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Appreciate some help profiling these CA events
Appreciate some help profiling these CA events
Hoping the xPAP veterans on here can confirm whether or not these CA's showing up in my data every night are:

1. Benign / xPAP-induced
2. Measurement errors (ie. not real)
3. Real / concerning CA's

I've been told by others here that CA's are normal during treatment and they are not concerning. I have to admit I don't really understand why they're not concerning, or what causes them. As far as I know, when you stop breathing you're technically dead unless and until your brain signals you to breathe again (hopefully). That's enough to get my attention.

Some CA's showed up on my sleep study during titration night, but the doctor's office told me that I "do not have" central apneas. They did not explain why they thought so. He hasn't seen my data yet, though I have a follow-up in a couple months.

Anyway, these events show up every night in my data. I've collected 2 weeks' worth of data so far. Pressures range between 4 and 9 usually, and average about 6 or so. AHI seems great, and overall the treatment I think looks great on paper.

Attached are screenshots of my performance last night. I've zoomed into a couple of the CA's, one of which lasts 22 seconds.

I'm not sure what's going on with the mask pressure during that time (why does it flatten out like that and become "noisy"?), but the interesting thing is that my respiratory rate and minute ventilation both dip as the inspiration time goes up. That seems to me like I'm actually not breathing. I'd appreciate your thoughts on it.

Thanks again!

- Worrywart

[Image: clear_airway_events.jpg] [Image: overview.jpg]
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RE: Appreciate some help profiling these CA events
Here's the whole-night view.

The chunk of missing data around 9AM is because I woke up, turned off the machine, and then decided I wanted to sleep in some more and turned it back on. I felt really tired today, despite the good sleep. On some nights the APAP drains me, but hopefully that means I'm working toward repaying my sleep debt (?).

I think the sleep doc. nailed my pressure range on the first try. I got very close to 10 cmH20 one night, but never actually hit it yet.

[Image: whole_night.jpg]
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RE: Appreciate some help profiling these CA events
5 out of 7 of those clear airway events are of 10 or 11 second duration. This means that if each of those 5 events were a mere 1 or 2 seconds shorter they wouldn't have been flagged as events, wouldn't contribute to AHI and you wouldn't even know about them. I would bet that if you were wearing a recording Pulse Oximeter during these 5 short duration events you wouldn't have found any evidence of significant desaturation. Events like the other 2 events are worth keeping an eye on, but do not warrant being overly concerned. These events look to me like many are probably due to hyperventilation (CPAP induced) and will most likely fade with time as your respiratory system acclimates to the positive air pressure.

Your leak level is very good, good enough that the waveform data should be considered valid data. It all looks right too. The mask pressure levels, tidal volume drops etc. indicate you aren't breathing during these events simply because you aren't breathing.

It's important to know some of the things that can make you stop breathing for a while (10,11 or even 20 seconds or so), even when your airway is clear, in order to understand why having a few CA events isn't all that worrisome.

CPAP induced CA is probably caused by hyperventilation - basically the positive air pressure messes with your breathing patterns and tidal volume causing your respiratory system to periodically take a short break while things even out. It could also be caused by the mask and machine being very efficient at washing CO2. In any case and whatever the cause, CPAP induced CAs usually decrease and subside with time (probably as you get used to breathing with the CPAP or maybe as your respiratory system adjusts).

It is natural for a healthy person to sometimes have a CA or 2 during REM sleep.

Many people get CAs recorded while wearing the mask while they are awake. It is natural to hold your breath when you are doing something like adjusting the mask, fiddling with the machine, shifting position in bed etc. If you hold your breath for a mere 10 seconds you score a CA event. These wakeful events should be completely disregarded.

It is natural to sometimes have CAs while shifting from wakefulness to sleep, during very light sleep or shifting back and forth from light sleep and wakefulness. This is due to the difference in breathing patterns when we are awake and when we sleep.

These things add up so that many people have a recorded clear airway event or two every now and then or even a couple per night and many people have several for the first couple months or so of CPAP use.

If it were me, I would just keep an eye on them and see if they substantially fade with time. If you are very concerned about them, you can get a recording Pulse Oximeter and see if any of these Clear Airway events correspond with significant desaturation (which I think is unlikely).

All of the above is just my take on things and I'm not a doctor - so, as always, if you are concerned with it you might want to press your heath care providers for an explanation as to why they feel there isn't cause for concern.

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RE: Appreciate some help profiling these CA events
I have a few comments in answer to your questions.

First of all, if the CA events occurred during your titration, but not when you were sleeping without the mask, that would lead to the conclusion that they were caused by the CPAP therapy itself, meaning that you don't have central sleep apnea. They are induced by the CPAP therapy itself.

