An APAP Shootout (sort of) on Academic Journal

[StillAnotherGuest]

Well, for starters, in the model set up in the bench study by the Barcelona group, assessment of snoring was included, and they also looked at prolonged flow limitation with leaks, obstructive apnea with leaks, and created a closed-loop patient simulation, generating a typical patient response to the application of increasing pressure (during which only 3 machines were able to succeed in inducing normalized breathing).

BTW, that group (Rigau, Monserrat, Farre, et al) is pretty sharp, their simulator isn't something they built in their garaje.

In the late 90's, when everybody was touting pressure transducers as the Gospel ("Look, the flow waves' gone! Isn't that great? Must be an apnea!"), more than a few people scratched their heads and said, "Y'know, this can't be right, a thermistor might not be the greatest technology, but it can't be that far off."

So anyway, these guys demonstrated that in order to make the pressure transducer measurements correlate with pneumotach (the real "Gold Standard"), you had to take the square root of the waveform signal to get it to match properly. That always struck me as pretty clever.

Relevance of Linearizing Nasal Prongs for Assessing Hypopneas and Flow Limitation During Sleep


SAG

[GoofyUT]

As I've already stated I believe most people with OSA can be well treated by any autopap set properly.

Rested Gal-

With all due respect, I strongly disagree. I know from my own experience that I failed miserably to secure "well treated[ed]" with a ResMed S8 AutoSet Vantage, and I IMMEDIATELY improved and have been well-treated since I switched to a REMstar Auto. Now, I have all the respect in the world for ResMed's fine engineering and design and I admire and retain my ResMed S8 Vantage, but I use it only in CPAP mode. And, I know of many others who have responded wonderfully to ResMed's auto-titration algorithm, but who failed miserably when they tried a Respironics auto-titrating machine.

I believe strongly that the algorithms of the various manufacturers are different in a clinically significant fashion and that its is NOT true that ".....most people with OSA can be well treated by any autopap set properly." This is why I continue to stridently recommend that those considering and prescribed auto-titration should allow themselves fair trials of the different manufacturer's auto-titrating equipment. I also believe that to advise otherwise is reckless.

And, i believe that this is what this entire vigorous thread is all about. i would like to add that I consider the arguments here regarding the scientific validity of iron lung studies to be specious. The answer to this dliemma is simple: Well controlled clinical trials with statistically appropriately-sized samples of real patients hooked to real machines. Medicine has been doing it for decades with new medications and medical devices. This methodology is long overdue in the nascent field of sleep medicine.

Chuck

[StillAnotherGuest]

So if you want to go from the bench to the bedroom and really judge treatment effectiveness, you'll either have to get PSG on APAP
SAG

This has also been called for in the unsummarized test paper which asked for somthing more than flow rate be measured...

And in a remarkable coincidence...
SAG

[-SWS]

Well, for starters, in the model set up in the bench study by the Barcelona group, assessment of snoring was included, and they also looked at prolonged flow limitation with leaks, obstructive apnea with leaks, and created a closed-loop patient simulation, generating a typical patient response to the application of increasing pressure (during which only 3 machines were able to succeed in inducing normalized breathing).

Another bench-test altogether with yet another methodology worth delving into. Thanks.

The answer to this dliemma is simple: Well controlled clinical trials with statistically appropriately-sized samples of real patients hooked to real machines.

So where are they for APAPs? Or perhaps the better question is why aren't they currently established for APAPs? Anybody have opinions on this one? Thanks.

[dsm]

As I've already stated I believe most people with OSA can be well treated by any autopap set properly.

Rested Gal-

<snip>

I believe strongly that the algorithms of the various manufacturers are different in a clinically significant fashion and that its is NOT true that ".....most people with OSA can be well treated by any autopap set properly." This is why I continue to stridently recommend that those considering and prescribed auto-titration should allow themselves fair trials of the different manufacturer's auto-titrating equipment. I also believe that to advise otherwise is reckless.

