What exactly is a "flow limitation" ?

" The results of our study show that the AED {Automatic Event Detection] tended
to overestimate the AHI when the manually scored AHI was
low and underestimate the AHI when the manually scored AHI
was high." https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3274337/

So, correlation was good (or acceptable), but what was not compared was the detection of "flow limitations". I'm not even sure that PSG clinicians attempt to detect FLs.


Do you know of any PSG comparisons that highlight automatic detection of flow limitations?

dataq1 wrote: ↑

Sun Dec 26, 2021 12:56 pm

However if an increase in pressure does not prevent similar "limitations or blockages" ... the machine has no more arrows in it's quiver.

Tis true but you know what they do in a sleep lab??? They increase the pressure because that's about all they can do as well.
Most of the time those arrows work well as long as the pressures are set optimally...either fixed or auto adjusting...doing the job that those arrows are supposed to do. The tricky part is that "optimal setting" thing. Difficult to do when we all can have that big YMMV sticker plastered everywhere.

Again it often happens that people want or expect the machine to do things it simply was never designed to do or is able to do. Or people expect the machine to fix sleep problems totally unrelated to airway issues and blame "cpap doesn't work" when actually they have unrealistic expectations.

Most doctors will look at the overall average AHI and maybe ask about your sleep and that's the extent of what they are satisfied with and if the AHI is less than 5...and you report still having crappy sleep their only idea is "give it more time"and that is the extent of their "help". Now there is some truth to that "give it time" thing but it doesn't mean we have to sit back and do nothing while giving it time.
Then there are a handful of doctors like Barry Krakow who do dig a lot deeper and are willing to try more outside the box kind of thinking beyond what cpap/apap machines can do but that involves different machines and in lab titrations and a whole different way of thinking.

dataq1 wrote: ↑

Sun Dec 26, 2021 1:27 pm

Do you know of any PSG comparisons that highlight automatic detection of flow limitations?

Not off the top of my head I don't but that doesn't mean they aren't there. Sorry. Maybe someone else has dug deeper than I ever wanted to dig.

This is one of those areas where I don't/haven't need to expend much area worrying about because I can't do anything about it anyway. I tend to target stuff that is within my control to do something about and not stuff I don't have any control over.
My time and energy and interest levels are limited anyway....I just don't have the inclination or need to prove that sort of stuff so I don't. My plate is pretty full as it is and getting fuller every day.

You can always review the flow rate graph yourself -- zoomed in -- to spot FLs. FLs are deviations from a nice rounded trace above the zero line. Sometimes there's a dent, sometimes a flat top, sometimes a bump/plateau combination. Some of them are flagged via the machine's algorithm, and some are not. In general, pressure support/EPR does a better job of reducing FLs than increasing the minimum pressure, because it gives breath-by-breath boosts as you breathe in, which helps you get past the limitation. Of course, as Pugsy says, none of the machine's capacities will help with swollen or clogged nasal cavities, but the tissues in the pharynx can definitely be affected.

lars_the_bear wrote: ↑

Sun Dec 26, 2021 3:33 am

So what, exactly, is a flow limitation?

Best wishes
Lars.

I do wish you'd quit posting a new topic for every random thought that wanders through your head.

palerider wrote: ↑

Sun Dec 26, 2021 5:13 pm

I do wish you'd quit posting a new topic for every random thought that wanders through your head.

And I do wish you'd stop being an a*shole, and get off my back.

But, thanks to the features of the forum software, I'll be getting my wish

BW, Lars.

Lars,

I don't think palerider is being an asshole. His is a perfectly reasonable request – one which is primarily for your benefit.

Think again about what you said a day or so ago – all this high-quality help you are getting for free vs the scant amount you've gotten from the doctors I assume you are paying.

And then comply, please, with this forum etiquette request.

RB.

rick blaine wrote: ↑

Mon Dec 27, 2021 6:27 am

I don't think palerider is being an asshole. His is a perfectly reasonable request – one which is primarily for your benefit.

If the users of this forum really prefer to have long threads with a jumble of different topics, then of course I will comply. It's not something I've seen on other forums -- quite the opposite, in fact. But if that's the way things are done here, fair enough.

But "perfectly reasonable requests" do not begin with a description of another person's "random thoughts." This is the mode of expression of an a*shole, however much his views are in line with consensus.

I really do appreciate the help I've had on this forum but not, to be frank, to the extent that I will let somebody insult me.

I apologise if I've misunderstood how the forum works, and if I've given offense to anybody else.

Best wishes
Lars.

A key difference between CPAP forums (CPAPtalk, Apneaboard, freecpapadvice) and others is that the purpose of many threads are specific to helping someone with therapy. Those knowledgeable about things CPAP like to review past information before making suggestions, so keeping an individuals therapy related posts to a single thread makes it easier for suggestions that account for past treatments attempted before offering new ideas to try. If folks have to search through past posts to find information they are less likely to respond.

Hijacking threads are not useful for anyone, so when someone introduces a new topic into a non-related thread it just causes confusion. New ideas belong in new threads.

