Phoenix Ambulatory Blood Pressure Monitor Project
8/27/2006 Meeting Notes




Status Review:

* Mike Callaghan: working with his adviser, Eph Sparrow on the technical validity of the idea in the Chen patent.

* Alex: He is working on this problem:
signal out of the amplifier =
[p(t)+m(t)]*h(t) +e(t)
= y(t) - output

p(t)=pressure of the pulse
m(t)= other mechanical force, artifact.
h(t)= input response of the amplifier
e(t)=statistical error

c= is the propagation of the media
L=0.025 m
c= 7 m/s
t=0.025/7=0.003 s

The experiment measures three pulses and produces a computed value.

L< 2CT(sub d).
T(sub d)= 1/f(sub d)
T(sub d) = time between consecutive samples,
f(sub d) = sample frequency, sample rate.

We need to solve for h(t). Potential techniques include de-convolution and blind convolution.

Bob: I suggest pulsing a balloon and create a peak detector, using a capacitor and operational amplifier. Recall that the systolic blood pressure is the point at which a doctor first hears the blood pulse as he/she reduces the cuff pressure. It is the point at which the cuff pressure equals the peak blood pressure if the doctor's hears it. Consequently, it depends on the doctor's hearing and is less than or equal to the peak blood pressure. The diastolic blood pressure is the cuff pressure at which the sound of the blood pulse disappears, or the cuff pressure is always less than the blood pressure. However, the doctor is still hearing a sound, but it is not sharp separation, and this depends on the doctor's hearing and training. A doctor will base this on experience of hundreds of patients. A doctor who sees 15-30 patients a day will be more accurate than one who sees very few. If you have a continuous blood pressure of 170 mmHg systolic it will cause the blood vessels of your kidney to break down and bleed. Also, the cause the vessels to weaken and other effects will occur. The most undiagnosed disease caused by weakened blood vessels is pneumonia, with the symptom of coughing up blood. Often disease names are assigned by symptoms and where the symptoms occur.

The problems that occur with too high systolic blood pressure is blood valves not closing at the proper point and this will cause an elevated blood pressure. Another problem is that if part of the tissue of the hypothalamus is dead because of a stroke, there will be poor control over blood pressure. To show how higher blood pressure can occur in the absence of adequate central nervous system control, occasionally a corpse will contract a muscle and move, because the nerve system causes muscles to relax; when it is no longer functioning, a muscle may contract; and when a mechanical constraint is removed, an appendage may move.

So, the systolic pressure is the contracting pressure of the heart, the diastolic pressure is the relaxing pressure of the heart.

El: Perhaps we can measure m(t) at the systolic and diastolic points, look for what is similar, then subtract it out and see if systole and diastole points are more distinct, then continue the process until it becomes maximally distinct. Then, analyze what was eliminated and create a conceptual model for it. Assume it is m(t), that something about the mechanical artifact is constant, and we identify it and remove it. Dave noted that this is the process of adaptive filtering, could be done by LabView and Alex confirmed that perspective.

Dave: Also, I am setting up a Wiki sensor team collaboration space, using Schtuff, at is free and provides up to 200 MB storage. Key features were storage space, simplicity, free, upload files such as pdf's, html compatibility, photographs, documents, and very flexible. The only other wiki that compared with this was because it had 2GB of storage. But Wikispaces wasn't as flexible or as simple to use. Simplicity was very important for us to enable others to participate in the discussions. The following link illustrates how easily a wiki can be created: .

Franz: We have found that finding the systolic pressure is more easily done. Finding the diastolic pressure is far more difficult. Historically, physicians initially measured the diastolic pressure, (only much later did they measure systolic) and it was felt that diastolic was more related to health. It is also more related to other physical measures such as solar wind, which changes on a weekly basis, e.g. 6.67 days, which is also related to the rotation of the sun, and the overall solar wind seems to have a 20 year cycle, and induces ionization in the body. Three similar physical factors are related to blood pressure: solar wind (solar magnetic field), earth rotation (earth's magnetic field) and cosmic events (cosmic rays). Many feel that solar wind cycles are correlated to incidence of war. Conceptually, systolic pressure is a measure of cardiac output, while diastolic pressure is a measure of peripheral resistance. Many companies have gone broke trying to measure diastolic blood pressure. There are conflicts between consistency and accuracy (precision) because the diastole signal is so much weaker.

Chris: 10 hrs to complete paper, and this week to go to China.

Larry: Visual Basic unit testing tool working in the spreadsheet, they weren't designed to work in spreadsheets. He is preparing a demo, either next meeting or the following.

Dave: The report on the team was submitted last Monday. We have LabView implemented. We don't need the filter board, we can simulate, emulate it in LabView. We don't need to design conditioning equipment, e.g. a low band filter, we can do it in LabView.

It would be nice to have some sort of signal that would correspond to blood pressure. We would like to have a blood pressure measurement tool such as a fake arm to perform tests upon; and a blood pressure measurement system including a blood pressure monitor. Perhaps the Halberg Chronobiology Center can provide us with a blood pressure monitor that provides a signal output to our LabView analysis system

Next Phoenix Project Coordinating Team Meeting: Sunday, September 10th at 2:30 p.m. in Mayo 748



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