Tidal volume and Flow limitations

[palerider]

Since trying to get through to you seems to be a lost cause, maybe you'd do better if YOU moved on? You might find people that are more tolerant of your refusing to accept that your theories are groundless if you proposed them elsewhere?

One thing I've noted since being here is that you, are more often, the TOXIC poster around this website.

Well, I'm sure your acting like you're the arbiter of behavior on the forum is going to affect my behavior.

better people than you have tilted at that particular windmill.

[Pugsy]

Folks...how about if someone has a problem with what someone says (or doesn't say) that they either take it private or start a new thread/topic to hash out disagreements?????

It's getting really old when I see snarky, shitty comments directed to anyone in what is supposed to be a helping thread.

Guess maybe I need a fresh "duke it out" thread where I can move personal attacks out of helping threads.

My patience level is sub zero lately.
If someone wants to point out someone's failings...take it private OR OUT OF A HELPING THREAD and beat yourselves to a bloody pulp.
Either that or I will just delete the crap throwing talk....your choice.

[clownbell]

The original question in this thread relates to an observation the OP made. He thought the phenomena were related but they were not.

This reminds me of the so-called "Butterfly Effect." A butterfly in South America flaps its wings and simultaneously something happens in Chicago. Perhaps someone will genuinely believe those things must be related, but in reality they are not. Pretty simple when you look at it that way.

[MMcG]

As someone new to CPAP therapy (ten weeks and struggling), I would be inclined to cut everyone here a bit of slack for being grumpy. It sort of goes with the territory after all!

[AmSleepnBetta]

"Thumbing through" and sorting some my digital breath images I noticed instances of rising FL flagging with sudden sharp drops within about a minute of a "late" Autoset pressure rise. Remembering the similar nature of this thread's OP image the following line of thought came to me.

FL flagging in the OP and my images may have grown more and more "severe" (with no TV drop) because of shape and breath timing changes alone. Airway and wave conditions (a short choke?) degenerated enough to cause a sudden real airflow restricton and tidal volume drop. Such drops are usually followed immediately by recovery breathing causing TV rebound as the OP and my image depicted.

Ideally my (now non-scaleable) readymade graphic snip below would have shown the usual OSCAR TV presentation zoomed a lot more vertically to show more clearly the volume change and timing.

The OP graph scale differences have to be taken into consideration. Nevertheless and to my notion's contrary, the very small, few second drop in TV (circled in blue) is more slight than TV drops shown by the OSCAR TV curve inside the three green rectangles. That small (OP) TV drop relative to the large sharp TV increase (recovery breathing?) begs more data for interpretation, begs FR and respiratory rate curves (if not a leak curve which often suggests intentional or reactive motion).

Here's a thought experiment connecting my image below to mine above. Think of inverting the whole slot with its FL flags having been colored inside with semi-transparent yellow. Then mentally place the FL axis exactly on top of the (red) axis of the TVd with the FL now hanging upside down. Once again, where yellow overlies red the red looks rust color, otherwise a lot more yellow is seen--yellow simply indicating some lack of FL and TVd agreement; the disagreement arises from the fact FL duration and "severity' are impacted by the three shape and timing factors, not just by TVd as is indicated in red and/or rust.

That mental image would be close to the one above, the main difference being that the breathing pattern above (FR, TV, and TVd) consisted of long ramp-like curve outlines, more than three of them. The FR curve below is not ramp like in outline.

It's to be expected that naysayers will claim it's all meaningless, fussy, wasted time and storage here. But pursuit of such things usually leads to better understanding of topics. Even blind alleys taken teach something. I think my later line of thought, here, is not only on topic but plausible.

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[ChicagoGranny]

This reminds me of the so-called "Butterfly Effect." A butterfly in South America flaps its wings and simultaneously something happens in Chicago. Perhaps someone will genuinely believe those things must be related, but in reality they are not.

That is not at all what the Butterfly Effect means.

https://en.wikipedia.org/wiki/Butterfly_effect

[palerider]

The thing that seems to have gotten lost here is that there is no connection between flow limitations and tidal volume.

TV reduction is a hypopnea, which is separate and distinct from a flow limitation. It would perhaps be more meaningful if the term were "flow rate limitation", not simply FL.

So, what we have are FRL and FVL, Flow Rate Limitations (typically called FL) and Flow Volume Limitation (called hypopnea).

FVLs are bad because you're not getting enough air.

FRLs are bad because you're working harder to get air, which disturbs sleep and reduces rest and recuperation.

Yes, you *can* have a reduction in TV that's coincident with FRL, but it's NOT required. There's no reduction in TV in the definition of a FRL (Flow Limitation), there IS a reduction in TV in the definition of a hypopnea (FVL).

There, I said something helpful.

[Bertha deBlues]

There, I said something helpful.

Yes, very helpful. If you could have explained it like that in your first response, all the bickering could have been avoided.
There, I said it.

[JLROhio]

There, I said something helpful.

Wow! Yes you did!
Not only very helpful but explained like a gentleman too!

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[dataq1]

The original question in this thread relates to an observation the OP made. He thought the phenomena were related but they were not.

Actually I'm the OP and I still think that a flow limitation should be reflective of a diminishment of flow. Since tidal volume is a measurement of breath-by-breath flow, diminished flow would/should relate to alterations in tidal volume.
That was the point of the Original Posting, thank you.


