Peak Inspiratory and Expiratory Flow Meter

1. Peak Inspiratory and Expiratory Flow Meter Team: Andrew Eley, Sarah Offutt, Darshan Patel, Eric Bader BME 200/300 December 2, 2005

2. Client:Christopher G. Green, MDPediatric Pulmonology UW HospitalAdvisor:John Webster, Ph.D.Dept. of Biomedical EngineeringUniversity of Wisconsin

3. Abstract • A device for measuring both peak inspiratory and expiratory air flow in a single device is desired. It will help prevent the misdiagnosis of vocal chord dysfunction as asthma. A prototype was built to measure these air flows. The design is a clear plastic tube that contains a plunger which pushes the indicator arrows depending on the air flow. The device was calibrated and tested with a rotameter. Future work includes manufacturing of better parts, obtaining a patent, and marketing for use.

4. Problem Statement • The goal of this project was to create a peak inspiratory and expiratory flow meter in a single device. Peak expiratory flow meters are used to monitor asthma and measure flows of about 700 liters per minute. Vocal chord dysfunction, which causes stenosis of air passages during inspiration, is often misdiagnosed as asthma. Having a peak inspiratory and expiratory flow meter in one device can help prevent a misdiagnosis of a patient’s condition.

5. Background • Asthma • Exhaling, air restrictions in the lower airways • Caused by external triggers • Treated with medications • Vocal Chord Dysfunction • Inhaling, air restrictions caused by vocal chords • Possible causes, exercise, nervousness • Treated with speech therapy

6. Background/Current Methods • Expiratory Flow Meters, use to monitor asthma • Exhaling force moves plunger • Portable • Measured in Liters/Minute • Breathing Zones • Inspiratory Flow Meter • Inhaling force moves plunger • Portable

7. Proposed Design • Design Criteria • Combination expiratory-inspiratory flow meter • Measure peak flow rates, 700 L/min expiratory, 400L/min inspiratory • Simple device using springs and disks • No use of electricity • Safe – clear plastic

8. Altered Design

9. Prototype Design • How it works • Dual Action • Inhaling/Exhaling • Plunger pushes Indicator Arrows • Springs balance the force on the plunger caused by the pressure difference • Scale on the side for reading measurement

10. Testing and Calibration • Used a rotameter to calibrate and test the inspiratory and expiratory flows.

11. Results

12. Results Cont.

13. Our Device --- Materials Clear plastic tube $1.97 End caps - plunger $1.96 Solid metal rod $0.82 Connecting rod $0.30 Springs $0.00 Project Expenses Estimated Cost with Manufactured parts $5.05 $4.50

14. Future Work • Device made from machined parts with higher quality materials • Indicators, plastic covering, removable mouthpiece • Replacement with a new set of springs to obtain a sufficient range with a linear relationship. • Add breathing zone indicators to show acceptable values for peak inspiratory and expiratory flow.

15. Future Work Cont. • Calibrate device with a more accurate method and with multiple trials. • Rotameter proved to be insufficient. • Possibly apply for a patent and find a company to manufacture this device for commercial use.

16. References • Allen, James MD. (2002). Vocal Cord Dysfunction. Retrieved October 2, 2005, from http://home.columbus.rr.com/allen/vocal_cord_dysfunction. htm. • American Lung Association. (2005, July). Asthma in Adults Fact Sheet. Retrieved October 2, 2005, from http://www.lungusa.org/site/pp.asp?c=dvLUK9O0E&b=22596. • Framingham School. (2005, June). Framingham School Health Services: Asthma. Retrieved October 2, 2005. from http://www.framingham.k12.ma.us/schoolhealth/health_info/ Asthma.htm.