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Project Statement: Impedance Cardiography is a medical procedure utilized in order to properly analyze and depict the flow of blood through the body. With this technique, four electrodes are attached to the body, two on the neck and two on the chest, which take beat by beat measurements blood volume and velocity changes in the aorta. However, this system withholds degrees of inaccuracy due to the mere fact that the electrodes are placed too far from the heart. Our collective goal is to design an accurate, reusable, spatially specific system that ensures more accurate and reliable readings.
In the final weeks of design a viable prototype has been constructed, this prototype was then tested and compared to both a traditional impedance test and a centered electrode impedance test. Form this it was determined that the constructed prototype presented a practical alternative to current methods of impedance testing. In the future we hope to perfect this prototype by building a phase demodulator which will filter out the unwanted EKG signal. We also hope to renovate the strap attachment making it easier for body placement and usage and finally we hope to devise a method of finding exactly what placement of electrodes gives the best signal.
The final constructed design prototype can be seen in the pictures above. It is made of a silicone rubber base upon which slits are cut on the ends, allowing an elastic strap to hold the system to the body. These slits are reinforced with a nylon plastic which decreases the chance of any ripping of the silicone to take place. Next, it is seen the base holds a matrix of modified electrodes. As seen in the picture below these modified electrodes consist of an extremely trimmed down base only including the electrode lead itself and the conductive foam on the bottom. It is also seen that in order to extend the electrode lead for easier hookup, a wire was wrapped around the lower part of the lead and then soldered to itself. The electrode was then threaded through the silicone base and the wire was tied in a knot in order to ensure a minimum movement in the electrodes. Lastly, looking on the underside of the prototype there is a hydrophobic mesh material. This is present in order to serve the purpose of prohibiting electrode gel to stray from one electrode to another. This would cause a short circuit and extremely distort the output signal.
| Week | Reporting Period Beginning | Activities |
|---|---|---|
| 1 | September 4 | Met With Graduate Students Amit, Ryan, and Elena, who are helping us with our project through Professor Webster |
| 2 | September 11 | Met With Client Professor Webster, and |
| 3 | September 18 | FIrst team lab to run over some simple electronics |
| 4 | September 25 | Had another team lab with electronics and met to discuss some preliminary designs and specifications |
| 5 | October 2 | Team lab with electronics and circuitry to help us begin to build some of our designs |
| 6 | October 9 | Designed midsemester Project Presentation, met multiple times to discuss designs |
| 7 | October 16 | Project midsemester Presentation |
| 8 | October 23 | Built preliminary Amplifier with our awesome Graduate Student Elena |
| 9 | October 30 | Debugged our amplifier |
| 10 | November 6 | Finished Amplifier and was able to get proper signal, built preliminary model to begin testing |
| 11 | November 13 | We continued to debug our amplifier and began to see some positive results from our electrode matrix |
| 12 | November 20 | Worked on finalizing our electrode matrix and continued to get positive results from testing comparing our matrix to four electrodes over the heart |
| 13 | November 27 | Built Final prototype and found it to be most successful |
| 14 | December 4 | Received positive results, the EKG is hiding our hopeful pressure wave from the heart, so we attempted to build a high-pass filter to isolate the pressure wave and were unsuccessful, next semester we will build a phase demodulator |
| 15 | December 11 | Finalized Paper and turned into Professor Webster, and Professor Tompkins |
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Project Design Specifications (Oct 11 2009, 24 kb) |
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Final Report (Dec 15 2009, 730 kb) |
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Mid Semester Report (Dec 15 2009, 358 kb) |
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Final Poster Presentation (Dec 15 2009, 1623 kb) |
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Mid-Semester Presentation (Dec 15 2009, 1157 kb) |