Now, how one quantifies flow limitations index is another matter entirely. According to the Apneaboard wiki on Flow Limitations http://www.apneaboard.com/wiki/index.ph ... limitation
See particularly: "How Phillips Respironics and Resmed Calculate Flow Limitations".
As to Resmed (post S9), two of the four elements used to calculate flow limitation are directly related to volume: ventilation change and breath duty cycle.

[dataq1]

FRLs are bad because you're working harder to get air, which disturbs sleep and reduces rest and recuperation.

Actually I spoke to my pulmonologist today about distortions in the flow rate curves, and his contention is that flat-topped inspiratory cycles are not problematic at all, and are generally seen in the general population that has undergone a PSG and have not diagnosed with sleep disordered breathing. (He provided me with medical journal sources - that I have not yet digested)

He went on to say that a flat-topped inspiration curve is only an issue if there is a corresponding diminished tidal volume, approaching the 50-80% reduction in ventilated volume for greater than 10 sec, (defined as hypopnea).

[palerider]

FRLs are bad because you're working harder to get air, which disturbs sleep and reduces rest and recuperation.

Actually I spoke to my pulmonologist today about distortions in the flow rate curves, and his contention is that flat-topped inspiratory cycles are not problematic at all, and are generally seen in the general population that has undergone a PSG and have not diagnosed with sleep disordered breathing. (He provided me with medical journal sources - that I have not yet digested)

He went on to say that a flat-topped inspiration curve is only an issue if there is a corresponding diminished tidal volume, approaching the 50-80% reduction in ventilated volume for greater than 10 sec, (defined as hypopnea).

Well, then, I guess it *was* a waste of time to try and answer your question, but perhaps others were enlightened. We all know that doctors are always right about what they think is going on with sleep apnea, which is why there's no need for cpap self help forums...

You're, of course, welcome to think whatever you want, since of course, you will anyway

[AmSleepnBetta]

@PR:

My view differs some. I believe you are focused more on what breathing irregularity descriptors mean technically among their uses; that as if hypopnea, for example, were the only condition involving tidal volume level reduction, which I dispute. I am focused on what is meaningful to our receiving and maintaining necessary tidal volumes despite puzzling signals of Resmed FL flags.

Glossing over, all apneas and hypopnea alike, if not some or all flow limits, are scored--if at all--according to criteria for drops in airflow, whether scaled as tidal volumes (TV) or, equivalently, as flow rate (FR) reductions of certain durations. Sure there are different names for accepted parsings of volume, rate, time, and name criteria. But all are related to maintaining adequate TV by maintaining timely and appropriate pressure, our tool for maintaining FR TV deliveries despite flow limitations, whether any limitation encountered be called apnea, hypopnea, flow limit or whatever.

Breath by breath tidal volume changes dramatically with flow rate and duty cycle changes. The breath by breath tidal volume wave is identical to the flow rate wave in its form. A change in FR is reflected exactly in tidal volume as indicated by the area between the inspiratory curve and the horizontal axis. Anything that changes FR changes tidal volume. (An increased duty cycle, Ti/(Ti+Te), widens the FR and TV curves and increases TV, a way we do inspiratory work longer to maintain TV better against flow limitations.)

My focus here has been conceptual, not at all prescriptive. I don't recall comment here on amounts (hard to look back typing here), just comments noting changes or values I noticed and what I've seen cited as normal or abnormal values for TV and duty cycles. I see any airway caused-sourced ventilation reduction as due to, can I say, an airway constriction of some kind that reduced airflow and TV. More specifically, my posts attempt to show the problems and to mention the tools for assessing TV and its drops in relation to Resmed FL flags. It all about trying to understand what Resmed FL flags mean relative to our important TV. Aside from that, I tried to interpret the OP graphic and stay on the topic of FL and TV variations and their connections.


@dataq1:

I entirely agree that there is reason to expect tidal volume reduction from real airflow constriction. But the Resmed flag may only indicate detection of a wave it "sees" listed in its table of wave shapes, not necessarily indicate a tidal volume reduction.

It may be your interest in the OP was to prepare only for your MD visit. Otherwise, it would be good to see your work.

I agree with your MD assessment and am glad it went well.

I see lots of small things in my present curves, like flattening and M-tips, that slightly affect tidal volume, but very little. I don't review OSCAR curves, spO2, Dreem hypnograms nearly as often and its been a long while since I used the accelerometer..

Using the approach I posted here, I reviewed much more troubled early-PAP sleeps and learned a lot, leaving still more to learn.

[palerider]

Glossing over, all apneas and hypopnea alike, if not some or all flow limits, are scored--if at all--according to criteria for drops in airflow, whether scaled as tidal volumes (TV) or, equivalently, as flow rate (FR) reductions of certain durations.

The issue is that while FL may frequently occur concurrently with TV reductions, that is not what a FL *means*.

My preferred way of illustrating it to people is to tell them to take a straw, and breathe through that for a while, you can take a FULL breath, ie, TV, it just takes more work, and those will be FL breaths, because the flow rate is depressed, not the flow volume

[dataq1]

My preferred way of illustrating it to people is to tell them to take a straw, and breathe through that for a while, you can take a FULL breath, ie, TV, it just takes more work, and those will be FL breaths, because the flow rate is depressed, not the flow volume

You have mentioned your illustration before, however what you are describing is respiratory effort.