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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: 7338
Replies to This Discussion
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Permalink Reply by RockRpsgt on
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John,
I am finishing my last night of work. I will look into your questions tomorrow while I am off. The reports I see at work are a little different then yours. If you could post a report it would be of great assistance. I have also recruited some help from our sister site. Hopefully you will get some great info.
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Permalink Reply by John Hedley on
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Thanks Rock
I will attempt to upload two sample reports from the oximeter manufacturer's pages. I hope you will be able to give some general guidance re Sp02 reports to assist all oximeter users. Many thanks.
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Permalink Reply by Tigers Fan on
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Hi John
I just lost a lengthy reply by going to see who and what Rock is. I see he suggests adjusting one's humidifier to control rain-out so I'm in disagreement with him straight away!
The nub of my long reply is that all the figures vary with the patient. The figures you are getting indicate what John at your present level of health does at night and never mind the non-existent 'normal'. A useful link to basal SpO2 - http://www.cpaptalk.com/viewtopic.php?f=1&t=28525&start=105
TF
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Thanks TF
I think in that case basal Sp02 is the average Sp02 throughout the recording, excluding the desaturation events - in other words a baseline for the user's "normal" Sp02 at night
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Wow Tigers Fan! Actually I believe my response was to keep the machine below your head. I have done sleep studies and used PAP in many different areas of my country. Each geographical region presented different climates. In some of these climates I was able to control my rainout problems with or without humidity. I have also been able to control mouth leaks with the same feature. This is not always a miracle cure, but in certain situations it will help. Something to consider before spending money as both are free options. ;)
Tigers Fan said:Hi John
I just lost a lengthy reply by going to see who and what Rock is. I see he suggests adjusting one's humidifier to control rain-out so I'm in disagreement with him straight away!
The nub of my long reply is that all the figures vary with the patient. The figures you are getting indicate what John at your present level of health does at night and never mind the non-existent 'normal'. A useful link to basal SpO2 - http://www.cpaptalk.com/viewtopic.php?f=1&t=28525&start=105
TF
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I agree that it is important to understand how you feel and why. understanding your own body is the healthiest thing anyone can accomplish. Where I disagree with you is over the "non-existent normal." What If a person is not intune with their body, feels good, and is asymptomatic. Knowing human abnormals versis healthy averages could save a life. For this reason we have normal or average temperatures, blood pressures, and of course oxygen levels. You would never tell a person with a blood pressure reading of 170/110 that this represents what your present health level does while your walking around during the day. Would you? I would not. I would tell you that this is a high rate. Everyone needs to know what the healthy human normals are if only to use as a tool in self evaluation.
I am no doctor so take what I say as you will.
Many different things can factor into a normal or average oxygen level. Altitude has a great deal to do with it. If it were me I would want to keep my own Spo2 above 90%. I would not get discouraged if I occassionally saw a drop to 88%. Desats are not always caused by an apnea or respiratory event. they can also be caused by movement, swallowing, or just plain ole breath holding. If I saw a large number of desats below 90% I would want to talk to my physician about it regardless of the 88% level. If I were to draw my Spo2 readings as a line I would want it to be as straight as possible.
In the lab while asleep a normal Spo2 is anything at or above 88%. Below this level is considerered to be moderate in severity. if the Spo2 drops and stays below 88% for 30 minutes or below 85% fpr 15 minutes I will add oxygen per AASM protocol.
http://www.aasmnet.org/practiceparameters.aspx?cid=102
I would also think about talking to someone about a high blood pressure, sugar levels, and or body temperature as these are not "normal" in a healthy person.
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Hi Rock
Neither John nor I are trained medics. We are not trying to diagnose ourselves because we are not trained - we rely on our GPs to tell us if we are out of kilter and to prescribe a corrective regime if we are. We both live marginally above sea level.
So, unless something has changed since our GPs last sent us home with a cheery, "See you in x months time", I believe we can safely assume that whatever our pulse oximeters are telling us is typical for us in a reasonable state of health. Our ownership of these meters is to assist us fine tune our PAP therapy, not to become physicians.
