From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.physics,sci.chem
Subject: Re: Carbon di oxide
Date: 27 Oct 1998 22:58:57 GMT

In <715f0f$qhq$3@node2.nodak.edu> thweatt@prairie.NoDak.edu (Superdave
the Wonderchemist) writes:
>
>AG (gamit@shani.net) wrote:
>: Carbon di Oxide levels may change perception and mood and blood pressure
>: according to my new thesis.
>: Would anyone has suggestions on a quick method of measuring level of CO2 and
>: O2 in blood.
>: Amir Gazit.
>
>Get a blood gas analyzer.


That's hardly quick, or simple.  You can get some idea of what blood
CO2s are by looking at end-tidal (alveolar) CO2 measurements (yes, I
know they aren't exactly the same, but the one can be a helpful
predictor of changes in the other, if other parameters stay the same).
End tidal CO2s can be measured easily and fairly cheaply by instruments
such as SensorMedic's "Tidal Wave" device.  For a huge study of CO2
concentration effects, I would think a Tidal Wave would be unavoidable.
Would a lot of calibration using blood gas data.

The gold standard, of course, is in-line blood gas monitoring.  But
you're looking at $10,000 to start, there, whereas you may be able to
borrow time on a blood gas analyser someplace.  And in-line stuff means
threading a catheter into an artery, as opposed to just sticking it.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.physics,sci.chem
Subject: Re: Carbon di oxide
Date: 28 Oct 1998 09:45:27 GMT

In <F1IHrt.HFq@midway.uchicago.edu> meron@cars3.uchicago.edu writes:

>Hmm, I wonder.  Since the blood color changes depending on O2 and CO2
>concentration, couldn't you get a quick and dirty result by comparing
>the reflectivity of a drop of blood at two different wavelengths?
>
>Mati Meron                      | "When you argue with a fool,
>meron@cars.uchicago.edu         |  chances are he is doing just the same"



Yes, you can do that for oxygenation (and that is how it IS done in
hospitals-- they put a little infrared clip on your finger, and the
oxygen saturation of your blood is measured non-invasively).  Alas,
color of blood depends on oxyhemoglobin content, and doesn't change
much with CO2 content.  In part this is because CO2 binding to
hemoglobin does not per se cause much of a color change, and in part
because much CO2 is not carried on hemoglobin at all, but rather
disolved as bicarbonate and carbonic acid in plasma, helped along by
the acid (hydrated protons) absorbed by hemoglobin when oxygen is
removed from it.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.physics
Subject: Re: Carbon di oxide
Date: 29 Oct 1998 09:06:53 GMT

In <F1JsnD.6u1@midway.uchicago.edu> meron@cars3.uchicago.edu writes:
>
>In article <7176p8$ar$1@news.ipf.net>, sysbl@ten.yako (Lorenz Borsche) writes:
>>In article <F1IHrt.HFq@midway.uchicago.edu>, meron@cars3.uchicago.edu
>>wrote:
>>
>>>Hmm, I wonder. Since the blood color changes depending on O2 and CO2
>>>concentration, couldn't you get a quick and dirty result by comparing
>>>the reflectivity of a drop of blood at two different wavelengths?
>>
>>How about reflectivity measured in the vein and through the skin?
>>Maybe resonance could do the trick?
>
>Well, Steve Harris already answered this, turns out it may work for
>oxygen but not C02:-(  So now we need something that couples well to
>CO2.  Sounds like one for Uncle Al.


  Uncle Al can make a lot of money if he can think of something.  CO2
is relatively easy to measure directly in *air,* due to that nice C=O
stretch in the IR region. In fact, that's how the various CO2
production analyzers used in medicine (the SensorMedics Tidal Wave,
CO2SMO, etc) do it.  But in blood there's too much other stuff to
interfere with that.  And measuring the spectral change in iron in
hemoglobin (as for oxygen) is out for reasons already mentioned.

From: sbharris@ix.netcom.com(Steven B. Harris)
Newsgroups: sci.physics,sci.chem
Subject: Re: Carbon di oxide
Date: 29 Oct 1998 09:14:49 GMT

In <717f4u$18c6$6@node2.nodak.edu> thweatt@prairie.NoDak.edu (Superdave
the Wonderchemist) writes:

>A guy upstairs uses RAMAN spectroscopy to determine binding of CO2, CO and
>O2 to hemoglobin and a host of porphoryns, but a RAMAN set-up would be
>even more pricey than a blood-gas analyser by a couple orders of
>magnitude.



   Interesting.  Can he get it to work through skin the question,
though?  A noninvasive method might be worth the price for a few
selected physiology studies.  Also, does Raman specroscopy see the CO2
in HCO3- and H2CO3?  If not, it wouldn't be much good for studying CO2
physiology in live animals.