The Relationship of EPR and Central Apneas

[Allessio77]

Does anyone know why Central apneas increase when EPR is on, and decrease when EPR is off?

I recently turned my EPR on to #2 to try to relieve some aerophagia that was bothering me (until recently I thought it was diet related but isn't). That setting did seem to help, but my centrals increase and raised my AHI to 7.47 from a May average of 1.1. The 6th night of EPR at 2 showed this chart:




I am just trying to understand the nature of the relationship between lower exhalation pressure and increasing centrals.

[jnk...]

There may be a number of reasons. One is that EPR is very close to bilevel, which some with blood-gas sensitivities can have issues with. (Some also have issues with the pressure changes of APAP.) Another reason may be that airway-narrowing can destabilize breathing to the point that centrals can be triggered. Stabilizing breathing has many aspects, mechanical and chemical. And few researchers these days buy into the concept that any given apnea can easily be classified as purely obstructive or purely central. Many events at their root share some aspects of both issues.

Some of us have found that we need to raise our pressure, or our minimum, when we engage EPR, since ResMed's form of that comfort feature can have a more powerful effect on our therapy than some other forms from other brands.

It isn't always a matter of understanding completely why something works. The thing is to find what works. We are all unique, just like everyone else.

[Pugsy]

People often think that the respiratory drive is triggered by oxygen levels in the blood stream...that when the oxygen levels drop the brain sends the signal to breathe.
That's not the case though. It's the carbon dioxide levels in the blood that the brain watches and it's when the carbon dioxide levels in the blood reach a certain point the brain sends the signal to "breathe" so we can get rid of the carbon dioxide.

Central apneas are when the brain doesn't send the signal because for some reason the carbon dioxide levels in the blood stream simply don't reach the level where the "breathe" command gets sent.

For some reason or other there is a small percentage of people who find that using exhale relief (doesn't matter what brand or what it is called) creates a situation where the breathing becomes unstable and too much carbon dioxide gets exhaled to quickly and the blood levels of carbon dioxide don't get high enough for the brain to send the command to breathe.
The inhale/exhale difference when exhale relief is used washes out the carbon dioxide too much.
Now why some people and not others...I don't have a clue and it's a very small percent of people who use any form of exhale relief that this happens to. Some might already be on some sort of medication that might suppress respiration but it can happen just because that's the way the person breathes and exchanges blood gases.

The higher the pressure support (the difference between inhale and exhale) the greater the chance for carbon dioxide to wash out too soon and the blood levels stay below the breathe trigger point and the brain doesn't send the signal to breath and a central apnea results.

Using EPR or any form of exhale relief creates a bilevel situation where the inhale and exhale are different. It's pressure support but called exhale relief because that's what it does.

Sometimes there is a fine line where when PS is used between washing out too much carbon dioxide and causing a problem and using some PS but not causing a problem.
I know one woman who has a problem with PS of 4...she gets like 15 centrals an hour but with PS of 3...maybe 1 and hour or even less. She needs the PS because her pressure to deal with her obstructive apneas are in the upper teens at times. She's lucky that she doesn't have a problem with PS of 3 (which would be equal to EPR at 3).

You might or might not be able to use EPR at 1 and not have an issue with centrals. I don't know if you have tried that or not or if you even feel the need to use EPR.

[Allessio77]

People often think that the respiratory drive is triggered by oxygen levels in the blood stream...that when the oxygen levels drop the brain sends the signal to breathe.
That's not the case though. It's the carbon dioxide levels in the blood that the brain watches and it's when the carbon dioxide levels in the blood reach a certain point the brain sends the signal to "breathe" so we can get rid of the carbon dioxide.

Central apneas are when the brain doesn't send the signal because for some reason the carbon dioxide levels in the blood stream simply don't reach the level where the "breathe" command gets sent.

For some reason or other there is a small percentage of people who find that using exhale relief (doesn't matter what brand or what it is called) creates a situation where the breathing becomes unstable and too much carbon dioxide gets exhaled to quickly and the blood levels of carbon dioxide don't get high enough for the brain to send the command to breathe.
The inhale/exhale difference when exhale relief is used washes out the carbon dioxide too much.
Now why some people and not others...I don't have a clue and it's a very small percent of people who use any form of exhale relief that this happens to. Some might already be on some sort of medication that might suppress respiration but it can happen just because that's the way the person breathes and exchanges blood gases.

The higher the pressure support (the difference between inhale and exhale) the greater the chance for carbon dioxide to wash out too soon and the blood levels stay below the breathe trigger point and the brain doesn't send the signal to breath and a central apnea results.

Using EPR or any form of exhale relief creates a bilevel situation where the inhale and exhale are different. It's pressure support but called exhale relief because that's what it does.

Sometimes there is a fine line where when PS is used between washing out too much carbon dioxide and causing a problem and using some PS but not causing a problem.
I know one woman who has a problem with PS of 4...she gets like 15 centrals an hour but with PS of 3...maybe 1 and hour or even less. She needs the PS because her pressure to deal with her obstructive apneas are in the upper teens at times. She's lucky that she doesn't have a problem with PS of 3 (which would be equal to EPR at 3).

