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Call for Excel VBA help: to support effort to clarify/understand FL
#41
RE: Call for Excel VBA help: to support effort to clarify/understand FL
Note: The following matter, focused on Resmed FL flags as this entire thread is, does not address any UARS flow restrictions which may only manifest/present in labored breathing, abnormally high I/E ratios and/or inspiratory wave tip deformations that are not flagged with FL markers.  The lattter two can be seen in OSCAR curves. But the markers of the more subtle sleep impairing UARS must be discerned from other and additional signs, as is most accurately done by a sleep lab employing a Pes measurement device or chest-effort  strap and the data those provide. That is not to say that what is discussed below is irrelevant to a UARS sufferer, because I don't believe there is a bright line between UARS and other flow limited breathing  as flagged by Resmed devices. "It" is a gradient thing.

@sheepless

    1. Re the 4-second steps:  

In my 6 years of Resmed-PAP-reading experience, I don't recall seeing any FL of any severity having a duration less than 4 seconds. I believe the sampling rate is 0.5 Hz, every 2 seconds, one factor involved here.

The algorithm apparently is set to a 4-second minimum display, not coincidently it seems, because at a RR of 15 each ventilation cycle is 4 seconds. There is no other connection to the variably spaced TV bars and their coinciding TVd bars (if any), which are computed and displayed at the precise end of an inspiration having variable duration.

    2. Re how duration is included in the OSCAR percentile summary:

I'm on shaky ground here, never having gotten it crystal clear and locked in memory just what has been said by AB tech people about the OSCAR FL-percentile summary. That said, my intuition is based on the fact that the PLD file column with FL severity values presents strings of numbers  (2 seconds apart as I recall) as follow:  ........0.0, 0.1, 0.1, 0.2, 0.2, 0.2, 0.5, 0.8, 0.6, 0.3, 0.1, 0.0, 0.0, 0.0, 0.2, 0.2, 0.2, 0.0, 0.0, 0.0, 0.0, 0.0 ....

Both of the first two non-zero values will probably show as 0.1 severity. The remainder of that first FL string will look like progressive stacking and unstacking in the graph. The series of "2s" will show as one FL with severity 0.2 which  will persist for up to 12 (= 3 x 4 ?) seconds and, in any case I believe, have a duration that is divisible by 2. How those strings add up and end is unclear. For example, I just looked at a stacked FL of 0.13 max severity which level persisted for 6 seconds. All FL do start and end on a whole "second mark".

    3. Percentile scoring:

My intuition is that the percentile score is based on the percentage of seconds (or 2 or 4 second intervals)  in  the sleep session being divided into size-ordered (increasing or decreasing sequence) counts of individual severity levels. The divisor and the weighting of each single severity value must be for the same number of seconds.

In conclusion, if my intuition is  correct, then both duration and severity are represented, as above, in, say, the 95th percentile (or whatever OSCAR's accurate percentile number is in the Summary).

    4.  "Stacking":

It only looks like stacking, stairs or layering. The look comes from the severity numbers increasing or decreasing as indicated above.

     5. My sense of the Resmed FL domain in general (noting that the fuzzy logic Resmed declares in its patents blurs many "edges" of my outsider's attempt at definition):

With a FL detection and flag the device algorithm is signaling any non-apnea inspiratory irregularity--as such irregular data can be viewed in FR curves--from a flow limitation just at or above the flagging threshold (in a then-prevailing I-tip deformation "climate" it has sensed) and ranging up to full a scale actual airflow limitation of 1.0 or close to it. 
If FL=1.0, the TV would be zero or very nearly so and the breathing stoppage shorter than that for any form of scoreable apnea. 

The FL warns of breathing interference of some kind on the basis of its detection of one or more troublesome tabulated or sensed wave forms, a RR disturbance or a TV drop. 

     6. In summary: 

Again, my sense is that the sum of the flag areas (i.e. duration times time) and how the total varies sleep session to sleep session could be helpful. Helpful in the same sense bars showing the spectrum green through red are used to indicate/suggest overall risk, contingent danger, hazard, etc., when one or more trouble and/or beneficial factors are involved. It's "the view from 30,000 feet", all things considered. Nevertheless, using another meme (?), the devil's in the details, which should be reviewed in some detail when there are notable changes from what has been understood and seen as normal.
I have no particular qualifications or expertise with respect to the apnea/cpap/sleep related content of my posts beyond my own user experiences and what I've learned from others on this site. Each of us bears the burden of evaluating the validity and applicability of what we read here before acting on it.  

