Need Resmed education

robertmarilyn · Post by **robertmarilyn** » Sun May 10, 2009 7:22 pm

dsm wrote:SWS
Thanks for that, makes sense, but, you didn't mention flattening & that is where I understand A10 will raise pressure if flattening is showing a repeated restriction that doesn't score as Hyp or Apnea. Resmed makes a big issue of monitoring the flattening & indexing it.
DSM

This is probably the night that -SWS is talking about (I have more examples of other nights):

-SWS · Post by **-SWS** » Sun May 10, 2009 7:24 pm

Doug, "flattening" is the criterion or term that Resmed uses to signal-detect "flow limitation"---and degree of flattening determines FL severity.

What is flattening?

ResMedSimon answers: When using a mathematical representation of the shape of the breath (flow time curve) to indicate the state of the upper airway, a "round" shape denotes an open patent airway while a "flattened" shape indicates a flow limited airway.

http://www.talkaboutsleep.com/sleep-dis ... itchat.htm

I would add that wave shape flattening is also the main way that Respironics and PB/Tyco each detect flow limitation as well. Essentially an adequately "flattened" flow signal amounts to scored "flow limitation" for all three manufacturers. But they each have unique, patented mathematical signal-processing methods to recognize those "flattened" flow signals that score as "flow limitation".

Now if you index the severity of that flattening, as Resmed does, then you have a great way of algorithmically ascertaining severity of that slight "flow limited" closure. So Resmed will respond uniquely, according to just how flat or not-so-flat any given "flow limitation" happens to be. Respironics and PB/Tyco each have some nifty flow-limitation signal processing detection methods and pressure responses as well IMHO. They each also have their share of patients for whom their proprietary algorithms are not well suited.

carbonman · Post by **carbonman** » Sun May 10, 2009 7:34 pm

-SWS wrote: Carbonman has the advantage of looking at his historical data to see exactly which residual signals sit above 12.5 cm in his case: A, H, FL, snore. Note that Respironics directly works with all four signal types above 10 cm---while Resmed works with two of those signal types above 10 cm (FL and snore) and three of those signal types below 10 cm (FL, snore, and A).

This is a great discussion. Thanks everyone.
Now, if I understand this, the Resmed will not respond to the events that
are displayed in these reports. Correct?

These are not typical nights, but most of my events are A or H.

dsm · Post by **dsm** » Sun May 10, 2009 7:41 pm

SWS

Thanks - that summarizes the points pretty well & I can see that how each manufacturer deals with the curve shape varies. I have always read Resmed as placing a lot of emphasis on it.

I also have assumed that there are two approaches, one based on flow & the other on shape & as already covered Resmed focus on shape. I gather that the Respironics algorithm adds the technique of probing if it thinks the flow is a problem, i.e. commences the 'chair' steps of lifting pressure sensing what that does then having another go & sensing what that does before dropping back to the starting point.

Thus far I have it as
- Resmed focuses on a fine analysis of the flow curve & indexes the shape - the index is used for further response action (raise pressure or lower it)
- Respironics focuses on flow analysis & probing when it detects flow issues that may be related to OSA vs CA

Going over these differences helps (certainly me) better understand the variance between the two main algorithmic approaches.

Tks DSM

dsm · Post by **dsm** » Sun May 10, 2009 7:49 pm

CarbonMan

There is a complexity in the statement 'not respond to' as there are events that the algorithm has already responded to & these were either treated or the events moved outside the boundary the algorithm will treat.

Resmed A10 will raise pressure if it sees the typical flattening taking place that leads to an apnea. If it doesn't it takes the safe path that without the pre-cursor flattening, the resulting event is more likely to be central in nature.

I believe the heart of all Auto treatment is pre-emption. I don't know of any Auto that actually raises or lowers pressure when a no-flow apnea is actively in progress (including in some cases, hypopneas). What I read says they wait for the event to pass & go back to trying to pre-empt the next event.

SWS has pointed out a feature of the Respironics that counts events in a time window & reacts differently based on that count. (flow based analysis).

The Resmed doesn't do the counting (AFAICT) but does track the flattening & remembers it within a time window.

DSM

-SWS · Post by **-SWS** » Sun May 10, 2009 8:11 pm

Doug, as it turns out, all three manufacturers focus very heavily on wave shape toward detecting "flow limitation". While Respironics and PB/Tyco issue a single pressure response for any and all detected FL,.... Resmed issues a unique/commensurate pressure response, depending on just how flat or severe that detected "FL" happens to be.

