1. Redesign of a Pulse Oximeter University of Pittsburgh Senior Design – BioE 1161 Ted Askar Sam Audia Jeffrey James Thomas Christophel April 13, 2004 Mentor: Sandra Gartner, RN

2. Background What is a pulse oximeter? Non-invasive tool for monitoring the percent concentration of hemoglobin (Hb) saturated with oxygen. Pulse Oximeter Processor/ Monitor

3. Light to Frequency Converter CPU Digital Display LED Driver VR LED IR LED Photodiode 1 2 3 4 Townsend et al. 1.Source sends two wavelengths of light (red, 600-700nm, and infrared 850-1000nm) through an appendage 2.Blood Hb absorbs red light while O2Hb absorbs infrared light 3.Photodiode measures LED intensities 4.A processor calculates the absorbance ratio which is then used to determine oxygen saturation 98%95%93%90%88%85%81%76%70% Background

4. Problem Statement Clip Models Poor attachment False alarms Increase in caretaker workload Sterilization Disposable Models Single use Non-reusable sensor Costly ~$16+ per unit Off-label use Semi-disposable models Complicated design High cost disposable wraps High cost reusable sensors Sterilization (sensor contacts skin)

5. Project Requirements Maintain attachment Minimize cost Reduce caretaker workload Reduce cost per unit Sterilization considerations Easy to use Audience Can be used in any traditional pulse oximeter application Any patient requiring monitoring of heart rate or O 2 saturation

6. Reusable model improvements Velcro TM Stronger clip Disposable model improvements Cheaper materials Semi-disposable model improvements Simpler adhesive/wrap design Eliminate contact between sensor and skin Initial Design Considerations

7. Proposed Solution Disposable adhesive Maintains proper positioning Cost effective alternative to other disposable models Polypropylene Sleeve Eliminate need for sterilization (no sensor contact) Ease of use Reusable sensor Low cost sensor Durable housing

8. Prototype 1.1 Disposable Adhesive Polypropylene Sleeve Reusable Sensor & Housing

9. Prototype 2.1 Construction + + Adhesive Trimmed Adhesive Polypropylene Sleeve Adhesive w/ Sleeve Reusable Sensor Adhesive w/ Sleeve and Sensor

10. Prototype Development Prototype 1.0 Prototype 1.1 Prototype 2.0 Prototype 2.1

11. Disposable Prototype Reusable Experimental Methods

12. Perturbation testing N=1 subjects 3 pulse oximeter models tested Disposable, Reusable, and Prototype Subject positioning Sat adjacent to testing table Shoulder approx. in 60° of abduction in the coronal plane Elbow approx. 0 degrees in the sagittal plane Elbow approx. at 90° of flexion 6 different hand positions Task Dropped 200gm weight to simulate a “yank” or pull on pulse oximeter cord Repeated 5 times for each hand position Data acquisition 1 if adhesive came off 0 if adhesive stayed on * if adhesive ripped or came loose

13. Pronated Suppinated Wrist Extension Wrist Flexion Neutral 90º Pronated Experimental Methods

14. Cardiovascular monitoring testing N=4 subjects 3 pulse oximeter models tested Disposable, Reusable, and Prototype Subject positioning Sat adjacent to testing table Shoulder approx. in 60° of abduction in the coronal plane Elbow approx. 0 degrees in the sagittal plane Elbow approx. at 90° of flexion Palm rested on table Task Assess subject O2 saturation and heart rate Repeated 5 times for each model Data acquisition Nellcor N-200 monitor

15. Experimental Methods

16. Data Analysis MS Excel ™ Data collection Data analysis Averages Standard deviations Figure/Table creation SPSS™ Data analysis Repeated measures ANOVA alpha value = 0.05 Post Hoc Paired T-Test

17. Perturbation Results Model SupinationPronationNeutral90 º PronationWrist FlexionWrist Extension Clip on 055550 Prototype 00000*0 Disposable 00000**0 Hand Positions *Ripped **Ripped and came loose

18. Clip-on Prototype Disposable * * Cardiovascular Results p=0.01 p=0.001

19. Clip-on Prototype Disposable p=0.745 Cardiovascular Results (cont.)

20. Discussion Our testing showed: Equivalence to predicate device (Nellcor D-25 Oxisensor ® II) Maintenance of attachment to digit