Our GPs said we are OK and did not speak of abnormalities. I'm not aware of blood pressure and temperature readings on an oximeter so they don't form part of this discussion.
Someone is born, some dies and any existing 'normal' has changed. What is normal for me may not be normal for you or for John. What is normal for a heavy smoking/drinking person is not normal for an athlete. In this context, John and I are not interested in the health of other people and what their norms are or are not - we purchased the meters for our own benefit and we can only take ourselves as 'normal'because our GPs didn't tell us we were not normal.
So I will both agree with you in general terms and largely disagree with you in specific PAPers-with-an-oximeter terms. For us, an oximeter is and should be no more than a toy and an indicator about PAP adjustments - beyond that is walking into danger due to our ignorance of oximetry.
You say you are not a doctor and that you will add oxygen in certain circumstances. Please scratch my itch - what do you do?
TF
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Ah! in reply to my own question - you're a sleep tech, Rock.
My disagreement with you about rain-out is not about keeping the machine below your head but about "and if that fails try adjusting your humidifier". My arguement is in the rain-out thread.
TF
RockHinkleRpsgt said:Wow Tigers Fan! Actually I believe my response was to keep the machine below your head. I have done sleep studies and used PAP in many different areas of my country. Each geographical region presented different climates. In some of these climates I was able to control my rainout problems with or without humidity. I have also been able to control mouth leaks with the same feature. This is not always a miracle cure, but in certain situations it will help. Something to consider before spending money as both are free options. ;)
Tigers Fan said:Hi John
I just lost a lengthy reply by going to see who and what Rock is. I see he suggests adjusting one's humidifier to control rain-out so I'm in disagreement with him straight away!
The nub of my long reply is that all the figures vary with the patient. The figures you are getting indicate what John at your present level of health does at night and never mind the non-existent 'normal'. A useful link to basal SpO2 - http://www.cpaptalk.com/viewtopic.php?f=1&t=28525&start=105
TF
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The following are Resmed definitions for their PAP devices:
Apnea is the temporary absence or cessation of breathing. An apnea is scored when there is reduction in breathing by 75% of the baseline breathing for at least 10 seconds.
A hypopnea is an episode of shallow or slow breathing during sleep. A hypopnea is scored when there is a reduction in breathing by 50% of baseline breathing for 10 seconds or more.
Oxygen Desaturation Index The mean value of the number of drops in oxygen saturation per hour
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* baseline breathing is taken at rest on room air. For most people this would be above 95%. I have COPD, my baseline breathing at rest on room air is usually 91%-92%.
When hospitalized, it seems to vary whether 88% or 90% is the low 02 saturation level indicating the need for the addition of supplemental oxygen.
Professional Oximetry
Oximeters usually define a desaturation event as a decrease of saturation by 4 or more. Compare that to Resmed's definition of apnea and hypopnea.
The event durations usually have to be w/in 3 minutes to qualify and event onset is definied as a decrease in Sp02 by 4 or more.
Pulse range is also usually identified and reported.
The professional oximetry reports to qualify for insurance coverage include reporting High, Low and Average Or Mean pulse and High, Low and Average or Mean Sp02 as well as Start and Stop time, Event duration, Low Sp02, Highest pulse and Time to high pulse.
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And, if you are interested, medicine is now beginning to recognize the importance of pulse pressure as well as the systolic and diastolic blood pressures. Pulse pressure is the difference between systolic and diastolic pressures, i.e. S - D = PP.
If I remember correctly the ideal BP for a normal healthy adult at rest is 110/70 giving a PP of 40, just as the high end of normal BP is now considered 120/80 and 140/90 is now considered the upper limit of normal BP bordering on hypertension.
So if you also have blood pressure problems you might want to investigate Pulse Pressure as well.
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Hi Rock, Judy and TF
I set out below two sample reports from the manufacturer of my oximeter.
and:
I am sorry that the images are small, but if you click them you see a larger image.
I would be very interested in your views as to the important markers to watch on these reports. I am afraid that my own reports are very different!
TF - are these the same reports as those produced by your oximeter please?
Incidentally the software also produces a detailed file print but I have not added a sample here because it runs to several pages.
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