Quick Check of Oximeters

sparky2 · Post by **sparky2** » Sun Feb 24, 2008 1:03 pm

If you clip on your finger oximeter and then hold your breath for a long time, can you see a response? How big is it? A couple of papers lead me to believe that a very significant drop (after a slight rise) should be noticed. Mine does not do this.

Sparky2

Papers:
http://www.geocities.com/CapeCanaveral/ ... veame.html

http://www.b-alert.com/Publications/Acc ... andout.pdf

Slinky · Post by **Slinky** » Sun Feb 24, 2008 3:08 pm

I can't answer your question but I can tell you this just to confuse the matter more for you.

These pulse oximeters, even the best hospital ones, can NOT differentiate between the amount of CO2 and the amount of 02 in your blood. They are counted as one and reported as SpO2 on your oximeter.

Holding your breathe "MIGHT" allow for more CO2 in your blood than usual as circulation delivers 02 and returns CO2 which "MIGHT" account for the lack of a drop in the SpO2 reading your oximeter reports. Just a guess on my part.

sparky2 · Post by **sparky2** » Sun Feb 24, 2008 3:22 pm

I thought the same thing when I read that CO2 looks the same to these units as HbO2.

Then I reasoned that, if that were the case, the things would never really work at all. Being confused, I searched and found those articles above that show (I think) response to these device's readings to breath holding.

I am hopeful that someone here either does this periodically just to see if their oximeter is still working correctly or that some will try it now out of curiosity.

Sparky2

Pirateghost · Post by **Pirateghost** » Sun Feb 24, 2008 3:24 pm

I've had two different meters. One is so sensitive I don't want it, the other is simpler to use. I don't know if either of them will pass that test you mention. Most of the chatter recently has been about finding a "decent" recording type oximeter that can be used at a low price. I guess your question should be which of the oximeters under $500 is the best for recording data. If I wanted some real accuracy, I would probably need a forehead sensor that will also pick up co2 which will probably cost over 2K.

sparky2 · Post by **sparky2** » Sun Feb 24, 2008 3:50 pm

I wasn't looking forth most accurate device out there - just one of acceptable accuracy. The links that I attached above pretty much show that the finger type oximeters suffer from a larger accuracy problem than most of the others, but not out of the ballpark for my uses.

In fact I was not seriously looking until I heard is this low-cost finger unit that has data logging. $2,000 is way out of my range of interest. I checked out the company and found that they seem to make decent products and have the right accreditations. Slinky warned me about something like it sounds too good to be true.

I expect that, on the hole, if one can live with finger pulse oximetry type of accuracy that this is as good as any and cheaper than most with data logging. I am just wondering if I got a lemon or .......?

Sparky2

mindy · Post by **mindy** » Sun Feb 24, 2008 4:28 pm

Sparky,

I just read somewhere recently that if you hold your breath the pulse oximeter won't register a drop in O2. It may have been in my SPO-7500 instructions but it could have been in some medical journal browsing.

Mindy

mindy · Post by **mindy** » Sun Feb 24, 2008 4:31 pm

Aha! My memory retrieval time is longer than it used to be! Just this morning I googled using the following terms: oxygen desaturation sleep

In one of those I found that reference to holding one's breath.

m

sparky2 · Post by **sparky2** » Sun Feb 24, 2008 7:08 pm

Thanks, Mindy.

I am searching with "oxygen desaturation sleep" right now. I added "breath" to the search so as to find your references more quickly. Did you look at the second article in my first post above?

Okay the ones I am finding show a response -
This article seems to say that the rate of fall of SaO2 is the same for obstructive apneas as for breath holding.
http://www.chestjournal.org/cgi/content ... t/85/2/181

It says that the measurements were done with an ear oximeter. I tried to insert a copy of figure 5 of the paper but could not get it to happen. In any case, it shows a subject holding their breath for about 40 seconds and the oxygen saturation going from about 99% to about 75%. It looks as though there is about a 10 to 20 second lag in the response as was shown in the other articles with forehead oximeters which I expect to be longer and perhaps not quite as deep with a clip-on finger device.

Hopefully some one will try it soon.

Sparky2
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sparky2 · Post by **sparky2** » Tue Feb 26, 2008 2:38 pm

I still have not found any definite resolution to the question. I went ahead and wore the thing last night anyway and did have one event of 87% for 30 or 40 seconds. I had an AHI for the night of 10.6 as I recall, so maybe there should have been more responses. It looks as though the response came as the result of a couple of hypopneas rather than some of the closely spaced apneas I had during the night.

At least this does show that the device is capable of going below 93%. That is at least some encouragement. I asked a nurse friend of mine to try the breath holding test at work. He said that he had done it before, but that by the time the thing just starts to drop, he has to start breathing again. I told him that this is consistent with the data I have found in the papers I have read, but that he must continue to observe the readings for another minute and note the lowest as there is quite along lag when monitoring at the end of a finger. He will try to do it today and I will see him tonight.

I started to go back and looked at the articles that I have read to see if they all had some amount of O2 depletion before doing the breath holding tests that had shown the sharp response. I recall that one test was done at high altitude and that a couple of them were done after a long period of strenuous exercise. One may have had the subjects simulate many apneas in a row over a long period of time before doing the data collecting. This would explain why Mindy and I have found seemingly conflicting references. I hope that is the case. I will keep the rest posted of the results.

Sparky2

mindy · Post by **mindy** » Tue Feb 26, 2008 7:56 pm

I finally had a chance to check last night's results (have 2 prior nights also). What I'm noticing is that my O2Sat numbers are *very* similar to what they observed in my sleep study. Mild desats to around 85%.

What surprised me is that my pulse rate went up as high as 94 although averages are around 70. I haven't looked at the timing of desat vs pulse rate yet.

Mindy

sparky2 · Post by **sparky2** » Tue Feb 26, 2008 9:56 pm

I wrote that last post from work - away from my data. Looking again the event was not 30 or 40 seconds long. It was a lot closer to 10 seconds.

I did not note earlier that during that time my pulse went from about 74 down to 65 and then up to 93 before returning back to normal about 10 seconds later.

Sparky2

Slinky · Post by **Slinky** » Tue Feb 26, 2008 11:38 pm

Yup, the pulse rate is responding to the lowered oxygen in the blood. I forget where it is posted now but Resmed has an excellent short online video actually showing the heart's response to slowed and/or stopped breathing. The link is posted here somewhere. From dim memory maybe try a search on "excellent video" or maybe it got posted under the light bulb or the red ball at the top of the page here.

Slinky · Post by **Slinky** » Tue Feb 26, 2008 11:56 pm

Here it is. Read thru the entire thread as well as there are some other excellent links.

viewtopic/t25644/THIS-Should-Be-A-Sticky-.html

ozij · Post by **ozij** » Wed Feb 27, 2008 12:18 am

Understanding Sleep Disordered Breathing

Resmed's excellent video . I think you will find it on cpap.com as well.

Be patient, it takes a very very long time to load, you may prefer to download it and the play it from your own computer. Make sure your loudspeakers are on.

I keep it in the "Newbie" folder in my Favorites....
I think its RipvanW who put it in his singature....

Slinky, do you know that Resmed once had cpaptalk on their "Education and Support" part of their site http://www.resmed.com/en-us/clinicians/ ... clinicians and no longer does?
O.

sparky2 · Post by **sparky2** » Wed Feb 27, 2008 12:39 am

Thanks for the links Slinky and Ozij. I am going through the other thread as the video downloads. I am on a modem - no DSL out here in the boonies.

Sparky2

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