Of my 3 once-needed, helpful, and adjunctive devices I have listed, only the accelerometer remains operative (but now idle). My second CMS50I died, too, of old age and the so-so Dreem 2 needs head-positioning band repair--if, indeed, Dreem even supports use of it now.



 
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#42
RE: Call for Excel VBA help: to support effort to clarify/understand FL
Here's another long post as I  attempt to review in some detail how I believe work in this thread has added to understanding of my flow limitations above and below the Resmed (RM) lower threshold for flow limitation flagging (FL). For now I am uncertain how to proceed unless I or someone else simplifies drilling down into and using easier methods than Excel spreadsheets for exploitation of the many detailed and disjointed data files Resmed (RM) smart devices create during our sleep. 

An opening reminder:  All my analytical work here has been and is anecdotal. It is all from one single bimodal (low and then high FL) night of what I think was my most richly varied SDB night near the beginning of my therapy. But I do believe my zig zagging toward understanding the FL flag here has clarified the meanings of those FL to some extent. But now I've hit a brick wall of patented algorithm secrecy where only plausible conclusions can be offered from analysis of and thinking about RM data graphs. Of course, numerous refinements can be done--in addition to corrections and clarifications. (I'd like to see graphs of moving averages of Tidal Volume [TV] groups and their drops [TVd] and how those compare to TV we see in OSCAR. Likewise, it would scratch my curiosity itch to see breath by breath and moving averages of the quotients of Inspiratory and Expiratory time [I-time and E-time].) 

First, an open question comes to mind begging closer reading of the Resmed patents, word from experts at this site and/or revisiting charts that often show FL amid continuously adequate TV levels. From a therapeutic point of view, is it not more important that  SDB patients know when their  ventilation (their Tidal Volume [TV] half breaths) have fallen below their healthy levels appropriate to their  weight, height,  sex and need for restful sleep  (all but the last being ICU ventilator setting criteria) than it is to know their TV has fallen from some higher to  lower level but is, at its lowest, still fully adequate ventilation?

As posted earlier, I assumed Tidal Volume drops(TVds)  that do not reduce TV below acceptable fixed minimum levels are irrelevant, just as I assume TV greater than locally quiet sleep need is (except, that is, as may be needed to recover from a brief TV deficit--recovery breaths). Only TV deficiency is a concern. But can variable or highly variable TV above the level of necessary TV be entirely innocuous, innocuous for those who present only that variability as a single possible sign of disease? 

My post no. 10 above noted an anomaly I've come to realize showed only a simple failure to understand  how all metrics fit together in the seemingly valid approach I'd taken. (An attached graphic addresses this matter.) The seeming anomaly was during a period of high FL when my graphs of TV drops showed few and no drops, no TVd for short periods. That was simply  because (duh! now the light comes on) actual TV for a time exceeded my assumed TV need of 0.5 L from which I had deducted actual TV to determine TVd. The vanished TVd was the result of "extra" actual TV > 0.5 L "washing out" all TVd, as the graphs revealed. 

Professionally published normal breathing TV ranges from 6 ml/kg to 8ml/kg  or, very approximately,  about 500 ml is usually cited. My VAuto currently shows mine as 480, 500, or 520 ml night long. The full range of TV need details can be found here, as can be seen elsewhere, by clicking the "Predicted Body Weight Calculator" link at: http://www.ardsnet.org/tools.shtml . Using my VAuto's 500 ml shows my spot in the TV range cited is at 6.25-6.5 ml/kg. 

But trouble is,  normal TVs are not constant through the night. That presents a dilemma. RM addresses this, as I understand now, with a FL flag marking the TVd from a recent average TV level for a number of inspiratory waves (IW.) My simpler (but hard and tedious to apply) approach ducks RM's complex burden of determining the moving TV average in my use of an approximate constant value, TVs of  0.48, 0.50 or 0.52 L.                     