<snip>

Chuck

[-SWS]

Now I am pretty sure that SWS & I would agree 100% that trying to bottle that type of a research test (to test if a particular machine brings on complex apnea), is going to be a monumental challenge to any researcher

Actually, I'm not 100% sure of my views regarding this subtopic. I think Chuck's very recent statement and SAG's earlier PSG statement get at the same statistically-oriented efficacy related goals. Yet, at the same time I agree with Doug's comment that underlying factor-diversity itself may render limited-scope study's a more formidable challenge than the many or most clinical trial scenarios. This area in particular is unfortunately not my strong suit. I would love to hear more about this sub-topic from others.

(on edit: when I made this comment I didn't realize that dsm was talking about CSDB exclusively. Rather I thought he was referring to vast factor-diversity in general, which would encompass much more than CSDB. I also like GoofyUT's opinion that SDB's current maturation cycle largely accounts for missing clinical trials. Does anyone think there may be any other reasons?)

[GoofyUT]

I also raise the ugly spectre (one of my own questions based on my observations) of Autos with their changing pressures being partly responsible for increases in 'complex apnea' (not 'mixed apnea' but complex - the one that is resistant to CPAP & contains components of pressure-induced apnea).

Now I am pretty sure that SWS & I would agree 100% that trying to bottle that type of a research test (to test if a particular machine brings on complex apnea), is going to be a monumental challenge to any researcher.

Doug-

With regard to your first speculation, i couldn't agree with you more. With regard to your second, the ability to contruct and conduct research designed to answer the questions that you pose is WELL within the grasp of extant medical research methodology. I believe that its absence is simply a matter of the field being too new, and SDB not being taken seriously until recently. We are where PMS was 25 years ago.

[dsm]

I also raise the ugly spectre (one of my own questions based on my observations) of Autos with their changing pressures being partly responsible for increases in 'complex apnea' (not 'mixed apnea' but complex - the one that is resistant to CPAP & contains components of pressure-induced apnea).

Now I am pretty sure that SWS & I would agree 100% that trying to bottle that type of a research test (to test if a particular machine brings on complex apnea), is going to be a monumental challenge to any researcher.

Doug-

With regard to your first speculation, i couldn't agree with you more. With regard to your second, the ability to contruct and conduct research designed to answer the questions that you pose is WELL within the grasp of extant medical research methodology. I believe that its absence is simply a matter of the field being too new, and SDB not being taken seriously until recently. We are where PMS was 25 years ago.

[-SWS]

Hey all, I wonder if I should summarize that other test, in which I think is more sophisticated (but still iron lung ) than this, and if yes, post in this thread or a new one.

We're still working on the comparatively "simple" one. Do you have any ideas or thoughts on any of this, SamCurt? Thanks for posting.

[meister]

The studies are flawed. The PAP machines are flawed. Why not use
a Dental Device instead? This thread is getting way too long ...
some of us are falling asleep minutes after inserting the TAP and
not waking up until the alarm goes off. However, no one wants
to study that situation. I will go back and crawl under my rock.

[-SWS]

some of us are falling asleep minutes after inserting the TAP

LOL! Many are undoubtedly falling asleep minutes after opening this thread.

However, no one wants to study that situation.

I think that has to do with what Chuck said earlier about SDB's premature point in the scientific maturation cycle.

It's good to see you and your humor, meister!!!! Glad the dental appliance is working out so well!

[rested gal]

As I've already stated I believe most people with OSA can be well treated by any autopap set properly.

Rested Gal-

With all due respect, I strongly disagree.

No problem, Chuck.

I'll highlight the words I think most important as qualifiers in what I said:

"As I've already stated I believe most people with OSA can be well treated by any autopap set properly."

Most -- not all.

Set properly -- which can take a good bit of trial and error in some cases, and the software to see what may be happening.

