CPAPtalk.com

Posted: **Wed Apr 16, 2025 6:15 pm**

Hi all,

Reaching out with a bit of a lengthy narrative that I'll attempt to truncate to move things along. Feel free to ask any follow-up questions and I will respond with as much detail as is requested.

I've had sleep-related issues for the last 15+ years (I am 28 now). Additionally, I had my tonsils and adenoids removed as a child, and I had sinus surgery when I was 17. I have had a few sleep studies, both of which indicated very mild OSA (highest AHI was roughly 6/hr), decent RDI (~15/hr), and moderately high spontaneous arousal (26/hr). I had to push to get an APAP, and that resulted in a decent number of "Clear Airway" events (more on that in a bit). I mentioned this to my pulmonologist, and she was perfectly happy to tell me I had "idiopathic hypersomnia" and prescribe whatever modafanil variant I wanted. However, I was already aware of OSCAR and knew enough to be dangerous, so I sought out a second opinion. Due to my CA events, he recommended an ASV, which I have now been on for a little over 2 years.

All that being said, I am still severely struggling. I have played with the settings constantly and, although my AHI is always nearly zero, I still feel exhausted and mentally drained each day. I've tried looking into it and have little to show for it. Regardless of what I do, I am unable to prevent all of the (almost entirely) unflagged arousals on my ASV. Looking back at my original APAP data, it appears that nearly all of my CA events were preceded by a large arousal breath, which where then often followed by loop-gain behavior. When I look at my current ASV results, it also appears that this loop-gain behavior is being unresolved by my ASV.

To me, my problem appears to be flow-limitation based. My thought is that once an arousal starts, my overactive, low-arousal threshold self kicks off a gnarly loop-gain scenario that is difficult to escape from. Unfortunately, despite the ASV's goal being to stabilize this behavior, it instead exacerbates the issue by increasing the pressure; each time the pressure goes up, I breathe in deeper/more often than my body wants to, and I attempt to hold my breath some more. The constant fluctuations in the pressure create a difficult situation when I am trying to re-establish my own breathing pattern.

Does this make sense? If so, is there a potential benefit in moving from an ASV to a purely Bilevel machine where I have more control over the pressure support? I'm reaching the end of what I can think of, and I'm getting rather overwhelmed... This is, of course, assuming that my arousals are coming from flow limitations and not something else.

Posted: **Thu Apr 17, 2025 10:06 am**

I have complex apnea and have switched to an AirCurve 10. I find that setting the minimum support to 0 helps. If the machine needs more it will take it. When I used APAP, EPR increased the number of central apneas dramatically. The minimum support acts a lot like EPR since it creates a constant differential between IPAP and EPAP. I think this reduces the amount of air retained in the lungs when exhaling, decreasing blood CO2. This thenn triggers the high gain instability. Everyone is different....

Posted: **Fri Apr 18, 2025 1:50 pm**

Sleepyboy97 wrote: ↑
Wed Apr 16, 2025 6:15 pm
Due to my CA events, he recommended an ASV, which I have now been on for a little over 2 years.

You posted one night of data from 2023. Here's a marked up version of that night's data:

It looks to me like all or most of the CAs in the red rectangles were more than likely part of sleep-wake-junk (SWJ) breathing, and might very well not be real central apneas. Certainly the first cluster of CAs occurred before you fell asleep and they would never have been labeled as CAs on an in-lab sleep test. All the rest of the red boxes also have the characteristic spiky-ness associated with SWJ, which begs the question of whether you were actually asleep when any of those events was recorded by the machine at the time.

You also write:

Looking back at my original APAP data, it appears that nearly all of my CA events were preceded by a large arousal breath, which where then often followed by loop-gain behavior.

And that more or less confirms what I just said: Most of the CAs recorded by your APAP were not real CAs that would have been scored on an in-lab sleep test specifically because you had already aroused. And the CA is just part of the normal process of trying to re-establish real sleep. The fact that you got trapped in a SWJ cycle was probably not because of the CAs themselves, but rather the whole novelty of trying to learn how to sleep well with an APAP blowing air up your nose all night long.

