Clear Airway Apnea = Central Apnea?

[Muffy]

well this is my original cpaptalk name - I did many posts as a guest. I understand that SAG / Muffy et al used my name (as we had run into each other at that other place) and became still another guest here once guest were not allowed to post links (he had also many posts as a guest).

The road down Memory Lane continues!

viewtopic.php?f=1&t=13613&p=115285

I wonder how those guys are doing.

SAG

[StillAnotherGuest]

Although I will share that I gave up (one of) my original screen names (deltadave) when a poster on TAS (remember when that forum was the Power Broker in the Sleep World?) did a song parody based on "Delta Dawn", and I became self conscious that "deltadave" would appear to be too feminine.

Muffy

[NotMuffy]

Although I will share that I gave up (one of) my original screen names (deltadave) when a poster on TAS (remember when that forum was the Power Broker in the Sleep World?) did a song parody based on "Delta Dawn", and I became self conscious that "deltadave" would appear to be too feminine.

YOU have a gender identity problem?

Look at me for cryin' out loud!

NM

[Muffy]

As it turns out the Weinmann technique really did match that more sophisticated single-frequency FOT method in the PDF document I linked several posts above:
http://content.karger.com/ProdukteDB/pr ... tNr=224278

Well this algorithm is certainly working out well:



CPAP pressure is merrily increasing in response to what is obviously a post-arousal central apnea. Big mistake.

While one might argue that FOT-based APAP algorithms need not necessarily worry about closed-airway central apneas because the patient is on some semblance of therapeutic CPAP and that scenario would theorically be less likely than if the patient were on ambient pressure, until somebody can produce peer-based review data that says their central apnea identification algorithm has a sensitivity >70%, this is nothing more than techno-flash.

BTW, this stuff has been out for 30 years. If it could be made to reliably work, why wait till now?

Interestingly, one of the FOT-based APAP algorithms used ballistocardiography as a subroutine to try to overcome the closed-airway central issue. How crazy is that?

Muffy

[ozij]

Although I will share that I gave up (one of) my original screen names (deltadave) when a poster on TAS (remember when that forum was the Power Broker in the Sleep World?) did a song parody based on "Delta Dawn", and I became self conscious that "deltadave" would appear to be too feminine.

Muffy

Although I will share that I gave up (one of) my original screen names (deltadave) when a poster on TAS (remember when that forum was the Power Broker in the Sleep World?) did a song parody based on "Delta Dawn", and I became self conscious that "deltadave" would appear to be too feminine.

YOU have a gender identity problem?

Look at me for cryin' out loud!

NM

Well I don't know about gender identity problems but SAG just signed as Muffy - I'd say that's one hell of an identity problem...
O.

[NotMuffy]

Well I don't know about gender identity problems but SAG just signed as Muffy - I'd say that's one hell of an identity problem...
O.

Sharp as always o.!

Unfortunately, your powers of observation are still only 50%.

dd

[ozij]

33% by now, I'd say, dd.

I got waylaid by that link.... went looking for the Muffin man on Brewery Lane, instead of down Memory Lane. Do you know him?
O.

[-SWS]

I got waylaid by that link.... went looking for the Muffin man on Brewery Lane, instead of down Memory Lane. Do you know him?

As it turns out the Muffin Man is secretly shacking up down Memory Lane in THIS thread.

...And I hate to get all serious (not really) in the midst of all this great fun, but:

After I read enough posts about central apnea, and figure out how to not induce centrals, or at least recognize what induced centrals might look like if I induce them, while increasing my pressure, I think I will look up the above referenced posts....sounds like they happened in the heyday of the forum before my time.

Can anyone direct me to the "How Not to Induce Central Apnea Thread for Dummies"?

So what's happening by the way of your treated apneas, Rebecca?

If you have just a few residual apneas, that's probably not such a big deal. But a few people do manage to machine-induce central apneas at significant rates. In those cases, fixed pressure can sometimes be a better modality to try than APAP. Bear in mind that when any non-SV APAP machine attempts to detect central apneas, it does so in an attempt to avoid pressure-treating those central apneas. That issue of trying to avoid undesirable pressure increases (in response to centrals) becomes a moot issue with fixed pressure. Additionally fixed pressure tends to be more friendly to underlying CO2-related homeostasis problems that can be exacerbated by APAP's varying static pressures...

[-SWS]

Interestingly, one of the FOT-based APAP algorithms used ballistocardiography as a subroutine to try to overcome the closed-airway central issue. How crazy is that?

Bear in mind my proven poor memory recall. Early in this thread I mistakenly thought Weinmann might have been using time-domain reflectometry...

