heath Care Patients with Aides and Devices in 2000 30 32 Table of Home Gare Cost SaviDngs s sict o eee x Rep MOI E pisi iw 31 Table 1 Blackfin Specifications 409 2 io sp Fera ao sor DP Ho sean CE FEET SE CET Pea 19 1 Introduction Due to the increasing number of chronic illnesses along with the shortage of nurses home monitoring is becoming more and more of a necessity Patients that require frequent healthcare monitoring can now have this done in the comfort of their own home An important tool for home health monitoring is the vital signs monitor Our accessible home vital signs monitoring system will have the capability to non invasively gather a patient s heart rate blood pressure blood oxygen level body temperature weight and respiratory rate and then send this data to their corresponding healthcare provider To send this data we will create a password protected encrypted website to which patients can upload their vital signs This accessible home vital signs monitoring system design is an accurate and consistent way to obtain a patient s vital signs regardless of the caregiver s skill level To accommodate all users including our clients the monitoring system was designed as simple and user friendly as possible To maximize the simplicity of our design and make it accessible to all of our clients the buttons on the front panel of the monitor will be
39. ood pressures and does so often Nevertheless we expect to see some slight differences in the measurements from our device and the sphygmometer because of the inherent degree of imprecision in manual blood pressure measurement This is why it is important to have a professional operating the sphygmometer Their experience with the device and the art of blood pressure measurement should reduce the likelihood of human error Finally the rapid cuff deflation will be tested by experimentation turning the vital signs monitor off during use 1 2 4 Respiratory Rate Respiratory rate will be measured using a thermocouple The thermocouple will be clipped to the client s nose and will measure the change in temperature caused by inspiration and expiration Fig 18 The thermocouple will convert the changes in temperature it detects to changes in voltage Through experimentation voltages thresholds will be set to define the changes in temperature that correspond to inspiration and expiration By counting the number of inspiration and expiration pairs that occur in a given period of time we can determine respiratory rate Figure 18 Image of Thermocouple Nose Clip The circuit for the thermocouple will be powered by the battery The voltage from the thermocouple will be linear over our range approx 65 F to 98 F so the signal from the thermocouple only needs to be filtered and amplified resister and capacitor values to be determined before bei
40. oscillometric method for blood pressure measurement was introduced to us In addition to learning new technical engineering applications senior design has also taught us to work and function as a group By working as group we learned to interact and communicate with each other to assess and resolve problems as well as rely on each other to make deadlines Since communication is an essential element of being an engineer working on these skills before we graduate will give us an edge over the majority of graduating engineers Whether we will be working with an engineering design team a team of healthcare professionals or in a corporate environment when we graduate we will need to use these group skills we are currently developing to drive a successful career 6 References 1 Al Nashash Hasan Electrical Safety of Medical Equipment University of Sharjah School of Engineering lt http www ewh ieee org r8 uae Elect_Safety _Med_Equip pdf gt 2 Basic Statistics About Home Health Care National Association for Home Care amp Hospice 2004 lt http www nahc org 04HC_Stats pdf gt 3 Blood Pressure Monitor lt http www circuitcellar com fi2003 abstracts F190abstract pdf gt 4 Chua C S and Siew Mun Hin Digital Blood Pressure Meter Freescale Semiconductor May 2005 lt http www freescale com files sensors doc app_note AN1571 pdf gt 5 DeMarre Dean A and David Michaels Bioelectron
41. ow Birth Weight Infants A Randomized Trial Pediatrics 92 no 1 1993 128 134 Bach J R Intinola P Alba A S and Holland LE The Ventilator assisted Individual Cost Analysis of Institutionalization vs Rehabilitation and In home Management Chest 101 no 1 1992 26 30 Field A I Rosenblatt A Pollack M M and Kaufman J Home Care Cost Effectiveness for Respiratory Technology dependent Children American Journal of Diseases of Children 145 1991 729 733 Close P Burkey E Kazak A Danz P and Lange B A Prospective Controlled Evaluation of Home Chemotherapy for Children with Cancer Pediatrics 95 no 6 1995 896 900 Note The study found that the daily charges for chemotherapy were 2 329 627 in the hospital and 1 8652 833 at home These charges were multiplied by 30 days reflecting the above per patient per month costs Rich M W Beckham V Wittenberg C Leven C Freedland K and Carney R M A Multidisciplinary Intervention to Prevent the Readmission of Elderly Patients with Congestive Heart Failure The New England Journal of Medicine 333 no 18 1995 1190 1195 William D N et al Safety Efficacy and Cost Savings in an Outpatient Intravenous Antibiotic Program Clinical Therapy 15 1993 169 179 cited in Williams D Reducing Costs and Hospital Stay for Pneumonia with Home Intravenous Cefotaxime Treatment Results with a Computerized Ambulatory Drug Delivery Sys
