Tidal volume and Flow limitations

[Morbius]

In theory anyway...a person could have a boatload of FLs and not know it and might be having some issues related to those FLs and in fixed mode....no clue as to what might be causing the issues if they were FL related.

Some stuff might be picked up by RERA flags, but perhaps a user with a record that shows a lot of FL in waveforms might submit some graphs. Then you'd have your smoking gun. Dayquill had an example where a FL was picked up as a RERA. But you need to find somebody with plenty of FL to try to figure this out.

[palerider]

I don't have a WAG to offer. I always thought that Respironics decision to not even flag FLs in fixed mode was kinda stupid way of doing things IMHO

There's a lot of stupid in the way Respironics does things, IMHO. like doing pressure probes *only* while breathing is nice and regular and *NORMAL*, and doing nothing when the breathing is irregular.

[AmSleepnBetta]

Pugsy, Morbius, any other knowledgeable member:

Relative to the linked NIH table below: Please, does any one of you have additional specific information about Resmed S10 Autoset detections of and responses to flow limitation at all levels?

As a Resmed-only user, it was good to see Pugsy and Morbius' details about how Respironics devices do or do not report flow limitation. Similar detail, not in the left column of the table below, may be available.

For example, Morbius has very helpfully informed us tidal volume, for the Resmed S10 I assume, is a moving average of tidal volumes of five inspiratory waves. Given time and inclination, one could run a trial from flow rate data and replicate the tidal volume wave we see in OSCAR. That done, one could have increased confidence in breath by breath analyses of such as tidal volumes.

Are there other similar details known about the S10 methods? What sources are there for such information?

Best I know or can guess, wishing to be better informed, Resmed and/or their inventors' patents protect a combination of such patent disclosures as we see online. My sense is that, much as in a cake recipe's list of ingredients, the patent discloses key elements underlying their overall patent rights--say, to their detection algorithm--they wish to protect.But the patent protected algorithm is the unique Resmed "recipe" for artfully combining all key device or method elements they have disclosed.

A separate but related item, a bit off topic: Which of the graphs presented by OSCAR are based on OSCAR derivations from its calculations based on raw data? From Resmed data tables one can see raw data identities, but different machines, the S10 and VAuto, differ. It would be helpful to see such answers from knowledgeable sources in one post and thread.

https://www.ncbi.nlm.nih.gov/pmc/artic ... bjectonly

[Morbius]

Pugsy, Morbius, any other knowledgeable member:

Relative to the linked NIH table below: Please, does any one of you have additional specific information about Resmed S10 Autoset detections of and responses to flow limitation at all levels?

As a Resmed-only user, it was good to see Pugsy and Morbius' details about how Respironics devices do or do not report flow limitation. Similar detail, not in the left column of the table below, may be available.

For example, Morbius has very helpfully informed us tidal volume, for the Resmed S10 I assume, is a moving average of tidal volumes of five inspiratory waves. Given time and inclination, one could run a trial from flow rate data and replicate the tidal volume wave we see in OSCAR. That done, one could have increased confidence in breath by breath analyses of such as tidal volumes.

Are there other similar details known about the S10 methods? What sources are there for such information?

Best I know or can guess, wishing to be better informed, Resmed and/or their inventors' patents protect a combination of such patent disclosures as we see online. My sense is that, much as in a cake recipe's list of ingredients, the patent discloses key elements underlying their overall patent rights--say, to their detection algorithm--they wish to protect.But the patent protected algorithm is the unique Resmed "recipe" for artfully combining all key device or method elements they have disclosed.

A separate but related item, a bit off topic: Which of the graphs presented by OSCAR are based on OSCAR derivations from its calculations based on raw data? From Resmed data tables one can see raw data identities, but different machines, the S10 and VAuto, differ. It would be helpful to see such answers from knowledgeable sources in one post and thread.

https://www.ncbi.nlm.nih.gov/pmc/artic ... bjectonly

Who are you?

And what have you done with ASB?

[AmSleepnBetta]

Unchanged, like precious and innocent Morbius is unchanged, it's good to be back at CT after meeting a deadline--these 14 days, without authoritative response, after my question for the benefit of Resmed PAP device users. Where's the great, exacting, clinician, teacher with his with-it shorthand? Waiting for this insect to be caught in his web again?

More constructively and naturally, here are quotations, partial answers I found for questions I raised 2/25/2022.

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4629962/ [the same source as used for the small graphic in my first post in this thread, as here https://www.cpaptalk.com/viewtopic/t183 ... l#p1399279

Note: footnote numbers have not been removed and those appear as odd numerals at various places in text.

