Tidal volume and Flow limitations

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dataq1
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Re: Tidal volume and Flow limitations

Post by dataq1 » Sat Jan 08, 2022 10:00 pm

AmSleepnBetta wrote:
Sat Jan 08, 2022 6:31 am
The image
I'm not sure what image you are referring to when you say "the image". Was it an OSCAR image that is upthread?

Your analysis attachment is very difficult to read. I am really interested in understanding. To that end, could I persuade you to post that image as a attachment to a topic (of your choosing) over on Apneaboard.com? (Attachments on that board are able to be expanded and printed)
Thanks for your work on this.
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AmSleepnBetta
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Re: Tidal volume and Flow limitations

Post by AmSleepnBetta » Sun Jan 09, 2022 1:30 am

I should have written "the image below . . .".

From my vantage anyway, if not yours, the image is still there.

I intend to post it, as you suggest, along with an annotated view of the whole sleep session, possibly tonight or by Monday.

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dataq1
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Re: Tidal volume and Flow limitations

Post by dataq1 » Sun Jan 09, 2022 10:41 am

AmSleepnBetta wrote:
Sun Jan 09, 2022 1:30 am
Thanks, I'll be looking for it.
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Re: Tidal volume and Flow limitations

Post by AmSleepnBetta » Sat Jan 15, 2022 7:51 pm

The image below displays the entire sleep session from which the 2-minute image of this linked post was taken https://www.cpaptalk.com/viewtopic/t183 ... 0#p1402930. All or most comments in the message box there apply to this post and its image below.

Annotations of the linked and below images are all I can offer as explanatory help at present, after having been careless and just losing (once again!) what I had foolishly drafted in forum software instead of in Wordpad, as I know to do from past losses but didn't heed. :oops:

I'll simply add:

1) All I, an unknowing novice, write about sleep should be taken with a cup of salt and will, I hope, be challenged with constructive criticism. Hopefully blunders and errors are few. In any case, don't change therapy in response to my work without consulting your sleep professional.

2) ON OP TOPIC: The closing annotations on the image below point out that the FL flagging does not correlate well, but spottily, with tidal volume drops, TVd.

TVd, as seen in the plotted tidal volume "drops, yes, er, "drops" rising above" the blue curve axis show breath by breath deductions from the study's assumed baseline TVb (=0.5L here). Spotty correlation arises from the fact that duty cycle (as in my "dC" plot), along with its cousin RR, can-be/or-are key components in FL size when dC or RR effect rises or is high as shown. Those rises or the high from timing add to any TV loss (duration and/or severity) indicated by the FL. You might note, however, good correlation with FR of TVd bars rising or descending from the TVd zero axis. Descending ones represent additions to the approximating, selected 0.5 L baseline tidal volume underlying the TVd zero axis. Rising and descending bars, particularly the larger more dense ones, correlate quite well with flow rate (FR) amplitude bursts and drops at arousals. Smaller variations of the negative TVd's that which point upward are more visible than can be confirmed by inspecting the densely packed FR curve. There the pixels-width of the data compressing curve tracing covers and obscures that and other short duration fine details.

3) Added value in the image below, such as it is, if it has any for readers, is exposure to what I have noticed, have grappled with and come to think about what is happening here and there--a novice's discovery and thought process aided by his added, improvised tools. It is amazing what our devices can tell us from accurate high data rate logs of pressures and flow rates.

Pub-2015112728-night.gif
Pub-2015112728-night.gif (362.02 KiB) Viewed 9090 times

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AmSleepnBetta
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Re: Tidal volume and Flow limitations

Post by AmSleepnBetta » Mon Feb 14, 2022 5:02 am

I'll glaze eyes over a bit with nerdy but relevant and important helps for understanding graphics I've posted earlier and am posting in this thread now. I still hope others will help by engaging in these flow limitation analyses themselves and that they might gain a litte better foothold if they see helpful fall out from my bumbling and hitting guard rails.