42. perature from the reference temperature AT T T in degrees Kelvin The reference temperature T o of the thermistor is given by the manufacturer and for medical thermistors it is usually around 300 K The temperature coefficient a can be calculated from the following equation d R T _ a P R T T where f is a temperature constant typically around 4000 K 9 The value of the resistors R used to linearize the thermistor will be determined from the reference temperature and other values given by the manufacturer p or a using the above equations For our use as an oral temperature probe the thermistor needs to be linearized calibrated around 98 6 F 37 C for a temperature range of at least 90 104 F 32 40 C When linearizing the thermistor we must be careful to keep the accuracy of the thermometer high 1 C so as to be able to take appropriate measurements After being linearized the signal will be sent to a low pass filter to remove any noise The cutoff frequency for the filter should be less than 40Hz to remove any noise from room lights and other sources p 8 Possible values for R2 and C are 2AR 1820Q and 2 2uF The signal will be sent to a non inverting amplifier to be amplified and then passed to the microprocessor where it will be analyzed and sent to an LCD screen to be displayed Fig 5 THERMISTOR RTI DC V Ut R2 C U2 D 1 1 82k Vo to microprocessor Differential Amp
43. ransmit it to a computer and the method in which we will communicate with healthcare providers 1 2 Subunits 1 2 1 Thermometer To measure body temperature a thermistor circuit will be used The thermistor will be in the form of a commercially purchased oral temperature probe The probe we have chosen for this is the Welch Allyn 02893 000 Sure Temp 690 Oral Probe from DREMed com for a cost of 74 00 before shipping and tax Fig 3 http www dremed com catalog product_info php products_id 1214 Figure 3 Welch Allyn Sure Temp 690 Oral Temperature Probe The thermistor within the probe will convert changes in temperature to changes in voltage Unfortunately thermistors are inherently non linear The Steinhart Hart equation describes the resistance temperature curve of a thermistor 16 774 bIn R cin R where T is the temperature in kelvins R is the resistance in ohms and a b and c are constants called the Steinhart Hart parameters which will be provided by the thermistor manufacturer This output can be linearized through the use of a Wheatstone bridge Fig 4 THERMIS TOR RTI VozW1 V2 Differential Amp Figure 4 Thermistor Linearizing Circuit 10 Thus the resistance of the thermistor RT1 can be modeled by the first order equation 10 R T R I aT where R is the resistance of the other resistance in the Wheatstone bridge a is the temperature coefficient and AT is the change in tem
44. s or rails The scale was also chosen because it is very inexpensive at 24 95 and it can be found at wholesalepoint com The scale has an on off switch and requires only one 9V batters for power As of now our main approach to connecting the scale to our device is a very simple and straight forward approach We plan on taking apart the scale and breaking the connection between the circuit and its digital display From here we just plan on simply connecting the scales circuit to one of our output displays instead The scale will already have been calibrated and tested by its manufacturer We will do additional testing by comparing known weight values dumbbells to the values displayed by the scale when we place the weights on it 1 2 6 Microprocessor The processor we are going to use for our design is the Blackfin ADSP BF535P Digital Signal Processor by Analog Devices Fig 20 This processor is extremely versatile due to the fact that it can function as both a microcontroller and a DSP Digital Signal Processor allowing for either 100 DSP 100 microcontroller or a combination of the two 7 This makes the Blackfin ideal for our design due to the fact that we are going to input and output the data like a microcontroller but use the digital signal processing features to analyze and filter the signals FIR and IIR filters The Blackfin will function like the traditional microcontroller taking the electric signals from 18 the transducer pa
