(06-30-2021, 09:37 AM)cathyf Wrote: Wow-- I need to track down definitions of some of these terms (I don't know what "duty cycle" means but I think I'm following the gist of it). But if I'm following what that ERS article is saying, I think that they are talking about people like me!
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Here's a picture of their [duty cycle vs. flow limitation] graph of different FR curves on top (figure 2 from the paper [2SleepBetta edit: the paper is linked in p.1 of thread]
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I think I even have a (half-baked) theory of how the EPR works for me. It allows me to have fast forceful expirations so that then the inspiratory phase can be longer and I can move more air over the extended period. ... [snips] ...(Also brings up another idea kicking around my brain for the last 7 years -- I'm a singer, and as anyone who has every sung in a group knows, 75% of choral direction is the director yelling "NO BREATH" in all those places you want to breathe, and "BREATH" in those few places the director wants to let you breathe. Maybe my breathing muscles are used to the concept of getting every molecule of air that I can when I can?)
cathyf grazes deeply the answer to many of her/our "FL posts" here at AB (as I touched on in bringing up duty cycle vs flow limitation research).
She wrote "I don't know what 'duty cycle' means" and then proceeded to write that EPR helped her "have fast forceful expirations" so she can have a longer "inspiratory phase . . . [to] move more air over the extended period". Then she connects the physical training benefits from her singing training, which helped her and singers get more air (tidal volume) per breath. Well, the formula for duty cycle is simple and it agrees exactly with cathyf's logic: the duty cycle ratio equals the total time of a single inspiration divided by the total time of the whole breath. The rub is that high duty cycle ratios (many of us must defend ourselves with in flow limited sleep) are a significant cause of fragmented sleep and hypoventilation.
Recently my study of flow limitations has shifted away from tidal volume drops at FLG to see more and more that high duty cycle ratios account for large parts and numbers of FLG. They explain a lot of her and our continuous, low mountain ridges-like Redsmed FL flag series (FLG). Lots of earlier and later work strongly suggest to me that minor deformations of inspiratory wave tips (minor tip out of roundedness) episodically may or may not draw FLG flagging and may be sleep-context sensitive.
I haven't looked at this, but will. It could be that a continous high duty cycle ratio will mark UARS. (If you have a hammer ya wanna pound down nails.)
cathyf, in Software Forum thread "
Call for Excel VBA help: to support effort to clarify/understand FL | Apnea Boardposted posted this link (Post #16) to a lot of her OSCAR screenshots (for one night), which I reviewed tonight
Jun19Study - Dropbox .
I won't elaborate much, but will attach a too-busy off-my-shelf image of one of her screen shots, "A", along with a new "B". "A" has had lots of discussion here at ApneaBoard (in sheepless FL expression thread plus), little if any of that, as I recall, dealing with duty cycle significance. In "A" cathyf shows tremendous capacity to "power through" high flow limitation for five miinutes with her high duty cycle ratio despite her extremely low tidal volume. "B" shows high FL along with fairly well-rounded inspiratory wave tips, but guesss what, it presents a continuous "moderated severe" duty cycle ratio (see severity levels figure in the referenced paper up-thread or in my earlier post). The high ratio, I'll claim, causes nearly all the FLG severity shown in "B". (Note: In graphic "B" consider the mention of red arrows stricken out. Duty cycle is lower there along with times of green arrows.)
Additionally I link to a view of the whole sleep session. In it you might spot the "A" and "B" times and will see duty cycle and breathing (from 30,000 feet).
attachment.php (1204×773) (apneaboard.com) . The upper graphic in the attachment shows measured tidal volume drop versus FL or FLG severity. The yellow mismatch of the upper graph only reflects the fact that TVd is strictly a tidal volume "loss" measure, whereas a FL or FLG shows not only TVd to some extent (if any), but also shows any duty cycle ratio effects and wave shape effects when applicable.
Note: I now regret dismissive comments I've occasionally made about FL or FLG from "phantom" flow limits. Ignorance. mea culpa. More and more I see that the Resmed FLG reflects detection of high duty cycle ratios along with bad-actor wave shapes and ventilation (tidal volume) reductions. To what extent shapes add severity, I now have little idea, but a deeper look at a couple areas of close agreement and wide disagreement of TVd and FL severity-like differences (in the linked graphic) might shed light on shape effects.