Treatment of sleep-disordered breathing with positive airway pressure devices: technology update

By Karin Gardner Johnson and Douglas Clark Johnson

Abstract:

'"Many types of positive airway pressure (PAP) devices are used to treat sleep-disordered breathing including obstructive sleep apnea, central sleep apnea, and sleep-related hypoventilation. These include continuous PAP, autoadjusting CPAP, bilevel PAP, adaptive servoventilation, and volume-assured pressure support. Noninvasive PAP has significant leak by design, which these devices adjust for in different manners. Algorithms to provide pressure, detect events, and respond to events vary greatly between the types of devices, and vary among the same category between companies and different models by the same company. Many devices include features designed to improve effectiveness and patient comfort. Data collection systems can track compliance, pressure, leak, and efficacy. Understanding how each device works allows the clinician to better select the best device and settings for a given patient. This paper reviews PAP devices, including their algorithms, settings, and features."

"Keywords: BiPAP, CPAP, iVAPS, AVAPS, ASV, positive pressure respiration, instrumentation, treatment algorithms, settings and features."

Selected excerpts pertaining to certain common Resmed PAP devices:

AutoCPAP

"ResMed’s RMS method determines ventilation from vari ance of the flow throughout the entire breath by comparing individual flow points to the mean airflow over a defined time period. The mean airflow is the zero-point between inspiration and expiration, thus variance from this mean divided by two equals the amplitude of the inspiratory flow. By taking the square root of the variance squared, outlying values receive less weight. A moving short time period (eg, one breath or 2 seconds) can be compared to a moving longer period (eg, 5 minutes) to evaluate for apnea or hypopnea.18 Apneas and hypopneas are typically defined as a reduction in ventilation below a percentage of recent breathing for at least 10 seconds, with varying methods used by different devices (Table 2)."

"ResMed also determines flow limitation. S8 AutoSet defines flow limitation using flatness of an inspiratory breath. The flatness index is calculated by the RMS deviation from unit scaled flow calculated over the middle 50% of a normalized inspiratory breath.4 From the S9 onward, flow limitation is calculated using a combination of flatness index, breath shape index, ventilation change, and breath duty cycle. Ventilation change is the ratio of the current breath ventilation to recent 3-minute ventilation. Breath duty cycle is the ratio of current breath time of inspiration to total breath time of recent 5 minutes. If a breath is severely flow limited, the flow limitation index will be closer to one and when the breath is normal or round, the flow limitation index will be zero.8" (Italic emphasis added)

"ResMed AutoSet evaluates flow every breath looking for apneas, snore, and flow limitation, but responds to flow limitation on a 3-breath average, has faster decreases in the absence of flow limitation and has a higher rate of pressure change to all responses (apnea, snore, and flow limitation) than AutoSet for Her.8,18 In comparison, ResMed AutoSet for Her evaluates the flow for every breath looking for apneas, snore, and flow limitation, and delivers a proportional increase in pressure depending on the degree of deviation of the event from normal, modulated by the current pressure setting and leak rates. If pressure is .10, then the response to flow limitation reduces and a louder snore is required to produce a response.8 Both AutoSet for Her and AutoSet respond less as leak gets higher."


A question:

As I recall, Morbius has informed us that Resmed tidal volumes are a 5-breath average. The report above states, " Ventilation change is the ratio of the current breath ventilation to recent 3-minute ventilation". How are the two closely related assertions reconciled? Is it simply that one number is the tidal volume average we see, as calcuated by OSCAR, the other a part of algorithmic control of PAP pressure changes?

[dataq1]

the tidal volume average we see, as calculated by OSCAR..... [emphasis added]

Just a quick point of clarification for me: Is the tidal volume (in the Tidal volume vs. Time of day graph) that we see in OSCAR, calculated by the OSCAR software or does OSCAR simply present Resmed's calculation of tidal volume?

[AmSleepnBetta]

the tidal volume average we see, as calculated by OSCAR..... [emphasis added]

Just a quick point of clarification for me: Is the tidal volume (in the Tidal volume vs. Time of day graph) that we see in OSCAR, calculated by the OSCAR software or does OSCAR simply present Resmed's calculation of tidal volume?

First, before a long rambling answer and other "catching up", here are a few words of explanation, regret and apology for my returning to Morbius some of the flavor of his ad hominem attacks. He has slung so much mud and trash, individual responses to all are more efficiently done en passant as the occasion arises--not by individual servings/posts to please the troll snapping at and nipping at my heels.