In other words, based on the one bit of data from 2023 and your own analysis that nearly all the CAs were preceded by a large arousal breath, it is more than a bit surprising that your sleep doc suggested an ASV machine since ASV machines can be even harder for people to learn to sleep (well) with. (And then add this fact: ASV machines also do nothing to address any problems with residual flow limitations if the EPAP setting is not high enough to prevent them since ASV machines don't increase EPAP in response to flow limitations.)

All that being said, I am still severely struggling. I have played with the settings constantly and, although my AHI is always nearly zero, I still feel exhausted and mentally drained each day. I've tried looking into it and have little to show for it.

You've also posted data from April 12, 2025 and April 13, 2025. Both of those nights show a lot of spiky-ness which can indicate that you're still spending a great deal of the night in SWJ: In other words, you may feel exhausted and mentally drained each day simply because you are not yet sleeping soundly with the machine. Rather, you are sleeping very lightly and probably spending far more time actually awake during the night than you may think. So here are some important questions:

1) Do you remember waking up frequently at night? If so, does that happen on most nights?

2) When you do find yourself awake in the middle of the night, does it seem to take a long time to get back to sleep?

although my AHI is always nearly zero

ASV machines are programmed in a way that typically results in a near perfect AHI, regardless of how well the patient is actually sleeping. Here's what I mean: Any time your ASV machine is even just a little bit unhappy with the stability of your inhalations, it steps in and starts increasing the pressure support (PS) by drastically increasing the IPAP while leaving the EPAP alone. This is the machine's efforts to "trigger" you to inhale deeply enough to prevent your inhalations from dropping low enough to score an apnea or a hypopnea.

For folks with central apnea or complex apnea who are sleeping well with their machines, this response manages to prevent the CO2 overshoot/undershoot cycle from developing, and that in turn prevents central apneas and hypopneas from occurring. The assumption is also that if the EPAP is set appropriately, the EPAP should be enough to prevent the obstructive apneas and hypopneas from occurring.

To me, my problem appears to be flow-limitation based.

If the flow limitations are real, in the sense that they are being caused by an airway that is in danger of collapsing, then those flow limitations can be considered to be obstructive in nature. And the usual "fix" would be additional EPAP. A Resmed AirSense APAP would increase the pressure with those flow limitations; a Resmed AirCurve VAuto would increase EPAP pressure (and hence IPAP) in response to those flow limitations. However, it looks like the Resmed ASV machine you are using is NOT programmed to increase the EPAP in the presence of flow limitations. (Increasing EPAP in response to obstructive events can cause more problems with central apneas for people using APAP/VAutos if they have a real, documented problem with either central sleep apnea or complex sleep apnea.)

My thought is that once an arousal starts, my overactive, low-arousal threshold self kicks off a gnarly loop-gain scenario that is difficult to escape from.

"This gnarly loop-gain scenario that is difficult to escape from" is usually described around here as getting caught in a prolonged period of SWJ: You're not really wide awake, but you're also not really asleep. Rather you are bouncing back and forth between very light sleep and short periods of wake. And prolonged periods of SWJ can best be described as bad sleep. And yes, prolonged periods of SWJ can leave you exhausted in the morning and make you feel really lousy all day long.

Unfortunately, despite the ASV's goal being to stabilize this behavior, it instead exacerbates the issue by increasing the pressure; each time the pressure goes up, I breathe in deeper/more often than my body wants to, and I attempt to hold my breath some more. The constant fluctuations in the pressure create a difficult situation when I am trying to re-establish my own breathing pattern.

In other words, your brain is fighting the ASV algorithm: The machine can't tell you're not sleeping. When you attempt to hold your breath because you feel like you're being forced to breath in deeper or more often than you want to, the machine thinks you are asleep and that your breathing is becoming ragged enough to suggest that your CO2 levels are no longer stable. So it wants to stabilize your breathing by encouraging/forcing you to breathe more deeply than you want to by increasing the IPAP. But of course, that make your brain want to hold your breath even more in an effort to stop the feeling of being forced to inhale more air than you want to inhale.

