Researchers Peterson, Skramsted, and Glumac at the Phoenix Ambulatory Blood Pressure Monitor Project, have successfully designed and tested a new non-invasive blood pressure monitoring device.
The purpose of the piezo film pulse sensor project is to identify and build a reliable, low power, low cost blood flow sensor. The sensor is intended for two proposed designs for the ambulatory blood pressure monitor (ABPM). They are: (a) an oscillometric cuff design (as a Korotkoff sound sensor) and (b) the blood flow velocity design.
The data show that piezo film can simultaneously monitor two pulse signals located at a fixed distance from each other. This forms a two-point blood velocity monitor that can be adapted for the measurement of blood pressure. The data show that a 12 inch (30 cm) span results in a time lag of about 32 milliseconds.
The technique worked quite well, but does need improvement. Additional experimentation is needed. The following ideas have been generated by the Phoenix group:
* Use a smaller piezo element for improved signal-to-noise ratio.
* Use a piezo cable. It is hoped that this will improve the sonic sensitivity (over the current sensitivity to mechanical movement).
* Attenuate extraneous acoustic vibrations that are transmitted up the cable. Layers of ‘Silly-putty’, ‘fun-tak’ and Sorbathane(tm) are good candidates for sonic absorbing materials that could be attached to the cable.
* Use an acoustic coupling compound (such as K-Y jelly) between the skin and the piezo film element.