"CA" Clear Airway Events

Hi everyone,


I'm a fairly new CPAP user. Diagnosed with an AHI score of 10 six months ago. I started with an AirSense 10 and P10 nasal pillows, but recently switched to the F30i mask because of a high leak rate with the pillows (15-25 leak rate on most nights), as an active sleeper.


Other settings:

AirSense 10

EPR = 1

Ramp on

Humidity = 5 with climateline tubing

Pressure range 6-10


Attached is a screenshot of my data last night with the F30i. The leak rate is way better, but I'm continuing to experience clear airway (CA) events, as noted by OSCAR. This was an ongoing issue before, with the P10 pillows as well. I had asked around on this forum, provided additional zoomed-in pictures of the CA events, and was told by several members that these episodes probably weren't central apneas.


I'm just wondering if I should still be concerned about the clear airway events, even if they aren't central apneas. Is there anything I can try to reduce these episodes? I'd previously lowered the EPR from 2 to 1 and that didn't seem to help much.


Thanks in advance!


Franko

Reducing (or totally turning EPR off) won't make any difference with the central apnea flagging UNLESS EPR IS THE TRIGGER for causing the central apneas.

Are your central apnea flags showing asleep breathing or awake/arousal breathing?
Important to know the difference.

Do you remember being awake very often during the night?

Pugsy wrote: ↑

Wed Jun 12, 2024 10:39 am

Reducing (or totally turning EPR off) won't make any difference with the central apnea flagging UNLESS EPR IS THE TRIGGER for causing the central apneas.

Are your central apnea flags showing asleep breathing or awake/arousal breathing?
Important to know the difference.

Do you remember being awake very often during the night?

Thanks for clarifying that point. Attached is a zoomed-in pic of some of the CA episodes. You had previously helped me differentiate central apneas vs. these CA events that I was having, and at that time you had mentioned that the data looked more like arousal-related breathing. I imagine these events would still be arousal-related?

I do wake up at night periodically as our toddler sleeps with us and occasionally (if we're lucky) disturbs our sleep in various ways. Are these arousal-related CA "flags" simply a function of my body being roused out of a deeper sleep? If so, it sounds like I have nothing to worry about with these events.

Franko39 wrote: ↑

Wed Jun 12, 2024 11:23 am

Are these arousal-related CA "flags" simply a function of my body being roused out of a deeper sleep? If so, it sounds like I have nothing to worry about with these events.

Yep....still look like arousal/awake breathing flagged events to my eye.
And yep....nothing to worry about except it points to not sleeping soundly but when we have known sleep disruptors (like the kids) it sort of comes with the parent territory.

Now this image below shows a truckload of centrals that are real asleep centrals. We aren't sure what caused this mess.
Long term cpap user (like well over 10 years) and this has happened only twice. Related to PS (pressure support which is sort of like what EPR might do) and it was decided to reduce PS by 1 and see what happens. As of yet no recurrence of the central truckloads but then twice in over 10 years doesn't mean much since the event was so rare anyway.

Thanks for confirming that.

It's amazing that you can differentiate real centrals and arousal events like that from comparing the two graphs. To me, my chart and the example chart you provided look the exact same in terms of the waveform appearance leading up the event.

For my own education - may I ask how you're able to determine that those events in your example are true central apnea events?

Franko39 wrote: ↑

Wed Jun 12, 2024 8:56 pm

For my own education - may I ask how you're able to determine that those events in your example are true central apnea events?

Probably spent 2 years or so putting the flow rate (breathing) under the microscope looking for sleep breathing vs awake/arousal breathing before I was comfortable with my own analysis. Asleep breathing is very regular and there's a predictable rhythm to it. Arousal/awake breathing can be very irregular when compared to asleep breathing.
I communicated with a couple of sleep techs for confirmation of what I thought I was seeing. I asked the pros. I spent a LOT of time educating myself.

Sometimes it's an easy observation but sometimes it isn't always so clear cut. Mainly you start with looking at the breaths immediately prior to the flagged event. If I see big gulps of air just prior to the flag I assume arousal/awake and then I know that we don't take big gulps of air when we air sound asleep. We just don't.

For all those asleep centrals I shared....I also verified with a sleep tech and another person with tons of experience dealing with centrals looking like that because his brother had them.

Your flagged centrals (at least the zoomed in ones you posted) are so obviously not asleep centrals that a blind man could tell. Yours aren't even the least little bit iffy or hard to know for sure.