I should have added that while I don't agree with SAG's take on the study that's being discussed in this thread, I do agree VERY much with something SAG brought out (regarding trial and error with different autopaps) in his first post:

And that's also assuming that failure to improve with APAP is a fault of the algorithm, and not some other issue (which is probably more likely in the great majority of cases).

As best I can remember, Chuck, you had the most important treatment issue already dialed in -- mask that suited you. And I think you had software for both machines.

I don't know about other issues that might have been factors -- state of health, other illnesses, congestion, allergies, meds, stress, weight changes -- the list could go on and on. Things that could be at play during the trial of one machine and not during the trial of another for some people, even if not for you.

For other people, mask problems, mouth air leaks, humidification problems including not enough or rainout, aerophagia, and just plain trying to get comfortable with this kind of treatment could make their "how I feel" results bad with a first machine and better with the second, as they began sorting through and "fixing" each problem that can interfere with "sleep."

But also, as best I recall, you were far enough along that you already had all that stuff in place. You were very methodical about considering everything you could think of that might make one machine not leave you feeling as good as the other. "Other issues" probably didn't apply to you in your trials.

So...yep....you landed outside the "most" that I mentioned...as do some other people. Glad you found the machine that worked for you. I still think "most" people are well treated by any of the major autopaps. And probably just as well by some of the lesser known APAPs.

[GoofyUT]

RG-

Again, with all due respect, you make the point yourself about why a particular APAP may not provide the best treatment for some people. Though the PRESSURE settings and range can be adjusted and should be adjusted according to the efficacy data revealed by the machine's software, the shape (slope) of the GRADIENT of the pressure changes that occur through the machine's titrations (both upward and downward) CAN NOT. It is the shape of those gradients that is determined by and DEFINES the algorithm that each manufacturer has developed to control the operation of their auto-titrating equipment. And, it is that proprietary shape of the gradient that contributes to treatment efficacy for some, and to treatment failure for others.

That is PRECISELY why it is NOT true that MOST people will be successfully treated by ANY well-set APAP. They will respond optimally only to an APAP which contains an auto-titrating algorithm with a shape that best matches the flow dynamics of that particular individual. And, one that poorly or sub-optimally matches those flow dynamics will NOT deliver optimal therapy, no matter how well it is SET, since no one can set the shape of the gradients.The manufacturer does this in designing the algorithm.

Now, the essence of this thread has explored this, and I think that we all agree that the science would be advanced if we could study the differences between the algorithms in a clinically meaningful way, and come to better understand the indications for one algorithm versus another. In much the same way that LOTS of reserach has been conducted to determine the indications for one anit-biotic versus another, or one heart med versus another, ACROSS A WIDE RANGE OF PRESENTING CONDITIONS. That can and must occur with regard to SDB as well.

But until that occurs, it is simply foolhardy to suggest that the machines are interchangeable and given suitable adjustment, each will deliver optimal or even adequate treatment. It is just not the case, for the reasons that I described above, and I have directly experienced this in my own case.

Chuck

_________________

CPAPopedia Keywords Contained In This Post (Click For Definition): auto, APAP

[StillAnotherGuest]

I should have added that while I don't agree with SAG's take on the study that's being discussed in this thread...

Oh c'mon! Those Barcelona guys are FABULOUS!

BTW, some other interesting results from that bench study concerned the machines employing forced oscillation technique (FOT) as a means to accurately discern central events and respond accordingly. Meaning, they don't respond, and do that quite well.
SAG

[dsm]

I should have added that while I don't agree with SAG's take on the study that's being discussed in this thread...

Oh c'mon! Those Barcelona guys are FABULOUS!

BTW, some other interesting results from that bench study concerned the machines employing forced oscillation technique (FOT) as a means to accurately discern central events and respond accordingly. Meaning, they don't respond, and do that quite well.
SAG

SAG,

Its taking me time but I detect a wicked & dry sense of humour here

DSM