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. |