CPAPtalk.com

-SWS wrote:

ozij wrote: One thing seeming to have got lost in the previous discussion is "what is a non-responsive A/H?" (or sustained A/H)?

A non responsive A/H is the apprearance of the second event within 3 minutes of the first above pressure is at the NRAH level. One apnea/hyponea at that level - nothing happens. A second, within 3 minutes, and bam, the pressure goes down.

I think I agree with the above, but I'm not sure. Looking at the graph below, let's define that the three-minute window is not the entire graph, from left to right. Rather the three-minute window is a running limit or "time out" period, after which pairs of apneas are no longer associated as being "first and second apneas" (as a traveling pair). To examine the graph below, we have exactly four such running windows, with each "three-minute-or-less" window having produced pairs of A and/or H events:

Above we have the first three-minute-or-less window with paired events just to the left of the first red arrow. Precisely at that red arrow is where the second of those two A/H events occurred. So you'll note the first event of that pair does not receive a pressure response.

The second three-minute-or-less window occurs between the first red arrow and the second. Within that second time-limited window, the first A/H event occurs somewhere/anywhere after the first red arrow. But the second of those paired events occurs exactly at the second red arrow. Again, it's that second event that causes our next pressure increase.

So in this graph, it can take up to nine minutes, via three pressure increments, before that NRAH threshold is reached and that 2 cm pressure drop occurs. In the case of strictly hypopneas, it can take longer than nine minutes to reach, since "onset pressure" is reset at pressures below 8 cm.

Agreed that the entire string of events is what Respironics considers "non responsive". On the graph above the eighth event is what triggers the NRAH flag or threshold to cause that 2cm pressure drop. There are exactly two events between each pair of arrows.

The sixth event causes us to reach the NRAH pressure limit. The seventh event sits graphically unidentified (to us) on that topmost plateau. Then the eighth event triggers that 2 cm pressure drop.

We did agree all along! .

Very interesting. Thanks for the clarifications and explanations, -SWS and ozij.

Both of you have been pointing out all along that the careful increases the Respironics designers built into how the machine is supposed to behave when presented with apneic situations have nothing to do with avoiding more pressure lest there be such a thing as a "cork in a bottle" or "egg sucking" scenario.

Both of you have been rightly pointing out all along that the careful handling of events that might sneak through despite preemptive measures, has to do with not increasing pressure unnecessarily just in case the airway is already open, as with a central apnea.

Thanks, Rested Gal. But I think we've all been learning along the way. In fact, to underscore that point, I'd like to make one of my many self-corrections:

-SWS wrote:So in this graph, it can take up to nine minutes, via three pressure increments, before that NRAH threshold is reached and that 2 cm pressure drop occurs.

That statement is incorrect. Starting with the blue arrow on the far left, we have four "three-minute-or-less" windows. That means it can take up to twelve minutes after that first apnea before the 2 cm pressure drop occurs.

There's plenty of other stuff I learned in this thread as well. And like, ozij I misunderstood just what an NR threshold was when I was first exposed to the subject matter long ago. At the time I didn't realize it could take so long to hit that NR state, and I even thought it was possible for that NR threshold to be met with one very long event (it's not possible). Sorting through the details and discussing these concepts always helps IMO.

-SWS wrote:

While further quoting Respironics ozij wrote:When the device encounters a non-responsive apnea or hypopnea, it will decrease pressure by 2 cmH2O and hold the pressure for 15 minutes. During this 15-minute "NRAH-hold" period, the pressure will be changed only in response to detection of a sequence of vibratory snore events. The reason for this increase in pressure followed by a decrease in pressure when an apnea/hypopnea is not responsive is to allow the device to respond appropriately to an event that is not treatable by increases in pressure, such as a central apnea.

Snore constitutes adequate means to differentiate respiratory effort. Thus there is no need to continue the cautious pressure-holding pattern relative to central-induction.