Two simple guidelines to help get targeted and specific advice to a request for help or understanding what is going on with therapy.

Jlfinkels wrote: ↑

Mon Dec 27, 2021 11:13 am

New ideas belong in new threads.

The title of this thread is : "What exactly is a flow limitation"?
OP was not asking for therapy advice,
It would be useful if Palerider identified exactly what random thought he was objecting to instead of playing moderator.

If the OP's question is not appropriate for Cpaptalk.com, then just say that the community is only interested is offering advice as contrasted to helping to educate while offering advice.

And NOW this thread has been HIJACKED, because we are not discussing " What exactly is a flow limitation? "

Jlfinkels wrote: ↑

Mon Dec 27, 2021 11:13 am

New ideas belong in new threads.

That sounds correct to me, for what it's worth, and it's what I've been trying to do. I really didn't expect rudeness for it.

BW, Lars.

dataq1 wrote: ↑

Mon Dec 27, 2021 11:35 am

Jlfinkels wrote: ↑

Mon Dec 27, 2021 11:13 am

New ideas belong in new threads.

The title of this thread is : "What exactly is a flow limitation"?
OP was not asking for therapy advice,
It would be useful if Palerider identified exactly what random thought he was objecting to instead of playing moderator.

That is my point exactly. My response was to his post about how to organize things. Therapy goes into a single thread to maintain history, other questions go into a different thread.

The gray area is when a general question, e.g. “what is a FL”, gets turned into a therapy related question. When that is the case it is up to the moderators how they want us to organize things.

Jlfinkels wrote: ↑

Mon Dec 27, 2021 11:50 am

That is my point exactly. My response was to his post about how to organize things. Therapy goes into a single thread to maintain history, other questions go into a different thread.

My apologies then, I sensed that you and @rick were admonishing Lars for having created a new thread.

And now back to the original program.....

lars_the_bear wrote: ↑

Mon Dec 27, 2021 3:14 am

palerider wrote: ↑

Sun Dec 26, 2021 5:13 pm

I do wish you'd quit posting a new topic for every random thought that wanders through your head.

And I do wish you'd stop being an a*shole, and get off my back.

But, thanks to the features of the forum software, I'll be getting my wish

BW, Lars.

You bet! I shan't darken forum experience with any more replies!

If I may take up a little of your time ...

1. In the course of six days, Lars has started five threads, the first one on Wednesday, 22nd December.

I note that in that first thread, ChicagoGranny sez to Lars:

(a) "You can get good help from the forum if you use OSCAR and post a typical Daily Details chart."

Now It may be that Lars did not understand CG to mean "post it here, in this thread." But CG did imply that very thing when she added: "Please stick to this thread."

2. On Saturday, 25 Dec 2021, in his fourth thread, Lars posted his 'First OSCAR data', and amongst other things, asked:

"If I don't have sleep apnea, what is the explanation for the machine increasing the pressure?"

And in that fourth thread, I answered that it might be four things other than apneas and hypopneas which could prompt the change – including flow limitations.

3. Later the same day – and still part of the fourth thread – Pugsy said in reply to Lars:

"I also need a regular screen shot of the detailed data report and this time include the Flow Limitation graph and omit the tidal volume graph."

That is where I think the question: "What exactly is a 'flow limitation'?" could have best been put by Lars.

But it wasn't. A pity.

4. Now, as a reminder, the second thread was started by Lars on Thursday, 23rd Dec (about coughs and colds), and the third thread was started by Lars on Friday, 24th Dec (about something going 'Clunk') – and these two threads, I think, can be regarded as being separate – at a pinch.

And in any event, they are what I consider minor matters or minor topics.

But the question: "What exactly is a "flow limitation'?" is (a) a major topic, and (b), clearly, in this context, a continuation of the fourth thread.

The average reader would, I think – and following the ideas in the study of language called pragmatic implication – be forgiven for thinking: "You're still asking about your own case."

Eg, If a guy has only been out with one gal (or a gal has only been out with one guy), and they they start asking about 'relationships' and "What does it mean when they ...?" you'd be forgiven for thinking: "They're not talking theory. They're talking about themselves." And that's what I think happened here.

IMHO, Palerider's post would not have happened if Lars had posted his first OSCAR data in his first thread.

And if Lars had posted his question about flow limitations right after Pugsy had first asked for that particular chart.

The moral of the tale really is: for this kind of material, keep it all in one place.

Now to re-inforce the notion of 'all in one place", dataq1 – if you had had in front of you - or near the top of one continuous thread – what Lars added to his first thread on Friday, 24th Dec at 7.29 ...

"I've had cardiac stress MRI (twice), stress ECG, two holter ECGs, cardiac echo (twice), lung function/gas exchange both standing and supine, tests for thyroid, diabetes, electrolytes, vitamin deficiencies -- the list just goes on an on. I am, apparently, in perfect health."

you would not, I hope, have thought there was any chance of Cheynes-Stokes or heart failure.