All of this begs the question: Do you even need an ASV machine in the first place?

In other words, back when you first started using the APAP machine, did you over-react to seeing the CAs in your data? Did your sleep doc just acquiesce to putting you on an ASV without really investigating whether those CAs recorded by your Resmed APAP were real or whether the CAs were being recorded at times when you probably weren't asleep or at least not very deeply asleep? Did the sleep doc bother to look through a whole night's worth of detailed data, including the wave flow, or did the sleep doc just look at the CAI and hear your concern about how high the CAI seemed to be?

Does this make sense? If so, is there a potential benefit in moving from an ASV to a purely Bilevel machine where I have more control over the pressure support?

Personally I do think you would benefit by moving from the ASV to either an AirSense APAP or an AirCurve VAuto. But not because you will have "more control over the pressure support". Rather it's because pressure support on the AirSense APAP/AirCurve VAuto is programmed in an entirely different way than it is on the ASV.

Here's what I mean by that:

On the ASV you are using, the EPAP is a fixed pressure and the PS is allowed to vary from min PS to max PS. When the machine is unhappy with your breathing, it assumes the problem must be central in nature and hence it only increases the IPAP by increasing the PS. And it's quite possible for the IPAP to increase by several cm H2O over a relatively low number of inhalations.

On the APAP and VAuto, the pressure support is fixed at a particular value. When the machine detects snoring or flow limitations or when obstructive apneas or hypopneas occur, both the EPAP and IPAP are increased by exactly the same amount until IPAP reaches the max (IPAP) pressure setting. So if your arousals are related to the flow limitations, the need for additional EPAP would be addressed by the machine. The downside, however, is that if you do have a real problem with central apneas, when a CO2 overshoot/undershoot cycle develops, the machine has no way to increase just the IPAP in an effort to encourage you to inhale more deeply and stabilize the CO2 level in your blood.

I'm reaching the end of what I can think of, and I'm getting rather overwhelmed... This is, of course, assuming that my arousals are coming from flow limitations and not something else.

I think there are two possible sources for your current arousals:

1) Flow limitations. Which indicate the need for more EPAP. So if you haven't tried increasing the EPAP on your ASV, you could try that. But how much of an increase might be needed is hard to determine specifically because your AVS machine is not programmed to respond to those flow limitations.

2) The ASV algorithm itself: You've already identified this as an issue when you described the "gnarly loop-gain scenario". The machine is misinterpreting your SWJ breathing as being central sleep apnea disordered breathing when the problem is not your breathing per se, but rather it's the fact that you can't get back to a nice continuous real sleep after that first arousal. And so your brain is fighting the machine's ASV algorithm and that's prolonging the SWJ periods and increasing the arousals.

Posted: **Fri Apr 18, 2025 2:07 pm**

FWIW folks the FL graph on the ASV report are grossly exaggerated when using ASV mode or auto ASV mode.
It's well known that they make huge mountains out of tiny mole hills.
The FL graph from the older trial with the APAP machine is much calmer and more in line with what we would expect to see.
My suggestion....don't go trying to kill the FLs you see on the ASV report because in all likelihood you will be chasing your tail.
The ASV algorithm for flow limitations can't be compared to the apap FL algorithm.

BTW you can manipulate the pressure support settings. You can set a fixed PS if you wish by setting the minimum and maximum PS to the same number. This would make the machine function more like the AirCurve10 VAuto bilevel machine and take it out of it's "I gotta kill the centrals" mindset.

Posted: **Sun Apr 20, 2025 4:59 am**

you can manipulate the pressure support settings. You can set a fixed PS if you wish by setting the minimum and maximum PS to the same number.

Unfortunately with the ResMed ASV the min PS and max PS cannot be the same.

Max PS must at least be 5 cm higher than min PS.

Posted: **Sun Apr 20, 2025 5:02 am**

GrumpyHere wrote: ↑
Sun Apr 20, 2025 4:59 am

you can manipulate the pressure support settings. You can set a fixed PS if you wish by setting the minimum and maximum PS to the same number.
Unfortunately with the ResMed ASV the min PS and max PS cannot be the same.