You might or might not be able to use EPR at 1 and not have an issue with centrals. I don't know if you have tried that or not or if you even feel the need to use EPR.

I think I understand!! CO2 signalling is the key. Thanks for the lucid explanation!

I apparently am on that fine line you mention, because the first 5 nights of EPR @2 were only slightly problematic as far as centrals go. I really did not change any other variable during this time period. But last night they rocketed to 47 during the night in clusters. I think I will try turning it to 1. Should I simultaneously do anything with my 7-11 pressure settings? ( "jnk" (above) suggest raising the pressure slightly. )

Pugsy, I would not even be messing with EPR except I have to try to get rid of the all day gassyness that I am experiencing. I learned that EPR is one approach. I am also sleeping on my right side and using a longer wedge pillow to fight this aerophagia.

[Allessio77]

Some of us have found that we need to raise our pressure, or our minimum, when we engage EPR, since ResMed's form of that comfort feature can have a more powerful effect on our therapy than some other forms from other brands.

It isn't always a matter of understanding completely why something works. The thing is to find what works. We are all unique, just like everyone else.

Did you increase your exhalation or inhalation pressure when j deployed EPR? I did not change mine when I turned the EPR on.
I would not be changing anything, but I want to get rid of the all day gas!! Its an unpleasant feature when dining out with friends!!

[jnk...]

Centrals are notoriously intermittent in that you can go several nights in a row with none at all then have a night with a bunch of them. That can be the nature of the beast. And it may not be pressure related when it happens. That can make it difficult to use AHI as a whole as a true gauge of what effect pressure(s) is/are having on your sleep.

Balancing comfort with efficacy can be a personal call for what settings you use.

I have to keep my minimum pressure up fairly high for comfort reasons, so I don't feel starved for air. But, yes, if I use an EPR of 1, I choose to raise minimum pressure by 1. If I use an EPR of 2, I choose to raise my minimum by 2. If I use an EPR of 3 (which is what I usually use), I choose to raise my minimum by 3. But like I said, I'm doing that for comfort. And in your case, you may find that not to be the case for you, if aerophagia is your primary comfort concern.

[Pugsy]

I think I will try turning it to 1. Should I simultaneously do anything with my 7-11 pressure settings? ( "jnk" (above) suggest raising the pressure slightly. )

No, I would only change one thing at a time.

Are you thinking the reduction during exhale is going to automatically be sub optimal and you need more pressure to compensate?
Yes, that sometimes happens to some people but it doesn't necessarily mean it will happen to all people if they decide to employ some form of exhale relief. I would evaluate the results first...like did it allow 1 or 2 more events or a truckload of events slip past the defenses.

Besides...remember Science 101...keep your variables to a minimum with any experiment so you can better evaluate the results.

At any rate...adding EPR for gassiness and then increasing the pressure to offset any potential sub optimal pressure...will more likely result in more gas and not less. You aren't really reducing anything.

If it were me and the gassy stuff was a problem and adding exhale relief also created a problem then I would look at the minimum and maximum pressures and maybe limit the max severly if I was spending much time near the max. Just because a machine wants to go higher doesn't mean we have to let it if the going there creates more problems than it fixes when it goes there.

[Allessio77]

I think I will try turning it to 1. Should I simultaneously do anything with my 7-11 pressure settings? ( "jnk" (above) suggest raising the pressure slightly. )

No, I would only change one thing at a time.

Are you thinking the reduction during exhale is going to automatically be sub optimal and you need more pressure to compensate?
Yes, that sometimes happens to some people but it doesn't necessarily mean it will happen to all people if they decide to employ some form of exhale relief. I would evaluate the results first...like did it allow 1 or 2 more events or a truckload of events slip past the defenses.

Besides...remember Science 101...keep your variables to a minimum with any experiment so you can better evaluate the results.

At any rate...adding EPR for gassiness and then increasing the pressure to offset any potential sub optimal pressure...will more likely result in more gas and not less. You aren't really reducing anything.

If it were me and the gassy stuff was a problem and adding exhale relief also created a problem then I would look at the minimum and maximum pressures and maybe limit the max severly if I was spending much time near the max. Just because a machine wants to go higher doesn't mean we have to let it if the going there creates more problems than it fixes when it goes there.

I appreciate the dictum of 'changing only one variable at a time' , and giving it a few nights.

I do have a concern about raising the pressure...seems to me that too high of pressure is the cause of the aerophagia! But I know if I lower the IPAP any, the Hypopnias will be back. I do want to hold open my airpathways.

This really is a balancing act. Just when I thought I had the formula that reduced my centrals and my AHI with NO leaks and a comfortable experience, this other issue comes along. Changing even one setting can throw a lot off...and trying to solve the gas, and get back to a central free, happy AHI life looks like it may be a challenge.

