What's that red curve in the Pressure graph? (Geek/nerd question)

[SummerTime]

Then again, I often make unfounded assumptions and have no idea what I'm talking about.

According to my wife, anyway.

And she's always right.

According to my wife, anyway.

[Rubicon]

So as I understand it, that "conceptual value" midway between IPAP and EPAP is useful to the algorithm used, since the algorithm was originally designed for APAP, not autobilevel. I assume something similar to that VPAP approach may also be done with Auto BiPAP and that the red curve is similarly a "conceptual value" for the machine's own use.

IDK if that value is used in the algorithm. It may have some value to the clinician (or user).

Viewing dsm's manual excerpt in it's entirety:

AutoSet pressure is a conceptual value. The patient is delivered an auto-titrated inspiratory and expiratory pressure based on the AutoSet algorithm, which has the AutoSet pressure as its midpoint. The AutoSet pressure is reported in data management and efficacy results information. You may also restrict the range of pressures in which the AutoSet algorithm operates, using the Min EPAP and Max IPAP settings respectively (see “Min EPAP and Max IPAP” on page 9). The VPAP Auto analyzes the state of the patient’s upper airway on a breath-by-breath basis and the AutoSet algorithm adjusts the AutoSet treatment pressure within the allowable range, according to the degree of airway obstruction. The AutoSet algorithm adjusts treatment pressures according to apnea, snore and inspiratory flow limitation.

We think of EPAP treating OA and IPAP treating Hyp and never the twain shall meet. However, if we simply consider "breathing events" or "no breathing events" you are left with looking a single number in treating events, and to "restrict the range of pressures in which the AutoSet algorithm operates" becomes simple. Appropriate? Got me. But as the ResMed "median" appears to be heavily weighted toward IPAP, it seems one thing you'd be doing is severely reducing PS, which might be a thought if you're CompSASing. In many cases you'd end up with a lot less pressure swings which has always been the knock against wide-open Auto (because you'd still need to have at least some events in order to order to chase events).

At least that's what your wife told me.

Oops.

[lazarus]

I agree that ResMed's approach to bilevel treatment differs significantly. (An always fixed [nonvarying] PS; ignoring H; and instead only watching breath shape [IFL], A [under 10 cm], and snore.) That's why I only used the statements in the RM manual as merely a way of illustrating how the basic approach of taking those two actual-pressure-delivery numbers (IPAP and EPAP) and reducing them to a conceptual number may be needed for an algorithm. That manual, as I recall (in storage these days, since I switched to APAP), has a nifty diagram showing that calculated "Autoset pressure" that confusingly gets reported to patients as if it were an actual pressure. The portion of the instructions (above) following "you may also" are words that I consider unrelated to the statements about the imaginary "Autoset pressure," since it relates to setting limits on actual delivered pressures, using min EPAP and max IPAP. Either way, RedMed doesn't have to worry about limiting PS as a treatment parameter since it is limited already by design with their approach to preprogrammed prescribed PS where IPAP and EPAP are always a set number (delta) apart, as I understand it.

But getting back to the real question in this thread of why OSCAR passes on a report of a value between IPAP and EPAP for the other brand of autobilevel in the pressure chart (not the breathing tracing chart), my assumption as an uneducated layman is that it can't be a real pressure, since it isn't IPAP or EPAP, so it must therefore similarly be a conceptual value (although seemingly calculated differently from ResMed's simple exact midpoint) used by the algorithm.

I know that my assumption has no accompanying documentation for that brand, so I would never expect a professor of any field to give much weight to my patient-based thought experiments. (And hopefully that won't lower my grade too much for this semester.) But I figured hey why not throw my musings out there into the mix just in case it accidentally moves the search along toward the two of you getting at the definitive answer soon.

I truly appreciate what you do here.

And my wife says, "Hi!"

Best to your family, sir, from us both.

[Rubicon]

Best to your family, sir, from us both.

Back atcha x2!!

[Rubicon]

I agree that ResMed's approach to bilevel treatment differs significantly. (An always fixed [nonvarying] PS...

Ummm...

[lazarus]

I agree that ResMed's approach to bilevel treatment differs significantly. (An always fixed [nonvarying] PS...

Ummm...

Sorry. I meant autobilevel, not bilevel.

A constant PS [RM] vs. the variable one in the machine RS1 asked the question about. I view that as a major difference because I consider the amount of PS to be the most important factor both in bilevel and in autobilevel treatment for SDB.

Just a personal view.

That said, correct away, my friend. I don't think RS1 will mind.

[robysue1]

I agree that ResMed's approach to bilevel treatment differs significantly. (An always fixed [nonvarying] PS...

Ummm...

Sorry. I meant autobilevel, not bilevel.

