CSA as a cause of OSA

[desaturator]

Hi all

I've been reading a lot of stuff, in an attempt to understand my weird breathing behaviour. In my quest I came across Dempsey, et. al, J Appl Physiol 116: 3–12, 2014 [1] which says this:

"[..] there is no precise boundary between central and obstructed apneas. For example, it has been known for some time that CPAP treatment or tracheostomy unmasks an underlying ventilatory instability and periodicity in many patients with OSA [...] Airway imaging studies during sleep also show substantial airway narrowing and even collapse to occur during hypocapnic-induced central apnea [...], often producing cyclical, so-called mixed apneas [...]." (emphasis mine)

I've read a lot on this forum about "treatment emergent" CSA, and how treating OSA with CPAP can sometimes elicit CSA. But this is the first I've read about CSA being a cause of OSA.

In my own OSCAR results I often see periodic breathing interspersed with reports of airway obstruction. I had assumed that the periodic breathing was being triggered in some way by the obstruction. But if Dempsey, et al. are right, then the opposite could be the case: my problem could be mostly central, manifesting itself as airway obstruction. If that were true, it would certainly explain why neither my AHI nor SpO2 show much relationship to the pressure I set.

I'm not trying to start another thread about my moans; rather, it's a general question: is the idea that CSA can be a cause of OSA a surprise to anybody else? Or does everybody except me already know about this?

Best wishes, DS

[1] https://journals.physiology.org/doi/pdf/...01054.2013

[SarcasticDave94]

That would be a new and different concept. I get the concept of Obstructive Apnea needing treated by PAP, which in some the PAP itself will cause treatment emergent Centrals. Going the other way, in that CA causes OA doesn't seem to me to add up as easily. Granted, I've done as much research about my respiratory illnesses as I'm willing to task myself with. I know what I have and how to treat them successfully. Regardless, interesting concept.

[desaturator]

Going the other way, in that CA causes OA doesn't seem to me to add up as easily.

Yeah, that was my impression, too. The authors of the paper say that the increased airway resistance is brought about by what they call an "asphyxic response" to chemoreceptor stimulation by hypoxia. I think what they're suggesting is something like the dive reflex, where the airway closes immediately to prevent inhaling water.

It isn't a recent paper -- 2014 -- so either later work has shown their statements views to be incorrect, or nobody has read the paper

Best wishes, DS

[Sleeprider]

An asphyxic response is hyperventilation, which has the potential to increase negative pressure in the airway resulting in airway collapse. It seems uncommon with CSA with the exception of people with a severe lag in the hypocapnic feedback loop. We more often see gradual attenuation to apnea followed by gradual increase in Vt, but sometimes abrupt onset of hyperventilation occurs, usually with arousal. Just my opionon

[sawinglogz]

My doc (who specializes in complex apnea, but is not one of the listed authors) told me at one point that CSA can drive OSA and not just the other way around:

One of the treatments he will try with some patients (who don't tolerate ASV) is acetazolamide. It's intended to address the CSA, and for some of his patients their OSA also disappears -- and they no longer need CPAP at all. Sadly, it didn't improve my sleep, with or without CPAP.

I'm not sure of the mechanism, perhaps your paper explains it. I was too sleepy to pursue it at the time.

[desaturator]

One of the treatments he will try with some patients (who don't tolerate ASV) is acetazolamide. It's intended to address the CSA, and for some of his patients their OSA also disappears -- and they no longer need CPAP at all.

Yes, I've see that here[1], which is a much more recent publication. I guess that would be an off-label use for acetazolamide, but it seems to be well studied.

Hmmm... this would explain a lot about my own condition.

Best wishes, DS

[1] Schmickl et al., Chest, 05 Aug 2020, 158(6):2632-2645
https://europepmc.org/article/MED/32768459

[Ratchick]

I mean... that would certainly explain why at one point my Autoset at one stage started to diagnose almost EVERY central even as an obstructive one... LOL

Are they talking about the central causing the airway to partially collapse, which then causes an actual obstructive apnea... or are they mentioning that the partial airway collapse during what starts as a central apnea then causes it to become a mixed apnea (i.e.starts off central, ends up obstructive)?

I'll have to pull the paper later and have a look. But as I said, I've seen not just in my results (because there's no way that I randomly had a night with an OI of 40 and maybe a CAI of 1 for 10+ hours) but another therapist on YouTube mention that some people with centrals have their apneas reported as obstructive on the machine too.

[desaturator]

Are they talking about the central causing the airway to partially collapse, which then causes an actual obstructive apnea... or are they mentioning that the partial airway collapse during what starts as a central apnea then causes it to become a mixed apnea (i.e.starts off central, ends up obstructive)?

They're measuring oesophageal pressure as an indicator of breathing effort. It seems that breathing effort starts to decrease (as indicated by change in oesophageal pressure), and then later the airway starts to collapse (determined by imaging), which results in an apnea which could reasonably be classed as obstructive. But ventilation has already decreased before the airway collapse, so this is neither a fully "obstructive" nor a "central" apnea as these terms are (IIUC) used.

The whole paper is worth reading, I think, but I can't help thinking there's more modern work in this area (but I can't find any).

BW, DS

[SarcasticDave94]

It almost sounds like a mixed Apnea then. Mixed Apnea are defined as a Central Apnea that changes to Obstructive Apnea.

[Geer1]

I haven't dug deep down into the nitty gritty of mixed apnea but they usually occur in this nature (central apnea that turns into obstruction).

Imo they are two different phenomenon and the mixed apnea occurs in people that have both issues (central and obstructive).

Imo the obstruction is negated during normal breathing because the body is actively breathing and the activity and air movement is enough to keep airway open. When the central apnea occurs the body is relaxed (taking a break from everything, including breathing) and there is no air flow thus making the airway more prone to have an obstruction occur.

Imo CSA is not the "cause" of the OSA. It just allows the underlying OSA issue to be more visible.