Here's a couple of examples.
First one here I have circled the asleep breathing in red. Notice how boring and predictable the breaths look.


and here is the same time frame and graph but not zoomed in so much.


If not circled in red then I wasn't asleep and all that mess after the circled area, along with the flagged events, aren't real asleep events and don't mean much except I wasn't asleep. This sort of thing I see frequently because I don't sleep so great because of back/pelvic pain issues.

Here's an example of my being asleep and then having an arousal (circled big gulp of air right before the flag and remember we don't take big gulps of air like that while asleep) followed by a central flag. This one most likely was what I call a turn over in my sleep central. Most likely I awoke briefly and turned over in bed and held my breath briefly while I was turning.
We do that you know...and not realized we are pausing our own breathing but the machine senses the pause. It doesn't know if we are asleep or not. It only measures air flow.



Here's another one (not mine) using SleepHQ software where I again circled the irregular breathing right before the flag.



This mess here...Not asleep at all. Not surprising since this segment was right at the beginning of the night.
Note how irregular it all is.....not rhythmic at all.

Hi Pugsy - I'm always fascinated by your explanations. Something you said here differs from a conclusion I had reached though, so maybe I can check that I really do understand what you're saying.

In your third example, I think you are saying that the CA isn't real because you believe you were not really asleep....you 'awoke'?

I see the exact same waveform occasionally in my Oscar and, using backup movement data from my oximeter and SomnoPose, I deduce that it IS real because - apart from the 'gulp', as you call it - there isn't a single example of an awake breath.

They all have the shape of sleeping breaths - both immediately before the CA and immediately after. There's no "sleep-awake" junk at all. I more often see the odd CA in the middle of sleep-awake junk and/or right after one of my "I am definitely awake" sniff-flags, and I consider those non-real.

Surely you couldn't be awake just for the 6s gulp and 10s pause in breathing, and instantly revert to sleeping?

BigWing wrote: ↑

Thu Jun 13, 2024 3:06 pm

In your third example, I think you are saying that the CA isn't real because you believe you were not really asleep....you 'awoke'?

Correct. The big gulp means I wasn't asleep.
Don't assume that since the breathing "looks" like asleep breathing that a person is really asleep.
I got tons of awake breathing that isn't SWJ (sleep/wake/junk) looking and looks like asleep breathing but I wasn't asleep.

See the example below....some obvious awake breathing and then it looks like I went to sleep and had a few OAs but I was NEVER asleep during this time frame. I was awake and holding my breath and doing an experiment to see if I could fool the machine and I did. It called those pauses in breathing OAs and not the expected centrals and the pressure increased accordingly. Just because we see what looks like asleep breathing doesn't mean it really is. I turned the machine off after the last "OA" flag. You can see where I stopped it. I know with 100% certainty I was never asleep during this experiment.

BigWing wrote: ↑

Thu Jun 13, 2024 3:06 pm

I see the exact same waveform occasionally in my Oscar and, using backup movement data from my oximeter and SomnoPose, I deduce that it IS real because - apart from the 'gulp', as you call it - there isn't a single example of an awake breath.

Believe what you wish...but if a sleep tech saw it he/she wouldn't agree with you.

BigWing wrote: ↑

Thu Jun 13, 2024 3:06 pm

In your third example, I think you are saying that the CA isn't real because you believe you were not really asleep....you 'awoke'?

I see the exact same waveform occasionally in my Oscar and, using backup movement data from my oximeter and SomnoPose, I deduce that it IS real because - apart from the 'gulp', as you call it - there isn't a single example of an awake breath.

What Pugsy is saying is that the big gulp of air is likely caused by an EEG arousal of some sort, and since the breathing before the arousal is normal, the EEG arousal is most likely a spontaneous arousal. She may very well have awoken just enough to change position in the bed a bit and then immediately went back to sleep.

The thing is: When we're awake---even for just a few seconds---our breathing is not controlled by the autonomic part of the nervous system, which does control our sleep breathing. And the handoff of breathing control to the autonomic nervous system includes a resetting of the CO2 trigger level for the message "inhale now" to be sent to the lungs. As part of that resetting process, it's common and normal for what looks like a "central apnea" to occur. When this kind of thing happens on an in-lab sleep test, it is not scored as a central apnea because the EEG evidence makes it clear the person is still transitioning to real sleep.