In many ways CA's are no different from OA's. Both are characterized by a lack of breathing for 10 seconds or more. Their dangers are two fold. One, they can cause oxygen desats which can be very harmful if you have enough of them, and two, they can cause arousals which interfere with your sleep and prevent you from getting the quality rest you need.

In your case your AHI is well below 5 so it doesn't matter if your AHI is dominated by CA's, OA's, or hypopneas. In fact, the good news is that as your body adapts to CPAP therapy the CA's will subside.

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RE: Appreciate some help profiling these CA events
Thank you both for the deailed responses. That was helpful.

Those oximeters that work with SleepyHead seem like a good way to keep an eye on things once in a while. Might think about getting one at some point.
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RE: Appreciate some help profiling these CA events
Had a bit of a scary moment in my sleep last night.

Last night was the first time ever that I've been jerked awake and realized I wasn't breathing. It wasn't a slow awakening. It was a sudden kick-in-the-pants eyes-wide-open event and I remember taking a breath before sitting up in bed. That breath felt like I was priming a pump, so to speak... like I had never breathed before.

Looked at my sleep data today and nothing looks unusual except that there's an "unspecified" event (10 seconds). I've only ever had one of those once before, when I first started treatment. Otherwise, I had only the usual mix of a couple hypopneas and a handful of "clear airway" events. SleepyHead reported an AHI of 0.77 for the night.

So I'm fairly confident at this point that I don't have central apnea but I'm curious what in the devil's name woke me up so violently like that. Is this something that CPAP causes?

The only difference from last night and other nights is that I had not gone to sleep the night before, so I had been very tired.
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RE: Appreciate some help profiling these CA events
What pressure did your AutoSet get to as you woke up? It may be that you want to open up your upper limit somewhat. Your current setting might be OK for most nights, but perhaps if you are extra tired, you need a little bit more pressure.

As for what woke you up, that specific event hasn't happened to me, but I have had something similar. Before starting CPAP, I had several occurrences of pulmonary aspiration while sleeping. [ Yes, that is as unpleasant as it sounds ]. At the start of each occurrence, I would immediately snap awake, sit up, and begin coughing. Perhaps something similar is happening with you, in that, now that you are consciously dealing with your apneas, your subconscious triggered on an unresolved apnea and immediately snapped you awake.
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RE: Appreciate some help profiling these CA events
Ron, I don't remember checking my pressure when I woke up. I went right back to sleep but if it happens again I'll remember to look. The strange thing is that my pressure didn't get close to my upper limit last night. It topped out at 8.

Here's a shot of the unspecified apnea event, and the full-night overview.

[Image: unspecified_event.jpg]

[Image: full_night.jpg]

Regarding coughing, yes, my CPAP has made me cough on several occasions but I'm usually still awake when that happens.
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RE: Appreciate some help profiling these CA events
Ok, I'm not a doctor, don't play one on TV, and haven't slept in a Holiday Inn Express any time in the recent past.

When I look at your flow rate graph, prior to the apnea event, it seems to me that you are in some sort of "pre-apnea" breathing pattern. Notice how you have several breaths, then have ~2 breaths worth of zero flow. I don't know why your AutoSet isn't keying in on that and bumping the pressure. It's supposed to look at the flow rate properties to anticipate apnea events.

Note how the mask pressure at the event is still at the reduced EPR pressure of 5. [ I presume your EPR setting is 2, based on that graph ]. If it were me, I would be tempted to zero the EPR to make sure that the airway is still splinted open between the previous exhale and the next inhale. In fact, I don't understand that EPR algorithm. What stops the airway from collapsing at the reduced EPR pressure once the actual exhale is finished? And if the reduced EPR pressure is supposed to be enough to keep the airway open, why does the pressure need to increase for the inhale, since it must already be open?

Take my advice for what you paid for it.
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RE: Appreciate some help profiling these CA events
(07-09-2013, 08:18 PM)RonWessels Wrote: Take my advice for what you paid for it.

It's rare, but sometimes what you get for free is worth more than what you get charged lots of money for.

Yes, my doc prescribed an EPR setting of 2. I don't know how important that is (why would the Rx script call it out if it wasn't necessary?) but I'm tempted to try disabling it. I have a follow-up in September where the doc will look at my sleep data, so I've been nervous about changing anything from what he prescribed.

You're right- my flow graph is littered with flow limitations. I have many, many more of those throughout the night when zooming into the graph, but they aren't registering as events (I guess they're too short).

I don't know why the machine isn't responding more quickly. From the menus I can tell you that it's got software version SX474-0907... for whatever that's worth. A lot of people have been demanding -0905 or newer from what I've read, but ResMed doesn't post release notes so it's anyone guess what the differences are.

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