My point, which may well be wrong,  is that except in extreme pathological breathing cases adequate normal breathing will vary enough to cause some RM flow limitation flagging, "FL".  If we know our acceptable minimum  TV level we can check our TV and MV curves and our  Inspiration to Expiration time ratios for breathing adequacy and dismiss innocuous FL and TV drops. The question remains:  is significant  ventilation variability bad at any and all TV levels?  As I hope I recall  correctly, the Sao Paulo SDB study showed that about 30 percent of untroubled, normal-breather- sleepers have a significant level of flow limitations without experiencing or showing evidence of poor sleep.

Onward to details of what I think I know more accurately. These are about flow limitations flagged by RM devices as FL:

1. A significantly reduced airflow, a drop in FR, will be flagged. But a constriction of airflow that comes from constant constriction of the airway and is mostly continuous will not usually be flagged. The latter causes more negative esophageal pressures and increased (compensating) work in drawing breaths giving rise to higher Inspiration times. The latter  may be discerned from deformations of the IW tip (dIWT) and other metrics RM devices provide. Those are graphed in OSCAR as Inspiration time and Expiration time. Either an Increased I/E ratio or an increased duty cycle, I/(I+E) are metrics used to describe this in sleep literature . 

2. Respiratory rate is figured-in by the RM algorithm in its flagging. How? I still have no idea unless it is an element "buried" in the duty cycle or, similarly, in the I/E time ratio. Some persons experiencing airway constriction will compensate with longer breaths with longer I-times and shorter E-times. Others will present higher respiratory rates. Either response is to increase and maintain needed ventilation,  but the slower deeper breaths are more effective ventilation because TV loss, dead space ventilation loss, is lower at lower RR if sufferers can breath deeper and maintain a lower RR.

3. One or more significantly  flattened inspiration curves will almost always be flagged.

4.  Other  wave shape irregularities--including two particular ones among them, the "M" tip and the "Chair" tip: Even a single slightly M-tipped inspiration wave (M-IWT) often causes a low severity 4-second FL flag, similarly that is true for some singular sigh-wave tips. The latter are asymmetrical  M-IWTs  that resemble the frontal view of a rabbit's head with its two ears, of course, but one ear is lopped-down.

Here is a  very murky FL interpretation  zone: one involving those common lengthy series of  similarly deformed and flagged dIWT. But note that the same wave train on another night or period of the night may not be flagged.
 
A series of M-tipped, Chair-tipped or other regularly occurring and somewhat misshapen dIWTs will sometimes--apparently when their detectability hovers near sensitivity or resolution criteria/limits  of the Resmed algorithm--  result in a broken series of separate small FL. 

But at other times, those misshapen dIWTs will seem to begin laying down continual contiguous FL layers that looks like a stacking of them upward, this as an all-"alike"-dWIT series often lengthens for long periods (minutes?). The  reality is that the FL severity value number increments upward one notch (0.01  or more) with each successive dIWT until a peak is reached and a drop ensues at some airflow or pressure change--for whatever reason. 

The first dIWT of the series will seem to lay and continue (?)  maintaining the bottom course of FL, the next wave of the series will lay and continue (?) a second course, the next (the third wave) will lay and continue, etc., with FL "severity" (i.e., by virtue of stack height) seeming to grow larger, but the visually detectable dIWt shape and TV value seem invariant. 

FL Severity is represented by "stack height" value according to RM and will overstated for the individual dIWTs in a lengthy series, but on the other hand, if a long duration low severity series of  irregularities (a long series of dIWT) has been flagged, it might (by MDs, that is) be deemed more serious and notable than scattered minimal FL. That latter evidence based judgment, if extant and plausible, would add a severity dimension for duration itself. Accordingly, all FL could/would have two dimensional severity along with a distinct duration dimension. 

See attachment.php (1497×920) (apneaboard.com)

At some point a change in dIWT forms or another FL criterion will stop the algorithm's stacking or stair climbing and , most usually, a "stairway" of FL steps downward will be taken--faster and steeper downward than they went upward. As always, a significant flow rate change triggers a RM device response which we will see in one or more OSCAR curves.

