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Pulse Oximetry
More and more of us are buying pulse oximeters, despite the fact that the majority of the sleep clinics in the UK seem to want to keep their patients in blissful ignorance of their actual sleep patterns.
However those of us who want to learn more about their sleep patterns face the problem that we are not trained in how to interpret the results given by these oximeters. My understanding from research data is that the results from pulse oximeters correlate very closely with full polysomnography. If that is right, oximeter users should be able to use their results to indicate accurately whether the pressure they are using is properly controlling their OSA.
To start this discussion I would like to pose the following questions, which are based on my own oximeter (CMS50F). Obviously there may be some other machines which give more, or better, information. If so, details here would greatly assist other users and potential users.
1. What is Basal SpO2(%) and is it significant?
2. My oximeter is pre-set with a "Desaturation Criteria Level" of 88%. What is the significance of this figure, and should I alter it up or down?
3.How low should the "Average low Sp02 %" be, before it is considered abnormal?
4. Is the "Average low Sp02 % < 88%" more, or less, important than the overall average?
5. My oximeter results show %Sp02 levels, and number of events, in bands of 5 i.e. 99-95, 94 - 90 and so on , with the number of events in each band. Should we be aiming not to go below 90 at all, or is the threshold level lower?
6. Is the time in each band significant, and if so what should we look for to show good OSA control?
7. Which overnight pulse levels are considered abnormal?
8. Can the oximeter results be converted into AHIs and if so how?
My apologies for setting out formal questions in this way, but I hope that Rock, and other members, will be able to give expert guidance on these points and others, to assist us all.
We would all benefit if we could understand :
a) the default settings to use
b) which readings indicate good OSA control
c) which readings are considered abnormal / undesirable
Views: 7366
Replies to This Discussion
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Permalink Reply by Tigers Fan on
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Hi John
To get the chart view as above, I used PrimoPDF (free version from CNet) to convert the oximeter file to .pdf and then converted the .pdf to .jpg using FM PDF to JPG (free version from CNet) and then the reply icon. as you said.
TF
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Permalink Reply by RockRpsgt on
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I was going to say that he did not fall asleep until around 3am. it makes sense to know that the mask was off.
Tigers Fan said:Like I said - I stole them!
I'm working on converting the oximeter output to a .pdf - done - and then the .pdf into a .jpg - not done. The trick about size has to be saving full-sized copies at the .jpg stage.
The interpretation is easy - he fell asleep without his mask on, woke up (surprise. surprise!) and then wore his mask for the rest of the night.
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Permalink Reply by John Hedley on
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Advice for CMS Pulse Oximeter users running Windows 7. Don't let Windows Update download an update for the Silicon Labs USB to UART Bridge (the system software which links the oximeter to the SPO2 computer software supplied with the oximeter).
The latest Silicon Labs driver does not work with the oximeter software and will stop you from uploading data to the PC.
I am not sure if this applies also to earlier Windows versions as well, but the moral is not to let Windows Update offer and then install non-microsoft updates. If you really want to update the non-MS software, go direct to the driver manufacturer's site and download from there. However, I have been told that in Silicon Labs case this will also break the link. Definitely in this case, if it's not broke, leave well alone.
Incidentally if there are any Windows 7 users who have done this and are now unable to upload their daily reports please let me know. I will tell you the procedure for mending it!
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Permalink Reply by Kath Hope on
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Thanks for this John. I know of someone who was having problems with the software so will direct them here to read what you've put!
John Hedley said:Advice for CMS Pulse Oximeter users running Windows 7. Don't let Windows Update download an update for the Silicon Labs USB to UART Bridge (the system software which links the oximeter to the SPO2 computer software supplied with the oximeter)...................................................
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Judy said that, "The difference is in the interpretation of a desaturation by the oximeter and the interpretation of an apnea by the PAP device. You can have an apnea that does NOT meet the oximeter's definition of a desaturation. Thus an oximeter reading is NOT sufficient to DX obstructive sleep apnea."
Assuming 'DX' means diagnose, her last assertion surprised me as that is exactly what a lot of hospitals in UK do. I've now stumbled across an article saying pulse oximetry can be used to diagnose OSA.
http://www.sleep-study.co.uk/finger-pulse-oximetry.html
I'm not trying to argue a point here, rather to reassure people that pulse oximetry is a quick and economical way of confirming your suspicions about having OSA. The print outs from it give you something to convince your GP as well.
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An apnea does not require a desat. You are right TF in that the info is better than nothing at all. Judy is right in that the information is not significant enough to diagnose(Dx) apnea. What if the desats are from some other respiratory problem? If this is the way OSA is Dx in the U.K. then they are guessing at assumptions. In the U.S. a negative ox reading will get you a sleep study very fast.
Tigers Fan said:Judy said that, "The difference is in the interpretation of a desaturation by the oximeter and the interpretation of an apnea by the PAP device. You can have an apnea that does NOT meet the oximeter's definition of a desaturation. Thus an oximeter reading is NOT sufficient to DX obstructive sleep apnea."
Assuming 'DX' means diagnose, her last assertion surprised me as that is exactly what a lot of hospitals in UK do. I've now stumbled across an article saying pulse oximetry can be used to diagnose OSA.
http://www.sleep-study.co.uk/finger-pulse-oximetry.html
I'm not trying to argue a point here, rather to reassure people that pulse oximetry is a quick and economical way of confirming your suspicions about having OSA. The print outs from it give you something to convince your GP as well.
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Maybe it would be better put this way:
An overnight oximetry "could" strongly indicate the need for an overnight sleep study for obstructive sleep apnea.
An overnight oximetry should never be used to rule out an obstructive sleep apnea diagnosis UNLESS SUPPORTED by other detection methods such as EEG, etc.
If you are sleeping and your 02 saturation is running at 98% and then you desat quickly to 92% and stay at 92% for 15 seconds before returning to 96% or 98%, your sleep is disturbed, you are kicked out of the deeper stage sleep into a lighter stage sleep and you've encountered an apnea. HOWEVER, you did NOT desat below 88%, you did NOT desat below 90%, so - according to the oximeter you did NOT desat.
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Mine would show that as an event. Do oximeters vary?
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Does your ox show sleep transition desats as well? When you fall asleep you oxygen levels drop. This happens again at REM onset.
Tigers Fan said:Mine would show that as an event. Do oximeters vary?
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Permalink Reply by Joe barnes on
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I now have my oximeter and can see the obvious (drops very low) don't know about anything else I should be watching or doing.
I thought about posting the results but as there is a limit on how many charactors displayed it is not possible to do this.
The only way I could see would be if anyone let me have their email address and I could do an attachment and then if they would be kind enough to give me some advice.
I noticed last night that at one time it dropped so low it went off the screen!
I also do not understand that if I am wearing the a/pap why do I still get these low drops
My email address is:- jabarnes@tiscali.co.uk
Thanks Joe
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I use my a/pap all night every night for the last 2 years.
About 1 year ago I left it off for 1 night and did not feel as good the next day but nothing remarkable.
I have since lost 3 stone and so Now I have the oximeter I left it off last night and today feel alfall.
when you see the oximeter figures it is not surprising.
I will not leave it off again
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