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GOAL
Our client Dr. Haughton is currently studying CSF flow during Valsalva maneuvers performed by children with Chiari I malformations. Current research suggests that CSF flow decreases during Valsalva maneuvers in these patients. The airway pressure device would help monitor the exhalation force exerted by each child during a Valsalva maneuver in the MR suite. Knowing the pressure exerted by each patient in the study would be extremely beneficial for data analysis and accuracy.
Design Team Members (from L to R): Kevin Johnson, Laura Sheehan, Jon Cappel, Noelle Simatic
DESIGN WORK
In order to finalize our prototype design, our team needed to decide which components to use. Design matricies were used to select a mouthpiece and valve.
Laura and Jon having fun while testing different nose clip and mouthpiece components of the design.
Our final design incorporates a pressure transducer and sliding plug mechanism for the closed surface simulating the Valsalva. The main tube has airway holes to allow normal breathing when the plug is in the open position. The end cap screws onto one end of the tube, and the mouthpiece attaches to the other. The tubing barb was screwed into the top of the end cap, and the tubing fits snuggly onto the barb. The transducer comes out of the side of the device and is attached to a connector. The connector is attached to wiring that goes to the lab jack.
Shown is a Solidworks representation of the inner workings of the design as well as a picture of the final prototype.
Solidworks drawing
Our completed prototype!
TESTING
The device was first tested to ensure that the plug would go back and forth inside the tube when a compressed air or vacuum source was applied to it. A 5 psi compressed air source offered reliable valve operation. After that, the transducer was inserted into the device and calibrated using a manometer (in mm Hg).
Next, the device was tested on group members to ensure that they could breathe through it in a comfortable and normal fashion. The valve was then closed to test out the transducer and measure airway pressure during a Valsalva maneuver. The maximum pressure that our team member exerted was 75 mm Hg; therefore, the device can withstand pressures of at least 75 mm Hg. This proved that our device can withstand the maximum pressure a child can exert (60 mm Hg).
The device is made almost entirely of plastic, and therefore there were no problems with MR compatibility. The device was tested by having a team member lie on the MR table and conduct a Valsalva maneuver. Even in the MR environment the transducer was able to measure the pressure effectively.
FUTURE WORK
Currently, the testing of the prototype device has been limited to volunteers within the MR suite with no imaging performed. A comprehensive performance test is required to characterize not only the feasibility of using the device in patient trials but also access the accuracy and repeatability.
In the future, the airway pressure device will need to be tested on human subjects. Prior to performing this type of testing, an Initial Review Application must be submitted to and approved by an appropriate UW-Madison Institutional Review Board (IRB). This application includes an outline of the testing which will be performed during the research and outlines any potential risks and benefits to the participants. The IRB will review the application to ensure that the type of testing proposed does not raise any ethical concerns and adequate protections for participants are in place.
Construction of our prototype is complete. We created calibration curves for the pressure transducer and did some initial testing of the device using ourselves as subjects. On Sunday, November 27 we were able to test the MR compatability of our device at the Weisman Center.
Both the initial testing and the MR environment testing were successful and proved that our prototype indeed works!
This Friday, December 2, 2005 we were scheduled to have our final poster presentation. However, due to a water pipe breaking in the ECB it was postponed until Friday, December 9. Our completed prototype will be on display and our presentation will include a demonstration and video of the device in action. We have invited Dr. Haughton to attend the poster session to see the project’s final result. The poster session will take place from noon until 2 pm.
| Week | Reporting Period Beginning | Activities |
|---|---|---|
| 1 | September 8 | Selected project, designated team roles, took team picture, set up client meeting |
| 2 | September 15 | Met with client, created PDS document, selected background research topics, discussed preliminary design ideas |
| 3 | September 22 | Performed background research, updated website |
| 4 | September 29 | Met with client, created information flow diagram, met with Pulmonary Research Lab and obtained supplies for prototype |
| 5 | October 6 | Began work on midsemester presentation, invited client to presentation next Friday |
| 6 | October 13 | Finalized midsemester powerpoint slides and practiced presentation |
| 7 | October 20 | Presented our midsemester powerpoint on Friday, Oct. 14. and worked on setting up a meeting with our client to finalize prototype design before beginning construction |
| 8 | October 27 | Made an itemized list of necessary components for our prototype; ordered transducer, bought cables & project enclosure box, called to inquire about balloon valve |
| 9 | November 3 | Began production of prototype including plastic tube, received transducer |
| 10 | November 10 | Met with client to review device design, decided to eliminate filter and make it disposable, attended human subjects testing lecture |
| 11 | November 17 | Electronics work on our prototype was completed. We were able to connect the transducer to the necessary sofware on a PC. We also finished up minor construction on our device such as epoxying new stoppers on the plug, etc. |
| 12 | November 24 | Calibration curves were created for the pressure transducer using manometer, preliminary testing was performed. HAPPY THANKSGIVING!! |
| 13 | December 1 | MR compatability was tested at the Weisman Center, remaining prototype construction was completed, final poster session was to be held on Friday Dec 2 but ECB was flooded so it was postponed to Fri Dec 9 |
| 14 | December 8 | Final report and design journals were submitted, final meeting with advisor scheduled, final poster session on Fri Dec 9, discussion of plans for next semester |
| 15 | December 15 | Final meeting with advisor |
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Midsemester Presentation Powerpoint Slides (Oct 13 2005, 6164 kb) |
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Final Poster Presentation (Dec 1 2005, 462 kb) |
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Product Design Specifications - updated 12/06/2005 (Dec 6 2005, 27 kb) |
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Final Paper (Dec 7 2005, 2611 kb) |
