Question Regarding Centrals

[Mopheus]

My untreated apnea was 50% centrals. After running my machine open at 5 to 15, I was getting very inconsistent AHI.
After bumping up to 9, I started getting under 2 AHI consistently, with about 30% centrals. I am now on 10 for a week
and my AHI is consistently under 1 for 7 days in a row. And no centrals, not one. I thought APAP didnt treat centrals.
So where did they go?

[palerider]

I thought APAP didnt treat centrals. So where did they go?

they don't the only way you can treat a central is to ramp the pressure up 10+ cm, which is what a ventilator does, and apaps aren't programmed to do that.

maybe your centrals were cause by all the other irregularity and disturbances to your sleep.

[LSAT]

Many Centrals are Clear Airway events (CA). When you turn over in bed or change position you may hold your breath for 10+ seconds....That's a CA.

[palerider]

Many Centrals are Clear Airway events (CA). When you turn over in bed or change position you may hold your breath for 10+ seconds....That's a CA.

*all* centrals are clear airway events, and *ALL* clear airway events are central.

if your airway isn't clear, and you're not breathing, then you're having some other kind of event.

they're the same thing, just different companies use different names to describe the same situation of 'no effort being made to breath and airway not blocked'.

[Guest]

*all* centrals are clear airway events, and *ALL* clear airway events are central.

Erroneous statements like those *almost* make me want to come back to the forum.

*ALMOST*.

[palerider]

*all* centrals are clear airway events, and *ALL* clear airway events are central.

Erroneous statements like those *almost* make me want to come back to the forum.

*ALMOST*.

and yet, here you are, spreading your sewage.

"clear airway apnea" was a term *MADE UP* by Respironics, and is pretty much unique to them, not general medical parlance, to refer to what their machine thinks is a non-obstructive apnea.

googling "clear airway apnea" -respironics yields at last test, a grand total of about 43 results.

for comparison, "central apnea" gives About 90,900 results

now, you and other simpering idiots can argue that "central" and "clear airway" apneas aren't just different words to describe the same situation based on what manufacturer's machine is reporting the event, but, that's just more of your bullshit.

[robysue]

Many Centrals are Clear Airway events (CA). When you turn over in bed or change position you may hold your breath for 10+ seconds....That's a CA.

*all* centrals are clear airway events, and *ALL* clear airway events are central.

Nope. I have to disagree with you on this one palerider.

On a PSG, a central apnea is scored when the airflow into or out of the lungs ceases for at least 10 seconds AND the belts show that there is no effort to breath AND the EEG shows that you are asleep. There is no effort to measure the patency of the airway on the PSG because the bigger problem is that the brain has forgotten to send the signal "Inhale NOW" to the lungs and diaphragm. It is possible for the airway to collapse during a central apnea. If you arouse enough to simultaneously open the airway and restart the breathing caused by the central issue, the fact that the airway was temporarily obstructed will never be detected or recorded on the PSG. On the other hand, if the brain starts sending "Inhale NOW" signals to the lungs and diaphragm, but there continues to be no airflow into the lungs, then it is assumed that the apnea started as a central event, the airway collapsed during the central event, and when the effort to breath resumes, the obstructed airway is now causing the event to look like (and behave like) an obstructive event. This kind of apnea is scored as a mixed apnea on a PSG. There is no way for our machines to determine when an apnea is a mixed apnea---i.e. a central apnea with an obstructed airway.

When our machines score a "CA" or a "clear airway apnea", there is a high probability that the event is a central apnea---if the event actually occurs when we are asleep. But there are a lot of things that can cause the brain to not send an "Inhale NOW" signal to the lungs for a long enough time to be scored as a 10-second pause in breathing. Many people's typical wake breathing patterns include 10 second pauses in breathing often enough to cause their machines to score lots of "false" CAs when they are lying in bed awake for a substantial amount of time. Many people have a tendency to hold their breath while turning over in bed, and those "hold the breath while turning over" episodes frequently get scored as CAs by our machine, but would not be scored as a CA on a PSG since they represent a normal sleep breathing pattern. Many people have one or two "sleep onset" CAs scored most nights when they are first drifting off to sleep. These events would NOT be scored on a PSG and they are NOT considered real, genuine central apneas.

It's also important to remember that both the Resmed FOT algorithm and the PR PP algorithm for detecting CAs vs OAs are not perfect. Some airways react in nonstandard ways to pressurized air and for a small number of CPAP users, there is a tendency for the airway to collapse whenever the effort to breath ceases. That means that for some people, machines may often mis-score a real CA as an OA since the FOT/PP algorithm indicates that air is not getting into the lungs. Our machines cannot measure whether we are trying to breath---they just assume that we're trying to breath unless the FOT/PP algorithm says air can get through, but not air is naturally flowing into or out of the lungs.