So take this with a grain of salt as well, since I'm going by that same memory or lack thereof... But I thought at one point there were at least a couple contending theories as to why ballistocardiography might have been revealing central apneas with such good specificity. One of those theories was that the open airway served as an acoustic albeit imperfect waveguide for heartbeat---whereas a closed airway obviously could not. So in the context of that predominate "open airway" theory... the above is very crazy as you say.

But there were some other contending theories regarding why ballistocardiography might have been revealing central apneas with such good specificity... And that's where my memory starts to get fuzzy but not even warm. I kind of thought one of those contending theories might have had to do with those cardiopulmonary pulsations or heartbeat somehow being more intense during central apneas compared to obstructive apneas.

But I'm under the impression that the heartbeat's acoustic "pulsations" traveling through an open airway (inefficient acoustic waveguide) is by and large the favored theory...

[Muffy]

Interestingly, one of the FOT-based APAP algorithms used ballistocardiography as a subroutine to try to overcome the closed-airway central issue. How crazy is that?

Bear in mind my proven poor memory recall. Early in this thread I mistakenly thought Weinmann might have been using time-domain reflectometry...

So take this with a grain of salt as well, since I'm going by that same memory or lack thereof... But I thought at one point there were at least a couple contending theories as to why ballistocardiography might have been revealing central apneas with such good specificity. One of those theories was that the open airway served as an acoustic albeit imperfect waveguide for heartbeat---whereas a closed airway obviously could not. So in the context of that predominate "open airway" theory... the above is very crazy as you say.

Right. But here is an example presented to illustrate the subroutine:



the increasing resistance in FOT should have labelled this as an obstructive event, but the subroutine identified cardiac oscillations in the FOT channel (while the airway is CLOSING?) and (in automatic scoring) labelled it a CA.

OK, that's slick, but I'd like to see them do that reliably on a large scale.

Muffy

[Muffy]

While one might argue that FOT-based APAP algorithms need not necessarily worry about closed-airway central apneas because the patient is on some semblance of therapeutic CPAP and that scenario would theorically be less likely than if the patient were on ambient pressure...

Y'know, if ResMed preserves the A10 algorithm, but activates FOT only at PAP > 10 cmH2O as a subroutine, I'll bet that would improve sensitivity.

Muffy

[Muffy]

As it turns out the Weinmann technique really did match that more sophisticated single-frequency FOT method in the PDF document I linked several posts above:
http://content.karger.com/ProdukteDB/pr ... tNr=224278

Well this algorithm is certainly working out well:



CPAP pressure is merrily increasing in response to what is obviously a post-arousal central apnea. Big mistake.

And yet, the controller seems to be initiating the appropriate response:



Must be another case of "the algorithm is willing but the technology is weak".

Muffy

[GumbyCT]

What have I wandered into?

You, my friend, have brought out the ghosts of xmas past!!! or is that passed for some others here.

Looks to me like the ghosts were awake ALL night again.

lmao

Even with new avatars raisin posts from xmas passed

[rested gal]

nothing more than techno-flash

What a great phrase.. "nothing more than techno-flash"
That's what dsm's I-so-desperately-wanna-be-regarded-as-an-expert posts bring to my mind so often!
I cringe every time I think about how newcomers who really are trying hard to learn as much as they can about sleep disordered breathing and the treatment machines may read dsm's voluminous mish-mash of "techno-flash" and think, "Wow, this guy must really know what he's talking about."

Then there's "techno-sound" -- -SWS's great posts. Very much recommended reading, imho.

And the muffin gang. 'Cept when it comes to argyle socks.

[-SWS]

Well this algorithm is certainly working out well:

...

CPAP pressure is merrily increasing...

Well, I observe this detection/response sequence in that graph above: 1) pressure increases in response to high airway resistance only after flow also drops, 2) then FOT suddenly detects an airway impedance drop, 3) thus the CPAP pressure no longer increases---but instead performs a very gradual pressure drop. By my take the FOT algorithm is administering the correct pressure response just as soon as airway impedance plummets along with that low flow.

And I believe the authors are citing that graph as a correct algorithmic response based on those same FOT-detected impedance variations as well.

Right. But here is an example presented to illustrate the subroutine:

Thanks for demonstrating with that graph... So it's really not all that crazy after all...

And in general it makes good sense that any one high-specificity detection routine can nicely supplement another high-specificity routine that happens to entail non-congruent sensitivity---assuming you have the real-time CPU cycles to dole out. Where one routine missed detection based on lacking sensitivity, the other routine can nicely pick up some margin of those missed events. While that adjunct approach boosts detection sensitivity, that's not to say its guaranteed to lend perfect or even near-perfect detection sensitivity.

but the subroutine identified cardiac oscillations in the FOT channel (while the airway is CLOSING?)

Well, we might want to revisit those contending theories about cardiac pulsations being more detectable for reasons other than open-airway wave-guiding. I'll see if I can dig them up for more techno-weenie chit-chat fun tomorrow...