I'd like to comment a little more on how snore detection helps with probability-based obstruction-versus-central differentiation. In the case of central hypopneas there is always some respiratory effort.

When snore occurs, airway narrowing (and thus obstruction) is "probability-implied" as significantly contributing to that reduced flow recognized as a hypopnea. Without either snore or an "obstructive-hinting" wave shape, there can be no implied method of differentiating obstructive-versus-central hypopneas with a flow sensor alone.

ozij wrote:Which brings up a further thought
Is the worst NR number on a Respironics just 1/8 of the total? How are the events in the preceding sequence counted? are they called apneas, or are they reported as NR retroactively?

Dunno. A very good question IMHO. Hope one of us gets a chance to dig for that answer. If you don't hear back from me it's because someone else answered first or because I still "dunno".





Doug, I wasn't picking on you at all. I thought your comment was humorous repartee. The reason I thought it was humorous repartee is because you and Bill were theorizing about something very different than Sullivan discovered. Sullivan and the rest of the industry thinks those vacuum-based occlusions nicely resolve with airway inflation. Even after Sullivan and his entirely brilliant understudy invented the first APAP, they continue to think their inventions are a viable way to address those vacuum-based airway occlusions (the entire industry seems to think that way, for that matter).

So you and Bill were quite literally talking about "the vacuum-based airway occlusions from hell". None of us have a medical term for what you two are proposing. So we've been loosely using terms like "cork theory", "super cork theory", and even at times "vacuum-based occlusion" (with the ever-so-crucial "from hell" part simply omitted).

So I honestly thought you were just pulling my leg when you took semantic issue with me for lack of a good working term for what you and Bill theorized. Walk into Sullivan's office with a milk bottle and egg to suggest that he has some serious problems afoot, and he'll just smile and point to the dunny, mate.

Kind regards, Doug! Because we are friends we can playfully rib each other. Please don't take any of mine to heart!

-SWS wrote:There's plenty of other stuff I learned in this thread as well. And like, ozij I misunderstood just what an NR threshold was when I was first exposed to the subject matter long ago. At the time I didn't realize it could take so long to hit that NR state, and I even thought it was possible for that NR threshold to be met with one very long event (it's not possible). Sorting through the details and discussing these concepts always helps IMO.

Absolutely!! Until you and ozij explained it in this thread, I too thought the NR flag in Encore Pro (and Encore Viewer) was marking a single non-responsive apnea.

-SWS wrote:These are the differences in the patent description that Bill cited earlier between apnea handling and hypopnea handling. I believe the differences to be based on statistical risk regarding central induction

Ya know, -SWS, I finally realized just where the technical battlelines really are in this discussion. The battlelines I see are between "pragmatists", and the "theorists".

Most who spend any time on this forum realize the huge disconnect between prescribed treatment and realistic treatment. The service providers (physicians, techs, RT's) as a group are woefully out-of-touch with patient needs. Yet, they don't view themselves as out-of-touch at all, at least not acording to the few who've wandered into this forum.

I guess you could call 'em theoretically based, cuz their practices sure ain't based on reality. The physicians have been certified though (OK, maybe not all of 'em ... ), a certification which presumably is not trivial. The RT's have been certified too (again, not a trivial undertaking as Eric pointed out). I don't know whether there's such a thing as sleep-tech certification, but I was impressed with the level of technical knowledge the last sleep-lab tech I encountered had. He knew his equipment well.

So, what's my point? Reality has been displayed on this forum daily for a very long time. Why bring it up in this discussion? I bring it up because it seems to me that the two sides of this discussion have followed very similar battlelines.

