Central apnea questions

[surferdude2]

For example if my morning report says central Ai was 5 for 8 hours of therapy for that night but virtually all of my central apneas occurred during a one hour period early in the morning like during rem sleep this could mean I'm having very damaging central events over a short period of time that isn't reflected in an "average" number..correct?

That's correct. Furthermore, a cluster of events that occur when you are awake can skew the average and cause undue concern. That's why it is important to know if you were asleep when the events were flagged.

For example, it takes me nearly an hour to fall asleep and during that time the machine flags several CAs and some OAs. The same thing happens when I wake in the morning and lay there for an hour or so. I disregard those events when figuring my AHI.

If your total AHI is usually five or less and almost all of your centrals are flagged when you are awake or in the process of waking up, I don't think you have anything to worry about. How do you feel? If you're AHI is under 5, even with the possibly phony CAs included and you feel good, you're doing fine. Not all CAs are destructive since you can create them swallowing or stopping the breathing cycle when rolling over from one side to the other. Anytime you interrupt your breathing for 10 seconds or more, the machine will flag an event.

On the other hand, if you have several CAs being flagged regularly all through the night, when you know for sure that you are asleep, and you don't feel rested, that's a different set of circumstances and may require a sleep test to see if a different machine is called for.

[old82]

Thank you...this is the confirmation I was looking for to further my knowledge of what's going on with me. I have clusters of up to 25 central apneas in an hour mostly during the early morning hours that have been lasting on average 15 seconds each and as high as 28 seconds and i'm concerned that my basic morning report doesn't come close to reflect this. I wake up feeling awful with the shakes and disoriented but this all goes away during the day. But I'm concerned with what I'm seeing and don't want to continue on thinking my basic morning numbers indicate that I'm doing just fine.

[surferdude2]

I think it's time to seek council with the doc and give him the details that you have witnesses. You obviously have some problem that needs attention. It may or may not be related to the CAs but that's a good lead for starters.

All the best, Dude

[old82]

For example if my morning report says central Ai was 5 for 8 hours of therapy for that night but virtually all of my central apneas occurred during a one hour period early in the morning like during rem sleep this could mean I'm having very damaging central events over a short period of time that isn't reflected in an "average" number..correct?

That's correct. Furthermore, a cluster of events that occur when you are awake can skew the average and cause undue concern. That's why it is important to know if you were asleep when the events were flagged.

For example, it takes me nearly an hour to fall asleep and during that time the machine flags several CAs and some OAs. The same thing happens when I wake in the morning and lay there for an hour or so. I disregard those events when figuring my AHI.

If your total AHI is usually five or less and almost all of your centrals are flagged when you are awake or in the process of waking up, I don't think you have anything to worry about. How do you feel? If you're AHI is under 5, even with the possibly phony CAs included and you feel good, you're doing fine. Not all CAs are destructive since you can create them swallowing or stopping the breathing cycle when rolling over from one side to the other. Anytime you interrupt your breathing for 10 seconds or more, the machine will flag an event.

On the other hand, if you have several CAs being flagged regularly all through the night, when you know for sure that you are asleep, and you don't feel rested, that's a different set of circumstances and may require a sleep test to see if a different machine is called for.

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Thanks Suferdude2
I don't understand how if it takes a 10 second event to record an apnea and you're awake and not holding your breath for 10 seconds the machine can record one???

As for how do I feel...terrible upon awakening but OK the rest of the day.I'm really confused and learning more every day.

[old82]

That's correct. Furthermore, a cluster of events that occur when you are awake can skew the average and cause undue concern. That's why it is important to know if you were asleep when the events were flagged.


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Surferdude2 Can you tell me which graph to look at and how to determine if I was asleep during events. I use the ResMed program.

[surferdude2]

The machines aren't perfect but they do pretty well at detecting changes in the breathing pattern. They must compare any changes using a predetermined algorithm (set of predetermined steps to solve a given problem) to solve for validity and type of event. That all sounds easy until you introduce such factors as swallowing, shallow breathing, breath holding during exertion and perhaps other things that we aren't aware of that affect the process. I know for a fact that CAs are flagged while awake and when I am breathing as normally as ever. Perhaps when we are awake, we pause breathing more than we realize. At any rate, CAs that are flagged when we aren't asleep aren't something to be concerned about. (unless they last longer than 5 mins. ).

If you are reasonably sure your CAs are occurring when you are asleep and they are causing you to feel bad upon arising from what would otherwise have been a good night of therapy, then by all means seek council with your doctor. If you think they are all occurring during the last hour of your sleep, then set an alarm to awake you an hour early and see if you feel better that day. That could be the proof that would motivate you and also give the doctor some insight into how to help you.

