Central Apneas

A few months ago I updated my cpap to a new apap that allows me to track my data. It's wonderful to feel in control. As a result of the data, I adjusted my pressure from 7 up to 11 with the result that my AHI dropped from the 10 to 15 range to the 2 to 4 range.

But, I'm still very fatigued even after several months. I'm curious if I could be having Central episodes due to the increased pressure. Does my machine recognize a Central episode and count it as an Obstructive episode? I don't know if it only recognizes efforts to breathe that fail, or if it counts lengthy periods of non-breathing and counts it as an Obstructive episode. Does the fact that my AHI is low mean that my fatigue is not caused by either Obstructive or Central episodes ... or could I have a low AHI but have a lot of Centrals?

Thanks.

Thats a good question....I don't know the answer, but I would like to know the answer...anyone?

you would have to consult with your original PSG sleep study report for any indication of CA (Central Apnea) or MA (mixed apnea) to understand if you are at risk of them.

If any CA or MA events showed up on that report, then you have to be cautious with any maximum pressure used.

Can the machine see and log Central Apnea?

Not accurately. No autopap can. If it is a Remstar and given enough of them to see, it can sometimes log them as a NR or Non-Responsive event. It usually takes 2-3 in a row for that to happen. By then you are usually awake.

In a sleep lab they have respiratory effort belts around your chest to determine if they are central or not. You don't have that at home. A 40-second central will look just like a 40-second apnea. So when you look at that report from your machine you have no idea if what you are looking at is a obstructive apnea or a central one.

When you are at risk of them and have the software you look for patterns to indicate if the event was central or not. They are usually present in clusters.

Snoredog wrote: You don't have that at home. A 40-second central will look just like a 40-second apnea. So when you look at that report from your machine you have no idea if what you are looking at is a obstructive apnea or a central one.

When you are at risk of them and have the software you look for patterns to indicate if the event was central or not. They are usually present in clusters.

Hey Snoredog, does the remstar software tell you specifically when the apnea was and for how long it lasted? or does it say something else?

THX,

Kent

The Auto usually tells specifically what the apnea was, at what pressure, and when it occured. Great stuff.

John, aside from Centrals which I know nothing about, sometimes we are seeing people who don't do well with Cflex.

Have you tried adjusting the cflex to different settings or turning it off completely? Just to test how you feel.

No. I thought that the C-Flex was helpful, so I hadn't tried adjusting it. I could experiment with that for a while.

Snoredog wrote:
Can the machine see and log Central Apnea?

Not accurately. No autopap can. If it is a Remstar and given enough of them to see, it can sometimes log them as a NR or Non-Responsive event. It usually takes 2-3 in a row for that to happen. By then you are usually awake.

In a sleep lab they have respiratory effort belts around your chest to determine if they are central or not. You don't have that at home. A 40-second central will look just like a 40-second apnea. So when you look at that report from your machine you have no idea if what you are looking at is a obstructive apnea or a central one.

Your last statement (above) makes it sound as if the machine does recognize all events, both obstructive and central, but it doesn't discriminate them. If that is true, then if I have a low AHI, that must mean that I'm not having many Obstructive or Central events. Is that true? Or, can I have many or extended Centrals without them being noticed by the software?

John:
I think that Linda's suggestion is a good one. Turning off C-FLEX is a fairly simple experiment to see if C-FLEX is giving you some breathing difficulty. If it is not giving you difficulty and you like/want the pressure relief upon exhale, then it is equally simple to just turn it back on.

Snoredog's comments about whether or not there were central's in your sleep study are also particularly germain. (Did I spell "germain" correctly?)

It is my understanding, based on what I've been told by a couple of respirologists, that any of us can toss some central's during sleep. Further, during a sleep study, when we are not accustomed to CPAP, it is entirely possible to have some centrals caused by the CPAP. During my titration sleep study, when I was not accustomed to CPAP, I had a bunch of central apnea's. The sleep doc told me that he was absolutely unconcerned about them as he thought they were pressure-related rather than central's driven by brain-stem disfunction. Snoredog's suggestion to check this out by looking at your PSG is a good one.

I know that the PB 420e does not increase pressure above 10 if it "thinks" the user is having a central apnea. 10 is the factory default and can be changed through the Silverlining software. I don't know if the other manufacturer's APAP's have a maximum pressure that they deliver if they "think" a central is happening but, I'd bet that they do. Perhaps other users that are familiar with this can speak to it.

schaefage wrote:

Snoredog wrote: You don't have that at home. A 40-second central will look just like a 40-second apnea. So when you look at that report from your machine you have no idea if what you are looking at is a obstructive apnea or a central one.

When you are at risk of them and have the software you look for patterns to indicate if the event was central or not. They are usually present in clusters.

Hey Snoredog, does the remstar software tell you specifically when the apnea was and for how long it lasted? or does it say something else?

THX,

Kent

The software will report when you have had:

Obstructive Apnea (OA)
Hypopnea (HI)
Flow Limitation (FL)
Vibratory Snore (SI)
Non-Responsive events (NR).

NR events are assumed to be central events because central events don't respond positively to cpap pressure.

For a NR event to be triggered on the Remstar it needs to see the event and increase pressure 3 times (it assumes they are obstructive thereby increases pressure), after the first increase it switches to monitor mode to see the response from the last pressure increase, if the event is still there, it increases it again by .5cm and monitors, if still exists after it does that a 3rd time it finally gets logged as a NR event and the pressure is immediately drops back to the onset pressure.