Max PS must at least be 5 cm higher than min PS.

Thanks for reminding me. I had forgotten.

Posted: **Wed Apr 23, 2025 8:14 pm**

Hi all - apologies for the lack of response; I had my notifications set up incorrectly.

I've tried using a fixed CPAP pressure this week with gradual increases to see if the centrals still happen - they really don't appear to. See attached. Breathing still looks pretty choppy in general.

Posted: **Wed Apr 23, 2025 8:18 pm**

Adding some additional close-ups of flow from the night with a fixed pressure of 16.0. I included a shot of an event, a clean patch of breathing, and an elongated section of "choppy" flow.

I borrowed a ResMed APAP from a relative that I plan to use tonight with EPR on in an attempt to reduce these additional flow limitations. I'm running into issues breathing out against the higher EPAP.

Posted: **Wed Apr 23, 2025 8:32 pm**

robysue1 wrote: ↑
Fri Apr 18, 2025 1:50 pm

Sleepyboy97 wrote: ↑
Wed Apr 16, 2025 6:15 pm
Due to my CA events, he recommended an ASV, which I have now been on for a little over 2 years.
You posted one night of data from 2023. Here's a marked up version of that night's data:

It looks to me like all or most of the CAs in the red rectangles were more than likely part of sleep-wake-junk (SWJ) breathing, and might very well not be real central apneas. Certainly the first cluster of CAs occurred before you fell asleep and they would never have been labeled as CAs on an in-lab sleep test. All the rest of the red boxes also have the characteristic spiky-ness associated with SWJ, which begs the question of whether you were actually asleep when any of those events was recorded by the machine at the time.

You also write:
Looking back at my original APAP data, it appears that nearly all of my CA events were preceded by a large arousal breath, which where then often followed by loop-gain behavior.
And that more or less confirms what I just said: Most of the CAs recorded by your APAP were not real CAs that would have been scored on an in-lab sleep test specifically because you had already aroused. And the CA is just part of the normal process of trying to re-establish real sleep. The fact that you got trapped in a SWJ cycle was probably not because of the CAs themselves, but rather the whole novelty of trying to learn how to sleep well with an APAP blowing air up your nose all night long.

In other words, based on the one bit of data from 2023 and your own analysis that nearly all the CAs were preceded by a large arousal breath, it is more than a bit surprising that your sleep doc suggested an ASV machine since ASV machines can be even harder for people to learn to sleep (well) with. (And then add this fact: ASV machines also do nothing to address any problems with residual flow limitations if the EPAP setting is not high enough to prevent them since ASV machines don't increase EPAP in response to flow limitations.)

All that being said, I am still severely struggling. I have played with the settings constantly and, although my AHI is always nearly zero, I still feel exhausted and mentally drained each day. I've tried looking into it and have little to show for it.
You've also posted data from April 12, 2025 and April 13, 2025. Both of those nights show a lot of spiky-ness which can indicate that you're still spending a great deal of the night in SWJ: In other words, you may feel exhausted and mentally drained each day simply because you are not yet sleeping soundly with the machine. Rather, you are sleeping very lightly and probably spending far more time actually awake during the night than you may think. So here are some important questions:

1) Do you remember waking up frequently at night? If so, does that happen on most nights?

2) When you do find yourself awake in the middle of the night, does it seem to take a long time to get back to sleep?

although my AHI is always nearly zero
ASV machines are programmed in a way that typically results in a near perfect AHI, regardless of how well the patient is actually sleeping. Here's what I mean: Any time your ASV machine is even just a little bit unhappy with the stability of your inhalations, it steps in and starts increasing the pressure support (PS) by drastically increasing the IPAP while leaving the EPAP alone. This is the machine's efforts to "trigger" you to inhale deeply enough to prevent your inhalations from dropping low enough to score an apnea or a hypopnea.

For folks with central apnea or complex apnea who are sleeping well with their machines, this response manages to prevent the CO2 overshoot/undershoot cycle from developing, and that in turn prevents central apneas and hypopneas from occurring. The assumption is also that if the EPAP is set appropriately, the EPAP should be enough to prevent the obstructive apneas and hypopneas from occurring.