[TyroneShoes]

We probably do not want to overlook the fact that flagged CAs are often false positives, even when you are asleep.

For example, I had an AHI in my home test of 55.7, but only 0.2% of those were CAs; the great bulk were OAs. That indicates a classic OSA condition. Once on XPAP, CAs began to outnumber OAs about 2 to 1, regardless of the various pressure and mask changes I have made, and continuously so for 4 months now, including a full titration study. Of course total AHI has eventually dropped to under 2 (although the percentage has been about the same when I had my worst treated nights with AHI still in the 20's), so I am not worried about the few CAs, particularly since many may be false positives. But I still look at them in SH to see if they are precariously long events. Luckily, none of this pushes me over the Mendoza Line characterizing me as a complex SA sufferer, so APAP seems to be the right machine for the job. But then YMMV.

OAs are a logistical problem with the airway that can be easily overcome with PAP, but CAs reflect a failure of the CNS to tell you to breathe, so they are a lot scarier, and I therefore want to keep a close eye on that. But that also explains why even an APAP or BiPAP will ignore CAs, as there isn't much they could do about them anyway other than diagnose and report them. Significant CAs indicate that possibly a ventilator-capable XPAP is needed, something that can push a breath on you if needed.

CAs can easily happen (or be flagged as happening) due to the prescribed pressure. There is a sweet spot for normal sufferers, where you try to get the lowest minimum pressure for opening the airway and preventing OA events. But there is a trade-off in that the higher the pressure goes the more likely CA events will flag, whether actual or false. So you also try to shoot for a pressure that is as low as possible to prevent this, while still staving off the OA events. But there is overlap, and in my case the main job of keeping the airway open (clearing all OAs) comes at a price of a few CAs flagging each night.

And of course if you use an APAP this helps titrate you to the best minimum pressure dynamically through the night, but it may aggravate the CA count even a little more (or actually help minimize them), which is why it is important to find that sweet spot. If on APAP, try to close the range as much as possible, with the important number being the minimum pressure setting.

Also, EPR can have a negative effect on CAs (along with the positive effect of providing a bit more comfort). So, it is recommended that lowering EPR can help, but of course at another trade-off, of comfort. But if using EPR it might be worth trying to carve it down from 3 to 2, 1, or even off; if it does not feel more uncomfortable, it may lower your CAs and be a worthy tradeoff.

So the bottom line question becomes (for me) "if I have virtually no CA events when NOT wearing the mask, which is the case, is it really my CNS failing and causing CAs to be flagged when I AM wearing the mask? Or is it some factor of XPAP doing this? Is the cause internal, or external?" Since I only get them while wearing the mask, I sort of have to lean to it being an external cause. Just wish I really knew.

So I do not know what your software is capable of, but you should parse the data with your pressure settings in mind and figure out if possibly the CAs are coming from having an incorrect pressure. 7 is not all that high, and unlikely that it is causing the CAs, but everyone is different. Certainly a topic to bring up with the sleep doc.

[surferdude2]

I realize that CAs may be created by a neurological defect but I think some CAs may be the result of an increase in the O2 saturation of the blood as a result of breathing against an elevated pressure. It's well known that exhaling against a pressure causes the alveoli to stay open longer and do a better job of transferring gasses into and out of the blood. With that increase in O2 saturation and lowering of CO2, the brain may signal that you are in danger of hyperventilating and act to slow down your breathing rate or delay the next breath enough to fool the machine into flagging a CA.

[Crimson Nape]

I don't know if this will be of any help but I've noticed that the Resmed S9 won't record any events while it's in a ramp mode. I have my S9 set in APAP @8-10cmH2O. Since it takes me almost an hour to get to sleep, I set the ramp to be 45 minutes with a 8cmH2O minimum setting. Now I don't have any events until the ramp ends and I'm asleep. I realize that I need for somebody else to confirm this before I say it's the gospel.

[old82]

I realize that CAs may be created by a neurological defect but I think some CAs may be the result of an increase in the O2 saturation of the blood as a result of breathing against an elevated pressure. It's well known that exhaling against a pressure causes the alveoli to stay open longer and do a better job of transferring gasses into and out of the blood. With that increase in O2 saturation and lowering of CO2, the brain may signal that you are in danger of hyperventilating and act to slow down your breathing rate or delay the next breath enough to fool the machine into flagging a CA.

Surferdude2 ,that sounds like a reasonable explanation of how ca's occur..I'm hoping you're right and that I don't have "dame brammage".

SGEARHART... I have my ramp set at only 5 minutes so can't be of help about the recording of ca's during ramp.
Old82