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+--- Thread: Why don't these flow rate curves count as flow-limited? (/Thread-Why-don-t-these-flow-rate-curves-count-as-flow-limited)
RE: Why don't these flow rate curves count as flow-limited? - Geer1 - 07-24-2021
EPR doesnt drop pressure too quickly, you don't even hit max pressure until the inhalation period is pretty much over.
Trigger sensitivity and rise time are the only two variables that would help inspiratory flow limitations. Increased trigger sensitivity will trigger pressure increase sooner which will provide more inspiratory support. Faster rise time will supply higher pressure earlier in the breath again providing more inspiratory support.
On the vauto you can adjust trigger sensitivity but not rise time. I have looked at some examples and I figured medium trigger and rise time were roughly the same as autoset EPR but I have never seen the data with same pressure levels on the same person to be able to 100% confirm this or if there is a difference. 2 minute zooms of normal breathing showing flow rate and mask pressure should help see if there is any difference (one view from autoset with EPR, another from vauto).
If there is no difference in pressure supply then the only difference would be calculation/reporting differences either in how the flow rate/pressure graph data is determined (in which case there may be a pressure difference we just are not able to view) or how flow limitation is calculated (should be able to view this empirically by comparing similar shaped flow limited breaths). Flow limited breath calculations are far from perfect and I still don't know exactly how Resmed does the calculation.
Edit: Jumping back to rise time that is why square wave with short rise times is used in people with insufficient inspiratory capability (COPD, hypoventilation etc).
RE: Why don't these flow rate curves count as flow-limited? - Geer1 - 07-24-2021
These machines calculating flow limited breaths differently is very possible. For example if you look at ASV data you will see far larger flow limitation values, I believe because the machine is programmed to amplify them so the machine is more responsive. It is possible they have reduced the flow limitation reporting on vauto (compared to autoset) to make it less responsive with pressure changes (rather than changing the pressure supply algorithm which is probably more complicated).
RE: Why don't these flow rate curves count as flow-limited? - cathyf - 07-26-2021
If I set OSCAR to about a 5-minute view and then hold the right-arrow key and watch the graph move over a long segment of time, it's like a movie. What I think that I see in the data is that on the autoset if I limit the max pressure to something more-or-less useless, I decay into a very nice regular even flow-limited breathing cycle which is punctuated by movement/arousals. At each arousal, I shake/sigh/whatever and my breathing resets to be not flow-limited for awhile and then slides right back into it. (Now that I've figured out how to use my dropbox and link an apneaboard post to it I'm free of the size & format limitations of APB attachments. I'm going to figure out how to make a screenshot one of those OSCAR movies.)
Right now I'm looking at this screenshot from June 19
https://www.dropbox.com/s/bjgpvcfxweju9n9/33155Screen%20Shot%202021-06-23%20at%2011.43.08%20PM.png?dl=0
specifically focused on that area between 5:00-5:20
https://www.dropbox.com/s/vabnxkuu2sus320/5.18_Screen%20Shot.png?dl=0
Interestingly, my fitbit saw that 5:21-5:22 bobble as a 1-minute awake -- which with the fitbit is about movement. The fitbit also saw it as just an awake in the middle of a short run of light sleep where I was bouncing in and out of REM sleep.
https://www.dropbox.com/s/te6up3sun0lr4h...M.png?dl=0
What I found interesting is that it clearly marked a "reset" in my breathing pattern.
Also, I have this notion I've been thinking about... Back when I was in high school and took anatomy-physiology, we did a simple lab. Each of us took her lab partner's pulse, then the lab partner jogged in place for 3 minutes, and then we checked the pulse again. In the case of my lab partner and me, it was a striking contrast. She was a nationally-ranked figure skater who went to the ice rink every morning and did an intense aerobic workout. I was an out-of-shape bookish nerd. Her pulse went from like 57 to 59 after 3 minutes of jogging. I had to stop jogging after one minute, and my pulse went from 90 to 180.
When I was in college I took a physiology class from a heart transplant surgery pioneer. He taught us how the circulatory system adapts to exercise -- what athletes call "training". We all have a resting state, and then when we need to do energetic movement, our hearts beat faster and we breath faster. But we have another source of reserve capacity, which is that we have ample amounts of hemoglobin and so if we need to carry more oxygen we just use more hemoglobin. The fundamental result of training is to increase hemoglobin levels to give a trained athlete more reserve. So my lab partner's heart didn't really have to beat much faster, because she had this deep reserve. Also, children with holes in their hearts are blue because they have very high levels of hemoglobin. The extra hemoglobin allows them to get adequate oxygen even though their circulation systems end up sending lots of deoxygenated blood out into the body -- they have so much hemoglobin that they can make up for the amount of blood bypassing the lungs.