The beginning of a stair laying or stacking process is easy to see and understand, but long runs of stair stepping or platform maintenance, it seems, can and  do absorb and incorporate new  series of FL signals from later dIWT which, when those series of moments arise, will  variably maintain the pre-existing severity platform and may build onto it until the elevated severity platform level will drop because of changes of FL conditions.  Sometimes it seems the FL platform has a tendency to seem "sticky" upward. It may be the algorithm maintains a longer term look-back register that resets the algorithm perspective and perceptions--part of the "fuzzy logic" RM's use.

Note: Neither RM nor its patents directly reveal all of (any of?) the significant control values that are  embedded in and used by RM device algorithms. But our analysis of RM curve data yields some useful inferences about significant values. For that it is back to "reading entrails", zig zagging and bumping into guard rails--hopefully not busting through them as I've droned on and in this thread.

Any readers' corrections, constructive criticisms and questions are welcome as always. 

A separate thread of mine will link back to his thread just as I link to it below now. Both it and this thread are focused on flow limitations and have some worthwhile links and graphics for those troubled by flow limitations to consider. Further, as I believe I have mentioned elsewhere, there is the difficult AB case of flow limitations presented by member cathyf (in her earlier FL-focused posts particularly) and the question about summarization of nightly FL raised by member sheepless:  both probe deeply into the problem of flow limitations and include many posts by Apnea Board experts and astute members. Those two recent discussion threads come to mind, but using Google to search the AB site I am sure much else of value can easily be found posted at AB as well as a wealth of key information in the Apnea Board Wiki.


Upper airway resistance syndrome (UARS) - Apnea Board Wiki


AHI < 1.0 now, but still tired? Is it UARS, RERA, arousals or FL in your FR peaks? | Apnea Board


flow limitations expressed as an index? | Apnea Board


Call for Excel VBA help: to support effort to clarify/understand FL | Apnea Board

attachment.php (2550×1650) (apneaboard.com)


attachment.php (1650×1275) (apneaboard.com)

   
I have no particular qualifications or expertise with respect to the apnea/cpap/sleep related content of my posts beyond my own user experiences and what I've learned from others on this site. Each of us bears the burden of evaluating the validity and applicability of what we read here before acting on it.  

Of my 3 once-needed, helpful, and adjunctive devices I have listed, only the accelerometer remains operative (but now idle). My second CMS50I died, too, of old age and the so-so Dreem 2 needs head-positioning band repair--if, indeed, Dreem even supports use of it now.



 
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#43
RE: Call for Excel VBA help: to support effort to clarify/understand FL
(07-25-2021, 10:05 PM)cathyf Wrote: 2SB -- I started with this screenshot

[snip]

I don't know if you can make anything of that...

Is there any way to get OSCAR to dump out the data in the flow rate curve? This
https://www.dropbox.com/sh/qku3ksg12xi9s...dFYRa?dl=0
is a link to my DATALOG/20210619 file from my data card -- not sure if it's possible to get the values for the flow rate curve over that region -- it might help to do more accurate calculations if you had the numbers and weren't trying to measure them off the pictures.

So when I look at that graph and compare the flow-limited with the not-flow-limited sides, it looks like the respiration rate is the same, and the minute vent is not really lower during the flow limit. Just eyeballing it, the flow-limited breaths are flatter and don't go up as high and are more squared off, while the not-flow-limited are taller and pointier and more like a triangle. Without measuring it carefully, I think that it looks like the area under those curves is the same on both sides -- which I think is what is meant by increasing the duty cycle?

Indications are you are not interested in my approach anymore (at this late date). Anyway, I had the intent and now the time to take a look at data for FR and FL in your first BRP and PLD files for June 19, 2021. Here is what results look like.

The attachment will speak for itself, but I point out that the lighter green TV presentation rises from the zero axis of the FR curve. That is not clear and there are probably other clarifications to be made. 

Two other comments:

1.  In the past I've found that when TVd "curve" values are zoomed the TV + TVd do add up to the assumed 0.5 L TV baseline value. In the graphic, which I haven't checked this time, the thick traces all squeezed together make it look like the sum would be larger, but I believe zooming to separate the little bar graphs would show the sum would be correct here, except for TV's greater than 0.5 L which penetrate and rise above the TVd-FL axis as mentioned in notes.
 
