Why don't these flow rate curves count as flow-limited?

[gettingbetter]

Thanks Geer1!  This is a great discussion!  And thank you for posting an example chart.  I'm using the Vauto as well (in S mode 7.4/5.2).  I won't post my chart here because I want to be respectful of Cathyf and not hijack a thread.  My rise in mask pressure seems to lag the initiation of spontaneous inhalation.

[Geer1]

It will always lag because the spontaneous inhalation is what triggers the increase of pressure. Using a higher trigger sensitivity decreases the lag and using a lower sensitivity increases the lag. One thing to note is that the lag isn't due to a time offset (higher sensitivity is not programmed to supply pressure faster) but rather the trigger point that starts the process changes (ie higher sensitivity setting is triggered at a smaller flow/pressure change).

An analogy to this would be using a brake pedal in a car. Some cars have sensitive brake pedals that apply full force after being depressed only a short distance (~ 1 inch), others you may have to push the pedal to the floorboards. The car will never start braking before your spontaneous foot movement starts and once your foot has started moving the car with the more sensitive brake pedal will react faster because braking is triggered after your foot moves only an inch rather than having to be pressed all the way to the floorboard.

If you think it is lagging too much try a higher trigger sensitivity. If that causes premature triggers then switch back.

[gettingbetter]

@Geer1:

Me being a novice, it's hard to know how much of a mask pressure delay is "too much".  On my graph, sometimes it looks like a small amount, but there are many times that my mask pressure is at its highest when my inhalation has already been completed.

[cathyf]

So I showed some 3-minute closeups of one section with the wild breathing, and the following section with the cardiogenic artifacts. Then the 3rd graph is of the vauto with a PS of 3. I put the mask pressure graph right above the flow rate graph.

https://www.dropbox.com/s/5zqj1jykac0lit...e.pdf?dl=0

It looks like the cardiogenic artifacts are no big deal to either ResMed version -- they have no problems finding the beginnings and ends of the inhales. But it must be that the trigger sensitivity prevents the vauto from getting into this vicious cycle where it's kicking the pressure down and not giving enough IPAP and making crazy things happen.

I still can't find any discussion of this outside of us! I did find this selection of textbook excerpts
  https://www.sciencedirect.com/topics/med...bstruction
which includes this:

Anatomy and Physiology of Upper Airway Obstruction
James A. Rowley, M. Safwan Badr, in Principles and Practice of Sleep Medicine (Sixth Edition), 2017
Phase of the Respiratory Cycle: Inspiratory Versus Expiratory Narrowing
Upper airway obstruction during sleep is characteristically attributed to inspiratory narrowing owing to a collapsing subatmospheric pressure against a hypotonic pharyngeal airway. However, several lines of evidence implicate expiratory narrowing as a possible mechanism of the initial narrowing. First, ventilatory motor output is an important determinant of upper airway patency. Oscillation of ventilatory motor output, during the characteristic periodic breathing of OSA, is associated with pharyngeal narrowing or obstruction at the nadir of the motor output, especially in individuals with a highly collapsible airway.127 Second, an obstructive apnea is often preceded by expiratory narrowing of the upper airway as evidenced by increased expiratory resistance128 or progressive expiratory narrowing, detected by fiberoptic imaging (Figure 111-11).119 Finally, although upper airway narrowing or occlusion occurs during a spontaneous or induced hypocapnic central apnea80 or induced hypocapnic hypopnea,40 pharyngeal narrowing during central hypopnea occurs during the expiratory phase only and is associated with increased expiratory upper airway compliance. Therefore upper airway obstruction may occur in either inspiration or expiration (Figure 111-12). Individuals with a high surrounding tissue pressure may be particularly susceptible to expiratory pharyngeal narrowing during such low ventilatory motor output and driving pressure.

I'm intrigued by the discussion of collapse on the exhale.

(also note the comment about centrals being an extension of the end of the exhale -- that's what my centrals look like -- I'll have those long tails on the exhale with the inhale not starting right away on every breath, then one of those pauses goes longer than 10 seconds and gets scored as a central.)

(Also I think that I can get a copy of the chapter of the book from my work. I'm wondering if I'll see figures that look like what we are talking about.)

[Geer1]

Gettingbetter mask pressure will always be at max when inhalation is ending. It is the ending of inhalation that triggers exhalation process and decline of pressure back to EPAP. The machine will hold IPAP until it notices spontaneous exhalation.

Cycle sensitivity is what determine how early the machine transitions from IPAP to EPAP (whereas trigger sensitivity is how early the machine transitions from EPAP to IPAP).

[Geer1]

But it must be that the trigger sensitivity prevents the vauto from getting into this vicious cycle where it's kicking the pressure down and not giving enough IPAP and making crazy things happen.