The image below is an OSCAR 52-minute view of a different period of the same sleep session as the 7-hour and 2-minute views linked farther below. The unstated strongest connection in this post to the OP is having as an example a period "a" when very low FL is associated with high TVd and why and how "a" is in contrast so markedly with period "h" presenting the opposite: a much higher FL level with some TVd but with some TVc larger than baseline TVb of 0.50 L as detailed below. Only tonight did I do a-h comparison spot checks. The only real driver of the difference seemed to be that the inspiration wave tips in "a" were significantly more rounded and regular than wave tips in "h". If confirmed more broadly it would show a seldom seen Resmed Autoset failure to flag FL, concerns another sleep forum member has expressed.

Note that TVd is a data and assumed baseline based tidal volume drop or loss, presumably from flow limitation and FL . It is my novel item calculated as here using an articially fixed "normal" baseline tidal volume of 0.50 L. TVd equals the assumed baseline of 0.50 L (i.e.,TVb=0.50 L) minus a single calculated (breath by breath) tidal volume (TVc) as used in my earlier posted notes and graphics from high rate Resmed data. The forumla below underlying the graph with blue colored trace is TVd = 0.50 L - TVc. Graphically the result is an "over 0.50 L" and "under .50 L" breathing tidal volume (TV) graph. Inverted (flipped over) as I use it makes TVd to FL comparisons easier by having drops in TV, TVd, point upward as FL do.

To date I've not taken the intended next step to compute, say, 2 or 3 wave TVc, having only integrated single wave breath by breath data to determine single inspirations TVc.


Referring to TVd in the graph with blue traces above. Extensive knife edged bottoms of TVd riser bars indicate my assumed baseline TVb = 0.50 L is too low at that time's breathing TV. Vice versa, extensive knife edged tops of descending bars indicate TVb is too low. On the other hand when the axis is roughly equally grassy above and below, along it then TVb = 0.50 L is the goldilocks TV there. So what, why not average the TV? Laziness and time are large components but, as can be seen in the graphs, significant knife edge extents and wooly caterpillar-like axis stretches say something--no specific ideas yet--about sleep stages and changes of various kinds. REM? DEEP? WAKE? LIGHT? Repositionings? Bad positions? FL lighter or worse periods?

The graphic:

--Highlights multiple causes of largest pressure rises.

--"Meshing" mentioned on graphic: It strongly suggests that tidal drop, TVd, profiles can be seen in serrations and gouges of the expiration wave profile. It makes sense. What is inspired is expired and typically for me, is expired more sharply than my inspiration.

--Seemngly paradoxically showing in "h" full measure and greater TVc than the baseline TVb of 0.50, yet has relatively high persistent FL with about the most moderate duty cycle (dC) along with higher level of pressure than in contrasting "a" and environs.

--The TVd graph axis knife edge until 04:30, for example indicates TVd are ovestated because local tidal volume was higher than baseline 0.50L. There should be at least short grass along the axis because normal breathing varies.

--Boxes c, d and f show impact of disturbed FR profile propagate strongly downward through graphs in expected ways.

https://www.cpaptalk.com/viewtopic/t183 ... 5#p1403444
https://www.cpaptalk.com/viewtopic/t183 ... 0#p1402930

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Morbius
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Re: Tidal volume and Flow limitations

Post by Morbius » Tue Feb 15, 2022 3:40 am

Can you highlight those observations that are clinically relevant?

TIA.

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Re: Tidal volume and Flow limitations

Post by Morbius » Tue Feb 15, 2022 5:00 am

Also on Saturday's graph, can you change the RR to something a little wider in this example (say 10-20. Play around a little to see what you get)? Right now it looks like the difference of a single breath/minute is a big deal.

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Re: Tidal volume and Flow limitations

Post by AmSleepnBetta » Tue Feb 15, 2022 5:56 am

@Morbius, thanks for the question.