2. The FL severities are 2 seconds apart in data and the easy way out I take is to plot their little bar graphs the same as done for all else. No smooth curves.

   
I have no particular qualifications or expertise with respect to the apnea/cpap/sleep related content of my posts beyond my own user experiences and what I've learned from others on this site. Each of us bears the burden of evaluating the validity and applicability of what we read here before acting on it.  

Of my 3 once-needed, helpful, and adjunctive devices I have listed, only the accelerometer remains operative (but now idle). My second CMS50I died, too, of old age and the so-so Dreem 2 needs head-positioning band repair--if, indeed, Dreem even supports use of it now.



 
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#44
RE: Call for Excel VBA help: to support effort to clarify/understand FL
Posting work done after my most recent post here, of cathyf's  curve data, has been delayed. She has not  responded to that work (good, so-so, or bad), nor to a PM.  Before posting it I'd prefer to check my latest work against cathf's RR, I-time, E-time, Leak and TV curves for the same approximate period 23:14:00 through 05:48:00, June 19-20, 2021 (or for the span of time bracketing the curves in the preceding post, if zone times are out of synch).

Closure on all matters in comments at right of the graphic in the previous post's  attachment is lacking, but desirable if possible. Those matters are shown highlighted yellow in attachment below. Latest work (it's tardy if that is cathyf's justifiable opinion) raised additional questions she may or may not--freely of course--choose to address either. 

I will  now or shortly post the latest work, as it is, it in my Main Forum thread "Low AHI<1.0? . . .". This case-study/exercise cathyf gave us (in her Resmed data which she made available in her post above) has been beneficial for me, at least (forcing shallow thought toward a deeper end). I recommend a look at it and comments there as soon as it is posted. 

CathyF's data  at links above here could be mined and processed for several answers, but not by  me as a newbie doing this; not as one more than OK with needing to get help, revisiting rusty skills, learning and trying many new Excel tools and discovering how to simply navigate and  build and (cursorily) check huge, newbie-inefficient, time gobbling files to arrive at--what I think are--valid calculations and helpful presentation results.
 
Bottom line, I hope cathyf will provide the 5-hour (+/-) frame filling OSCAR views of the curves along with her recommended 3-5 minute zooms (at or straddling) the key differences and transitions marked "a" to "h" in the previous graphic. Unfortunately, needing to recoup limited AB attachment space, cathfy found it necessary to delete graphics that would have answered some questions.

For the present, pending any always-welcome questions or technical criticism, the goal of this thread has been reached and made visible. I believe it has (anecdotally touching only two limited cases) sufficiently (?) shown both some concordance and some mostly explainable disparate relationships between the Resmed algorithm's cautionary FL flag and  tidal volume, TV, including  TV drops, TVd. Accordingly, my latest work, being focused on inspiration time, Ti, duty cycle, dC, and their relevance to fL, will be posted in my "Low AHI <1.0? . . ." Main Forum thread where discussion and analysis of all aspects of the flow limitation topic, fL, and member therapy-case illustrations of it--no therapy guidance is intended  there--are the most welcome.

Notes: 

1.   Here is my non-standard, inconsistently wobbling shorthand:  all restrictions of airflow except apnea ("fL") , drop in a tidal volume ("TVd"), time duration of one inspiration ( "Ti"," I-time" or "I") , time duration of one expiration (Te or E), total single breath time ("Ttot"), percentage of the duration of a single breath that is inspiration time is duty cycle ("dC").

2.   About 2/3 or more of top of  the red -colored band touching the entire top axis of the graphic is from oversizing  cathyf's (artificially fixed) baseline TV at 0.5 L from which her TVd was estimated. The typically cited 0.5 L average adult TV "became" embedded with constant later-seen effect, in her and my sleep sessions shown (and noted? I hope) in later posts of  this and my other threads. Though I've mentioned other values, the bottom of the top gray bar shows her TV for the session averaged about 0.4 L, which would cause a 0.10 L oversizing/overstatement of her TVd. 

3.  For convenience I may misuse the finding distinguishing  terms "false negative" and "false positive" as if those were being used by an hypothetical advocate of the red colored graph's firm (?) findings about TVd.