I was going to wait out the Aerophagia issue, but instead of getting better over the months, it is getting worse. That's why I decided to mess with my settings. (after I researched the possible approaches).

[jnk...]

For some of us, not consuming anything other than water within 3 hours of going to sleep helps aerophagia.

[Pugsy]

This really is a balancing act. Just when I thought I had the formula that reduced my centrals and my AHI with NO leaks and a comfortable experience, this other issue comes along. Changing even one setting can throw a lot off...and trying to solve the gas, and get back to a central free, happy AHI life looks like it may be a challenge.

It can be quite a balancing act for sure.
If it were me I would first try to figure out if the centrals were real or not. If not real they simply don't count in the evaluation process.
Then if the bulk of the centrals were real I would look at how many and not expect to be "central free" because remember ...an occasional central like a sleep onset central is normal and not a cause for concern.
Then I would look at the aerophagia symptoms...evaluate just how miserable I was from it and look to see how many apnea events I would have if I dropped the pressures just a little so that the belly was better. It's why I said sometimes we have to make compromises.

And while the number of centrals towards the end of the night might look alarming...assuming they are real...I would add a recording pulse ox to things just to see if they were affecting the oxygen levels.
Compare the oxygen level results with the centrals happening or what happens if a few hyponeas slip past the defenses because of lower pressures.

First thing I would do though...figure out if those centrals are the real deal or not.
Do you know how to do that? Takes some education and a good place to start is Jason's videos here...all of them.
http://freecpapadvice.com/sleepyhead-free-software

While I don't normally have aerophagia issues I have had a couple of occasions to experience it and it was so bad I was physically ill all day. It was miserable. Given a choice between feeling like that all day and letting a handful of hyponeas slip past the defenses I would gladly let the hyponeas happen because they are going to hurt me nearly so bad as the aerophagia does.
But that's just me....and I value how I feel all day a lot. I would be unwilling to make myself sick all day just to stop a few hyponeas or even OAs. If the difference was between having an AHI of 1.0 and hurt like hell and be sick...or having an AHI of 3.0 and not be miserable. I would take the higher AHI in a heartbeat.

[Allessio77]

"While I don't normally have aerophagia issues I have had a couple of occasions to experience it and it was so bad I was physically ill all day. It was miserable. Given a choice between feeling like that all day and letting a handful of hyponeas slip past the defenses I would gladly let the hyponeas happen because they are going to hurt me nearly so bad as the aerophagia does." says Pugsy

This was exactly the place I was in....it just was getting worse and ruining my day. I was willing to tolerate a few OA and Hyp to get back to normal, but the AHI of 7+ scared me.
Before this experiment with EPR, I was averaging only 3 central a night and MOST of them looked like junk to me. With the EPR at 2, not only did I have a ton of centrals, but they were grouped in 4 clusters becoming more numerous as the night progressed. They reminded me of what my chart looked like when I began PAP back in Dec...they certainly looked more disturbing to me with the chyene stoke waveform joining the individual CA's.

Anyhow, I am going to drop my EPR tonight and see what happens before I do anything else.

I just wish the GAS-X would have worked and I wouldn't even have an issue!

[Pugsy]

The AHI of 7 plus above...the bulk of it was the CAs/centrals.
If they are real and EPR is the culprit...you've got some wiggle room in terms of maybe letting a few OAs or hyponeas slide if you were to simply reduce the pressure and not even need to use EPR. The obstructive part of that AHI is really very small.

Like maybe drop the max to 9 and simply not let the machine go over 9. So minimum of 7 and max of 9 and no EPR. See if that helps with the aerophagia. Have you tried a lower max? If so, what were the results? Just because a machine wants to go higher doesn't mean that we have to let it go higher if the going higher causes a problem.

[palerider]

Some of us have found that we need to raise our pressure, or our minimum, when we engage EPR, since ResMed's form of that comfort feature can have a more powerful effect on our therapy than some other forms from other brands.

It isn't always a matter of understanding completely why something works. The thing is to find what works. We are all unique, just like everyone else.

Did you increase your exhalation or inhalation pressure when j deployed EPR? I did not change mine when I turned the EPR on.
I would not be changing anything, but I want to get rid of the all day gas!! Its an unpleasant feature when dining out with friends!!

EPR DROPS pressure when not exhaling, giving you a limited bilevel... here's an example of what it does to the pressure (starting at 13)

[palerider]

There may be a number of reasons. One is that EPR is very close to bilevel,

EPR is so close to bilevel that i can't see any significant difference

Top line is an autoset with EPR3, middle line is a vpap auto PS3 and easybreathe on, bottom line is what happens when easybreath is off... for comparison.

[jnk...]

I have zero talent for reading squigglies. But it seems EPR gradually slopes, and bilevel maybe goes more flat then dips?

I honestly have never fully grasped the interaction of pressure and flow and how that interaction affects comfort and therapy.

And I admit I might not be able to feel the difference between S8 3cm-PS VPAP and S9 3cm-EPR CPAP in a blind test.