A constant PS [RM] vs. the variable one in the machine RS1 asked the question about. I view that as a major difference because I consider the amount of PS to be the most important factor both in bilevel and in autobilevel treatment for SDB.

Just a personal view.

That said, correct away, my friend. I don't think RS1 will mind.

Yes, Auto BiPAP should be used for PR's auto bilevel machines and their algorithms for increasing pressure.

And yes, VAuto should be used for Resmed's auto bilevel machine and their algorithms for increasing pressure.

And yes, auto bilevel ought to be used for talking about both and/or a generic question.

But it's rather like Xerox vs. copier machine: Us mere mortals all too frequently just use BiPAP to refer to all bilevel machines and Auto BiPAP to refer to all auto bilevel machines.

It is true that there are important differences in the PR and Resmed algorithms for adjusting the pressures on their auto bilevel machines. And the biggest difference is that PR does use a variable PS, where Resmed does not. Another difference is that the Resmed auto machines are more aggressive in increasing the pressure that PR auto machines are.

In my own case, I've become quite used to that variable PS through the 11 years I've been using PR Auto BiPAP machines. I can't prove anything since I've never used a Resmed VAuto, but I do believe the fact that my PR Auto BiPAP seldom increases my EPAP above its minimum setting is a large part of why I was able to finally tame the aerophagia monster that moved into my bedroom when I first started PAPing using a Resmed S9 AutoSet in the fall of 2010. (My IPAP often increases from its minimum of 7cm to my MaxIPAP of 9cm.) I've also wondered if the less aggressive pressure increases on the PR machines was also a reason that I've always had much less aerophagia on the PR machines than I had with the S9 AutoSet.

As for why I chose the PR System One Auto BiPAP for my first bilevel: In December 2010, the Resmed S9 VAuto was still vaporware: Yes, Resmed had announce that an S9 VAuto would be released, but no-one knew when. And the S8 VAutos Resmed was still selling required a proprietary data card reader for getting to the detailed daily data and that proprietary data card reader was already hard, if not impossible, to find. And the S8's didn't record the flow rate data. The PR System One Auto BiPAP existed, used an SD card, and there were ways of getting your hands on the Encore Pro software needed to look at the detailed data, including a flow rate chart for just the last night. (This was all pre-SleepyHead, which is the predecessor of OSCAR.)

But I have wondered through the years whether I would have done about the same, or better, or worse using a Resmed VAuto with its fixed PS algorithm and much more aggressive tendency to increase pressure.

And now I am wondering about what machine I ought to be thinking of getting next: My Dreamstation is 6 years old and under recall with no replacement date in sight. And I'm turning 65 next summer, so that means the switch to Medicare is imminent. And the AHI on my diagnostic sleep tests was composed almost entirely of what was then called "hypopneas with arousal"---aka the "alternate" definition of hypopnea, and Medicare did not recognize those as "real" hypopneas" because there was no associated 4% O2 desasts. And you take those out of my diagnostic AHI, and it goes from 23ish to 3.5. But all of that's detailed in another thread.

[lazarus]

I consider your story of taming the aerophagia beast to be one of the most amazing stories I've heard, and it seems the PR version of auobilevel is one of the heroes of that story. I'm not sure you would have been able to do much auto-ing with an RM autobilevel. Seems to me you chose wisely.

I considered my brief use (trial) of PR autobilevel to show that it could treat me as effectively overall as the RM version, but it would have taken me a few more weeks to get used to the differences in feel. And at the time, I was still a bit sensitive to slight central-ish/mixed instability that has resolved now.

It makes me angry that financial considerations and worries play such a role in treatment choices.

If I found myself presently comfortable with, and well-treated by, variable PS, I would be hesitant to switch brands, myself. To me, the "benefit" of RM in general is comfort. But if you are comfortable and adapted to the delivery of PR, that may not be a decision factor for you. And with your aerophagia problem, you might run the risk of having to lock in a RM autobilevel to straight bilevel if you switched.

In my case I decided (after using autobilevel for many years) to be happy with (partially for financial reasons) the 3cm spread of RM APAP pressure relief, which is, in my view, very close to the feel and treatment success of bilevel. It turned out well for me, but I have no idea if that would turn out well for anyone else. I basically pay out of pocket, so I convinced my primary doc at the time to write an Rx for APAP so I could use that for my online purchase instead of using the autobilevel Rx my sleep doc had written years earlier. That saved/saves me quite a chunk of money.

[robysue1]

If I found myself presently comfortable with, and well-treated by, variable PS, I would be hesitant to switch brands, myself. To me, the "benefit" of RM in general is comfort. But if you are comfortable and adapted to the delivery of PR, that may not be a decision factor for you.

