LOW AHI vs actual REAL quality sleep

[quiescence at last]

I have been getting a good night sleep at CPAP Auto varying between 6 and 13.5 cmH2O, getting RDI between 4 and 12. I recently went seeking after my "better" night sleep.

In the last 2 weeks, I have shifted to straight CPAP with C-Flex of 2, and gradually adjusted from about 7 cmH2O to 12 cmH2O. I stayed at each setting for about 3 days. Some days I have gotten RDI under 2, and AHI under 2. Finally, at 12 cmH2O, I experienced aerophagia, and ceased to press any further.

When I actually noticed the aerophagia, it was while trying to fall asleep. I would take about 3 breaths, and then feel the overpowering urge to burp. This would continue for better than 5 minutes, well beyond my normal rate of falling asleep. I didn't say I couldn't stand it, or it is horrible, just unpleasant and undesired.

I have now converted to APAP with A-Flex of 1, and range 11 to 12 cmH2O. My initial night (usually the rocky one for any setting) I got and RDI under 4. I will try this for a dozen or so nights, and see how this works.

I telling you because, as MobileBasset indicates, sometimes you have to take yourself where the machine wasn't automatically taking you - in order to get better sleep. In my prior setting of 6 to 13.5 cmH2O, I rarely got to a pressure above 9 cmH2O, and my average pressure was about 7.2 cmH2O.

good luck, all.

QAL

[TyroneShoes]

...the term arousal and the term apnea event are so different they cannot be describing the same thing...

...There are many apneas that resolve without arousal per se. There are many arousals that are not scored as apnea or even hypopnea. Case in point, RERA or respiratory effort related arousals are detected by some machines, and those wave forms do not resemble the hypopnea or apnea events. There are arousals that are not connected with any apnea, such as periodic leg or arm movement, or from being startled by noises inside or outside. There are apnea that get resolved by central nervous system feedback, without arousal; there are apnea caused by mechanically overventilating which may not lead to arousals. My natural arousals throughout the night are not the product of apnea...

They are different, but are very closely related. Most arousals are caused by apneic events, and that is the core of the definition of RERA events.

You are very correct, not all arousals are respiratory-event related, of course. Two cats having a gang-bang in the alley can arouse you. "BEEP BEEP BEEP" as the garbage truck backs up at 5 AM. Underlying worry about work or a family member can affect the quality of your sleep.

But the bottom line is this: the only feedback the xPAP has is measuring the back pressure of your breathing. That is the ONLY thing it knows, and it bases every guess it makes on that. The algorithm is clever, and it can tell by how that pressure changes throughout a breath cycle whether what is going on is considered an apnea, and can even guess pretty accurately at what kind of event it is.

But is has no earthly idea whether you are aroused or not, because it has not even the basic ability to even know if you are asleep or awake. Just as it guesses at what events you are having based on the waveform of your respiration, it is also guessing on whether that arouses you, and how much. But that is a secondary interpolation very far removed, which makes it much more of a wild-ass guess than even it guessing whether you had an event or not, which is also not based on direct evidence, but on a supposition that if you breathed a certain way, that may be characterized as an event.

And this is why there is a niche where an infrared cam can help figure this out. The cam or motion detection system can SEE whether there was something that appeared to arouse you. The xPAP is blind, and can't see any of that, and maybe it should not be making assumptions just because that can be used as a superfluous empty marketing advantage, when it likely holds very little value, something in direct conflict with providing accurate, useful medical data. It's a damned medical device, not the next iPhone.

The S10 is the generation of machine from Resmed just after the S9. The S9 did not "report" RERA, while the S10 does. Did the basic algorithm change, or improve to allow this? Probably not. An APAP treats apneic events (some of them, anyway, it essentially ignores CAs and hypops, only noting that they happen, although pressure alone can help them). Pressure is what "treats" SA, and RERA is included under that umbrella.

What changed is the reporting. Resmed could not be seen as lacking, so although the algorithm likely did not change, the marketing did, so they could be "me too" to PR and the others that were already "reporting" RERA, something all of them are simply guessing at in the first place, and something treated by pressure, just like other events, which is what the xPAP had provided all along. Hype is alive and well.

You may have notice me using the word "guess" a lot here, because that is what the xPAP does, and is all it can do. And you all know what "assume" does to "u and me", and what that word means without them.

But an xPAP, even if it is claiming RERA detection capability, is making claims that are probably a little far fetched. A PSG has a good idea regarding arousals. The xPAP is taking a blind guess based on questionable soft data.

