EWH: Low Cost Pulse Oximeter Jonathan Meyer Bogdan Dzyubak Matt Parlato Joe Helfenberger
Question �Q: What would be a useful device in hospitals of the developing world? �A device to check oxygen saturation within a subset of patients. Pulse Oximeter
Pulse Oximeter �Detects blood Oxygen saturation �Prevention of complications by identification of hypoxemia �Used in cases where symptoms and feedback is limited �Under anesthesia �Unconscious (critical care) �Chronic conditions checkup �Infants
Why aren’t pulse oximeters common in developing countries? ~ Price is too expensive ~ BCI Finger. Print® Octive. Tech 300 C $692. 00 $265. 00 Devon Medical C 202 $99. 99 EWH Target Price: Under $8 for final probe cost Photos: http: //www. google. com/products? q=pulse+oximeter&scoring=pd, http: //www. buyemp. com/product/1040108. html, http: //www. devonsuperstore. com/detail. aspx? ID=189
Oximetry principles �Light is shined through blood vessels �Absorption occurs in skin, veins, and arteries �Arteries carry oxygenated blood (affects absorption)
Oximetry principles (cont. ) �Two LEDs shine light of 660 and 940 nm �detected by photodiode on opposite side �Ratio of absorption is used to calculate oxygenation �Only changing signal is used �Frequency of 0. 8 – 2 Hz
Probe Types �Transmittance – finger or ear �Reflectance �Requires underlying bone – forehead or sternum �Needs more light or better detectors �Offers different design possibilities
Considerations and limitations �Precision should be within 5%, preferably 3% �Cost should be low �Final product manufacturable at $8 �Should be durable and/or easy to repair �Convenient to use �Compatible with driver circuit
Design Options: Finger Probe Phototransistor (top) 2 LEDs (bottom) Pros Convenient for spot checks Unreliable peripheral circulation Comfortable Fingernail polish Wears out easily
Design Options: Forehead Probe 2 LEDs 3 Phototransistors Around head Around Head Pros Cons Durable Inconvenient to adjust headband Reliable circulation Low signal resolution Versatile adjustment Possibility of misuse Works on all age groups
Design Options: Ear Probe Ear Strap 2 LEDs Pros Convenient for spot checks Reliable circulation High signal resolution Phototransistor Cons Moving parts, possibly not as durable Adjustability is lower
Design Options: The Matrix Weight Finger Forehead Ear Cost 10% 7 7 8. 5 Accuracy 25% 5. 5 6. 5 7. 5 Ease of Use 20% 9 5. 375 6. 25 Range of Use 20% 8. 5 7. 625 6. 25 Durability 25% 4. 375 7. 625 7. 25 Total 100% 66. 7 68. 3 70. 4 EAR PROBE WINS!!!
Future Work �Issues to Address are: �Finalize housing design �Proper mounting of electronics �Determination of exact voltage and current specifications �Addition of filters �Mechanical testing of device durability
Goals for this Semester Test the probe’s accuracy and ease of use 2. Mechanically test the probe’s durability 3. Develop working prototype 1.
Conclusion �Goal: A pulse oximeter probe must be designed that is not only durable but is accurate, cheap, and can be used for a variety of patients �Transmittance through the ear �Robust mechanical design that will be: �easy for the doctor to use and adjust �extremely durable