45. ss Plastic Solutions to manufacture our casing In order for this company to manufacture our case we need to submit an AutoCad drawing of the final casing design Since we will not know the exact size and placement of all 6 holes for the LCD screens and the various I O ports in the casing the design will be submitted in the spring semester when all the parts have been ordered and more about the final design is known Toolless Plastic Solutions requires no tooling or molds and therefore will be a cost effective way to obtain an enclosure for our design 6 The company uses CNC Computer Numerical Control machining and fabrication process to build plastic casings We will not know the exact price of the casing until a design is sent for a quote 2 Realistic Constraints The main source for medical instrumentation standards is the Association for the Advancement of Medical Instrumentation AAMI They provide for purchase the current standards of medical device design and use These standards must be followed in 26 the design and production of our device to ensure that it is acceptable and safe for our clients and the health care community This device has been designed with the economic constraint of cost in mind We have a maximum budget of 2000 to build a working prototype of our device so parts were chosen carefully A balance had to be maintained between using parts that meet the needs of our design and not overspending our budget It
46. ssing them through an analog to digital converter and processing the information Like the PIC microcontrollers the Blackfin contains an internal analog to digital converter There are many advantages for us in using digital signal processing rather than traditional 100 microcontroller functions Microcontrollers can be cheap and easy to assemble but are difficult to calibrate and modify Using DSP one can more easily design and modify their work due to the fact that it is all computer based Thus one can rely on their software based filters much more DSPs are also much faster than microcontrollers A typical PIC microcontroller has a clock speed of about 20 MHz whereas the Blackfin has a clock speed of 350 MHz Table 2 We will use the PF pins I O ports on microcontrollers on the Blackfin to function as inputs for the transducers and outputs for the LCD screens and speaker Due to the Blackfin s abilities it should be the only microprocessor we need for our device We also chose to use the Blackfin due it its versatility in programming code The Blackfin can take C C code as well as LabVIEW VI s Since we have had more experience using LabVIEW we felt that LabVIEW would be a more suitable code to program the processor When designing a product with Blackfin many helpful tools are provided to the engineer to aide in the design which has already been purchased by the Biomedical Engineering department These include simulation software a
47. tem The American Journal of Medicine 97 no 2A 1994 50 55 Note The estimated hospital cost day patient is 417 and the estimated savings day patient is 262 These costs were multiplied by 30 days reflecting the above per patient per month costs Figure 32 Table of Home Care Cost Savings 2 When patients choose or have the option to enter home care they free up hospital beds for more acute cases give doctors more time to work with sicker people and many times patients they are happier at home than in the hospital But patients can not be cared for at home unless they have the proper technology to do so Our accessible vital signs monitoring device is a simple easy to use method to monitor patients health at home It can be operated by patients their families and physicians making it an ideal device for the home environment Since vitals signs are saved on a USB flashdrive to be uploaded to a secure website patients are not even stuck at home but can take their rechargeable battery powered vital signs monitor with them if they need to monitor their vital signs This offers flexibility and comfort to patients Economically the design for our device will reduce some of the costs of healthcare Vitals sign monitors and many of these are not accessible currently range in cost from 2500 up to 5000 Most of the monitors that measure the same four vitals 31 signs as our device heart rate blood oxygen saturation bloo
48. tion to the electrical safety issues it was also made sure that the operator of the monitor does no harm to the patient while taking measurements Each instrument used to obtain measurements was carefully chosen to be as simple and safe as possible Out of the four vital signs being obtained the only one which needs skill to operate would be blood pressure Using the blood pressure cuff incorrectly could not only cause the monitor to record the wrong vital signs but also harm the patient Squeezing the blood pressure cuff too tightly could injure the patient To minimize this potential hazard we will use an automatic blood pressure cuff allowing the person who is taking the readings to have no prior skill Since the people taking the vital sign readings are elderly or young the automatic blood pressure cuff makes gathering data relatively simple Even though the automatic blood pressure cuff is simple to use it is still not completely foolproof 4 Impact of Engineering Solutions Much of the technology used in our design for an accessible home vital signs monitoring system is not new but the manner in which it is being employed is valuable There are few if any accessible vital sign monitors currently available Patent and web searches have not devices on the market comparable in that regard to the device that we have designed The design of an accessible vital signs monitor will improve the quality of life for those individuals with hearing an
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