What is central sleep apnea ?

General Discussion on any topic relating to CPAP and/or Sleep Apnea.
Architect
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What is central sleep apnea ?

Post by Architect » Thu Jun 23, 2022 4:28 pm

Hi, I've noticed central sleep apnea is mentioned alot at the forums. Online articles are very confusing.....

My Fitbit charge states I wake 2-3 times during sleep every night, but upon waking I don't remember waking up at all.

Example today my Fitbit data awake 3 times, My air 0 AHI.

I've downloaded Oscar, just haven't set it up yet, till I fully understand how to install, setup, use.

dataq1
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Re: What is central sleep apnea ?

Post by dataq1 » Thu Jun 23, 2022 5:08 pm

Generally central apnea is reported when there is no air flow for a period of 10 seconds AND simultaneously no indication of an airway obstruction.

I don’t know how (or if) centrals can be observed in Type 4 sleep studies.
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ChicagoGranny
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Re: What is central sleep apnea ?

Post by ChicagoGranny » Thu Jun 23, 2022 5:09 pm

Architect wrote:
Thu Jun 23, 2022 4:28 pm
I've noticed central sleep apnea is mentioned alot at the forums. Online articles are very confusing.....
Obstructive: can't breathe
Central: won't breathe*
Architect wrote:
Thu Jun 23, 2022 4:28 pm
My Fitbit charge states I wake 2-3 times during sleep every night, but upon waking I don't remember waking up at all.
Fitbit is notoriously inaccurate. But if yours is accurate, your sleep is wonderful.

*Obstructive: Your brain wants you to breathe, but your airway has collapsed. You awaken, however briefly, and get your airway to open.
Central: Your airway is open but your brain fails to send out the order to breathe. There is something wrong with your central nervous system.

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ozij
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Re: What is central sleep apnea ?

Post by ozij » Thu Jun 23, 2022 7:41 pm

ChicagoGranny wrote:
Thu Jun 23, 2022 5:09 pm
*Obstructive: Your brain wants you to breathe, but your airway has collapsed. You awaken, however briefly, and get your airway to open.
Central: Your airway is open but your brain fails to send out the order to breathe. There is something wrong with your central nervous system.
Obstructive: + you struggle to breathe but can't.
Central: you're not trying to breathe, there's no struggle.
In both cases, it's the changes in oxygenation and co2 in your blood that make your brain wake you up however briefly and start breathing

The word "Central" in "Central Sleep Apnea" comes from the "central" in "central nervous system" aka CNS. In central apena, when you're asleep, your CNS stops sending "breathe" messages for too long, and therefore your sleep is interrupted.

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ozij
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Re: What is central sleep apnea ?

Post by ozij » Thu Jun 23, 2022 7:56 pm

Architect wrote:
Thu Jun 23, 2022 4:28 pm
My Fitbit charge states I wake 2-3 times during sleep every night, but upon waking I don't remember waking up at all.
ChicagoGranny wrote:
Thu Jun 23, 2022 5:09 pm
Fitbit is notoriously inaccurate. But if yours is accurate, your sleep is wonderful.
In the other hand, my Polar Ignite 2 has a sleep report in it app on the phone in which the interruptions - are very well correlated with OSCAR's reports. I will have arousal related CA's, and the Polar will record arousal. I rarely have obstructive events so I can't vouch for that....

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Respirator99
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Re: What is central sleep apnea ?

Post by Respirator99 » Thu Jun 23, 2022 8:13 pm

ChicagoGranny wrote:
Thu Jun 23, 2022 5:09 pm
Obstructive: Your brain wants you to breathe, but your airway has collapsed. You awaken, however briefly, and get your airway to open.
Central: Your airway is open but your brain fails to send out the order to breathe. There is something wrong with your central nervous system.
While that's more-or-less true, there needs to be a bit of finesse to the statement, lest people start thinking they are about to have a neurological breakdown. The urge to breathe is moderated by the amount of CO2 in the bloodstream, which is monitored by the carotid bodies in the neck. A genuine CNS disorder (eg caused by a trauma, drugs, or idiopathic) can be the problem when CA is present even when people are not on any form of breathing treatment. However the levels of CO2 can be affected by other factors including the gas balance changes brought on by xPAP treatment. More "efficient" breathing will wash out CO2 so it never reaches the concentration needed to trigger the carotid bodies, which in turn don't signal the brain that it's time to take a breath. This is why many new users see some central apneas, and why the situation can be made worse by the use of EPR.
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Re: What is central sleep apnea ?

Post by ozij » Thu Jun 23, 2022 8:21 pm

Respirator99 wrote:
Thu Jun 23, 2022 8:13 pm
and why the situation can be made worse by the use of EPR
Because EPR makes the flushing out of CO2 more efficient?

What about an inhale / exhale difference higher than 3 - as is possible in Bi-Level machines wouldn't that increase CA even more? And if not, why not?

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Respirator99
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Re: What is central sleep apnea ?

Post by Respirator99 » Thu Jun 23, 2022 8:38 pm

ozij wrote:
Thu Jun 23, 2022 8:21 pm
Because EPR makes the flushing out of CO2 more efficient?
Yes
What about an inhale / exhale difference higher than 3 - as is possible in Bi-Level machines wouldn't that increase CA even more? And if not, why not?
There are many different types of bilevel machine and some can make central apnea worse if not properly adjusted. The gold standard for treatment of CSA is adaptive servo-ventilator (ASV), which can vary the pressure support on a breath-by-breath basis.
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Re: What is central sleep apnea ?

