Nice work!

Thanks!

It drives me nuts when I see an elegant solution, then say "Wow, that's simple". I started out with an idea, and when it didn't work, I stopped.

Thanks Ron! Now to detemine blood pressure... There should be some sort of correlation betwen slope and pressure, or am I totally off on that assumption?

After reading how those blood oxygen finger clip thingies (photoplethysmograph) work, I guess there must be some correlation, But I can't imagine how you could get numerical values.

 

Great work!

As far as blood pressure, my best guess would be to use the radial component of velocity in the arterial/venous wall.

This can be done by finding the doppler shift -- cannot be done with an LED, unfortunately, but can be done with an open can cheap laser diode/photodiode couple . . . since the dopper shift wavelength is dependent on the original wavelength, i would suggest an ir laser to begin with . . . perhaps a laser gutted from a cheap cd-rom sled?

i did some basic experiments with this about a year ago and had good results at the fingertip. if you can quantify the velocity of the arterial wall, you should be able to do it.


OR, this just hit me, (duh), you measure the magnitude of the pulse with the plethysmography circuit at two known distances from the heart, or two known distances from each other, and see how the wave either propagates period, or diminishes from one detection to the other. you can derive some quantitative information from that.

 

With a few changes, the circuit could be made to work with a single supply.

 

Nice work!

It drives me nuts when I see an elegant solution, then say "Wow, that's simple". I started out with an idea, and when it didn't work, I stopped.

Thanks Ron! Now to detemine blood pressure... There should be some sort of correlation betwen slope and pressure, or am I totally off on that assumption?

One Guy:

You would really appreciate this:
http://www.paulgraham.com/taste.html

This is my favorite essay of all times. I try to emulate it whenever I can.

Eric