I can hope, for example, the unknowing, unrested UARS-like sufferer who scans such as this thread, who has low AHI and gets little sound professional advice or ear, if any hearing at all, can come to guide or change his or her sleep care provider upon seeing his flow limitation and breathing workloads may be high. Hope he would check that or at least see there may be a member somewhere near whom I could send him to for possible solution. That would be a clinical benefit when not getting such from whom and when its due.

Meanwhile, I often suggest in posts how sufferers can check their I/E ratios, better yet, convert I and E to duty cycle if they desire and I point out criteria studies and Resmed have shown for assessing duty cycle ratios. Some DIY sufferers pick up on other approaches: (a) what time length and percentage of inspiration times they have lying in the range--very crudely 45%--between the OSCAR Summary Median and 95% value and (b) the I/E ratio, presented like 1:1.8 by the Sleep Report screen of VAuto. Hopefully it is presented by other devices too.

Some experiment adjusting/titrating lifestyle, foods and/or prescriptions guided by selected metrics presented by OSCAR

Many "treated" (AHI<5) are on these forums because of their unaddressed chronically fragmented sleep with AHI near zero. I see good forum monitors get them to go to ENT's when the breathing work and its arousal problem is seen as it is. Often times a mere switch to a bilevel like the excellent Resmed VAuto suffices--usually done out of pocket as I had to do.

Many have had the problem, get deep into the weeds and share what they can to help.

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Re: Tidal volume and Flow limitations

Post by AmSleepnBetta » Tue Feb 15, 2022 6:13 am

Morbius wrote:
Tue Feb 15, 2022 5:00 am
Also on Saturday's graph, can you change the RR to something a little wider in this example (say 10-20. Play around a little to see what you get)? Right now it looks like the difference of a single breath/minute is a big deal.
I need help to understand what you are asking, You mean a 10-20 minute view within bounds of which image? The image posted Saturday? Sorry to be dense.

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Re: Tidal volume and Flow limitations

Post by AmSleepnBetta » Tue Feb 15, 2022 6:36 am

Just a note: A klutz handling forum messages, I lost what will be posted addressing the puzzling aspects of the 52-minute view in items "a" and "h". Most briefly put, I see need to compute rolling averages of at least two I-waves for calculation of drops from an/some appropriate tidal volume average which will do the job--just more work. There should not have been any puzzlement. The baby step idea of continuing to use a fixed baseline TV of 0.5 L, somehow, was the problem, nothing puzzling, just didn't see it. Where baseline was too high for a time the TVd would be similarly high and vice versa.

@Morbius
I had a post in the works and did not see your later message until just before my request for help.

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Re: Tidal volume and Flow limitations

Post by Morbius » Tue Feb 15, 2022 3:09 pm

AmSleepnBetta wrote:
Tue Feb 15, 2022 6:13 am
I need help to understand what you are asking, You mean a 10-20 minute view within bounds of which image? The image posted Saturday? Sorry to be dense.
I was referring to Sat Jan 15, 2022 8:51 pm, 8 posts up. Respiratory rate (RR) is set to 13.5 - 17.0 and was looking to change it to 10-20 BPM to try to get a better handle on what's happening there, but NM. There's just too much crap going on there to get a good read on what's happening.

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Re: Tidal volume and Flow limitations

Post by Morbius » Tue Feb 15, 2022 3:40 pm

AmSleepnBetta wrote:
Tue Feb 15, 2022 5:56 am

Meanwhile, I often suggest in posts how sufferers can check their I/E ratios, better yet, convert I and E to duty cycle if they desire and I point out criteria studies and Resmed have shown for assessing duty cycle ratios.
Where? ApneaBoard?

That looks like a pretty busy board.