Trigger sensitivity does not affect IPAP to EPAP process, it only affects EPAP to IPAP transition.

The only settings that affect IPAP to EPAP are Timin and cycle sensitivity. Timin will ignore spontaneous effort and maintain IPAP for the length of Timin, cycle sensitivity determines when the machine will transition from IPAP to EPAP if Timin is not active.

[cathyf]

It's clear that the vauto just controls this stuff better...

Here's autoset:
   
https://www.dropbox.com/s/wbs1khttxf91mf...s.png?dl=0

here's vauto:
   
https://www.dropbox.com/s/0j3r9klr2cnkwh...e.png?dl=0

(So why oh why didn't ResMed implement EPR of 3 as a PS of 3.0 with the same settings as the defaults for all of the vauto settings? Why doesn't the autoset function just call the vauto function with the default arguments?!? I could see this if ResMed was licensing software from someone else and had to pay a per-machine license fee for each vauto as opposed to their own in-house sw for EPR, but ResMed owns all of this software!)

[2SleepBetta]

Here is a link  to a pulmonology site's piece on diaphragmatic dysfunction which uses the term paradoxical about seven times. An entry in their search box of "paradoxical" yields 15 hits (not scanned).

https://journalpulmonology.org/en-diaphr...r=buscador (could not get it to hotlink, but tried it and it works)


I scanned the former piece, and saw some lesser pieces, and can see some connections but think Geer1's pressure timing explanation is most helpful. That is because (my) experience of paradoxical breathing (PB) and what I am aware of was episodic and for a time and/or it may be connected with breath timing matters Geer1 raises. My sense is the VAuto handles/can-handle the PD matter concerning me (us Cathy?) but wouldn't fix--perhaps would mitigate--chronic or acute diaphragm disease or injury.

Some heart disease involvements  were mentioned in connection with PB in other places. Not much found that I can see relating to the problem, just the matter of mistimed diaphragm action for us it seems, not sick diaphragms nor other nerve problems (MS, brain injury, et.).
---------------
Note to you, Cathy, I have a post worked up with matter from your PLD file you made available in my "Call for VBA help ..." thread. [S]heepless brought up need for ways to better express FL summaries. Belatedly working on the TV and TVd files you provided--more to post soon from them-I wandered off and decided to summarize, in some fashion for consideraton, the FL in your first PLD file for June 19, 2021. I am posting it in sheepless' thread. Your info is/became a vehicle for a slow response to sheepless.

Its the same data and graphics you have posted, don't remember where. Its from your night of that  example with peak FR of 5 L/min which TBMx and others of us were discussing .

[cathyf]

One helpful note I think 2SB -- I think that we should call this "Thoracoabdominal Asynchrony" (TAA) rather than PB -- because PB is Periodic Breathing, which is something else!

(Interestingly, TAA and PB are the inverse of each other. PB is where multiple breaths make up each period in a super-oscillation, while TAA is multiple oscillations in a single breath.)

[Geer1]

Asynchronous breathing is a better term, not sure when I started calling it periodic breathing as I originally called it asynchronous breathing. Most people that have had it saw improvement once switching to vauto but here is an example of someone that improved by increasing EPR alone. 

http://www.apneaboard.com/forums/Thread-...s-going-on

Your autoset example shows clear asynchronicity between the machine and your breathing effort. It shows what appear to be very large cardiogenic oscillations triggering the machine prematurely and the machine being out of sync with your breathing.

I have had one episode of this sort of breathing last year so I looked up that data again as I was curious how it started (and know more than I did back then). I see that I was having larger than normal cardiogenic oscillations for some reason and at first it was pretty much regular breathing with large oscillations and then the machine started to prematurely trigger. From there the breathing got progressively worse as the machine and my breathing effort became more asynchronous. 

Here is the beginning of my data which shows large cardiogenic oscillations and only the odd premature trigger.

   

And here is the data after it has degraded further. The machine was regularly supplying two pressure pulses per breath and my body was trying hard to exhale. 

   

I am curious if yours and sleep2beta situations start out as cardiogenic oscillations and then degrade as well.

In looking at my data more closely I just realized that one thing my vauto does more accurately is calculate my inspiration and expiration times properly. My autoset always got confused by cardiogenic oscillations and would report my inspiration as 2+ seconds. My vauto has correctly measured inspiration between 1.14 and 1.26 all 35 nights I have used it. 

I think what this is all saying is that the autoset has a higher trigger sensivity and gets prematurely triggered more often. This throws it out of sync easier and makes it report inspiration times improperly. I will have to try a high trigger sensitivity on vauto and see if that makes it act more like my autoset.