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Finding My AHI using a Contec CMS50F Oximeter?
#1
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Finding My AHI using a Contec CMS50F Oximeter?
Hello AB!

I have recently bought a Contec CMS50F and I am having trouble finding my AHI using OSCAR along with the 'Smart Device Assistant' software. I imported the .SpO2 recording file from last night into OSCAR and it would only show a couple of graphs (Pulse and SpO2) under the Daily tab along with the SpO2 Desaturations (25.19/h) is that the same a AHI?

It's showing 188 total events of Desaturation, at a rate of 25/hour. Is this equivalent to AHI?

How can I find my AHI using OSCAR and a Contec CMS50F Oximeter? A screenshot for reference is attached.

All help is really appreciated,

Thanks  Cool


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#2
RE: Finding My AHI using a Contec CMS50F Oximeter?
You are having a significant problem with the relative position of your head.  Look at the use of a soft cervical collar to resolve this.  Look at the wiki linked in my signature.
I misread the charts as including Obstructive events, sorry.
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#3
RE: Finding My AHI using a Contec CMS50F Oximeter?
You will not be able to obtain an AHI from an oximeter. You will need a CPAP, or a trained sleep technician with an EKG, to determine your AHI.
Crimson Nape
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#4
RE: Finding My AHI using a Contec CMS50F Oximeter?
(01-04-2022, 12:55 PM)w43l Wrote: How can I find my AHI using OSCAR and a Contec CMS50F Oximeter? A screenshot for reference is attached.

You can't. There is no defined relationship between the SpO2 desaturation index and AHI. 

In my personal data, the ratio between SpO2 desaturation and AHI varies wildly, with no pattern visible. Just glancing at a dozen days where I used the CMS50F, I see the ratio of SpO2 desaturation index to AHI vary from a factor of 6 to 100.

I am are that there are papers that suggest that the Oxygen Desaturation Index (ODI) can be used as a predictor for AHI. However, I don't know whether OSCAR's SpO2 desaturation index is completely equivalent.

So, bottom line, if you want to find out if you have sleep apnea, you need to test with a sleep apnea testing machine, not a pulse-ox like the Contec.
Useful links
Download OSCAR (current version is 1.4.0)
Best way to organize charts
How to attach charts to your post

Apnea Board Monitors are members who help oversee the smooth functioning of the Board. They are also members of the Advisory Committee which helps shape Apnea Board's rules & policies. Membership in the Advisory Members group does not imply medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.
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#5
RE: Finding My AHI using a Contec CMS50F Oximeter?
(01-04-2022, 01:07 PM)Gideon Wrote: You are having a significant problem with the relative position of your head.  Look at the use of a soft cervical collar to resolve this.  Look at the wiki linked in my signature.

Never looked into soft cervical collars! I for sure will now! Thank you for your help and the massive contributions to this community! Cheers!

(01-04-2022, 01:51 PM)Crimson Nape Wrote: You will not be able to obtain an AHI from an oximeter.  You will need a CPAP, or a trained sleep technician with an EKG, to determine your AHI.

I had a suspicion that this was the case, thank you for clarifying that! Cheers!

(01-04-2022, 02:52 PM)GuyScharf Wrote: You can't. There is no defined relationship between the SpO2 desaturation index and AHI. 

In my personal data, the ratio between SpO2 desaturation and AHI varies wildly, with no pattern visible. Just glancing at a dozen days where I used the CMS50F, I see the ratio of SpO2 desaturation index to AHI vary from a factor of 6 to 100.

I am are that there are papers that suggest that the Oxygen Desaturation Index (ODI) can be used as a predictor for AHI. However, I don't know whether OSCAR's SpO2 desaturation index is completely equivalent.

So, bottom line, if you want to find out if you have sleep apnea, you need to test with a sleep apnea testing machine, not a pulse-ox like the Contec.

Amazing input! I am currently looking into that study and will defer to a CPAP machine for getting an accurate AHI reading Smile

Your response was extremely helpful! Thank you for taking the time to contribute to this beautiful community! Cheers!
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#6
RE: Finding My AHI using a Contec CMS50F Oximeter?
My apologies, I assumed the blue in the events were hypopneas. My error.

As others have said you cannot get AHI from oximetry data.
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#7
RE: Finding My AHI using a Contec CMS50F Oximeter?
(01-04-2022, 06:22 PM)Gideon Wrote: My apologies, I assumed the blue in the events were hypopneas.  My error.

As others have said you cannot get AHI from oximetry data.

Got it, Thanks again Gideon!
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#8
RE: Finding My AHI using a Contec CMS50F Oximeter?
I can say that while my apneas DO line up with my desats very nicely, the ODI doesn't - some nights, the ODI is really high but overall my AHI is lower, while on my BAD nights, my OHI is really low, as in single digits, simply because I go into a SpO2 drop and STAY there for an hour or two at a time, while I'm having 30 or 40 events per hour. So as the others have said, you'd need really to see because you can (as I have found) desaturate quite quickly with a flow reduction without an associated event being registered because it doesn't meet the criteria.
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#9
RE: Finding My AHI using a Contec CMS50F Oximeter?
In case anyone is still interested, I used by Viatom SleepU last night and ran its report, comparing it to OSCAR data:

OSCAR SpO2 desaturations: 36.05/hour
Viatom ODI 3%: 5.3/hour
Viatom ODI 4%: 2.0/hour
AHI: 0.53
Useful links
Download OSCAR (current version is 1.4.0)
Best way to organize charts
How to attach charts to your post

Apnea Board Monitors are members who help oversee the smooth functioning of the Board. They are also members of the Advisory Committee which helps shape Apnea Board's rules & policies. Membership in the Advisory Members group does not imply medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.
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#10
RE: Finding My AHI using a Contec CMS50F Oximeter?
(01-05-2022, 06:31 AM)Ratchick Wrote: I can say that while my apneas DO line up with my desats very nicely, the ODI doesn't - some nights, the ODI is really high but overall my AHI is lower, while on my BAD nights, my OHI is really low, as in single digits, simply because I go into a SpO2 drop and STAY there for an hour or two at a time, while I'm having 30 or 40 events per hour. So as the others have said, you'd need really to see because you can (as I have found) desaturate quite quickly with a flow reduction without an associated event being registered because it doesn't meet the criteria.


Great input! The conclusion is these markers are not that correlated and need to be measured separately, SpO2 is just one metric amongst others that paints a very small part of a bigger picture. I am getting a CPAP machine soon.

One last question, will my ResMed AirCurve 10 VAUTO be able to tell me my AHI prior to it opening up my airway? Like a "before therapy AHI/ODI" and my AHI post-therapy? Or the only way to find out my AHI pre-CPAP is to do a sleep study? Meaning can a CPAP machine+OSCAR give me an idea of how many events I WOULD have had if I didn't use the machine that night or does it only give you the AHI post-therapy of that same night?

I am asking this because I don't currently have access to a sleep study (Waiting list too long), and I want to know where I stand currently before therapy for tracking purposes.

Cheers Smile

(01-05-2022, 10:30 AM)GuyScharf Wrote: In case anyone is still interested, I used by Viatom SleepU last night and ran its report, comparing it to OSCAR data:

OSCAR SpO2 desaturations: 36.05/hour
Viatom ODI 3%: 5.3/hour
Viatom ODI 4%: 2.0/hour
AHI: 0.53

This is a great way to solidify what others have stated! ODI and AHI are not necessarily always correlated and this demonstrated that beautifully :Smile Thank you GS!
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