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Re: Tidal volume and Flow limitations

Post by AmSleepnBetta » Tue Feb 15, 2022 8:53 pm

Responses, @Mobius:

First:


The 52-minute view adds little if anything clinically related that is not covered in, mainly, the 7-hour view or the 2 minute view posts. It is just a view above ground level that reveals interrelationships and some features l better than the view from 30,000 feet (7-hr). I like to see three levels and expect others may too.

Fortuitously blundering along, it occurs to me to check this out later, suspecting what I see is only an accident of local baseline errors noted just above. It's the visual "meshing" fit/match of the FR expiration curve profile with the upper profile of the biased TVd curve. It is pronounced in the graphic, particularly at largest FL, higher dC time and pressure rise. A rolling average TVc would likely wash out the prominence of baseline-exagerration TVd effects just as the latter washed out TVd from FL in box "h"--referring again to my 52-min view write up and later corrective note posted just above.

Second:

You asked, maybe challenged: Where I suggested how readers could check their inspiration work time. I believe I lost such comment as I may have drafted in a reply regarding the "dubious 45% between" median and 95% values. On the other hand, I may have backed off from doing so because skew between mean and mode can be large. I've applied the idea on occasion for my work. But here are other approaches as follow.

This very thread: Tue Nov 16, 2021 2:17 am:

https://www.cpaptalk.com/viewtopic/t183 ... l#p1399478

MY OPINION: I see one value of these nerdy TV-TVd-FL exercises, as above and explained (?) below, as helping me/us understand when there is need to look at lengthening Inspiratory times, unusually large and persistent I/E ratios, or better than I/E ratios, higher duty cycle ratios (Ti/(Ti+Te). Look at those indicators when sleep is unrestful with a low AHI. Look at them when the zoomed FL have high severity values or are of long duration;...

... lengthening inspiratory time relative to expiratory time indicates more work is being done to get needed TV and there can be some or all the more usual negative consequences of apnea, maybe worse because sleep medicine often overlooks insidious flow limitations.

Redmed devices show your whole night's I/E ratio 1/1.8 = 0.56, for example. Better than that, with OSCAR you can put the Inspiratory time curve above the Expiratory time curve and look at FL where curves diverge widest. Note the higher ratios, and how persistent they are and how they vary night to night. This is one of the ways to help decide if a certain food, Rx or activity is helping or hurting your sleep.

This thread: Sat Jan 08, 2022 5:31 am:

https://www.cpaptalk.com/viewtopic/t183 ... 0#p1402930

...(c) breathing work done as shown in the duty cycle ratio dC=Ti/(Ti+Te) and (d) all the other most relevant curves OSCAR presents showing Resmed sleep data from air flow.

The main takeaway--beyond whatever interrelationships the image may help one understand better--is highlighted as item "b" and explained some as matching item "B" in the text box below "b". Box "b" values are readouts from Insp. and Exp. Time curves where the green cursor intersects the two curves (Insp. curve above Exp. Curve) where the curves diverge and are most apart in the view. The same can be done by anyone having certain Resmed devices that report or make data available to OSCAR for showing inspiratory and expiratory times. The method can be used to assess sleep work done to fight flow limitation (whether flagged by FL or shown as any form of apnea or neither).

The single relevant research I've seen determined that normal sleepers, as tested, had a duty cycle ratio ("dC", I call them) of about 0.42 and sleepers with severe upper airway obstruction (UAO) had a ratio of about 0.53. As mentioned elsewhere, a Resmed patent application noted, however, that the ratio is about 0.3 for sleeping state and 0.4 for wake state.

See the graphic's curve illustration using I-E spread, cursor and box "b" as well as the annotation "B".

ELSEWHERE:

07-01-2021, 02:51 AM

Obviously I'm not a doctor, and have only guessed at what assessments I've made of what you present. In the image below I did the best I could with your small (lesss than photo sharp) image, rough tools and shaky hands to show you your Duty Cycle (= Time to inhale/(Time to inhale + Time to exhale) for one breath and its I/E equivalent look. DC, fairly new to me (except for old stick arc welders) is often used and is stated as a level, range or condition benchmark. In the ERS paper they show, for the small study, pre-dosing "normals" had DC, men and women, of 0.40, as I recall. But when they were dosed with air deprivation the severe FL level was 0.51.