On the one hand we hold up those few rare and valuable tidbits of data the equipment manufacturers have made public as if they contain fundamental truths, as if the company has tons of supporting data hidden away to justify the machine behavior. Maybe they do. Maybe they don't. I'm inclined toward believing the latter, but that's just my opinion. I'm sure they know a lot about blowers and pneumotach sensors, but I haven't seen anything that convinced me they really know much about apnea? If the M-series machine is an indicator, they sure don't know beans about ergonomics. While such a poor design might be forgiveable in many products, the loss of focus on the patient interface seems disturbing in a product which is such an important part of the patient's life. It seems clear that the company couldn't have done any serious testing of the product with real people. Given the outspoken preference displayed by folks on the forum for the older Respironics machines, it seems to me that the giant step backward taken with the new M-series suggests that the company may now be every bit as out of touch with patients as physicians and DME's are. Is there a reason to think they have any better or realistic understanding of apnea processes?

I'll grant that at least one person at each manufacturer must be well-versed in the relevant medical literature, but that's not exactly confidence inspiring, at least not to me. That doesn't mean that he could tell you much more about complex sleep apnea than what's already been cited here a dozen times in this thread, the 10 cm line-of-demarcation. Sure, he could point to a Cheyne-Stokes machine and proclaim it has a wonderful algorithm, but is that algorithm reality based or based on a poorly constructed data gathering experiment conducted by theorists to share with other theorists? Why should we offer equipment manufacturers any more exalted status in this discussion than this forum generally provides to physicians and DME's? The manufacturers have made it clear that their customers are not patients and the new M-series machines underscores that point.

So what's my point? The epiphany, really ...

The discussion seems stalled, at a veritable stalemate, unable to move beyond those few points substantiated with concrete data from the manufacturers. Paradoxically, that makes it an oddity among cpaptalk discussions.

Regards,
Bill (wondering also if he missed the explanations regarding cork point 2 ...)

NightHawkeye wrote:Sure, he could point to a Cheyne-Stokes machine and proclaim it has a wonderful algorithm, but is that algorithm reality based or based on a poorly constructed data gathering experiment conducted by theorists to share with other theorists?

Think -- clinical trials.

rested gal wrote:Think -- clinical trials.

LOL. I know ya didn't mean to, but thank you for underscoring my point, RG.

Regards,
Bill

Bill, you have every right to think an entire branch of science is either absolutely clueless or nearly 100% conspiracy-unified---while two ordinary guys on a message board zeroed in on a much better explanation with "stuck-cork" theory.

More power to ya!

NightHawkeye wrote:

rested gal wrote:Think -- clinical trials.

LOL. I know ya didn't mean to, but thank you for underscoring my point, RG.

Regards,
Bill

Not quite...

Here was your point (emphasis added by me):

NightHawkeye wrote:On the one hand we hold up those few rare and valuable tidbits of data the equipment manufacturers have made public as if they contain fundamental truths, as if the company has tons of supporting data hidden away to justify the machine behavior. Maybe they do. Maybe they don't. I'm inclined toward believing the latter, but that's just my opinion. I'm sure they know a lot about blowers and pneumotach sensors, but I haven't seen anything that convinced me they really know much about apnea?

Well, that's your opinion.

Of course the design of an xpap machine is going to start with theory. Theory that at that time reflects what is known, or thought to be known, in the medical community about sleep disordered breathing.

You sound like you think the manufacturers' theorists and designers don't "really know much about apnea." I think they do. What they know is an ongoing, evolving, learning experience -- as it is in EVERY field of medicine. And in everyday life, for that matter.

You say you haven't seen anything that convinced you "they really know much about apnea." I think the evolution of machines all the way from Dr. Sullivan's reverse vacuum cleaner motor to today's adaptive servo ventilators is very good evidence that "they" really do know quite a lot about apnea.

For one thing, they've known all along that the throat is not a bottle and the tongue is neither a cork nor an egg.

-SWS wrote:Bill, you have every right to think an entire branch of science is either absolutely clueless

Your summary is an exaggeration of what I said, to be sure, but not totally off-target either. With the bull's eye worth 10 points, I'd give the summary two points.