IMO you have, as usual, a good question dataq1.

Given that raw TV data is recorded by the Autoset and VAuto Resmeds every 2 seconds and that acronymic Morbius states TV is a 5-wave average, I gotta say OSCAR time vs TV plots are as calculated by OSCAR. The research paper indication of 3-minute ventilation (three minutes of inspiration-expiration cycles) levels suggests to me that that relates to PAP machine control of pressure and not directly to what we see in OSCAR's time-TV curve. It's a muddle for me now as it has been and is my reason for largely avoiding the TV average that has less noise but hides low level flow limitation for example.

To get away from such matters (and contrary to Morbius' obfuscations-- or is it just ignorance?--about my "novel" or unusual, if not novel, TV-method) I numerically integrate, as any high school AP math student could, the 25 hz FR data to get single inspiration wave areas, those single areas being representative of tidal volumes. Each calculated TV, that is, each area between the inspiration curve and the zero axis below it, is the sum of all the inspiratory wave's slice-volumes, Tv:slice:vol = flow rate X 0.04 sec. Of course, the numerical approximations using different algorithms (e.g. mid-point vs. trapezoidal method) produce various estimatable small integration errors. For me the fact that the integrated TV curve is visually an exact copy of the FR curve (in 2- or 3-minute views) indicates the simple mid-point rule suffices. (Note: Morbius has been rankled or derisive about the .04 sec slices--don't think those are among his "really hates".)

Similarly, Morbius chortled about my I and E curves being subject to the same lagging error as in the 5-wave average TV. It's his usual slash, burn and salt the seedbed tactic, whatever motivates it. My key I and E values come from the breath by breath analyses and are not from averages. Further to the accuracy issue, higher rate data, say 50Hz, would be better and certain refinements can be made but burnishing can come later, e.g., interpolations for 0-axis crossings at Exp. start. It's good to know Morbius sees a 33 ml tidal volume drop from a FL is insignificant (i.e., 33ml is equivalent to zero,complicitly supporting PR's "[no relationship between FL and TV]"); it suggests for the record Morbius would OK high pass filtering out of cardio tv up to 33ml, which would smooth some of my curves better than my smaller filter criterion.

All that said about TV above, there is a place for TV averages because, say, my and others' natural breathing can have long cycle periodicity to cause, say, 60-second undulations in peak FR and in TV which cause breath-breath TV to vary up or down, say, 50ml. Those cycles, as are evident in some of my graphs, cause under- and over-statements of tidal volume drop, TVd, when I use a fixed TV baseline as in the "over-under 0.5L graph" from the formula "TVd=0.50 L - TVc", TVc being TV as calculated from integration of the FR curve.

Of course, Morbius "exacting" nature will point to how I suggest 0.500 hz I and E curves be arranged I over E and then be checked for divergence visually and then be checked numerically using the cursor readouts at left. I don't give a rip about the exact times there, just the ratio--the extra breathing effort periods are the concern wherever those and durations are significant--I/E near 1.0 and above, dC near and above 0.5, at least when there is fragmented or unrestful low AHI sleep.

We have my still-unanswered question about TV averaging and Ventilation in my most recent post here.

Under the orange colored bars of the graphic below we have definitive raw airflow data defined directly in Resmed BRP and PLD file data-structure tables. The tables with numeric values are written in the bottom-most layer of flow-related data on the SD card in the DATALOG session-date folder.

A tidal volume datum value (TidVol.2s) is recorded on the card every two seconds. TidVol.2s is low rate 0.500 Hz data as shown below in PLD files which the Resmed Autoset and VAuto have recorded.

Apparently, a SWAG here, relative to Morbius' 5-wave average, OSCAR adds up the values of TidVol's for the just-completed rolling packet of 5 waves and plots that average in the TV window--doing likewise for each successive wave. Apparently, again, this is the basis of Morbius' claim of 20% error in averaged ? TVs.

Beyond the 20% just mentioned, Morbius has claimed needs of special equipment or more zooms to get meaningful results (e.g. pneumotachometer, I and E readings at the cursor location). Sorry, we gotta do the best we can with what we have where we are for now--try to get better stuff as soon as we are able. That goes for we seekers and novices trying to illuminate murky things by digging into and taking them apart--then suggesting what we think might be tried to do better. Sorry to say, after lots of my wheel spinning, bumping into guard rails and strewing some mistakes in my "notebook of wordy and sometimes obscure posts", here and elsewhere, I can point to only three relatively solid advances. I think those have added some value to dataq1's OP and encouraged others to dig into their data analysis too.

