Phoenix Ambulatory Blood Pressure Monitor Project
8/26/2007 Meeting Notes




* Schlentz: Didn't get 2 things done: Information about 1) field programmable gate arrays, 2) piezo film. How big a piece can we get and the cost?

* Jim: He purchased the additional piezo film for Ashok and Inanc's sensor project, requested by Mary Jo and approved by El for reimbursement. Ashok, Inanc and Jim used an Omron wrist cuff that provides a measure relative to pressure and location, compared with the piezo film signal, when you feel a strong pulse, you get a strong signal. Now when we get 3 of the commercial films, 28 u, 54, 110 microns, with different backings -- 5 mm, they have a protective coatings. Largest has adhesive on it, so you can slap it on. We don't think we can have a adhesive and get a variable electrode. Bob: There is a material called Tegaderm, to hold the sensor wherever we please, it does not cause skin reactions, it is adhesive, some sort of colloid, made by 3M. If it adheres to aggressively, you can use Mepilex Border instead. Jim: we ccan use a saucer like shape so that it provides pressure. The material configuration would be: Skin, pieso film, pressure element, and adhesive over-structure cover. The pressure element provides a wave spring. If the wave spring was serrated, it would push in lots of places, we would get a good signal and will more likely pick up the pulse. See Bellvue Wave Spring. Perhaps the active area would be a square around the wrist bone. The second place would be the inside of the elbow. Because the film is working in a shear mode, it is nonlinear so you want it bowed (curved). If we put multiple electrodes, we would have an electrode array, Perhaps an independent electrode at each corner of the diamond shape. Bob: it would function as a strain gauge, electrically isolated from each other, like a wheatstone bridge. Jim: is there a potential difference across the conductive service, like a charged pump, pumped by the piezo effect, a different that would be meaningful, giving us much more information about that arterial wave. A second sensor could compute the transit delay. However, we need to know the distance. If it were a fixed distance through flex circuitry, we would know it, even if it were folded to fit the size of the arm. Bob: Is there still a signal strength is affected by temperature: v=at. Larry: Germaine had a concern about accuracy of the Omron ABPM, so we want to be careful how we use it in calibration. Bob: it is useful now. Jim: no one really knows what these measurements mean anyway. We calibrate to a Millard catheter, which is inserted in an artery, which is probably a film, to produce blood pressure, not SBP or DBP. SBP and DBP is an artifact used to measure BP.

* Larry: Has been working with Franz and Germaine to automate the production of the Sphygmochron report for Germaine as an internal website. HCC would like it made available to massive use by others. The University's IRB objects because it wouldn't necessarily mediated by the researcher to assure that the subjects are properly informed. Larry wants to assure that we are operating in a way that is approved.



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