Carbonman, those are really good graphs to discuss IMHO. So we can discuss them all if you'd like. I'll throw in my two cents about that first graph before calling it a night. Then other posters can add their own comments----even disagree if they happen to have a different take. So here's that first graph again:

First Hour-and-a-Half- Essentially identical to CPAP at 12.5 cm. You can see the algorithm searching upward for any possible improvement in patient flow, but always returning to 12.5 cm pressure for lack of detected improvement. Resmed would not have trolled, but the trolling is not beneficial "treatment". It's just a pressure-search test.

First Three Isolated H Events- Respironics won't respond to single-occurrence H or single occurrence A. Resmed would not have responded to those either.

First Three FL Events- Resmed just may have responded earlier, thereby preventing that follow-up OA cluster by using preemptively-elevated pressure.

That Follow Up OA Cluster- Respironics hikes the pressure, but too late to prevent the OA cluster. That short pressure hike is pretty much the only thing that night---besides pressure-search tests----that distinguishes your night from CPAP at 12.5 cm. And that short pressure hike may not have truly accomplished anything---other than closing the barn door right after the OA animals escaped.

I'm definitely not bashing Respironics or Resmed. I'm just explaining what I think happened on that particular chart. Goodnight all!

dsm · Post by **dsm** » Sun May 10, 2009 8:30 pm

SWS

Good and simple explanation - works for me

Tks

DSM

dsm · Post by **dsm** » Sun May 10, 2009 10:09 pm

There is a side issue to the way the vendors respond to curve & flow - that is that all the Auto patents I have read emphasize the importance of not raising pressure on an in-flight no-flow apnea (at least an apnea as identified in most brands). I can't recall if this response is the same for hypopneas, i.e. if a hypopnea is happening then raise pressure while it is happening. I think that all brands are much the same in this respect, and that is 'NO PRESSURE ADJUSTMENT' while an apnea or hypopnea is active.

Again, the design purpose of an Auto is to preempt apneas & hypopneas. The closer the current operating pressure is to where a hypop/apnea might occur, the better the chances of premption as the machine will cover short pressure gaps much quicker than big ones - which in turn is why the wise heads among us say how dumb it is for RTs to send someone home who was titrated at say 13 CMs, with their Auto low pressure set to 4.

Most Autos will raise pressure by about 2 CMs (up to 3 CMs max) over 2-3 minutes then pause (for up to 3 mins) then start sampling again. If a machine has to shift from say 9 CMs to 13 or 14 CMs to preempt an apnea, there is a fair likelihood the apnea will occur 1st & the machine arrive late to the party. That is sometimes why we see AI events when we expect the Auto to have prevented them.

Part of the concern over changing pressure when an event is in progress, is that Autos do a 'best guess' as to the nature of the event between it being OSA & CA. OSA events will usually be preceeded by FLs (with distinct flattening). The main concern (as argued by Resmed) is not to increase pressure if the event looks like it is central as doing so may increase both the severity and number of such events. A10 seems to be as intent on preventing complex apnea occurring as it is on preempting OSA events. Respironics approach their analysis (clearly by including flattening analysis as SWS has said, and as is explained in their patents) by both probing (via pressure steps over a few minutes) and also analyzing the flow curve of FLs. It seems that Resmed argue that they have developed sophisticated flattening analysis algorithms & don't need to do the probing (they certainly don't do it).

From all I have learned I am less worried about (for me) pressure increases occurring if hypopneas are in-flight & certainly not at all if typical FLs are in-flight. Having used ASV machines for over 12 months I can see on a nightly basis that both brands will ramp pressure as high as 20 CMs 12-16 times a night & I would say that after 12 months, my therapy is the most effective & satisfying it has ever been. So while at one time I would have believed that rapid pressure increases are a bad idea, my two ASVs seem to prove that wrong repeatedly. I know that ASVs are intended to do that rapid pressure raising to 'normalize' irregular breathing but both Resmed and Respironics open the door to OSA folk when they began stating their machines will effectively address complex apnea and their titration process starts with epap setting to eliminate core OSA. Now, before the 1st sentence in this current paragraph triggers any reaction, I want to qualify it by stating it is imperative to have epap set correctly and also that my remark may not really apply to OSA sufferers whose OSA is heavily obesity or neck structure (short thick) based. Certainly for my OSA, repeated rapid pressure increases do not appear to be any sort of issue. Traditional thinking (IIRC) has always been that rapid pressure increases would (could) trigger arousals & disrupt sleep, but, I think those who argue in favor of big gaps (i.e. 6-8 CMs) between epap & ipap don't think so any more & certainly ASVs will jump as much as 10 CMs within 3 breaths (they do limit max pressure increase within 1 breath to approx 3 CMs).

