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Why don't these flow rate curves count as flow-limited?
RE: Why don't these flow rate curves count as flow-limited?
So this one is interesting as it shows me transitioning out


Ok, I'm not sure about calling it paradoxical breathing, though-- I was reading up on that, and it's also called "flail" and is life threatening (like you break multiple ribs and your chest no longer is physically capable of inflating and deflating your lungs.) I'm not even seeing desaturations. Found this fascinating journal article https://erj.ersjournals.com/content/41/6/1454 which is a case study of a woman with MS who developed paradoxical breathing when she got lesions on the part of her brain that controls the synchronization of breathing muscles.

Looking again at the picture of the full night last night -- I set OSCAR at a 2-minute zoom, started at the beginning of the night, and held down the right-arrow. I recorded it and it's an 84MB screen movie. It is absolutely terrifying to watch!

I had my appointment with the sleep doctor today. He flat out told me that with an AHI of 1.4, my apnea is well-controlled and basically I'm a hypochondriac  Dont-know They refused to read the data on my cards, and wrote in my chart that I only used CPAP for 15 of the last 30 days because I used the vauto for half and the autoset for half.

(we have a link to the ResScan software download, right? I'm going to load the vauto data into it and generate the report and ask them to add it to my chart.)
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RE: Why don't these flow rate curves count as flow-limited?
Isn't my example below more like paradoxical breathing, PB, instead of cardio effects, not to say the latter isn't shown too?

But unlike my current cardio signal, which shows up mainly near end of expiration--possibly in I-tips at times as well--the reversal of expiration flow rate shown here occurs a lot in the initial highly negative slope before maximum exhale rate. 

Greer, if convenient, I'd appreciate a link to whatever you have on PB. My previous read about it focused on how PB was detected using the chest belt signal of effort opposite that of the diaphragm, as I recall. Will see what else can be Googled up.

I had quite a bit of what is illustrated back then. Asking about it here (?) someone suggested that FR profile had to do with leakage of the esophageal sphincter. Given the aerophagia I some times experienced back then, and knowing nothing, I rested with that and it did pass.

Irrelevant, I suppose, a bovine aortic valve replacement (by TAVR through my wrist) had been implanted 2 months earlier. But the episodic pattern shown here had been present as early as 3 months before the TAVR. (Never had a heart attack, PTL, in a normal active life--work, sports, military, high altitude backpacking--with increasing valve leakage from childhood rheumatic fever.)

I thank cathyf, Greer and others for the continuing education about reading the curves from OSCAR.
And, regarding my post above with its bad guess, I'll not hesitate again to ask for a 2-minute view (from 1000 feet)  Oh-jeez .

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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RE: Why don't these flow rate curves count as flow-limited?
Wow, 2SB -- your curves look like mine!

I'm pretty mind-blown by this paradoxical breathing info. Years ago I noticed that I really have to think hard and puzzle it out in order to figure out whether I'm exhaling or inhaling at a particular point in time. And I think it's because I am aware of a heretofore impossible-for-me-to-describe (unpleasant) sensation when I breathe. I'm now wondering if what I'm feeling is my chest expanding on exhale and compressing on inhale. It goes along with a weird pulling/choking sensation in my throat.

I've got to get to sleep! More thoughts tomorrow...
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RE: Why don't these flow rate curves count as flow-limited?
2sleepbeta I have only researched it minimally and don't have much good info on the subject. Paradoxical breathing may not even be the correct term it is something I have been calling this as it appears to be some sort of out of sync muscular action. Potentially it is somehow related to heart action as it often appears to be in a heartbeat pattern but it definitely isn't a normal cardiogenic oscillation which is low amplitude and only usually seen at moments of rest (like you said at end of exhalation prior to inhalation starting). Whatever this is it is powerful enough to temporarily reverse flow while both inhaling and exhaling and it happens quite rapidly with a fair bit of displacement of air. The only other type of breathing I have seen somewhat similar flow rates in (but never as consistent) is rem sleep breathing and that is due to the partial paralysis that occurs, I figure that supports that this could be caused by some asynchronous muscle activity (maybe the accessory breathing muscles rather than just diaphragm/intercostal muscles).

I have now seen this sort of breathing in 4 or 5 people that have all had it resolve/improve with increased pressure support. I believe it is related to respiratory effort and causing things to get out of sync but its just a theory of mine somewhat supported by the few cases seen so far.
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RE: Why don't these flow rate curves count as flow-limited?
I created this PDF of a 20 minute run which shows my typical breathing on autoset. It's broken up into 4-minute segments, and you can see it get more and more out of control and then it settles back down again.


The fourth of the five segments is where things get really wild. I'm noticing:
  1. The machine doesn't report much in the way of flow limits -- I think that this is totally outside of the ResMed algorithm's ability to make sense of things.
  2. The recorded respiration rate quadruples, but that's obviously because the machine has no idea when one breath stops and the next one starts.
  3. This is autoset and the EPR is 3, but once the machine loses the ability to detect whether I'm inhaling or exhaling, I think that all goes to crap as well.
Somehow the vauto just prevents this train wreck, even when I've got the PS set to 3.0! So the vauto is more than just pressure support!

There's another interesting thing about this... The first 2 days I was back on autoset from vauto, my breathing didn't do this. The next two weeks it did it every night. And it appeared to get worse over the first week. Maybe there is some sort of "training" effect from the vauto? I have also noticed that I can't produce clusters of positional apnea on command anymore after 2 months on vauto.