4.   As pholynyk reminds us in a related thread post, everything "airflow" in OSCAR PAP device data  is based solely on time logged data from one or the other of mask pressure or mask airflow data as measured by our machines.  

The graphic:

There is good apparent agreement on the presence or absence of FL and TVd, but visually large and lengthy apparent disagreement  on their Resmed severity and TVd extents . Apparent (visual) disagreement (23% of session) grows in three segments  as their times near 'b', 'e', and 'g' of the graph. Given the raw  data and my mere "accidental" graph scaling it appears that FL indicates much greater "Resmed severity" than my TVd estimate as times approach graph areas 'b', 'e' and 'g'. 

Comparing TVd measure to FL scaling, 0.0-1.0, is an orange to apples comparison. We have only disparate indications of one distinct thing, TV-based estimation of TVd drop on one 
hand, and FL flags, on the other hand, as the latter may only mark and rate the shape of a Ti wave, saying nothing at all about TVd, though seeming to because FL flags mostly do so for most fL affected people and their sleep. Other curve "reading" and interpretation will shed light here, particularly FR and I-time curves and zoomed I-wave tips, for example.  IMO, maintenance of restful TV level and ventilation is the core of what we are about here and in all sleep medicine..

It appears there are about 20 minutes total (7%  of session) in five false negatives at about 23:45, 00:35, 03:55, 04:35 and 05:25.; similarly,  there are about 32minutes  (11%...) out of about  90 minutes (30%...) of seeming agreement (rust fully covers only red) that is actual (absolute?)  or strong FL-TVd agreement at about 02:30 and 04:20.

Nearing closing, here I reflect unbaked ideas and notes from latest dC and Ti work:

The following graph related comments  were not in my prior post and graphic which indicated those 6 lingering questions  I hoped cathyf would address . Only accidently will comments about new work here address those, but those 6 do relate to points below and latest work. 

Pending more input, if any, and more thought, here go observations from late work that can be seen to some extent in the earlier and present attachment:

 A large drop in Ti and duty cycle, dC, occurred from 'c' to 'e'. Note that light green TV there shows consistently and proportionally the largest TV level (compared to FR amplitude) and is most consistent vs the diminishing amplitude of the FR curve and vs those factors the rest of session except where a second disproportionately larger TV occurred again at 'f' to 'g'.  Those two time segments, particularly the 'c'  to 'e' one maintained the largest session TV levels in the session. Breathing was more efficient, more TV per breath and ventilation cycle. Apparently RR dropped cutting dead space loss, one of the possible positive factors here. I didn't sample "h", but after "c" a RR single point-sample (3 minutes) showed 11 as RR as I recall.

Notice that high TV levels 'c' to 'e' and after 'g' are accompanied by large FL flagging.

However, Ti and dC work raised questions.  Most of the session time, a somewhat less grassy curve 'c' to 'e' showed session Ti changed little from 2.0 sec  as duty cycle ("breathing-work" time)  dropped from 0.80 (+/-) elsewhere to about 0.45 'c' to 'e' (as seen from 30,000 ft). Most of the dC plots, except 'c' to 'e', are highly grassy (wide swings 0.45 to 0.8 dC and higher) and they are also  alternatingly gappy or nearly solid. I have seen wake dC cited as typically about 0.4, sleep dC about 0.3. 


Given cathyf's appropriate questioning and documentation of highly questionable Autoset airflow detection data one needs to be informed by other curves, ones portraying meaningful accurate data I hope, before forming conclusions about anything in earlier or later analyses of her data.

   
I have no particular qualifications or expertise with respect to the apnea/cpap/sleep related content of my posts beyond my own user experiences and what I've learned from others on this site. Each of us bears the burden of evaluating the validity and applicability of what we read here before acting on it.  

Of my 3 once-needed, helpful, and adjunctive devices I have listed, only the accelerometer remains operative (but now idle). My second CMS50I died, too, of old age and the so-so Dreem 2 needs head-positioning band repair--if, indeed, Dreem even supports use of it now.



 
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#45
RE: Call for Excel VBA help: to support effort to clarify/understand FL
There are three parts to this overlength post.

