Obstructive Disappeared & Central Created

[Reuven Gruber]

My sleep study showed AHI of 31 with no central apneas. After 1 week of therapy I have no obstructive apneas but now have central apneas at a low level (total AHI averages around 2. Is this normal?

[SuperSleeper]

Hi Reuven, welcome to Apnea Board.

First off, a 2.0 overall AHI is very good. Quite good, in fact, for your first week on CPAP.

Second, it's somewhat "normal" that you might be getting a few "central" apnea events. Most would say that there's little difference (as far as damage to your body) from the effects of central events vs. obstructive events. Both are equally bad. But, as long as your overall AHI remains below 5.0, you're doing very good.

I wouldn't worry about an AHI of 2.0 at all, even when most of the events are centrals. It's my guess that these centrals might even reduce over time.

Wish I could get my AHI to that level. I'm jealous!

Hopefully others can chime in with their thoughts as well.

[Peter_C]

Food for thought: I am happy when my AHI is ten or less. - Just perspective. The bigger question to ask yourself; are you yet starting to sleep better, wake more rested, feeling less drowsy during the day?

We use numbers because the Docs can't watch you sleep and watch you all day long 24/7/365, so, we use numbers. The assumption is; OSA is no longer a problem for our body as long as we can keep our AHI below five. And, many folks live by the numbers and enjoy actively watching them, comparing them, and yes, even feeling great because they got 0.0 two days in a row - I even started a new thread the first time I got 0.0 AHI.

In my book you're doing wonderful! And, many people get some centrals when starting therapy find they go away with time. But the point here is, you're doing great even if they don't go away.

[zonk]

My sleep study showed AHI of 31 with no central apneas. After 1 week of therapy I have no obstructive apneas but now have central apneas at a low level (total AHI averages around 2. Is this normal?

Unlike the sleep study, the machine cannot tell whether you're awake or asleep. Apneas scored while you're awake can be discarded

AHI total of 5 and lower is normal while on PAP, keep an eye on it and bring it to the attention of your doctor at next followup

From http://www.resmed.eu/us/clinicians/about...clinicians
A diagnosis of central sleep apnea (CSA) requires all of the following:
An apnea index > 5
Central apneas/hypopneas > 50% of total apneas/hypopneas
Central apneas or hypopneas occurring at least 5 times per hour
Symptoms of either excessive sleepiness or disrupted sleep

As for normal, everyone is different, for some its normal to have few central when starting out and for others EPR can causes few centrals too

[kfujioka]

My sleep study showed AHI of 31 with no central apneas. After 1 week of therapy I have no obstructive apneas but now have central apneas at a low level (total AHI averages around 2. Is this normal?

Unlike the sleep study, the machine cannot tell whether you're awake or asleep. Apneas scored while you're awake can be discarded

AHI total of 5 and lower is normal while on PAP, keep an eye on it and bring it to the attention of your doctor at next followup

From http://www.resmed.eu/us/clinicians/about...clinicians
A diagnosis of central sleep apnea (CSA) requires all of the following:
An apnea index > 5
Central apneas/hypopneas > 50% of total apneas/hypopneas
Central apneas or hypopneas occurring at least 5 times per hour
Symptoms of either excessive sleepiness or disrupted sleep

As for normal, everyone is different, for some its normal to have few central when starting out and for others EPR can causes few centrals too

I had the same happen to me but my centrals are more like between 11 and 17.
You are doing very well!

[archangle]

Go into your airflow waveforms and see how long the centrals last and how completely you stop breathing. Often, when you look they're not really that alarming, but if they're really long, you may need to worry.

I find this easier to check with SleepyHead, but you can do it with ResScan as well.

[old82]

Go into your airflow waveforms and see how long the centrals last and how completely you stop breathing. Often, when you look they're not really that alarming, but if they're really long, you may need to worry.

I find this easier to check with SleepyHead, but you can do it with ResScan as well.

Archangel...could you go into some detail specifically using ResScan as to the title of the specific chart to examine airflow waveforms and how to manipulate it to see the airflow waveforms and how to determine how long they last and what you consider an acceptable length of a CA before you would be concerned as you mentioned above.

[TyroneShoes]

It appears that classic OSA sufferers who have few if any CA events while untreated, can start to show CA events under treatment. It seems that it is very common, and it appears to be due to pressure and EPR settings, which is why we try to keep those both as low as we can while still keeping the airway open.

But no one seems to be able to explain exactly why we have them at all. The "CNS disconnect" theory does nothing to explain why being under treatment ironically creates CAs that were never there before.

I had one, maybe two (index of 0.2) CA events in my home study (untreated), but they are regularly twice as prevalent now as non-CA events with the mask on, and it has been that way every night for well over 100 nights now. And no one can explain that either.

Additionally, many people have posted that they see reports of CAs during times when they are wide awake (with the mask on). Just coincidentally, I had 25 CA events just last night, which is unusually high for me (8 other events, AHI of 4.9 which is 2-3 times higher than normal for me). But over half of the CA events were clustered in the 5 minutes just before I took the mask off, and I had been wide awake for at least 30 minutes and breathing normally.

Having been investigating this here on the forum, I was also cognizant of this potentially happening, so I was also very careful during that period to continue to breath normally; there is absolutely no way that I stopped breathing for 15 seconds at a time, 13 times in a row during that 5 minute period.

So I am puzzled by why the machine might behave like this. It seems more like a flaw than anything else. And if you look at these CA events closely on the SH graphs, the IPAP/EPAP signatures look absolutely identical to the CAs from when I actually was asleep, all being 10-18 seconds in length.

They are "ghost" flags. They are right there in black and white on the report, you can see them on the graphs, but they didn't really happen, which makes no sense at all.

[archangle]

Archangel...could you go into some detail specifically using ResScan as to the title of the specific chart to examine airflow waveforms and how to manipulate it to see the airflow waveforms and how to determine how long they last and what you consider an acceptable length of a CA before you would be concerned as you mentioned above.

I find it much easier to see the data in SleepyHead. It's called Flow Rate.

ResScan calls it "flow."

Find the event in your graphs, look at the flow data and see how long you stopped breathing.

As for how long, there's no easy answer. In theory, 11 is bad and 9 is OK, because that's how they score AHI. In practice, 30 seconds is a lot worse than 11 seconds. Look at your data and think about how long you are going without breathing.

[Sleepster]

My sleep study showed AHI of 31 with no central apneas. After 1 week of therapy I have no obstructive apneas but now have central apneas at a low level (total AHI averages around 2. Is this normal?

It's normal. Many people report having even more centrals. They will subside.

The thing is, AHI is not a very precise indicator. If you had a AHI under 5 during your sleep study you'd be diagnosed as not having sleep apnea and there would be no prescription for CPAP therapy.

You should be focusing on your leak rate and compliance rate instead.

After that the best indicator is how you feel.