This weekend's project is a deep dive into the internet's wisdom on what elliotg calls "bad breathing pattern and high respiration rate"
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RE: Why don't these flow rate curves count as flow-limited?
It doesn't accurately record flow limitations because they aren't obvious flow limitations and these machines have limited capability to interpret complex situations like this. When delving into these minute details like you/we are the only useful information is the flow rate and mask pressure curves. Any summary data calculated by a simple computer program will not interpret this data correctly. Respiratory rate is a great example of this, almost any human can clearly look at this data and see where the true inhalation starts and stops but we do so by ignoring the data that we know is garbage. One day these machines may have more complicated programming or artificial intelligence but until then they are simple programs that have limitations and we need to take that into account rather than believing the summary data provided. These machines can't even effectively flag apnea (whether or not it is central or obstructive and whether or not you were asleep or post arousal) things like flow limitation and respiration rate are far beyond their capability.

The only difference in autoset vs vauto imo is timing controls. The pressure waveform seems the same to me on base settings but it can be modified with the timing controls available on vauto.

Potentially the addition of Timin (which your autoset doesn't have) holds IPAP long enough to overcome restriction and continue a full breath. I remember you previously had shallow breaths before that wouldn't always trigger/hold IPAP and that may be the main difference you have on vauto.

My understanding is that your body does change once finding ideal settings and that is why the recommend coming off CPAP for 3 days prior to an in clinic sleep study (if getting sleep study without CPAP use). If I remember right my sleep tech commented about it being related to inflammation but I haven't looked that up to know if it is true. It does potentially explain the slow decline you have noticed using the different less effective machine. We know that improvement upon finding ideal settings is slow so it makes sense to also see a slow decline if settings are worse.
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RE: Why don't these flow rate curves count as flow-limited?
Right -- the goosing of the recorded respiration rate when the respiration rate is clearly the same makes it pretty obvious that the machine has lost track of when breaths start and end. (Although in my case my exhale is always deep and sharp and quite regular even when the inhale is doing the crazy gyrations, and a better algorithm would see that.) And where I started this thread 3 months ago was complaining that the flow-limitation algorithm was missing obvious flow limits. But flow limits are all about measuring subtle variations in the shape of the inhale -- and for sure when you get to the place where the machine can't even find the freaking inhale it's not going to come up with anything but a "WTF!" for the flow limit score! In fact my complaint is not that the machine is missing FLs, it's that the machine is reporting zero in three completely different cases and the machine knows "which zero" is going on. When the machine posts a zero as flow limits, sometimes it means that the machine calculated that the breaths aren't limited, and sometimes it means that it was in the middle of measuring an apnea, and sometimes it means that the machine doesn't have the frigging foggiest clue what is going on! 

What hadn't really sunk in before is that if the machine can't tell whether I'm exhaling or inhaling, then it can't deliver EPR.
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RE: Why don't these flow rate curves count as flow-limited?
(09-24-2021, 10:43 PM)cathyf Wrote: What hadn't really sunk in before is that if the machine can't tell whether I'm exhaling or inhaling, then it can't deliver EPR.

Yep. I believe Resmed uses what ends up looking like a minimum flow rate (but is probably done by a change in pressure measurement) to determine when to start increasing pressure. Your spontaneous breathing effort needs to provide that minimum flow rate in order to trigger the increase. Then when the machine notices the opposite change in flow rate (spontaneous exhale) it drops pressure. 

This is where that strange breathing that I call paradoxical breathing becomes an issue and it also potentially explains why the vauto treats them more efficiently. This paradoxical breathing creates spontaneous breathing that swings back and forth across 0 flow rate which confuses the machine and an autoset will stop supplying pressure multiple times through the breath. All of a sudden your EPR of 3 is actually acting as an EPR of around 0.5 because you are never actually fully build up pressure. 

The vauto has Timin which forces the machine to continue to increase the pressure for a minimum amount of time regardless of spontaneous effort. This potentially allows the pressure to build to a high enough point that your spontaneous breathing doesn't cause a reversal of flow and then a full PS is reached and a better quality breath is taken. 

The vauto also has other timing controls (specifically trigger and cycle sensitivity) that allow a person to account for some irregularities like this and better time the pressure increases to the persons spontaneous effort. Cardiogenic oscillations are notorious for kick starting PS too early because they occur while you are still finishing exhalation but can be high enough amplitude to kick the machine into supplying PS, the vauto then uses Timin to hold that for a set time and the supply of pressure isn't in sync with your spontaneous effort. This is why they recommend using lower trigger sensitivity in people prone to cardiogenic oscillations, the machine will then ignore more of those bumps and provide the pressure at the correct time. It is also probably the reason that higher trigger sensitivity helps some cases of central apnea because the machine can react to very small efforts, lock in pressure increase with Timin and coax a breath out of the patient that otherwise would have just had a very small blip of spontaneous effort. 

Timing controls are often overlooked and thought of as comfort settings but the reality is that what makes things uncomfortable is an improperly timed pressure increase/decrease which is not only uncomfortable but also poor quality therapy. I wish they would incorporate timing controls into the autoset with defaults so they don't have any effect but available so that they can be used in the cases of users that benefit from the better timing but don't need high pressure support.
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RE: Why don't these flow rate curves count as flow-limited?
Hi Cathyf:

I get the cardiogenic oscillations on every breath.  Do you use the Vauto's trigger sensitivity on default (medium), or do you use a lower setting?
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RE: Why don't these flow rate curves count as flow-limited?
gettingbetter, I also have cardiogenic oscillations on most breaths and normal works for me.

You can see how it ignores the earlier oscillations and starts supplying PS on spontaneous inhalation (green line).

You should be able to get an idea of whether your breathing is in sync by comparing your flow chart to mask pressure chart.

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