A: It begins with links to my post dealing with new work I mentioned would be posted in my "Low AHI<1 . . ." thread where it belongs. (In that effort it corrects a blunder in this thread (in post no. 44 as in "Errata" no. 3 below).

B: It ties down a couple of loose ends, open questions, that were highlighted with yellow in an image linked above. 

C: It has corrections of the three most important blunders I am aware of in this thread.

**********
A

Here is a link to an explanatory post for the Image of my latest most significant work and graphic, which is posted in and belongs in my other main forum thread, "Low AHI<1 . . ." , as mentioned in a post above. 

That post (no.39 there) , with its image, corrects, without mention, a blunder in my most recent post to this thread. That blunder, above (in post no. 44), is item 3 under "Errata"  below, which I cannot edit out of the post with a disclosure why.

http://www.apneaboard.com/forums/Thread-...#pid418077

Note about the correcting image: the left end of the title of the lower graph (orange, blue and gray) has a typo; duty cycle (dC) is shown as =Ti/Te. It should have been =Ti/(Ti+Te) or Ti/T total.

***********
B

These comments deal with certain yellow highlighted  "open" and other items in the side bar graphic of the following post as noted with A, B, C ... below

http://www.apneaboard.com/forums/Thread-...#pid417124 

http://www.apneaboard.com/forums/attachm...?aid=36352

-Presently there are no more zooms.

-A:  There is very little actual disparity. It's an error from using a widely quoted average for this case. Almost all the red color in a red band or ribbon along the upper axis should not be there. It overstates the tidal volume drop, TVd. Only the red grass hanging like icicles (mixing metaphors) from the ribbon there now should show (and those should hang from the axis). That is because the red extent was computed from TVd=0.5 (L) - TV, but it should have been TVd= 0.4L - TV.  My embedded incorrect assumption, of the time, was that the very typical 0.5 L TV should be baseline for this member's TV (since I had no rolling average TV for a baseline).

-B:  In others' threads I've posted researchers' illustrations about NED, negative effort dependence, after recently coming to learn about it. Roughly, it is the case where greater breathing (inhalation) efforts reduce air flow as more and  more effort is made to increase the flow. In NED the  inspiratory waves have a distinctive, scooped wave shape pattern and transition into that wave formation in a series of NED waves is replicated as each more normal wave morphs into the form (at and after the airflow choke point, I assume).  Google it, if interested.

-C: Part A, the first of the three parts of this post, takes into account inspiration times and, to an extent those times and the duty cycle graph address this in part as well. I would like to have had the RR from OSCAR for the data and, if not lazy and having more time, I could have calculated RR from the FR curve, like I did I and E times.

-E: Unknown. Not entirely explained by B just above, nor is the red showing to the right of "g" in the graph.

-G: Member would have to zoom the FR curve and look at inspiratory tips. Disparity is apparent (but more apparent than real?). It must be kept in mind that the FL is a tetraguous symbol: it may indicate any combination of 1- 4  factors:  Various FR wave shapes, the flatness shape, a drop in TV and the duty cycle (or RR). My sense is there is close agreement of FL and TVd on whether or not there is a flow limitation, but there is no close or reliable relationship between the severity of TVd (TV drop) and the severity a FL flag indicates. However, in the graph, except at "e" and "g" particularly,  there seems to be a correlation of severity rises and drops. 

-H: Somehow the start and end time were omitted. As in  the graph above, for this 4 min  zoom, FL y-extent is larger than TVd.  I believe "h" relates to "b" above as indicated in sidebar. All the upper graphs show the unusual unaccounted for low FR and TV showing in the notches of the green waves and the largest solid rust, the yellow and the rusted over red. This episode has never been fully explained, to my knowledge. Though it has been discussed a lot in a current SWF thread by  sheepless regarding need for better summarization of FL in OSCAR daily view sidebar.

-Overall: As mentioned just above in G, the apparent discrepancy between FL and TVd at 03:30 and 05:00 is just that. Apparent. There is no reason they should be the same given the 4-way meaning of a FL. Anecdotally,  though, the rust and yellow ending at "b" and "e" and, less so, that in "g" tend to show that both FL and TVd "think alike" about "greater severity" of largest flow limitations.