And quiet relaxed wake breathing can look like sleep breathing. The "glitches" in wake breathing (and the earmark of SWJ breathing) is that once we're awake enough to start concentrating on something, we start to do things like unconsciously hold our breath for a few seconds while doing something difficult. Or taking a few deep cleansing breaths (in an attempt to settle our nervous system down), which not only can trick the xPAP machine into increasing the "baseline value" of the running 2 minute "average" for the flow rate used to determine when the airflow has decreased enough to potentially score an H or an OA or a CA. Or all kinds of other things. But for all those "other things" to affect the flow rate, we have to stay awake or semi-awake long enough for a normal part of wake breathing to both occur and persist long enough to trick the machine into thinking we're having a sleep disordered breathing event while asleep.

Surely you couldn't be awake just for the 6s gulp and 10s pause in breathing, and instantly revert to sleeping?

Actually it's not that uncommon if you go through lots of flow rate curves with a fine toothed comb. Super-short arousals happen. And not all of them turn into arousals that last long enough to create a jagged, obviously awake (as in what the heck made you wake up?) breathing that lasts for several minutes.

If you go through your own flow rate data with an open mind to the idea that not every flagged event must be real if you don't remember being awake, you will most likely be able to start noticing patterns in your own breathing. At the start, pay attention to the beginning and end of the night to see if you can identify when you clearly fell asleep and stayed asleep as well as when you first started to arouse before you remember waking up for the day. Those periods will give you plenty of hints as to what your longer middle-of-the-night arousals might look like. But in general, if an isolated event happens after a big breath or two, it's most likely a false flag---a sleep transitional "central" that got flagged, quite possibly as an OA or an H instead of a CA. And if normal sleep breathing resumes immediately after the event, that's additional evidence the event was probably sleep transitional.

In my own data, an isolated real event will most likely normal or near normal breathing right before it, then the event, and then obvious "arousal" breathing after the event. But then, the vast majority of events on my (multiple) diagnostic sleep studies have been "hypopneas with arousal"---i.e. I tend to arouse before a scoreable O2 desat occurs.

Now personally I find it difficult to sort out chains of real events from SWJ breathing. I don't often see clusters of events at times other than when I would expect to be awake or half-awake: the beginning and end of the night; during a wakeful period that I happen to remember; or immediately before or immediately after a point where I obviously was awake enough to turn the machine OFF and then back ON even if I don't remember waking up to do that.


For what it's worth, here's an isolated hypopnea from my own data that I have every reason to believe was real:



The surprising thing here (for my data) is that there is no evidence of an arousal at the end of the event.


Here's another recent isolated OA that shows sleep breathing right up to the event and the arousal breathing afterwards. My guess is this was a real event:



You'll notice sleep breathing right up to the event. And the event ends in a big inhalation that is typical of an arousal.


And finally, here's a spontaneous arousal that is clearly not related to my breathing and where the ragged stuff didn't last long enough to get flagged as an H or an OA or a CA:



Most likely I aroused just enough to adjust my position in bed while sort of holding my breath and then immediately went back to sleep.

Pugsy - thanks again for the explanations! It's quite reassuring to hear that you are confident that my CA events aren't true centrals. One less thing for me to worry about!

Pugsy wrote: ↑

Thu Jun 13, 2024 3:47 pm

Don't assume that since the breathing "looks" like asleep breathing that a person is really asleep.

OK - that is certainly something new for me to consider. I could have sworn I have seen the experts stress many times that sleep breathing looks nothing like awake breathing though (and that's what my own studies have suggested so far).

I was awake and holding my breath and doing an experiment to see if I could fool the machine and I did. It called those pauses in breathing OAs and not the expected centrals....

I too would expect the machine to flag that (deliberately holding your breath while awake) as a CA. It is supposed to explicitly test for an obstruction!

BigWing wrote: ↑

Fri Jun 14, 2024 3:41 pm

Pugsy wrote: ↑

Thu Jun 13, 2024 3:47 pm

I was awake and holding my breath and doing an experiment to see if I could fool the machine and I did. It called those pauses in breathing OAs and not the expected centrals....

I too would expect the machine to flag that (deliberately holding your breath while awake) as a CA. It is supposed to explicitly test for an obstruction!

It all depends on how you wind up holding your breath. In my case, I'm pretty sure that when I'm consciously holding my breath that I force my epiglottis over the top of my windpipe just like I do when I am swallowing. And if the epiglottis is over the windpipe for any length of time, the FOT algorithm that Resmed uses is going to detect a blocked airway, and score an OA.