All I may have accomplished in this thread is to (1) clarify (as in my first post of my far earlier work) the nature of the relationship between the FL flag (yellow and rust) and the computed tidal volume drop (TVd) (red and rust color) as seen in the top graph. Yes, there are minor flaws I'd like to spruce up, (2) show the value of looking at and understanding info in the I and E curves, the I/E and duty cycle ratios, for those with fragmented sleep and (3) show how novices can blunder along and tease apart relevant info for his own and others' benefit. I dare say few have learned much from Morbius' acronym rich and lab-abstruse pirouettes and that's a shame, because I believe he could and might still show us more. Show us the key things the unrested low AHI person should check, try, or try to gain from their care provider.

Oh yeah, the logical tautology explicitly written in this thread that there may be no TV drop from a flow limitation if PAP treatment against flow limitation is fully effective at a time or if higher breathing effort, a higher duty cycle or I/E ratio, has addressed it. Then there is Morbius' refusal to rebut PR's claim (post no 2?) there is no association between TV loss and FL. The latter is akin to why a few known-bad policemen are kept on the force among the vast majority of police who are good. The three monkey solidarity "virtue": one must neither see, hear nor speak ill of the striking derangement of "one of ours" we want to protect, even if we do not want to keep the offender among us.

Readers caused a rather sharp rise to 7,000 views/clicks before Morbius'--BM--arrival. Yes, there have been about 21,000 views now, quite possibly because Morbius has a following, has done constructive things not evident in his show here. As mentioned, the first 7,000, BM, surprised me beyond belief. Why the response? My guess is so many hunger to understand their flow limitations, their unrestful low AHI sleep, their strange FR curves. It reminds me of my same concerns before getting the VAuto (out of pocket) to replace my Autoset. Among much else I wanted to see clear portrayals of what a true "EEG" arousal looked like in the FR curve. People are looking for answers.

The graphic below is an attempt to show how and where probing novices can find and access raw Resmed data to aid their quest for better sleep. Square on OP, it shows both Autosets and VAutos provide 0.500 hz "TidVol" and FL data. I believe other files, SAD, EV and other file types present oximeter and other data. Those are broken out when the EDF browser unpacks the session folder inside the DATALOG folder on the SD card. There are complete listings of various airflow related data the PAP machines record--noting about oximeters nor motion devices.

One can use spreadsheets to analyze and graph the data. Of course there are OSCAR provisions for importing oximeter data. Some of us use the Somnopose importing feature of OSCAR to import approrpiately structured and formatted motion and position data.

[Rubicon]

... here are a few words of explanation, regret and apology for my returning to Morbius some of the flavor of his ad hominem attacks.

Returning??

RUFKM?

You got pwned!!

[AmSleepnBetta]

This post swerves slightly off topic by looking at a different flow limitation, a kind of expiratory flow limitation, those caused by palatal prolapse (PP). In deference to Morbius, who will likely find or artfully invent ways to take exception, even if it is "only" a typo or a misspelling, I may present below a mere case of lip or mouth leakage, not PP. But I do think it is a simple case of PP, a case where the Resmed VAuto algorithm gets confused and wrongly elevates, displaces, the OSCAR-depicted FR 0-axis upward about 6 to 8 L/min for all breathing except two correctly depicted expirations between 04:39:40 and 04:39:55. Another way of putting that is to write that instead of showing actual leaks the algorithm showed leaks as expirations and showed no leaks, which is not possible.


Working from same raw flow rate data OSCAR used in its display of FR and other sleep metrics, I replicated with Excel the FR (L/sec) curve to have a basis for some level of confidence in work to be done on the same data to find air volumes. Further, I easily determined and bar- or "bristle"-graphed the breath-by-breath inspired volumes (BBIV) and the SD card BRP data file's claims--its false positive claims--of exhaled volumes.


A substantial part of the beginning and ending of most all inspiration rises and drops can be seen far below the zero axis; even that tiny notch we see just before inspirations start is far below the axis.


The bristles of the graph showing individual I and E wave volumes mark, as usual, the volumes and the beginning and ending times of inspirations and expirations, all those well below the FR 0-axis in all but two instances.