Sludge/Morbius wrote a lot about how machines can mis-score CAs as OAs when he was still posting here.

Also, it's important to understand this as well: ASV machines treat a particular kind of problem with central apneas that are part of sleep disordered breathing: They treat central sleep apnea where the apneas are caused by the development of a CO2 overshoot/undershoot cycle. It's the CO2 level that drives the respiratory cycle and in a CO2 overhoot/undershoot cycle, the brain has trouble reacting correctly to the CO2 levels. There's an overshoot component---you blow off too much CO2 by (slightly) hyperventilating and this leads to a suppression of the respiratory drive. And there's an undershoot component---you are breathing so shallowly that the CO2 builds up to a level that is capable of triggering hyperventilation. It doesn't matter which comes first: Once the cycle starts, it can go on for 5-10 minutes or more and at the nadir of the cycle you wind up with central hypopneas (if the effort to breathing doesn't completely cease) or central apneas (if the effort to breath does cease completely.) An ASV machine kicks in with the triggered breaths during the "undershoot" part of the cycle---when you're not breathing sufficiently deeply to keep the CO2 levels from growing, the machine steps in and attempts to keep blowing enough air into your lungs to prevent the CO2 levels from growing enough to trigger the next round of hyperventilation and CO2 overshoot.

As for whether an ASV machine is mandatory for treating central sleep apnea: There is some real controversy in the sleep medicine community about that as well. Sludge/Morbius also posted about that multiple times before he left the forum. In some people with documented CSA problems, the the mere fact that there is positive air pressure at all times when using CPAP, APAP, or BiPAP is enough to prevent the CO2 levels climbing to the point to trigger the undershoot/overshoot CO2 cycle from starting. When that happens, the patient's central sleep apnea responds quite well to CPAP, APAP, or BiPAP. And that's actually why a lot of insurance companies (and sleep docs) will want to start a person with CSA off with CPAP or BiPAP: If the simpler machine fixes the problem, there's no need to put the person on the more expensive and much harder to titrate machine. The fact that many people also find that there's a steeper learning curve to learning how to sleep well with an ASV also factors in to the decision to first see if CPAP or BiPAP will take care of the CSA problem.

[palerider]

Many Centrals are Clear Airway events (CA). When you turn over in bed or change position you may hold your breath for 10+ seconds....That's a CA.

*all* centrals are clear airway events, and *ALL* clear airway events are central.

Nope. I have to disagree with you on this one palerider.

On a PSG,

in the context of cpap treatment, and cpap reports, I stand by my statement.

if you want to drag EEGs and lab PSGs and chest effort sensors into the mix, then there's no such thing as a "clear airway event" which really, is nothing but a respironics creation to avoid calling what they're scoring a 'central' like resmed does.

if you want to talk about THAT view... then here's another take on the whole thing: https://www.youtube.com/watch?v=xallwxPCg84

[robysue]

Many Centrals are Clear Airway events (CA). When you turn over in bed or change position you may hold your breath for 10+ seconds....That's a CA.

*all* centrals are clear airway events, and *ALL* clear airway events are central.

Nope. I have to disagree with you on this one palerider.

On a PSG,

in the context of cpap treatment, and cpap reports, I stand by my statement.

if you want to drag EEGs and lab PSGs and chest effort sensors into the mix, then there's no such thing as a "clear airway event" which really, is nothing but a respironics creation to avoid calling what they're scoring a 'central' like resmed does.

Palerider,

Our machines will clearly mis-score a true central apnea if the airway collapses after the central apnea starts. That does not change the fact that the apnea is a central apnea---i.e. the apnea was caused by lack of effort to breath. But the collapsed airway will make our machine mis-score the central apnea as an OA.

And it is not uncommon in some people's breathing patterns for the airway to collapse after a central apnea starts. If you happen to have that kind of a breathing pattern, it is possible for the CPAP to misscore a significant number of CAs as OAs.

It is, however, much more difficult for our machines to mis-score a real OA as a CA. If the airway collapses and that's the cause for no air getting into or out of the lungs, then the FOT/PP algorithm is very likely to detect the obstruction and score the apnea correctly as an OA.

To be clear:

Our machines are not very likely to mis-score an OA as a CA.

Our machines will mis-score CAs where the airway collapses after the CA begins. The initial cause of a the apnea is NOT the obstructed airway, and the apnea should not be scored as an OA. But the FOT/PP algorithm will detect the blocked airway and score the central event as an OA.

Our machines also assume that all hypopneas are obstructive in nature. That also is an invalid hypothesis for people with central sleep apnea: It is possible that at the nadir of the overshoot/undershoot cycle that breathing does not cease entirely, but the effort to breath is so slight that the reduction in airflow meets the criteria for a machine scored H.