[Treatment] interpreting data: curious wakeup followed by lots of apneas

[doodat]

I've recently started CPAP and I'm trying to optimize my therapy and understand the data. I have a lot to learn but I'll start with one particular scenario I found this morning that I would like explained. Here's the sequence of events:

a) woke up right before 8:29am. I know because I looked at the time on my phone. I woke up with a fast heart rate (which is what first clued me in to taking a sleep test originally)
b) I was still feeling pretty drowsy so I stayed in bed with my eyes closed, trying to fall back to sleep.
c) during this time my nose was congested, and i remember taking deep breaths
d) after almost an hour of this, I still couldn't fall back asleep. Possibly made worse by the congestion. So I gave up, took off the mask, turned off the machine
e) fell asleep right afterwards, slept well for an hour, even had a dream, woke up not drowsy.

Looking at my CPAP data for the night, most of the night was relatively good with low AHI. Around the wake-up, the machine did not record any RERA event. And then for the next hour, proceeded to record a ton of OAs and CAs. This series of apneas then skewed the overall AHI for the night to be 8.22. The graphs for the relevant section are attached.

My questions specifically:
1) The high OA and CAs for the period after waking up: are these real apneas or are these false positives? And more importantly, is this type of breathing pattern harmful for my health regardless of whether they're real apneas? Recall that during this period, I was mostly awake I think (not 100%, still pretty drowsy with eyes closed, maybe i had spurts of sleep that I don't recall), and also that my nose was congested. I should note that I've taken sleep test with nasal spray to clear the nose, so I am reasonably sure that my OAs *do not* come from nasal congestion.
2) throughout the whole apnea episode, my flow limit stayed low. I thought the flow limit indicated obstruction? What does it mean when the machine records OAs when there is little flow limitation?
3) the wake up at 8:29am: was this provoked by apnea? The machine recorded nothing related to the wakeup -- no apneas and no RE events before that time. But i definitely woke up, and in the past, waking up with a fast heartrate was indicative to me of being caused by apnea. Did the machine miss something here?
4) waking up tired with the machine on, cannot fall back asleep, and then sleeping well with the machine off: this happens to me on many nights. This doesn't sound right? How can i stay asleep the whole night with the machine on and wake up well rested given the above?

Thanks all in advance!

[staceyburke]

It looks like you had some positional apnea! Many times it happens when your chin drops to your sternum cutting off your airway. It happens many times from sleeping on your back. Or did you change your pillows to a thicker one? 

Whatever it is you need to stop getting into that position. No change in settings: pressure will clear this type of restriction.

[doodat]

Are you saying the apneas after waking up were the result of my position shifting after waking?

But i distinctly remember turning to my side in addition to lying supine after waking up, so I was in more than one position. Moreover, I was actually more or less awake the whole time.

(Also something related: my first sleep test result showed lots of apnea while supine and almost no apneas while on my side. I did a few more nights of sleep study after that one, including with nasal spray, and all subsequent results showed severe apnea in *all* positions. Never figured out the reason for this discrpency.)

[staceyburke]

We look for grouped 0a or H events to show potential apnea. Those are certainly grouped. If you were awake, each of the Oa recorded were 10 seconds or longer (as well as each of the centrals) - were you holding your breath while awake? I don’t think so and if not the best bet is positional apnea.

[doodat]

But if I were not getting air while awake, shouldn't I remember this part? Perhaps I'd be more awakened if I were gasping?

[staceyburke]

Positional apnea is while you are asleep. Probably the apnea woke you up, you stayed in the same position and when you went to sleep returned to the same position and had positional apnea again and it started over again until you woke all the way up or finally changed position.

[doodat]

Positional apnea is while you are asleep. Probably the apnea woke you up, you stayed in the same position and when you went to sleep returned to the same position and had positional apnea again and it started over again until you woke all the way up or finally changed position.

This does not really match what my memory says. I was more or less awake for the hour after 8:29am. Although my memory was indeed hazy because I was drowsy, so it's possible but I don't consider it to be very likely.

Edit: And suppose that your hypothesis is indeed true, why do the OAs come with associated CAs? And also my second question: what's the relationship between flow limit and OAs? My understanding is that limitations -> OA, but in this case I had OAs with almost no flow limitation.

[staceyburke]

Ca are open airway - the Cpap is trying to determine if it is a open airway by pulsating a little burst of air if it goes through it says it Is a Ca if it does not go through it records an Oa. In a sleep study they have wires all over you and a chest belt on determining if it is a central which is different than an open airway. A clap just is not great in determining which it is. You can look up the difference between a central and a clear airway

A flow limit is a small apnea you can see how they are classified in my signature.

[doodat]

Ca are open airway - the Cpap is trying to determine if it is a open airway by pulsating a little burst of air if it goes through it says it Is a Ca if it does not go through it records an Oa. In a sleep study they have wires all over you and a chest belt on determining if it is a central which is different than an open airway. A clap just is not great in determining which it is.  You can look up the difference between a central and a clear airway

A flow limit is a small apnea you can see how they are classified in my signature.

So what you're saying is, the CAs are miscategorized OAs because the machine's detection is not as accurate as sleep test?

I see what your signature says, hence my original question regarding the flow limit. To rephrase that question: if I see OAs, shouldn't the flow limit be at 80%-100% then? But I see that the flow limit at the same time is close to 0.

[staceyburke]

Once a flow limit has lasted 10 Seconds it is no longer a flow limit it then is classified as a H or Oa.   It is a continuum you either have a flow limit or a H / Oa not 2 of them together or 3 of them together... It is either a FL, H or Oa.  

Think of it this way:  driving 5 miles over the speed limit is 20$ fine but if you are going 20 miles over the speed limit you are given a 50$ fine not 20+50 and if you are going 50 miles over the speed limit you might not be charged with speeding you would be charged with reckless driving and a 200$ fine not 20+50+200...  I hope I explained it because I don't know how else to say it.