So detecting a NR event can take a while, if the central event went away on its own say after the second pressure increase the machine then pats itself on the back as doing a fine job and logs those 2 events as obstructive (they very well could have been central). You only see them when there are 3 in a row. 1 or 2 in a row they are considered obstructive. Same for central hypopnea, those are even harder for the machine to detect.

Identifying the events seen as non-responsive is technically correct way to identify them and works in the Remstar's favor. It also saves them from admitting the machine misread the event in the beginning and increased pressure 3 times to a central event. Calling them NR it can say they were events that didn't respond to pressure.

If you have found your sweet spot or ideal pressure, both type of events should be at their lowest which is what you want. This is why you can increase pressure and see your AHI score actually go up.

In general, obstructive events should go down with increased pressure. Central apnea events will generally increase in frequency along with pressure. When they titrate you in the lab they increase pressure until events subside and offers the best sleep and/or triggers a central event, for example attempting to eliminate a vibratory snore. Once the central event is seen they usually back off the pressure and settle back down to the pressure that offered the best sleep prior to that triggering the central. If you wake up the test is over.

Let's say you snore and the lab says your final pressure is 9cm. In reality the lab tech could have been chasing a snore and seen a central happen at 9.5cm. So they seen that 9cm offered the best sleep, didn't totally eliminate the snore but didn't trigger any more centrals.

So now you be-bop down and buy a autopap and set it to a range of 8 to 11 or you set the Min. pressure to 9cm what the lab says so it functions just like a cpap. So you say to yourself, well if the lab guy didn't get it right you'll give yourself some room to increase and so you leave the Max pressure up at 15 or 16cm thinking the lab guy didn't do a good job.

So you snore, nearly all autopaps on the market will chase a snore, so your at 9cm on the Min side, lab report says at 9.5 we start seeing centrals but you still snore and the machine says hey got to eliminate that snore so it increases pressure to 9.5cm snore continues, it increases to 10cm, it sees these FL's, HI's and OA's, so it increases again (in reality the machine went over your 9.5cm threashold for triggering centrals, only sees them as obstructive and responds with pressure until that snore is gone or you wake up and stop the process).

One thing about Central apnea, when it happens during the night and it doesn't take many, it nearly always takes you back to a wake state and the next day you will feel really bad like you are dead.

You can still use an autopap, you just have to know your own limits then use avoidance tactics and they can work fine. More times than not the lab guy really did do a good job and your pressure was right on and set there for a reason, a reason you or your autopap cannot see.

Great explanation Snoredog, thanks!!!

It's complicated. I was given a copy of my sleep lab report and it mentioned that I had some Centrals, but they offered no details. They titrated me at 7 in my first study and 6 in my second study. I remained very fatigued and my AHI was quite high. So, I increased it, initially using an APAP. I did very well at 11, so I set it at CPAP mode and my AHI has been acceptably low, but my fatigue has not improved much even over the months.

Should I ask for a more detailed copy of my sleep report, or do they not provide highly specific details?

[quote="John Galt"]It's complicated. I was given a copy of my sleep lab report and it mentioned that I had some Centrals, but they offered no details. They titrated me at 7 in my first study and 6 in my second study. I remained very fatigued and my AHI was quite high. So, I increased it, initially using an APAP. I did very well at 11, so I set it at CPAP mode and my AHI has been acceptably low, but my fatigue has not improved much even over the months.

Should I ask for a more detailed copy of my sleep report, or do they not provide highly specific details?

Thanks again for the info. I was given a complete copy of the report, both by the sleep lab and by my MD. Neither copy included a titration table. The report only incidentally mentioned that I had a few Centrals with no specifics provided. Similarly, there was no information about my sleep when at higher pressure levels.

I will eventually ask for another study, though I have had two in two years.

John, you already have excellent feedback from the other postersbut I'll add a few cents worth re centrals.

The issue with a central is that it is a cessation of respiratory 'effort'. An obtruction is of course due to an air way block but lots of 'effort'.

As WillSucceed pointed out the sleep study involves strapping on a sensor that can measure the respiratory 'effort' & thus they can tell if you are experiencing a central or a block.

The machine generally can't tell the difference. If someone is experiencing a set of centrals, the machine may guess by following sets of rules (algorithms)

Here is a hypothetical situation
> cessation of airflow - over x secs bump up pressure by 1 cms, wait 5 secs smaple again
> repeat 3 times, if nothing then revert to where we were as this may be a central

Apaps & a cpaps cannot treat centrals - they have nothing the can signal a person to resume breathing. A Bilevel that has timed mode can be used to 'nudge' the sleeper to breathe again.

The above hypothetical was very simplistic as the real algorithms have a lot more rules such as if pressure is already at 10 cms then don't even try to adjust to this flow cessation.

Also if you added up the seconds in the above algorithm example it is easy to see that 40 secs could easily pass while the smapling is going on & most centrals & blocks are cleared by arousal well before 40 secs (the average length IIRC is about 8 secs).

Apaps are good at 'pre-empting' apneas by looking at remebered patterns of flow limitations & usually increasing pressure before a block actually can form.

DSM

Snoredog wrote: One thing about Central apnea, when it happens during the night and it doesn't take many, it nearly always takes you back to a wake state and the next day you will feel really bad like you are dead.

Amen to that. If I use a pressure any higher than 10cm then I sometimes get an NR. Let me confirm they are not fun. When I wake up the next morning after having one I can tell right away without even downloading the smartcard what has happened. Ouch.