Comfort plus effective treatment is the real key to adjusting to any kind of PAP therapy.

And it's worth remembering that comfort really is in the eyes, nose, stomach, and brain of the beholder.

There are lots of folks around here who have used both Resmed and PR machines for more than a night or two. And many of them have a strong preference for one brand or the other. Resmed lovers do seem to outnumber PR lovers. And I think that part of that is for many people Remed's EPR is genuinely more comfortable than PR's Flex systems. But I also think for most of those people, the rapid pressure increases on the Resmed machines are not problematic in the sense of triggering wakes or aerophagia.

But there are a minority of people like me who don't happen to thrive on Resmed machines. And in my case it was a combination of a whole bunch of things.

In my case I decided, partially for financial reasons, to be happy with the 3cm spread of RM APAP pressure relief, which is, in my view, very close to the feel and treatment success of bilevel. It turned out well for me, but I have no idea if that would turn out well for anyone else.

You are like most people around here: EPR does seem to act as a poor man's bilevel with a PS=3 for a lot of people.

But I was the exception: When using my original S9 Autoset, I had EPR = 3 because I really could not exhale fully without it, but I found EPR irritating as well: The problem was the machine starts increasing the pressure just before the very end of the exhalation. And that made me feel like I was being forced to breath sooner than I wanted to and inhale more air than I wanted to. Which fed the aerophagia. And the insomnia. And the aerophagia and insomnia then fed off each other creating a real royal mess of my sleep.

For what it's worth, PR's Flex system feels even worse to me than Resmed's EPR: The Flex systems start increasing the pressure even sooner than EPR does. It's more like the pressure starts to increase as soon as you rate of exhalation starts to decrease. As a consequence, the very first thing I did was turn Bi-Flex OFF. With Rise Time = 3 and Bi-Flex set to Off, the increase in pressure comes at the start of my inhalation rather than at the very end of my exhalation. That small difference in timing was critical to me when I was taming the aerophagia.

It makes me angry that financial considerations and worries play such a role in treatment choices.

It makes me angry as well. Far too many people have to accept compromises based on what their insurance company will pay and what they can convince a DME to sell them when they're still sleep deprived enough to be rattled by the whole process of starting PAP.

No wonder there's a big failure rate for the folks who never discover a place like cpaptalk. I know that if I had not discovered this forum before I got my first machine, I would have been stuck with a brick and I really doubt I would have had the patience to sort it all out: It would have been far too easy to simply conclude that therapy was simply never going to work because I crashed so hard and so suddenly at the start of PAPing. And without the good folks here, I would never have known what questions to be asking the sleep doc's PA on my all too frequent semi-emergency appointments during those first dark, grim months of PAP therapy in 2010.

[lazarus]

This forum was crucial in saving my life during my early days of PAP. I wouldn't have made it past night one. Slinky, Rested Gal, SAG, -SWS, Ozij, and others all played crucial roles with their posts. And I'm sure your body of work online sharing your adventures and approach has saved lives and will continue to do so for years to come.

And trust me, you don't need post numbers here to be recognized, effective, or respected. Many of us switch names on a regular basis in order for the content, style, and approach of our posts to speak for themselves.

Thank you for developing and maintaining your reputation for helpfulness, openness, humility, and generosity of spirit.

May you find answers/solutions for all problems that arise.

Good sleep to you.

-jeff (jnk, jnk..., etc.)

[lazarus]

you don't need post numbers here to be recognized, effective, or respected.

I've always realized that I'm an idiot, but it just now hit me that I tried to tell a mathematics professor that 'it isn't really about numbers.'

Sometimes I need just to shut up.

[robysue1]

you don't need post numbers here to be recognized, effective, or respected.

I've always realized that I'm an idiot, but it just now hit me that I tried to tell a mathematics professor that 'it isn't really about numbers.'

Sometimes I need just to shut up.

As a mathematician, I can say, It's not (always) about the numbers. But numbers are fun anyway.

[ozij]

you don't need post numbers here to be recognized, effective, or respected.

I've always realized that I'm an idiot, but it just now hit me that I tried to tell a mathematics professor that 'it isn't really about numbers.'

Sometimes I need just to shut up.

As a mathematician, I can say, It's not (always) about the numbers. But numbers are fun anyway.

.... and 2 minutes ago on another thread I had to smile when I first noticed our mathematician's signature...

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It makes me angry that financial considerations and worries play such a role in treatment choices.

Don't know why.

EVERYTHING follows the 90-10 rule when it comes to money (actually EVERYTHING follows the 90-10 rule period).

Anybody who got stuck with a poor provider-- physician, DME, sleep center-- it's their own fault.

[Rubicon]

Combine that with the ungodly percentage of "quiet quitters"-- yup, no surprise at all.