So where I'm going is that I wonder if I have simply adapted to the flow-limited breathing by developing excess capacity. So that's why I see the pauses at the end of each breath especially when the breaths are not flow-limited. (I refer to them as my "marching llamas" because the expirations look like feet, and the tops of the inspirations with their M shapes look like ears -- and then the pauses with their heart artifacts remind me of the gaily patterned serapes that are on the backs of llamas in Andean folk art.) You can see how some of those little pauses are longer than others, and occasionally one gets to be longer than 10 seconds, and it's a central apnea. (I call those the dachshund breaths -- because there's the legs and the ears, but then the flat back is freakishly long.) But, anyway, all that goes on without desaturations, which suggests that the reason that my breathing pauses is simply because I don't need to breathe that much. Very much like my high-school lab partner whose heart didn't beat very fast while she was just standing around or doing light exercise -- it didn't beat very fast because it didn't need to beat very fast.
Another factor which might matter is that I'm a singer. As anyone who has ever sung in a choir knows, about 90% of practice is the director shouting "no breath!" at all those points in the music that you want to breathe. So by day I'm singing in complete long phrases without taking a breath, and by night I'm breathing through a narrowed airway -- it seems perfectly plausible that I would develop significant excess capacity!
This is a link to the parent directory of the June 19 study: https://www.dropbox.com/sh/llfz3rbdtkcd8...1oAPa?dl=0
The png files that start with 3xxxx are all screenshots that I posted (those are the attachment IDs...) The full night is there, along with the fitbit screen shot.There is also the 5.20 folder which has a bunch of screenshots in series -- and those are full-screen OSCAR shots and you can see that the minute vent during the after-reset not-flow-limited breathing settles back to just a little above the flow-limited breathing.
I think that I should set up a web cam, too. I have been watching my dad (the one who I think has CNS hypersomnia) sleep in front of the TV. When he is sleeping in a chair, he cycles every 10-15 minutes where he leans forward, rubs his face, settles back in. I wonder if I'm doing the same thing?
RE: Why don't these flow rate curves count as flow-limited? - 2SleepBetta - 07-31-2021
(07-04-2021, 04:56 AM)2SleepBetta Wrote: It helped tremendously for you to flatten out the cardiogenic effects that obscured the beginning of many inhalations and cut the ratio of the curve trace width (in pixels) vs the I and E scaled widths. The change in ratios is striking. I won't take time to check but think the error might be fairly consistent--a combo of randomly shaky hands on the mouse, the thickness of the curve trace vs shorter wave widths and, possibly, some distortion of the FR curve and perception of it all when zoomed out. Anyway all ratios are much improved in that series as would be true of the preceding waves.
Reference is to http://www.apneaboard.com/forums/Thread-Why-don-t-these-flow-rate-curves-count-as-flow-limited?pid=401856#pid401856
Wow, the first curve was a shot in the dark, one facing the wrong way. The second one, still
.Upon learning recently (thanks to pholynyk) that Autoset's do not log I and E times, I plotted and zoomed my (Post 13? ) curve, as at the link above, using the Resmed BRP data file cathyf provided. The upshot was, for me, that even the seemingly much improved attempt in #13 was a waste of time. There were a few good calls, but too many so-so, and poor calls at that image's scale when measured.
'Will not try that again unless each inspiration curve spans a minimum of, say, a half inch, preferably more, across the screen being used for the "mousing" to take measurements along the axis. Two factors: not only confusing cardiogenic wave effect, but also the excessive ratio of curve-line-thickness to breath span ratio. Where is the real curve amid those crowded pixels?
The linked curve is suggestive of how to do it if comes up about Autoset I and E times. If using OSCAR yourself at full screen, you can use the cursor to pick off more accurate times.
RE: Why don't these flow rate curves count as flow-limited? - cathyf - 07-31-2021
Things get weirder...
For the last two nights I have slept without a cervical collar, propped up on pillows, on my back, deliberately chin tucking -- what two months ago was a way that I could call down, at will, a total sh**storm of positional apnea. I want to see how the vauto would behave.
I now cannot produce the positional apnea! I can't even seem to sleep with my mouth open! I seem to have trained myself to behave in my sleep! Or something!
[attachment=34326]
Screen Shot 2021-07-31 at 11.16.32 PM.png
https://www.dropbox.com/s/l3ix31l72rtxl3w/34326_Screen%20Shot%202021-07-31%20at%2011.16.32%20PM.png?dl=0
[attachment=34327]
34327_Screen Shot 2021-07-31 at 11.26.55 PM.png
https://www.dropbox.com/s/wyepj0d3qw1o4zl/34327_Screen%20Shot%202021-07-31%20at%2011.26.55%20PM.png?dl=0
how's that for unexpected?
