Peak Inspiratory and Expiratory Flow Meter BME 200 300 University of Wisconsin Madison December 7 2005 Team Darshan Patel BSAC Andrew Eley Team Leader Sarah Offutt Communications Eric Bader BWIG Client Christopher Green MD Pediatric Pulmonology UW Hospital Advisor Professor John Webster Department of Biomedical Engineering University of Wisconsin Table of Contents ABSTRACT 3 PROBLEM STATEMENT 3 BACKGROUND 3 DESIGN CONTRAINTS 6 ALTERNATIVE DESIGN 1 DOUBLE BARREL 7 ALTERNATIVE DESIGN 2 TASER 8 PROPOSED DESIGN 3 SNIPER 9 FINAL DESIGN 13 TESTING AND CALIBRATION 16 FUTURE WORK 18 CONCLUSION 19 REFERENCE 20 APPENDIX A 21 APPENDIX B 23 2 Abstract A device for measuring both peak inspiratory and expiratory air flows in a single device is desired Currently it is common to monitor and diagnose asthma by periodically measuring peak expiratory flow Vocal chord dysfunction is a disease that is often misdiagnosed as asthma but cannot be cured by asthma treatments To monitor and diagnose for vocal cord dysfunction peak inspiratory flows are measured The final design must be cheap lightweight and easy to carry around Three design ideas are presented but only one will be pursued Future work entails additional research design improvements and further testing and calibration Problem Statement The proposed project is to create a peak inspiratory and expiratory flow meter as a single device Peak expiratory flow meters are used to monitor asthma and measure flows of about 700 liters per minute Doctors sometimes misdiagnose vocal chord dysfunction narrowing of the airways at the vocal chords during inspiration as asthma Peak inspiratory meters are used to monitor and diagnose vocal chord dysfunction Having a peak inspiratory and expiratory flow meter in one device can help prevent a misdiagnosis of a patient s condition Our device will measure the peak flow at which a person can inhale and exhale air Background Asthma occurs in the lower airways from the trachea down to the alveoli air sacs Asthma is an expiratory problem caused by a narrowing of the airways and an increase of airway resistance There are three common causes of asthma pictured in Figure 1 The muscles surrounding the bronchial tubes can tense causing the airways to contract Another cause is the inflammation and swelling of the bronchial tube lining The third cause is Fig 1 Common causes of asthma Green Island Graphics 2004 3 excess mucus production which fills the airway leaving a small opening for air to pass Asthma typically occurs in episodes following exposure to triggers such as exercise cold or substances in the air Framingham School 2005 Asthma is a common condition which is easy to treat and monitor There are two measures taken to treat asthma medication for long term effect and medication for quick response Long term asthma medications called anti inflammatory agents reduce the swelling and sensitivity to triggers This medication is taken daily Quick response medications called bronchodilators act principally to open the airways by relaxing bronchial muscle American Lung Association 2005 In order to monitor asthma doctors prescribe the use of a peak expiratory flow meter Vocal cord dysfunction occurs in the upper airway specifically the larynx A person with vocal cord dysfunction usually experiences difficulty inhaling Vocal cord dysfunction occurs when the vocal cords do not open and close properly during breathing or speech Allen 2002 Typically this occurs during exercise or nervousness Since the symptoms wheezing and coughing are similar to those of asthma vocal cord dysfunction gets misdiagnosed as asthma Treatment for vocal cord dysfunction is speech therapy One way for doctors to diagnose this correctly is to measure peak inspiratory flow Multiple designs of peak expiratory flow meters are on the market today whereas only a couple of inspiratory flow meters are available Peak expiratory flow meters are designed to help diagnose and monitor asthma All of the expiratory flow meters are similar in internal design but vary in outward appearance The internal structure consists of a thin plate or plunger attached to a spring The plunger pushes up a lightweight 4 plastic indicator that corresponds to a flow rate in liters per minute The force exerted by exhaling moves the spring and plate Along the side of the incremental ruler are three colored arrows These arrows correlate to different zones and are specific to the user If user measures above the green they are in the controlled zone Below the red zone is the danger zone and a user should seek medical attention Between these two in the yellow two peak flow readings in the yellow zone over a 48 hour period tell you that it may be time to call your doctor for an adjustment in your medications Allergy com 2005 Each of the three peak expiratory flow meters pictured in Figure 2 have advantages and disadvantages that should be considered for a final design The far left design is from Personal Best It comes in a self contained case which makes it easy to carry around and keeps it clean Its shape is more rectangular allows it to fit easily in bags and purses The company also made it user friendly by making it Fig 2 Current flow meters dishwasher safe Air escapes from this design from the top which limits the complexity of air loss in determining the flow rate The middle design is from ASTech It is cylindrical in shape It is by far the heaviest of the designs and is slightly awkward to carry around The advantage of this is it is more durable and presumably will last longer The design also has only air holes at the top The last of the designs is the most portable of the three It is from a company called Spirometrics It can fit easily in one s pocket It is also dishwasher safe which makes in more sanitary This disadvantage in this design is that the air can escape from holes on the outer perimeter of the circular airflow way This complicates the calibration of the flow rate The other problem of having air 5 escape on the sides is that the user has more specific instructions on where to hold it If the user is not paying attention it could affect their reading The In Check is an inspiratory flow meter pictured in Figure 3 It like the three expiratory flow meters is portable Fig 3 Inspiratory flow meter Alliance Tech Medical 2005 The In Check is made of plastic and stainless steel It is easy to clean and durable enough for home use It also comes with removable mouth pieces One thing to
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