***********

C

I reviewed the entire thread intending to find, among its many flaws, the most egregious ones which must be corrected (at this late date). Please accept my apologies as I confess to having misgivings along the way, but rather than fix a problem that came to my attention, I wanted to and did continue working on my later thread of "thinking" as presented in links above.

Errata: The top three among those I am aware of at this time:

1. The "Sao Paulo study":

I  characterized it  poorly. Here is the informative quotation I should have posted, along with this  link  https://academic.oup.com/sleep/article/3...63/2558944  to the study done by  prominent sleep medicine leaders.

"Conclusions: Inspiratory flow limitation can be observed in the polysomnography of normal individuals, with an influence of body weight on percentage of inspiratory flow limitation. However, only 5% of asymptomatic individuals will have more than 30% of total sleep time with inspiratory flow limitation. This suggests that only levels of inspiratory flow limitation > 30% be considered in the process of diagnosing obstructive sleep apnea in the absence of an apnea-hypopnea index > 5 and that < 30% of inspiratory flow limitation may be a normal finding in many patients."

2. Early use (e.g., post No. 9)  of "MV" for minute volume was incorrect when I thought I was using the term for tidal volume, later properly understood to be shown as "TV".

3. I got ahead of myself in my most recent post in this thread: 'must have had a sense of doing so in outwardly hesitating to  show graphic support for the statements I did make here  (see strike outs inside quotation below). My copying of a formula down a column was faulty. All seemed OK, even the outrageously high and wrong duty cycle--with insufficient checking , thought and knowledge--pending receipt  of final confirmation through data I hoped Cathy would provide. My error, not Cathy's. Lacking her info I should not have posted anything without generating and applying the needed information myself from her data I held--as I later did to complete that work phase.

Surprised and pleased to have many readers click on this thread, I've wanted to present something new in each post, the most recent one dealing with Inspiratory time and duty cycle. Both are great helps in spotting and assessing subtle inspiratory flow limitation, whether or not it is only seen in deformed tips of inspiratory waves or is also seen at FL flags.

"Pending more input, if any, and more thought, here go observations from late work that can be seen to some extent in the earlier and present attachment:

" A large drop in Ti and duty cycle, dC, occurred from 'c' to 'e'. Note that light green TV there shows consistently and proportionally the largest TV level (compared to FR amplitude) and is most consistent vs the diminishing amplitude of the FR curve and vs those factors the rest of session except where a second disproportionately larger TV occurred again at 'f' to 'g'.  Those two time segments, particularly the 'c'  to 'e' one maintained the largest session TV levels in the session. Breathing was more efficient, more TV per breath and ventilation cycle. Apparently RR dropped cutting dead space loss, one of the possible positive factors here. I didn't sample "h", but after "c" a RR single point-sample (3 minutes) showed 11 as RR as I recall.

"Notice that high TV levels 'c' to 'e' and after 'g' are accompanied by large FL flagging.

"However, Ti and dC work raised questions.  Most of the session time, a somewhat less grassy curve 'c' to 'e' showed session Ti changed little from 2.0 sec  as duty cycle ("breathing-work" time)  dropped from 0.80 (+/-) elsewhere to about 0.45 'c' to 'e' (as seen from 30,000 ft). Most of the dC plots, except 'c' to 'e', are highly grassy (wide swings 0.45 to 0.8 dC and higher) and they are also  alternatingly gappy or nearly solid. I have seen wake dC cited as typically about 0.4, sleep dC about 0.3. 

"Given cathyf's appropriate questioning and documentation of highly questionable Autoset airflow detection data one needs to be informed by other curves, ones portraying meaningful accurate data I hope, before forming conclusions about anything in earlier or later analyses of her data."
I have no particular qualifications or expertise with respect to the apnea/cpap/sleep related content of my posts beyond my own user experiences and what I've learned from others on this site. Each of us bears the burden of evaluating the validity and applicability of what we read here before acting on it.  

Of my 3 once-needed, helpful, and adjunctive devices I have listed, only the accelerometer remains operative (but now idle). My second CMS50I died, too, of old age and the so-so Dreem 2 needs head-positioning band repair--if, indeed, Dreem even supports use of it now.



 
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