On a tech support topic... I sent 2SleepBetta & TBMx dropbox links to my images of my two data cards and my spo2 files. I think that 2SleepBetta would like to load my files into OSCAR under a profile for me so that he can manipulate the curves in OSCAR himself and do more exact measurements. But he's having problems figuring that out. Can any of you guys help him out? (And also, I'm not crazy about posting those links in a public thread, but anybody else who's interested can PM me.)
RE: Why don't these flow rate curves count as flow-limited? - 2SleepBetta - 08-01-2021
cathyf,
How were your sleeps and what is the trend backward from those new graphs?
Have you any idea why the upper FR has the string of funnel shapes having, most often it seemed, the small FL at spikes of FR as well as small FL scattered in between. The funnels, as I recall, are no stranger to your nightly FRs. It looks like you may or may not micro-awaken, and after a clearing FR burst something begins "closing" the airway until the cycle repeats.
With benefits of the VAuto, I suggest going down to a vertical window axis no more than 0.5 high so smallest FL can be seen easier.
Thanks for the call for helpful directions. I still have an empty OSCAR profile for your results. My starting obstacle was that the single bundle of the whole set of your files for one session with history, as those come from the the Resmeds, was reported to be too large a zip file to download. I could not open it there with anything I had (software or knowledge) to piece it out. Once I can get at them, the EDF browser unpacks 'em (PLD and BRP edfs) and converts them to text files easily. I did use your 6/19 BRP file to check earlier I and E work, as shown in this thread, and regret results were not worthwhile. Have to "live and learn" limitations.
If you found time and inclination, any program you might code easily and make accessible--with a simple user interface--that would time-order the various data files and output them (as PLD and BRPs) as one edf or txt file would be a huge help. Hint hint. Our tech pholynyk confirmed I was dreaming that such might be carved out of OSCAR which does all that and so much more in seconds.
RE: Why don't these flow rate curves count as flow-limited? - cathyf - 08-01-2021
Ok, I think I do my data management a little differently than other people do
I almost never load directly from my card into OSCAR. I have a directory on my computer which has the structure of the card. Every day I copy the new/changed files off my card into the directory, eject the card and put it back into my machine, then load OSCAR from the computer. I now keep those directories in my Dropbox, and that's what I sent you the links to.
So create a directory -- call it something like cathyAutoSet/
From my Airsense10dir folder, copy down 3 files -- Identification.crc, Identification.tgt, STR.edf -- into cathyAutoSet/
From that folder, copy down the SETTINGS folder into cathyAutoSet/
Create a DATALOG folder inside into cathyAutoSet/
go into the Airsense10dir/DATALOG folder and look for particular days of interest. The folder with the 2-hour-long hypopnea is 20210619/ -- it's got 44 files in it. Copy that folder into your cathyAutoSet/DATALOG.
At that point if you do an OSCAR import and select your cathyAutoSet/ directory, you should get that 20210619 OSCAR page showing details.
The trick is that I am pretty vague about how the SETTINGS and STR.edf files work -- that's the summary data, and I'm not sure how far back it goes. If you want to download more days, you might have to purge data that you already have in order to force it to load the DATALOG data after it already has the summary data.
My autoset data goes through June 6, and then the data in the vauto directory takes over.
All of the SpO2 files are in one set of directories, dated the same as the folders in the DATALOG directory. After the first couple of nights, I always start the pulse-ox at the same time as the APAP. I also keep both clocks pretty well sync'd, so if they seem out, you can load on the basis of the clocks, too.
RE: Why don't these flow rate curves count as flow-limited? - cathyf - 08-01-2021
And the question of how was my sleep -- it was actually pretty bad. I got a splitting headache both nights and woke up groggy, so I sure felt like I'd had a bunch of terrible apneas, but my SpO2 levels were fine? Maybe the headaches just come from the awkward sleeping position?
... I dunno... *sigh*
RE: Why don't these flow rate curves count as flow-limited? - cathyf - 08-01-2021
Yes, it was silly of me to generalize from two examples and declare that I could stay positional-apnea-free without a cervical collar.
https://www.dropbox.com/s/ti1mtlseu8juzou/Screen%20Shot%202021-08-01%20at%205.10.44%20PM.png?dl=0
What is different is that with the vauto vs the autoset is that with the autoset there is a constant background of flow limits, but with the vauto the FLs are tied to the event storms.
Again I feel pretty crappy from this...
RE: Why don't these flow rate curves count as flow-limited? - Geer1 - 08-03-2021
The lack of positional apnea could be due to the lack of opening your mouth which could be due to the lack of body feeling the need to breath/exhale from mouth which could be due to the higher PS. Those examples still show some of what appears to potentially be restricted breathing periods, they aren't flagged by flow limitations (which is an imperfect data point) but you can see times where flow rate is smaller or declining and then followed by an arousal (large increase in flow rate).
Your flow rate graph still doesn't look good (too many arousals) but the question is if that is due to restricted breathing or not and if higher PS will help.