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Spirometers are used to diagnose many pulmonary diseases including chronic respiratory diseases that affect approximately 300 million people. Many of these people do not have access to a spirometer because current models are expensive and operation requires the presence of a trained technician. The purpose of this project is to develop a low-cost spirometer usable without the aid of a trained technician. The project includes the physical design of the spirometer, software development, and designing a universal interface.
From left to right: Andrew Dias, Andrew Bremer, Jeremy Schaefer, Jeremy Glynn
Dr. Van Sickle is also maintaining the Open Spirometry Network where more information about the project can be found, including his blog.
The team has built a prototype for our design with a pressure sensor, a T-shaped body, and a one-use cardboard mouthpiece.
Depicted above are a SolidWorks model of our final design, a cutaway view of the spirometer, and a photograph of our prototype. Included in this design is a constriction that will increase differential pressure across the sensor leads.
We used a low-noise A/D converter and amplifier chip made by ZMD to process the signal from the pressure sensor. The final design gave good reliability, so we will maintain the general principle as we move forward in the project. However, inner diameters will be increased to meet American Thoracic Society requirements for flow resistance.
We performed testing at constant flows and we were able to obtain a quadratic curve correlating output (proportional to pressure) with flow.
The figure shows the output of the signal conditioner chip (proportional to pressure) graphed against flow. Standard deviations for 10 second samples with a sampling frequency of 100 Hz was less than 0.05% for all samples. A more rigorous testing apparatus will be developed to verify data accuracy. In addition to testing flow, we tested volume measurement capabilities using a 3-liter syringe. After scaling data, the spirometer measures volume to within three percent of 3 liters consistently.
The team also made a step-by-step instructional video that would explain the Forced Vital Capacity procedure to the patient using the spirometer.
Above, two screenshots from the video depict proper blowing procedure and incorrect procedure (coughing, slouching, taking an extra breath)
|Week||Reporting Period Beginning||Activities|
|1||January 23||Assigned team roles, conducted preliminary research, began PDS|
|2||January 30||Completed first draft of PDS, compiled list of components for designs, completed BME 310 spirometry lab|
|3||February 6||Ordered sample pressure sensor, received preliminary design feedback, assigned research topics|
|4||February 13||Received pressure sensor, Arduino board, programming manual|
|5||February 20||Built simple circuit with pressure sensor, continued SolidWorks modeling, found potential material suppliers|
|6||February 27||Developed mid-semester presentation, ordered additional sensors, discussed production of coaching videos|
|7||March 6||Completed midsemester report, basic testing on pressure sensors|
|8||March 13||The team took a week off for spring break and came back ready for action|
|9||March 20||Worked on circuitry and A/V material; set up meetings to advance both of these components|
|10||March 27||Debugged circuit, performed pressure calculations and testing using a syringe of known volume|
|11||April 3||Met with ZMD representatives and obtained A/D and amplification chip, eliminating the need for a circuit. Ordered anemometer for flow testing. Purchased prototype fabrication materials.|
|12||April 10||Obtained anemometer for flow testing, began spirometer body construction|
|13||April 17||Continued spirometer body construction, filmed sample A/V clip|
|14||April 24||Completed spirometer body, performed testing, completed poster|
|15||May 1||Completed final report|
|Midsemester Presentation (Mar 9 2009, 358 kb)|
|Midsemester Report (Mar 11 2009, 548 kb)|
|Final Poster Presentation (Apr 29 2009, 1002 kb)|
|Final Design Report (May 7 2009, 734 kb)|
|Product Design Specifications (May 7 2009, 76 kb)|
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