-SWS wrote: ... or nearly 100% conspiracy-unified

I never said any such thing. Didn't imply it, either.

ozij wrote:Which brings up a further thought
Is the worst NR number on a Respironics just 1/8 of the total? How are the events in the preceding sequence counted? are they called apneas, or are they reported as NR retroactively?

O.

Ozij touched on some things I've been wondering about for a long time. And that is.....how do the "events" that are detected and recorded by the various machines (and the software) ACTUALLY compare to what would be seen in the sleep lab?

Since these machines are based on air flow, and have to read a "pattern" of events before it decides to act......how many of those events would be scored by the equipment in the sleep labs?

Did I actually have four or six hypopneas last night?......or was it just the two that showed up on the Encore report?

Also:
Do my machines when set in straight-pressure mode (CPAP) report the NON-APAP (snores, hypopneas and apneas) events the same as the APAP machine? (since it doesn't need to respond to those and more types of events)

"SAG" (Dave)......are you reading this thread?


Den

NightHawkeye wrote:

-SWS wrote:Bill, you have every right to think an entire branch of science is either absolutely clueless

Your summary is an exaggeration of what I said, to be sure, but not totally off-target either. With the bull's eye worth 10 points, I'd give the summary two points.

-SWS wrote: ... or nearly 100% conspiracy-unified

I never said any such thing. Didn't imply it, either.

Glad to hear that, Bill. Because that's exactly the way I completely misinterpreted your statement.

Theorists aren't so bad. You are one in this thread. The difference between our theorizing here and real-world theorizing is that real-world theorizing is bound by brutal peer-review and the rest of the brutal scientific method.

Everyone here and there (i.e. that branch of science in the real world) seems to agree there are plenty of outstanding SDB problems to solve.

rested gal wrote:For one thing, they've known all along that the throat is not a bottle and the tongue is neither a cork nor an egg.

And therein you illustrate with high precision the batteline in this discussion - an entrenched inability to move beyond points provided for illustrative purposes.

Should I apologize for debunking your long-espoused theory about how Respironics APAP's zap apneas when they occur, with solid evidence from the manufacturer, I might add.

Regards,
Bill

I can take a speculative crack at some of those, Den:

Wulfman wrote: Ozij touched on some things I've been wondering about for a long time. And that is.....how do the "events" that are detected and recorded by the various machines (and the software) ACTUALLY compare to what would be seen in the sleep lab?

I think the APAP machines will try to score everything they see. The results should be different than the PSG for two reasons in my opinion: 1) event scoring criteria is unfortunately not universal, and 2) a single APAP data channel truly never will score, on whole, anywhere nearly as well as a PSG with much better equipment.

That, of course, says nothing of other relevant factors such as why some people can't sleep during PSGs to be accurately tested. Or the fact that many nights of inferior data can sometimes be much better than a single night of superior data toward detecting variability and trends in general. Just my opinion.

Wulfman wrote: Since these machines are based on air flow, and have to read a "pattern" of events before it decides to act......how many of those events would be scored by the equipment in the sleep labs?

The precursors that are bona fide sleep events should always get scored by all manufacturers IMO. The precursors that are simply subtle hints, but not bona fide sleep events, should not get scored.

Wulfman wrote:Did I actually have four or six hypopneas last night?......or was it just the two that showed up on the Encore report?

When Respironics takes a pass on the first of each pair of hypopneas, even that first hypopnea is scored for exactly what it is: a hypopnea. The other manufacturers are supposedly scoring any and all detected events despite PAP therapy. The following morning we see a residual or "treated" score when we look through our reports.

Wulfman wrote: Do my machines when set in straight-pressure mode (CPAP) report the NON-APAP (snores, hypopneas and apneas) events the same as the APAP machine? (since it doesn't need to respond to those and more types of events)

I think in all cases the machines are bound to score any and all events that come down the pipe, despite treatment. Ideally they are scoring far fewer events than no treatment at all. Again, I offer nothing more than my own non-expert interpretive opinion.