11-12-2021, 04:04 AM


...[our] experts have shown us that one of the best ways to assess seriousness or extent of flow limitation (whether it is flagged or not), is to look at whether inspiration time is increased. As they know, better but slower measurements are the I/E and duty cycle (Ti/Ttotal ) ratios.

One way to spot high ratio periods is to put the Inspiratory time curve above the Expiration time curve and look at flow limited areas where the two curves diverge widely. It's not fool proof because the I-times can be shorter along with shorter E-times and have a high I/E or duty cycle ratio when the two curves are not widely divergent.

On the graphic I note that an increased duty cycle is preferable to an increased respiratory rate when dealing with flow limitation. That's as if we have a choice of which to use in sleep. Not so unless there is some kind of breathing training (Buteyko's methods?) that we could do to shift away from RR toward a duty cycle response.

12-12-2021, 03:04 AM

---1. RM users can see on their device screen Sleep Report their Ti and Ti/Te (or I/E average like 1:1.8 which equates to 1/1.8=0.56 or duty cycle=Ti/(Ti+Te)=1/(1+1.8) = 0.36)

---2. Further, check significantly lengthier periods of wider divergence between the "Insp. Time" and "Exp.Time" curves OSCAR presents. First drag the Insp. Time curve next to and above the Exp. Time curve. At a wider-spread time spot that is of longer duration than most periods drag the cursor from spot to spot there and jot down some time reading pairs from the upper left corners of the two viewing windows where values show and do change as you move the cursor.

---3. Check a few ratios by dividing Ti by Te. Those ratios far larger than the I/E=0.56 shown above can (if they do not always) present a problem you may wish to review with your sleep doctor or . . . experts (among which I am not, though I might offer my thoughts while you await their attention).
01-26-2022, 02:02 PM

I looked at inspiration and expiration time (I and E times) in all your OSCAR summary tables and without exception they are inverted (I-time greater than E-time) at least in the Med and 95% columns, all columns I think. Further, I looked at this view attachment. . . just now, others variously and not focused as much. Disproportionately long I-times take sleep-work in themselves and do cause arousals fragmenting sleep.

Expanded RR Graph, which I think you requested:
15112728-RR.GIF
15112728-RR.GIF (22.69 KiB) Viewed 7977 times
Ignore the emoji I could not eliminate, but tried. The item should show 1/(1+1.8 ) = 0.36

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Re: Tidal volume and Flow limitations

Post by Morbius » Wed Feb 16, 2022 3:59 am

AmSleepnBetta wrote:
Tue Feb 15, 2022 8:53 pm
You asked, maybe challenged: Where I suggested how readers could check their inspiration work time.
Actually, that was "where you suggested where", not "where you suggested how".

i.e. "ApneaBoard", "cpaptalk", etc.
AmSleepnBetta wrote:
Tue Feb 15, 2022 6:13 am
Sorry to be dense.
Au contraire, the density is all mine.

But at the risk of "doing a palerider" I would submit that your Guide to Understanding Oscar Reports is the equivalent of a Rube Goldberg Machine-- an exceeding complex explanation for the obvious.

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Re: Tidal volume and Flow limitations

Post by Morbius » Wed Feb 16, 2022 4:11 am

Now, my responses will not be quite as thorough as yours because

1. Using something like WordPad prevents post loss but I ain't doing that.
2. Signing up for an image host allows posting of images, but I ain't doing that.
3. Long drawn-out posts provide-- well I don't know what they provide. So I ain't doing that.

So to the point:

I have not see where all that flash provides clinically relevant help.

Stuff like "duty cycle" is (or perhaps "may be") only helpful to the ResMed algorithm.