In addition to BBIV the bristle graph shows expiration volumes according to the up-down, or y-axis, misplacement of the zero axis, those volumes being the greatly exaggerated areas enclosed by the zero-axis and the expiration curve. Near mid-duration time, two expirations' curves lie almost on or exactly on the indicated zero-axis. My overall sense of the FR curves is that those two instances are correctly displayed without any expiration, but wrongly displayed without leak. All other expirations are false positive expirations which should have been shown as leaks--none of them LL in terms of volume, but LL, perhaps, in terms of near instantaneous leak flow rate? Dunno, don't care right here now.

One sum of all the tidal volumes and expiration volume bristle results in a residual volume of -0.2 L. Visual inspection of the bristle curve with the FR curve shows that leaks shown as expiration tend to be and remain in balance with BBIV within a couple to three waves.


You will have to look at the bottom of this post to see the pertinent PP image. The site or BBCode would not allow my placing the image here as I would prefer.

I did not want to start this post with silliness that follows: next a bit more of the side show attending my trespassing without portfolio on local fiefdom turf:

... here are a few words of explanation, regret and apology for my returning to Morbius some of the flavor of his ad hominem attacks.

Returning??

RUFKM?

You got pwned!!

Whiff.
Strike one!

The next quote and the one after are from this thread: https://www.cpaptalk.com/viewtopic/t183 ... l#p1407224

If we were to calculate inspiratory volume and expiratory volume with ASB's .04 Waveform Slicer, the expiration looks to have simply disappeared!

Strike two! But you are arguably half right about mere invisibility and not at all right about significant or detectable volume, of some E-spikes. About 9 out of 20 E-spikes do not show at displayed scale. Meaning: no significant volume. Close looks for missing tiny E bristles reveals that.

But if you have palatal prolapse, it has to be mouth exhalation, otherwise there'd be no exhalation at all.

Frankly, I find that "classic" PP waveform a little confusing. Why, when PP supposedly starts, does tidal volume drop? PP is a one-way valve so inhalation shouldn't be affected. Or has baseline -0- dropped because of an LL?

Ball one! Rubicon's count is 2 and 1. I don't know about the tidal volume drop. Am not convinced of it in the TV bristles nor in the OSCAR average.

Morbius? Lots of whiffs, strikeouts, and maybe a double and a couple of singles among his nearly 30 at bats here out of his 6000+30 times at bat.

[Rubicon]

Strike one!

Strike two!

Ball one!

Rubicon's count is 2 and 1.

Play a lot of baseball, do ya?

[AmSleepnBetta]

Obviously not. Your last swing was a high and long trajectory foul hit, not a ball. Got a big piece of the ball landing in the stands just past the pole.

[Rubicon]

Your last swing was a high and long trajectory foul hit, not a ball. Got a big piece of the ball landing in the stands just past the pole.

I need an X. This is just too painful.

[AmSleepnBetta]

CORRECTION!

After revisting data and after benefitting from geer1's valuable corrective commentary--yes that "geer1" listed on PR's recommendations of foes--I must and do correct essentials of my previous post. Please accept my apology for that grossly incorrect post.

Why did I blunder? Two factors: viewed in OSCAR there are instances at expiration endings, endings below but almost on the zero-axis crossing point, where there are cursor-position read-out values of 0.0 to about 0.01 for flow rate. Below the zero axis flow rate values must always be negative. Apparently those are tiny artifacts either from how the algorithm determines the zero axis position or from how OSCAR graphs them: those were isolated tiny artifacts, yes, but huge systematic errors or significant errors of any kind, no. Second, compounding the first error, I saw the sharp up turn at the end of expiration as the beginning of inspiration--which it only looked like with that little notch before the right angle turn upward of the curve which soon ends the expiration.

Simply put, there were no leaks, indicated expirations were expirations, inspirations and expirations began and ended on the zero axis.


One sum of all the tidal volumes and expiration volume bristle results in a residual volume of -0.2 L. Visual inspection of the bristle curve with the FR curve shows that inspiration and expiration tend to be and remain in balance within a couple to three waves.

[Rubicon]

After revisting data and after benefitting from geer1's valuable corrective commentary--

Yeah. geer1 may have replied, but everybody else on the planet knew that.

If you understood the rest of the thread you referred to, The Cran Method would given you the solution:



Your waveform had no loss of volume:



And when we're talking about missing 210 ml. relative to a total of 6600 ml. that has a +/- of 20%, that's absolutely insignificant.

Rubicon from the corner for the win...

Nothing but net!

Get back on the bus and go home!

[Rubicon]

Further, these EFLs have obvious palatal vibration:



This isn't a case of being unable to see the forest for the trees..

The whole MF forest is on fire!