Phoenix Ambulatory Blood Pressure Monitor Project
3/7/2004 Meeting Notes
Jay Rabel, firstname.lastname@example.org,
Two approaches, pressure cuff & blood velocimeter.
Cited Blood Pressure Measurement, from 1999 CRC Press, LLC
Auscultatory: blood pressure cuff, increases blood pressure, reduces pressure until some blood gets through (systolic pressure), then reduce until the sound ceases (diastolic pressure). From artery partially open to completely open, highest pressure to lowest pressure.
So, Wade has been looking at low power approaches. Piezo-electric film: 90 volts & very low current. Piezofoil from Amp/MSI. Navy uses for passive sonor, piezo-cable typically used for high frequency 10's of kHz, but what about low frequency. So he designed a low pass filter. 1 - 12 Hz. Bob Schlentz says that for long time period, 1/10 Hz. The circuit will use a 10 Ohm , 33 dB at the 50 Hz point. TLB 2244 at $1.46 in quad pack. Want low current amps at low voltages. If under 14 mA, can use AA batteries. Maybe 200 uA total. Through Express PCB, about $50 to produce the board. To put in into the Public Domain, uses Richard Stallman's Copyleft, it allows anyone to use or disseminate it as long as they retain it, "Copy and Distribution is preserved in any medium, as long as the Copyleft statement is preserved." The copyright is an expression of an idea, does not protect the underlying design. To protect the design, use a patent. To place the patent in the public domain, either give it away or use a Patent Invention and place it in the public domain.
Using a DSP uses a lot of power and decreases battery life. Alternatively, just collect data and post-process.
Wade suggests that we make a prototype, get two boards built, about $60 per board, total ~$120,
Bob suggests using A/D to flash memory, USB/RS422 to main instrument, which accepts , parses the data packet of date,name, time, info transferred into people readable information at frequent intervals (1/sec), into a memory in main instrument, process data and show an envelop of the peak of pressure and minimum for the time, process the envelop and produce the CHAD for use by the Chronobiology lab. Then, we need to calibrate, measure actual blood pressure vs our measurement. If the sensor were oscillometric, must have that sort of measurement, the cuff measurement and our distal peripheral measurement, a display/report that determines the match to the cuff measurement, and repeat the calibration points frequently to show that the ambulatory instrument hasn't been damaged or wanders. Now, can we get any new information that would be useful for Chronobiology.
Wade says Compact Flash Card typically uses 300 mA, $20-$30 each. USB ~ $20. Ethernet ~ $30. Alternatively, just remove the card and transfer it to the collector unit. However, using the card pushes price so high it can't be exchanged for "a bushel of yams."
Bob suggests that we collect raw data and process it to blood pressure measurements in central non-worn unit.
Wade has reviewed Pulse Velocity patents and simulated them to determine their components. Found that they are putting a DC current and reading . Wade has drafted two project proposals. Piezo-film sensor - a blood flow sensor with deliverables: evaluate the completed sensor with Public Invention Release and written report. Second is Pulse deliverables, IR parts, layout, BOM, evaluated completed sensor, PIR, and written report. Another project: movement sensor: only take measurements when the body is steady. Bob suggests that 2 people per project, total of 13 people.
Bob suggests that when we use any polyester film (piezo-electric films are such), what are the guidelines in using them on people.
Get a website. Have it globally available. Wade will start, El will get an IEEE website for the Phoenix group.
Diabetes, 0.01 mm per mm rise in blood pressure, small but useful for a blood pressure gain measurement for capacitance, and gain afterwards. Eg. the arterial wall is a dialectric material. How big a signal, how much motion, for blood pressure & vessel measurement
Another measurement: How to measure the relative position of the senor wrt to the top of the heart. Perhaps use a distance transducer.
Another idea: How to make blood flow measurements using the time to measure the wave passage. Then, measure the forward and backward/retrograde wave,
Bob: Would like to have this project done in 6 weeks.
Wade: will start the website and begin the design of the board. Will send El the projects. We need a project list & a bibliography, a hit counter.
El: get a website
Bob: Present his results
Next meeting 3/21 2:30p,
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