Sleep Testing - Skewed Results?
Greetings. I am a new CPAP user and I'm both pleased and a little shocked by my early results. My sleep test returned a result of 51 events per hour and the recommendation came back as URGENT need for immediate treatment. Needless to say I heeded the warning and was soon set up with an AirSense 11. The results have been astounding: In two weeks my AHI has been consistently under 1 and often below .5. I'm thrilled with this result but a little perplexed at the dramatic turnaround.
My question is this: It occurs to me that my sleep test only measured airflow through my nose, which is I believe the standard practice. I have been a mouth breather for years and that night would have been no exception. Could it be that my diagnosis was artificially amplified for this reason? To be clear, there's no question I have sleep apnea but perhaps it's not as bad as the test made it seem by only measuring airflow through my stuffed up nose. Further, if this was in fact a miss, is that a bug or a feature of the testing system?
Interested in thoughts...
RE: Sleep Testing - Skewed Results?
Usually a sleep technician will recognize if you're mouth breathing and move you to a full face mask. What type of mask did you wear during your test? If you were wearing a full face mask, I would think the results would be accurate.
Remember that a sleep test is just one night in time and you will more than likely see varying results night to night.
Your current results with an AHI under 1 indicates you are well treated with your A11.
The AHI of 51 was "before" treatment.
It would be a good idea to ask for a copy of the test for your records.
If you have it, post it here, redacted of personal information. Also, ask for a copy of your perscription.
RE: Sleep Testing - Skewed Results?
(06-10-2022, 10:14 AM)OpalRose Wrote: Usually a sleep technician will recognize if you're mouth breathing and move you to a full face mask. What type of mask did you wear during your test? If you were wearing a full face mask, I would think the results would be accurate.
Remember that a sleep test is just one night in time and you will more than likely see varying results night to night.
Your current results with an AHI under 1 indicates you are well treated with your A11.
The AHI of 51 was "before" treatment.
It would be a good idea to ask for a copy of the test for your records.
If you have it, post it here, redacted of personal information. Also, ask for a copy of your perscription.
Thanks. I'll post my test results when I can but the key point here is they did NOT give me a full face mask for the test. The only thing measuring airflow was a narrow tube in my nose that did not form any kind of a seal. Nothing at all in my my mouth.
RE: Sleep Testing - Skewed Results?
The "narrow tube" probably was just oxygen. I'm not sure how they do a study in BC.
The first part of a sleep study is where they wire you up with tons of probes, no mask.
They can determine how bad your apnea is.
The second part of a sleep study is the titration, where you wear a mask and they can determine what pressure best treats your apnea.
RE: Sleep Testing - Skewed Results?
If your test was at home with no mask like the one like I had originally, it is indeed a sensor. I had the same concerns as you, but my O2 desaturated impressively to show mouth breathing was not working for me either. I suspect your oximetry was similar.
RE: Sleep Testing - Skewed Results?
Hi Doogmeister,
I'm going to assume that you likely had an at home study that did not involve a full face mask or an observing technician. (Many doctors and clinics are now relying on at-home sleep studies because of the cost and the very high demand on full in-laboratory observed sleep studies.)
You are correct, that since the measurement of hypopneas was measured (aka scored) based on flow AND you were occasionally mouth breathing, that the HI (Hypopnea Index) is inaccurate.
So the next thing to look at is the number and duration of Oxygen Desaturations. BTW, Oxygen desaturations do not (numerically) contribute to your AHI.
So, by all means get hold of your sleep study, look for the desaturations, IMO the number is not nearly as important as the frequency and duration, and compare that with your basal (resting- but not sleeping) or nominal saturation.
Good Luck, and if possible report back.
06-11-2022, 09:02 AM
(This post was last modified: 06-11-2022, 09:03 AM by CorruptAlligator.)
RE: Sleep Testing - Skewed Results?
That's quite interesting, and very good observation. I know for a fact that sleep home tests are not accurate compared to lab tests. I should have known that it's only sensing the air movements around the nose with the tubes there. I can't believe equipment like that is standard.
RE: Sleep Testing - Skewed Results?
It's been quite a while, but I think my in-lab sleep test used a breath sensor with three prongs, two up and on down. I'm not sure of that, though
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RE: Sleep Testing - Skewed Results?
The Resmed Apnea Air Link system (used by many sleep labs for HOME based sleep studies) utilizes a standard 2-prong nasal cannula. The sensing mechanism is in the data collection module, there is nothing special about this cannula or the tubing.
If air is passing across the lips, the cannula and the measuring system never "catches and counts", so the displayed (or reported) breath flows are inaccurate. The degree of that inaccuracy is proportional to the fraction of air flow that is "missed".
RE: Sleep Testing - Skewed Results?
Thanks for all the replies. It sounds like my suspicion was right. I would have been breathing at least 75% through my mouth, therefore the results were likely way off. The good news is my pillows mask seems to have opened my sinuses and I'm getting a perfect sleep score every night (AHI below 1). Interesting thing is, I only get that score if I sleep on my side. If I roll on my back I immediately close up and the machine blows so hard it all comes out my mouth. Sleeping on the right side is better than my back by I seem more congested than when I sleep on my left side.