21. Economic Benefits Significantly lower price Low cost reusable sensor Low cost disposable adhesive sleeve Market size 33.6M per year (US hospital patients) New York Times (www.chetday.com/medmistakes.html)www.chetday.com/medmistakes.html Distribution Medical supply companies

22. Competitive Analysis Reusable pulse oximeters (clip) Nellcor Durasensor ® $250 Nonin Onyx ® $395 Disposable pulse oximeters Nellcor Oxisensor ® II ~ $16 per single use unit Semi-reusable pulse oximeters Nonin Flex Sensor System $107 reusable sensor $0.85 replaceable wrap Nellcor Dura-Y ® $371 reusable sensor

23. Competitive Analysis Strengths Price Sensor equivalent to disposable models (~$16) Disposable adhesive sleeve equivalent to wraps (< $1) Secure attachment No contact between sensor and skin Weaknesses No competitive sensor design No competitive processor/monitor design

24. Constraints Economic Origin of medical grade materials Origin of electrical components Outside distributor costs Regulatory Limited exposure biocompatibility testing Cytotoxicity Sanitization Irritation or intracutaneous reactivity

25. Quality System Considerations Manufacturability Simple Design 3M Transpore ® adhesive Polypropylene sleeve Encase sensor/emitter in pliable rubber Human factors Ensure biocompatibility of disposable adhesive sleeve Insulate electrical components Ease of use

26. FDA Regulation TITLE 21--FOOD AND DRUGS CHAPTER I—FOOD AND DRUG ADMINISTRATION DEPARTMENT OF HEALTH AND HUMAN SERVICES PART 870--CARDIOVASCULAR DEVICES Subpart C--Cardiovascular Monitoring Devices Sec. 870.2700 Oximeter. (a) Identification. An oximeter is a device used to transmit radiation at a known wavelength(s) through blood and to measure the blood oxygen saturation based on the amount of reflected or scattered radiation. It may be used alone or in conjunction with a fiberoptic oximeter catheter. (b) Classification. Class II (performance standards). US Food and Drug Administration: http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?FR=870.2700

27. Project Goals Research Potential hazards Sensor designs Types of adhesives Design Low cost reusable sensor that maintains accuracy of current competitors A disposable adhesive that maintains attachment Prototyping Acquire materials Construct a prototype Testing Prototype vs. disposable and reusable models

28. Task List – BioE 1160 AudiaJamesAskarChristophel ResearcherModelerManufacturerPrototype Tester Research the potential hazards. Conceptual designCircuit design of pulse oximeter Pilot test the new adhesive with pulse oximeter Research current pulse oximeters (competitors) Model the adhesivePurchase adhesives and pulse oximeters Test new adhesive design verses current models. Research possible size, type, and shape of adhesives. Model the pulse oximeter Assemble prototype device Perform data analyses of the results Specific aims (SBIR) Relevant Experience (SBIR) Significance (SBIR)Experimental Design and Methods (SBIR)

29. Updated Task List – BioE 1161 AskarJamesAudiaChristophel ResearcherModelerManufacturerPrototype Tester Research the potential hazards. Conceptual designCircuit design of pulse oximeter Pilot test the new adhesive with pulse oximeter Research current pulse oximeters (competitors) Model the adhesivePurchase adhesives and pulse oximeters Test new adhesive design verses current models. Research possible size, type, and shape of adhesives. Model the pulse oximeter Assemble prototype devices Perform data analyses of the results Specific aims (SBIR) Relevant Experience (SBIR) Significance (SBIR)Experimental Design and Methods (SBIR)

30. Project Results Research Design Conceptual design Disposable adhesive sleeve Reusable sensor Prototyping Four prototypes developed Testing Perturbation tests Cardiovascular monitoring tests

31. Future Recycling program for disposable pulse oximeters Means of acquiring low cost components Easily made compatible with disposable adhesive sleeve Design emitter/sensor for use with our adhesive Develop a durable sensor housing Design a monitor for our system

32. Acknowledgements Sandra Gartner, RN Mark Gartner, M.S. Shouchen Dun, M.S. Jesse Fisk, M.S. Funding: Department of Bioengineering