Vanderbilt Senior Design 2010: Non-Electronic Blood Pressure Assist Device

1. Vanderbilt Senior Design 2010:Non-Electronic Blood Pressure Assist Device Members: Laura Allen (ChBE) James Berry (BME) Casey Duckwall (BME) David Harris (ChBE) Mentor: Prof. Baudenbacher

2. Blood Pressure Assist Device • The Engineering World Health (EWH) Organization proposed the challenge: • Can a mechanical adjunct for a sphygmomanometer be designed to amplify the oscillatory pressure signal? • Can the design be used by minimally trained users to identify at least systolic pressure? (Ideally diastolic too)

3. Developing World Usability • Self-sustainable • Power supply from mechanical or solar means • Low Cost: Less than $10 • When produced in quantities of 5000+ • Mechanical adjunct to sphygmomanometer • Eliminating the need for Korotkoff sound identification • Identify at least systolic • Pictorial instructions for all users

4. Rationale • Cardiovascular diseases kill more people worldwide than any other disease1 • Even a leading cause in developing nations, where AIDS and malaria receive greater attention • Hypertension is a primary risk factor for cardiovascular illnesses • Managing blood pressure is vital for long-term health of cardiovascular disease patients2 • Diagnosing hypertension can be challenging in developing countries

5. Literature Review • Patent search did not reveal any useful information • Researched the science behind blood pressure • Investigated different methods of measurement • Identified a range for oscillation frequencies

6. Preliminary Data Collection • Findings indicate that measuring blood pressure by observation of sphygmomanometer alone is unreliable • Our final design should be within ±10mmHg per reading, taking into account that normal blood pressures vary by ±3mmHg with each beat

7. Results from Commercial BP Device • Commercially available electronic blood pressure devices in the range of $40 yielded extreme variations in blood pressure readings, going so far as to place some individuals in both stage 2 hypertension as well as hypotension. • Furthermore, these readings were extremely variable between measurements on the same individual, varying by more than 20mmHg for systolic.

8. Project Budget

9. Circuit Specification • An electronic approach yields 5 new design elements • Power Supply • Filtering • Amplification • Readout • Transducer

10. Circuit

11. Power Supply • Reusable • Solar cell - $3.45 in bulk • 3.4V, 25mA • Sufficient voltage output • ±3V operational amplifier rails • ~2V LED, 20mA

12. Filtering and Amplification • Literature suggests frequency range of 20-80Hz • First-order active filtering using • High-pass filter > 10Hz • Low-pass filter < 100Hz • Amplify signal to approximately 2V in passed range

13. Output • Two monochromatic LED • 1) Power light - Demonstrate sufficient power to the device • 2) Indicator light – Light up during pass-band frequencies

14. Transducer • Pressure Sensor: $3.65 in bulk • NovaSensor NPC-100 • Developed for usage in biomedical diagnostics • Sensitivity ±1% • 5µV/V/mmHg • Linearity ±1% • For physiological range • Full range -30mmHg to 300mmHg • Test operating resistance to compute peripheral resistor values

15. References • WHO. “Fact Sheet: The Top Ten Causes of Death.” WHO. November 2008. Accessed October 28, 2009 http://www.who.int/mediacentre/factsheets/fs310_2008.pdf • Pickering TG. , Hall JE, Appel LJ, Falkner BE, Graves J, Hill MN, Jones DW, Kurtz T, Sheps SG, Roccella EJ; Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research. Recommendations for blood pressure measurement in humans and experimental animals: Part 1: blood pressure measurement in humans: a statement for professionals from the Subcommittee of Professional and Public Education of the American Heart Association Council on High Blood Pressure Research. Hypertension. 2005 Jan;45(1):142-61.