I will also make a guess, which is that how aroused one becomes due to an apneic event is very variable. I never had an arousal I knew about for the first few decades of my life, but it's probably not likely that a study telling me I had and AHI of 56 untreated means this developed for me overnight.

So the guess part is that an apneic event can be more of a problem for people who react to them in a stronger way. I know that much of the reaction can be unconscious, and that you never really may know there was an arousal, which means that the amount of stress they are causing may be similar, but there are lots of SA sufferers who find conscious arousals to be problematic. I'm just not one of them.

The other thing to not forget is that AHI is a dumbed-down indicator. you can have 60 OA "events" per hour exactly 9.9 seconds long, and your AHI will be zero. Or, you can have 60 events of 10 seconds each and your AHI will be 60, and also, you can have 10 events of 60 seconds each and your AHI will be 10. But the total time in apnea for those last two scenarios is exactly the same, and the O2 desat may be very different, and maybe in more dangerous territory for longer events.

So AHI is fuzzy and inaccurate, and is only a general indicator. Its useful for what it is, but misleading about the real underlying issues. O2 desat is an analog issue; it happens on a scale, based on time flow. An apneic issue is not perfectly unproblematic at 9 seconds and then is a big issue at 10 seconds and holds the exact same importance when the event is 60 seconds long.

[PaytonA]

TyroneShoes,

I got lost in your post. Would you please summarize your conclusions. It might help others too.

Best regards,

PaytonA

[surferdude2]

I agree with everything he said and the way he said it. I like things to be explained in detail and to offer a wide range of possibilities. The point that the length of the OA events is rarely mentioned yet can be of more importance then the frequency of shorter events is well worth pondering when considering how well our therapy is working.

Soooo, since I'm obviously obtuse, I disapprove of the allegations and yet defend the alligator er.. alleger.

[SuperSleeper]

At the risk of me also sounding obtuse, I actually like a really detailed explaination followed up by a short summary paragraph. So if I have time to read the details, I do. If not, I read the summary to get the gist of what's said. Best of both worlds.

[sonicboom]

Lots of great info QAL and Tyrone confirming what I had suspected all along. My point, however, was its a good place to start when you have a low AHI and still feeling tired. Ultimately, it's likely something a doctor might need to address if simple adjusting of your machine doesn't change anything.

At the risk of sounding repetitive Tyrones conclusion is well stated..... "AHI is fuzzy and inaccurate and is only a general indicator. It is useful for what it is but misleading about the real underlying issues."

[storywizard]

Lots of great info QAL and Tyrone confirming what I had suspected all along. My point, however, was its a good place to start when you have a low AHI and still feeling tired. Ultimately, it's likely something a doctor might need to address if simple adjusting of your machine doesn't change anything.

At the risk of sounding repetitive Tyrones conclusion is well stated..... "AHI is fuzzy and inaccurate and is only a general indicator. It is useful for what it is but misleading about the real underlying issues."

yes I agree...

thanks for the detailed post...

Storywizard

[PaytonA]

Okay, are we saying that AHI is fuzzy and inaccurate because it does not take everything into account or are we saying that the machines can not accurately determine if we are breathing or not and for how long we are not?

[pholynyk]

It's not that AHI is 'fuzzy'. It's an exact calculation of event count divided by total time. It's a simplified measure of sleep disruption.

It's just that it may not be the most useful measure of sleep disruption. ETA: It doesn't measure duration or severity of the event.

I tend to look at Total Time in Apnea and divide that by total time. Even that may not be really good because most hyponeas are counted as 10 seconds regardless of actual duration. Of course, since my sleep is usually broken, I really should try to subtract off the non-sleep time, as best I can guess it.
I don't have a recording pulse oximeter, but I would like to see how it's data correlates with my sleep data,too.

[eseedhouse]

Okay, are we saying that AHI is fuzzy and inaccurate because it does not take everything into account or are we saying that the machines can not accurately determine if we are breathing or not and for how long we are not?

AHI was designed as a diagnostic guide for physicians and as such is based on sound science and is a useful number. It isn't "fuzzy" in any sense I can understand that word. It's quite precise in fact. It's the real world that fuzzy, not the AHI.

But like any precise number it can't and doesn't capture all of the reality of what we deal with as Apnea suffers. We as proactive patients should look beyond it.

It's like inches or centimetres, which are also precisely defined. But if you use a ruler to precisely measure something five times you are likely to come up with at least four different results. It isn't the inch or centimetre that is fuzzy, it's reality.