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[CPAP] Advice for Central Apnea and Complex Sleep Apnea
Advice for Central Apnea and Complex Sleep Apnea
Quote from another thread (thank you Gideon) - "What happens is (simplified version) that too much CO2 gets flushed from your system resulting in the lack of drive to breathe as the CO2 levels go below your apneic threshold."

I wish I'd joined this board earlier. I've just found out about hypocapnia today. I'm waiting for a sleep study for my central apnea but I fear I may wait a long time here in Canada post Covid. I'd be grateful for any advice or links to information on Central Apnea, hypocapnia and how to set up my machine using Oscar reporting to minimize the impact.

Generally I do pretty well with my Airsense 10 Autoset with pressure set between 5 and 10. I get few OA, and get more CA. I have long spells where my AHI is 2 or less. Even then I find myself waking up with a slightly rising heart rate most nights (my resting heart rate is 56 and I wake with it around 65-70). And I'm never quite sure why I wake, except that after a few seconds awake my heart rate takes off like a train and can hit 120-140. Oddly sitting partly up and leaning on my left elbow seems to be the best position to get my heart rate under control. Typically I get it under control using breathing techniques around 100 BPM or less but on occasion as I say it takes off.

Periodically however, and always following a night when I've had tachycardia, I end up with a bizarre phenomena, where every 5 minutes or so, my O2 level drops below 90 to as low as 85 (triggering an alarm at 88) even with my mask on. Around 92 I start to feel light headed and am woken up again. I use breathing techniques to get back to say 96, but as soon as I fall asleep again my O2 levels drop and I go through the cycle once again. Typically this sequence of events starts about 4 hours into sleep. I then go through the same exercise for several consecutive nights. I don't think I have a major issue with leakage, although I have nothing to compare with.

This morning, searching for information in frustration, I came across a study on Hindawi - Complex Sleep Apnea - published on 16 Feb 2014. In the study Complex Sleep Apnea is described and talks about the lack of CO2 in the blood stream leading to Central Apnea events, and that these events can happen at least 5 times an hour (in my case it's generally between 8 and 12).

The study refers to a period of suppressed respiration and when I check my Oscar reports I saw a period of low tidal volume that develops during sleep getting progressively lower over time. Say from 380ml to 180ml over three hours. The low point occurs just prior to me waking up.

It now appears that over the first three or four hours of sleep the level of CO2 in my blood stream diminishes to the point where I can have CA's of 20 to 30 seconds. But oddly enough, I don't always see a CA prior to waking. It's as though the level is so low my brain wakes me up. Then I end up with low O2 after handling the original tachycardia using breathing techniques, at which point it seems the low CO2 kicks in, and for the next few hours I have CA events continuously.

According to the article the latest technology ASV's etc minimize pressure to prevent 90% of OA but no more, judging that excess pressure is a risk for CA.

Is there any advice on how to set up an autoset machine for the best maximum pressure? Or links to information on the topic of Complex Sleep Apnea. Or suggestions or information about how to increase the level of CO2 in the bloodstream (though obvioulsy within reason!).

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RE: Advice for Central Apnea and Complex Sleep Apnea
Every case is somewhat different. Post your daily charts and a 10 minute zoom of your CA events to see if we can verify the cause. Unlike most places on the web, we like to base our suggestions on data with that data mostly coming from OSCAR. And how long have you been using a CPAP.
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RE: Advice for Central Apnea and Complex Sleep Apnea

Thanks! Probably not the best data but I've attached PDF's for May 8th evening. Let me know if you prefer some other format.

I've been on CPAP since 2017. I was diagnosed with severe sleep apnea with 38 OA events during a 7 hour sleep. Treatment was Resmed with pressure set at 5 and later 6, I had a fair few OA events, but few CA. I switched to the Airsense 10 Autoset in I think 2020. Initial pressure range was 5 to 12. 12 was way to high for me so I switched to 10. I often have zero OA events, so clearly that part works well, but I have the occasional weeks where I have high numbers of CA events.
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RE: Advice for Central Apnea and Complex Sleep Apnea
Essentially all your Centrals are occuring while you are awake. I strongly suspect that they are positional and mostly obstructive in nature. Any bed or pillow changes since before this change has occured?

Since you started CPAP in 2017 it is extremely unlikely for these centrals to be Treatment Emergent aka complex apnea. 2-3; months is typical for treatment Emergent Central apnea to go away.

I still want to see 10 minute views of a couple of your CA groups, I need to see the individual breaths.

I really don't think our usual therapy tweaks will work for you.
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RE: Advice for Central Apnea and Complex Sleep Apnea
Please, please please keep all your info in one thread.  In your case it is VERY important.
I just read about two very important factors in the other thread.  Please detail you S.A. here and how it affects your rib movement.  And about how your neck is curved and managed at night.

Right now I'll say that an ASV is NOT the right device for you, and I'm even more convinced that you CAEvents are mis classified obstructive events.

I think that an IVAPS device may be in your future courtesy of your S.A. and you should wear a cervical collar at night to relieve the positional cervical alignment issue I'm pretty sure is causing a lot of your immediate problems.
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RE: Advice for Central Apnea and Complex Sleep Apnea
            I've lived with Spondylosing Ankylosis for 30 years. I have curvature of the neck, and a rounded back which means that when I lie flat my head is several inches from level. I have limited rib cage movement, but this was improving with physio, until Covid stopped that. I'm a frustration to my local ultrasound lab because when I breath deeply there's very little rib cage expansion. Maybe an inch.

However despite the neck curvature I use a relatively thin, firm pillow at night and lie on my back. If I use a thicker pillow or double pillows I get more OA, not to mention neck pain. Sometimes I wonder how much support the pillow is actually providing.

I find that the nasal pillow masks are less stable if I lie on my side. I guess that could just be me not setting up the mask correctly.

I noticed the cervical collar discussions, but hadn't really come across them before. Is there one you'd recommend? Or is there somewhere I can read about their purpose. 

More detailed charts attached. Let me know if I need to add more data.

You're correct that most of my CA's occur while I'm about to fall asleep. I get into a cycle of low O2, accompanied by light headedness, after which I breath more deeply, and then try to sleep again - at which point I get low O2 and the cycle continues. These cycles tend to be about 5 to 10 minutes. Sometimes they're longer because I do sleep and then wake a few minutes later.  I can go through this cycle for up to three hours, though usually I get fed up and get out of bed. 

The clustered CA's typically occur after significant tachycardia. I'll wake with a slightly elevated rate, then a few seconds after waking the heart rates shoots up, and I following breathing exercises to try and control the heart rate. When I fail to stop it hitting say 120 BPM, and frequently have a series of CA's afterward.
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RE: Advice for Central Apnea and Complex Sleep Apnea
Basicly I want to see this chart, but replace Mask Pressure with Pressure, and vertically squeeze enough to also include Flow Limits.  Then 10 minute view including the left sidebar.  

I have a link in my signature about soft cervical collars and positional Obstructive Apnea.  I'm trying to see more of what your central look like on a breath by breath basis.
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RE: Advice for Central Apnea and Complex Sleep Apnea
Let me know if I still haven't provided the right screenshots.


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RE: Advice for Central Apnea and Complex Sleep Apnea
Hi pw, you mentioned, Tachycardia 120bpm, while resting trying sleep? May be also worth consider investigate if is undiagnosed? such as Arrhythmias from episodes re SVT Tachyardia "Flutter" alternative may include some Atrial Fibrillation?
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