To me, my problem appears to be flow-limitation based.
If the flow limitations are real, in the sense that they are being caused by an airway that is in danger of collapsing, then those flow limitations can be considered to be obstructive in nature. And the usual "fix" would be additional EPAP. A Resmed AirSense APAP would increase the pressure with those flow limitations; a Resmed AirCurve VAuto would increase EPAP pressure (and hence IPAP) in response to those flow limitations. However, it looks like the Resmed ASV machine you are using is NOT programmed to increase the EPAP in the presence of flow limitations. (Increasing EPAP in response to obstructive events can cause more problems with central apneas for people using APAP/VAutos if they have a real, documented problem with either central sleep apnea or complex sleep apnea.)

My thought is that once an arousal starts, my overactive, low-arousal threshold self kicks off a gnarly loop-gain scenario that is difficult to escape from.
"This gnarly loop-gain scenario that is difficult to escape from" is usually described around here as getting caught in a prolonged period of SWJ: You're not really wide awake, but you're also not really asleep. Rather you are bouncing back and forth between very light sleep and short periods of wake. And prolonged periods of SWJ can best be described as bad sleep. And yes, prolonged periods of SWJ can leave you exhausted in the morning and make you feel really lousy all day long.

Unfortunately, despite the ASV's goal being to stabilize this behavior, it instead exacerbates the issue by increasing the pressure; each time the pressure goes up, I breathe in deeper/more often than my body wants to, and I attempt to hold my breath some more. The constant fluctuations in the pressure create a difficult situation when I am trying to re-establish my own breathing pattern.
In other words, your brain is fighting the ASV algorithm: The machine can't tell you're not sleeping. When you attempt to hold your breath because you feel like you're being forced to breath in deeper or more often than you want to, the machine thinks you are asleep and that your breathing is becoming ragged enough to suggest that your CO2 levels are no longer stable. So it wants to stabilize your breathing by encouraging/forcing you to breathe more deeply than you want to by increasing the IPAP. But of course, that make your brain want to hold your breath even more in an effort to stop the feeling of being forced to inhale more air than you want to inhale.

All of this begs the question: Do you even need an ASV machine in the first place?

In other words, back when you first started using the APAP machine, did you over-react to seeing the CAs in your data? Did your sleep doc just acquiesce to putting you on an ASV without really investigating whether those CAs recorded by your Resmed APAP were real or whether the CAs were being recorded at times when you probably weren't asleep or at least not very deeply asleep? Did the sleep doc bother to look through a whole night's worth of detailed data, including the wave flow, or did the sleep doc just look at the CAI and hear your concern about how high the CAI seemed to be?

Does this make sense? If so, is there a potential benefit in moving from an ASV to a purely Bilevel machine where I have more control over the pressure support?
Personally I do think you would benefit by moving from the ASV to either an AirSense APAP or an AirCurve VAuto. But not because you will have "more control over the pressure support". Rather it's because pressure support on the AirSense APAP/AirCurve VAuto is programmed in an entirely different way than it is on the ASV.

Here's what I mean by that:

On the ASV you are using, the EPAP is a fixed pressure and the PS is allowed to vary from min PS to max PS. When the machine is unhappy with your breathing, it assumes the problem must be central in nature and hence it only increases the IPAP by increasing the PS. And it's quite possible for the IPAP to increase by several cm H2O over a relatively low number of inhalations.

On the APAP and VAuto, the pressure support is fixed at a particular value. When the machine detects snoring or flow limitations or when obstructive apneas or hypopneas occur, both the EPAP and IPAP are increased by exactly the same amount until IPAP reaches the max (IPAP) pressure setting. So if your arousals are related to the flow limitations, the need for additional EPAP would be addressed by the machine. The downside, however, is that if you do have a real problem with central apneas, when a CO2 overshoot/undershoot cycle develops, the machine has no way to increase just the IPAP in an effort to encourage you to inhale more deeply and stabilize the CO2 level in your blood.