Post by Pugsy » Thu Jun 23, 2022 9:42 pm

ozij wrote:
Thu Jun 23, 2022 8:21 pm
What about an inhale / exhale difference higher than 3 - as is possible in Bi-Level machines wouldn't that increase CA even more? And if not, why not?
For some people any bilevel pressure can cause the carbon dioxide wash out too much and centrals can pop up in numbers that are a problem...for some people even a 1 cm difference between inhale and exhale can cause that problem.
It's not all that common though.

I have a friend who needs a minimum pressure of around 16 or 17 to do a good job preventing the airway from collapsing.
For years she used the ResMed apap machine and did fine with it. Then it came time for a new machine and her doctor thought a bilevel with more exhale relief would maybe be more comfortable so she got the ResMed Auto Bilevel....I think the S9 model but it might have been the AirCurve 10....time flies.
Anyhow they started her out with PS of 4 and ooops...too many centrals. No one at her doctors office could figure it out because she didn't have any centrals to speak of on the APAP. By the time I got involved we were scratching our heads trying to figure out what the deal was....averaging 15 centrals per hour and sometimes more.

Then one day she mentioned "I never had centrals with EPR at 3 on the APAP" and here we were use PS of 4 on the bilevel.
Her doc was talking ASV and all that... I told her lets just try PS of 3 and we might get lucky...and we did. The centrals essentially stopped except for a rare one here or there. She needed the exhale relief because her starting pressures were so high.

Why such a marked difference with just a 1 cm difference...beats the hell out of me but she was very happy to get it all figured out.
I use a PS of 4 on my machine and I rarely get any centrals except for the ones that I get when I am awake. :lol:
I think Palerider uses 6 PS (if I remember right) and he never gets centrals either.

I never could get a good grip on why some people have a problem with any bilevel situation and other don't. I just know that while it can happen to some people it isn't really all that common. We see it here of course because what we get here for the most part is people coming here with problems. The people who use bilevel either with EPR or PS and don't have a problem don't have a reason to come here. So it is understandable that it might seem more of a problem than it really is.
Happy cpap campers have no need to come here.

I just filed it away with thing about higher pressures causing centrals...yes it can but there's an awful lot of people using some really high pressures and they don't get centrals from it.

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Architect
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Re: What is central sleep apnea ?

Post by Architect » Thu Jun 23, 2022 9:52 pm

Thanks to all for central apnea education :D

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Re: What is central sleep apnea ?

Post by Architect » Thu Jun 23, 2022 10:15 pm

Hi Pugsy, have a question for you. My Bipap is set to Max Ipap 25.0, Min Epap 14, PS 6,.

I had discussion with sleep clinic tech back in April 2022, shared the deeper I sleep, it's the length I stop breathing, which concerns me.

Bipap set to auto.

Sleep tech replied: The machine is set to drop pressure by 6 cm, when you inhale which may be to much ?

Readjusted to Min Epap 15, PS 5,.

I'm not waking up anymore, having dreams not breathing 2-3 minutes.

So is tech sharing, pressure drops by 6 on inhale pressure 25 = 19. If I drop PS by 3 then pressure 22 ? If I need more pressure on inhale.

So confusing, Rofl !!! Thanks for assistance.

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Respirator99
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Re: What is central sleep apnea ?

Post by Respirator99 » Thu Jun 23, 2022 10:46 pm

Pressure support doesn't drop the pressure as you're exhaling, it increases pressure as you inhale. Your tech seems to be confused with EPR (exhale pressure relief) which does drop the pressure on exhale. To determine your effective pressures, you need to add PS to EPAP to get IPAP. So if your EPAP is 15 and PS is 6, then IPAP is 21. IPAP = EPAP + PS. Your Max IPAP is just that - a maximum, not to be exceeded. If your EPAP goes up to (eg) 20 and PS = 6, then your IPAP would be 20+6=26, but the max has been set to 25 so the machine won't go above that.
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Re: What is central sleep apnea ?

Post by palerider » Thu Jun 23, 2022 11:41 pm

ozij wrote:
Thu Jun 23, 2022 7:41 pm
In both cases, it's the changes in oxygenation and co2 in your blood that make your brain wake you up however briefly and start breathing
That's not quite accurate.

absent neurological problems, low CO2 in the blood depresses the respiratory drive, until CO2 builds back up and then breathing resumes without an arousal, this shows up as centrals because there's no effort to breathe.
excess ventilation can cause this in some people, but they aren't kicked out of their sleep stages because of it, oxygenation has nothing to do with respiratory drive.

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Last edited by palerider on Thu Jun 23, 2022 11:46 pm, edited 1 time in total.
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ozij
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Re: What is central sleep apnea ?

Post by ozij » Thu Jun 23, 2022 11:42 pm

Thank, Respirator and Pugsy.
Those explanations were very clear and helpful!

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Re: What is central sleep apnea ?

Post by palerider » Thu Jun 23, 2022 11:43 pm

ozij wrote:
Thu Jun 23, 2022 8:21 pm
Respirator99 wrote:
Thu Jun 23, 2022 8:13 pm
and why the situation can be made worse by the use of EPR
Because EPR makes the flushing out of CO2 more efficient?

What about an inhale / exhale difference higher than 3 - as is possible in Bi-Level machines wouldn't that increase CA even more? And if not, why not?
EPR (and to a greater extent PS) increase ventilation, increased ventilation drives down CO2.

The 'basic rule' for bilevel treatment is that oxygenation happens at EPAP and ventilation (CO2 removal) happens with PS, want more oxygenation? increase epap, want to blow off more CO2? increase PS.

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