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PICList Thread
'heartbeats'
1999\02\10@141227 by Stan Ockers

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                           Subject:                        Time:    1:04
PM
                           heartbeats
2/10/99
                                                            Date:
Does anyone know an easy way to convert heartbeats to pulses that a PIC
could read?  I'm not interested in the amplitude but just the time between
beats.  I would like to have a PIC log the times between beats to tell
when they become irregular, especially when I'm asleep.

They must do it somehow for the bands that runners sometimes wear around
their chests.  I also  remember reading somewhere that IR is sometimes
used but no details were given.

Any help would be greatly appreciated,

Stan Ockers (spam_OUTockersTakeThisOuTspamanl.gov)

1999\02\10@150843 by Mark Willis

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Stan Ockers wrote:
>
>                             Subject:                        Time:    1:04
> PM
>                             heartbeats
> 2/10/99
>                                                              Date:
> Does anyone know an easy way to convert heartbeats to pulses that a PIC
> could read?  I'm not interested in the amplitude but just the time between
> beats.  I would like to have a PIC log the times between beats to tell
> when they become irregular, especially when I'm asleep.

 The oxygen saturation and pulse rate sensors I've seen all TOO much of
when Robin's in hospital, have a red LED and a photosensor, perhaps an
IR pair as well, in something rather like a large plastic clothespin (I
know what they look like but didn't feel like disassembling them while
there <G>)

 You clamp it onto a finger and watch the light conductance waveform
for pulse rate, I know I've read before how they determine O2 saturation
but don't remember just now.  Basically, the blood pressure changes
change the light transmission through the skin <G>  I imagine you could
use this on a wristband or whatever as well, sort of a "back-scattering"
mode of the same thing.

 I thought that the chest tubes were mainly for breathing rates, (They
measure pressure changes from the tube's being stretched as your chest
expands/contracts) but it's entirely possible that an FFT or high pass
filtering or something on there - some devious wonderful trick - would
also disclose a pulse rate?  Anyone know?  Interesting things to learn
in this field for myself, I'm not much good on bio-sensors yet I'm
afraid <G>

 Mark

1999\02\10@165519 by Scott Dattalo

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On Wed, 10 Feb 1999, Mark Willis wrote:

> Stan Ockers wrote:
> >
> > Does anyone know an easy way to convert heartbeats to pulses that a PIC
> > could read?  I'm not interested in the amplitude but just the time between
> > beats.  I would like to have a PIC log the times between beats to tell
> > when they become irregular, especially when I'm asleep.
>
>   The oxygen saturation and pulse rate sensors I've seen all TOO much of
> when Robin's in hospital, have a red LED and a photosensor, perhaps an
> IR pair as well, in something rather like a large plastic clothespin (I
> know what they look like but didn't feel like disassembling them while
> there <G>)
>
>   You clamp it onto a finger and watch the light conductance waveform
> for pulse rate, I know I've read before how they determine O2 saturation
> but don't remember just now.  Basically, the blood pressure changes
> change the light transmission through the skin <G>  I imagine you could
> use this on a wristband or whatever as well, sort of a "back-scattering"
> mode of the same thing.

Check out patent #5,243,992. A sensor SRI developed and patented is
described there.

Scott

1999\02\11@022825 by Oyvind Kaurstad

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{Quote hidden}

You could also take a look at http://www.masimo.com

The have a bit information on the technology used in pulse oximeters.

They claim to have developed a better system than
the conventional "red over infrared" approach. They call it SET.

But you can take a look at their website for more details.

Regards,
-Oyvind

1999\02\11@045618 by Russell McMahon

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HP do one for their pulse oximeter and the clip on part is
essentially a throw away part.

HP did a writeup in a relatively recent HP journal which gave
EXTENSIVE detail on what they did and why and how. They clearly think
that (Don Lancaster's opinion au contrare) patents will protect the
important protectable parts and that its too hard for you-and-me
(pulse oximetry that is, not pulses per se).

HP journal is available online I believe from HP.
Here's the reference
   HP journal
   February 1997
   Pages 39 - 53 (3 articles)

       39    A new family of sensors for pulse oximetry
       48    Volunteer study for sensor calibration
       52    Neonatal sensor clinical validation

   Fascinating stuff.

The clip part from HP gear should be readily available, not too dear
and well engineered.

Pulse oximetry uses the 2 LEDs as a reference - the visible is not
affected by varying haemoglobin but IS affected by gross blood flow
while the IR led has an absorption band affected by Oxyhaemoglobin.
For pulse either and or both could be used.



{Original Message removed}

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