I'm reaching the end of what I can think of, and I'm getting rather overwhelmed... This is, of course, assuming that my arousals are coming from flow limitations and not something else.
I think there are two possible sources for your current arousals:

1) Flow limitations. Which indicate the need for more EPAP. So if you haven't tried increasing the EPAP on your ASV, you could try that. But how much of an increase might be needed is hard to determine specifically because your AVS machine is not programmed to respond to those flow limitations.

2) The ASV algorithm itself: You've already identified this as an issue when you described the "gnarly loop-gain scenario". The machine is misinterpreting your SWJ breathing as being central sleep apnea disordered breathing when the problem is not your breathing per se, but rather it's the fact that you can't get back to a nice continuous real sleep after that first arousal. And so your brain is fighting the machine's ASV algorithm and that's prolonging the SWJ periods and increasing the arousals.

To answer the main question here - I was on the CPAP for several months prior to that point, so I was pretty confident that I was acclimated to the machine.

Honestly, because I never went through any kind of real titration, I think the high number of CA's was likely because my pressure wasn't high enough. I also noticed (and still notice) that changes in pressure setting really cause a lot of arousals for me. My pulmonologist never wanted me to try a CPAP to begin with, and she more or less kept telling me to just give up on the CPAP because I just had "idiopathic hypersomnia." I got a second opinion from a doctor who said there were "central hypopneas" on my sleep study and to try for an ASV since it was "the nuclear option," so I went with that. I was under the impression that I truly just had central sleep apnea, and tried to power through with my 0.0 AHI nights on the ASV. However, I was convinced that I needed the pressure as low as possible because I thought it was causing more apnea events as the pressure increased. I also got terrible aerophagia on nights when I had a lot of pressure support swings.

Now, looking through my data, I'm pretty sure those are all related to arousals and SWJ. Now I'm trying to figure out where to go from here (i.e. purchase a BiLevel?).

I'll also add in here that I have a pretty severely deviated septum, and I am getting that fixed in about a month.

Posted: **Thu Apr 24, 2025 2:31 am**

Sleepyboy97 wrote: ↑
Wed Apr 16, 2025 6:15 pm
I have had a few sleep studies, both of which...

If so inclined, post those results. as well as a SleepHQ with the lowest CPAP or APAP settings you got.

TIA.

Posted: **Thu Apr 24, 2025 8:47 am**

Nocibur wrote: ↑
Thu Apr 24, 2025 2:31 am

Sleepyboy97 wrote: ↑
Wed Apr 16, 2025 6:15 pm
I have had a few sleep studies, both of which...
If so inclined, post those results. as well as a SleepHQ with the lowest CPAP or APAP settings you got.

TIA.

As requested, I've attached the print out of the sleep study report.

Posted: **Thu Apr 24, 2025 9:15 am**

Sleepyboy97 wrote: ↑
Wed Apr 16, 2025 6:15 pm
...my pulmonologist, and she was perfectly happy to tell me I had "idiopathic hypersomnia" ...

With 411.5 minutes of sleep marred by 55 awakenings and 158 arousals, you do not have "idiopathic hypersomnia".

Posted: **Thu Apr 24, 2025 9:17 am**

Nocibur wrote: ↑
Thu Apr 24, 2025 9:15 am

Sleepyboy97 wrote: ↑
Wed Apr 16, 2025 6:15 pm
...my pulmonologist, and she was perfectly happy to tell me I had "idiopathic hypersomnia" ...
With 411.5 minutes of sleep marred by 55 awakenings and 158 arousals, you do not have "idiopathic hypersomnia".

OST, let me change that to

you cannot have "idiopathic hypersomnia".

Posted: **Thu Apr 24, 2025 9:19 am**

Sleepyboy97 wrote: ↑
Wed Apr 16, 2025 6:15 pm
loop-gain behavior

Ain't got any of that either.

Posted: **Fri May 02, 2025 5:21 pm**

Just wanting to follow up and see if anyone has additional input after seeing the results with a higher EPAP and no centrals...

CPAPtalk.com

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