#2 Just to restate the significance of what I am saying, if an ASV is limited to say 20 CMs for Ipap max, and say (as in my case) epap is at 10 CMs, then for the short spell max ipap is active, my epap to ipap gap is 10 CMs - what I once would have called ridiculous, but, it happens constantly typically 12-16 times per night) with my ASVs and I get what I consider is great sleep.

DSM

carbonman · Post by **carbonman** » Mon May 11, 2009 6:08 am

-SWS wrote:Carbonman, those are really good graphs to discuss IMHO. So we can discuss them all if you'd like.

SWS, really appreciate your analysis.
I would very much like to hear your thoughts on the other graphs.

-SWS wrote: And that short pressure hike may not have truly accomplished anything---other than closing the barn door right after the OA animals escape.

Even though it's too late, doesn't the pressure increase "shorten" and
lessen the effect of the oxygen loss and brain response due to the OA???
Decreasing the "avg. time in apnea".

-SWS · Post by **-SWS** » Mon May 11, 2009 8:18 am

carbonman wrote:
-SWS wrote: And that short pressure hike may not have truly accomplished anything---other than closing the barn door right after the OA animals escape.
Even though it's too late, doesn't the pressure increase "shorten" and
lessen the effect of the oxygen loss and brain response due to the OA???
Decreasing the "avg. time in apnea".

That's a definite possibility for the second and third apneas embedded in that sequence of pressure steps, carbonman. There are multiple physiologic scenarios buried in that ambiguous sequence of tick marks.

So before moving onto the next chart, let's make it a point to discuss that cluster in depth. Some of those considerations will also be relevant for that chart showing the NR score. So more comments from me about your OA cluster and that preceding FL cluster later...

Mar, thanks for posting that! That chart----with abundant A and H above 10 cm---and absolutely no APAP pressure response, demonstrates my earlier statement:

In discussing which signal types get pressure responses below and above 10 cm I wrote:That situation is undoubtedly why Resmed is forthright, to this day, in describing to clinicians exactly which signals do and do not receive direct pressure responses:
Below 10cm- FL, snore, and A
Above 10cm- FL and snore only

I would add that "flattening" is specifically severity-indexed "flow limitation" according to Resmed. Respironics and PB/Tyco each maintain their equivalent statistical index for FL as well. So their algorithms are also very preoccupied with their own proprietary wave shape analysis and complex FL indices.

robertmarilyn · Post by **robertmarilyn** » Mon May 11, 2009 10:26 am

-SWS wrote: Mar, thanks for posting that! That chart----with abundant A and H above 10 cm---and absolutely no APAP pressure response, demonstrates my earlier statement:
In discussing which signal types get pressure responses below and above 10 cm I wrote:That situation is undoubtedly why Resmed is forthright, to this day, in describing to clinicians exactly which signals do and do not receive direct pressure responses:
Below 10cm- FL, snore, and A
Above 10cm- FL and snore only
I would add that "flattening" is specifically severity-indexed "flow limitation" according to Resmed. Respironics and PB/Tyco each maintain their equivalent statistical index for FL as well. So their algorithms are also very preoccupied with their own proprietary wave shape analysis and complex FL indices.

You're welcome If I have to have the misfortune of being the poster child of such things, it's at least nice to know my charts can be useful I have more of the same from last night
mar

carbonman · Post by **carbonman** » Mon May 11, 2009 10:48 am

-SWS wrote: So before moving onto the next chart, let's make it a point to discuss that cluster in depth. Some of those considerations will also be relevant for that chart showing the NR score. So more comments from me about your OA cluster and that preceding FL cluster later...

..ah, roger that Houston....we're...ah...standing by.....

jnk · Post by **jnk** » Mon May 11, 2009 12:06 pm

This is an interesting discussion. But it raises questions in my mind.

I wonder if using one brand's estimates of events with its definitions, detections, and reactions are easily applicable to how another brand might, or might not, have defined, detected, and reacted. Don't different brands define, detect, and react to precursors differently? If so, isn't it very difficult to guess what different brands would do in different situations based on the detections, definitions, and reactions of one brand for one person on one night with no PSG data to know what really happened, let alone what would have happened?

For example, isn't it impossible to know whether another brand would have been riding at a higher baseline pressure to start with, in reaction to it's detection and reaction to precursors, and would thus have prevented all the events in the chart, or if it would have been riding at a lower pressure based on its interpretation of precursors and then had many more events to contend with, or ignore, as the case may be? And wouldn't the question of whether either brand's estimates of events would accurately report what wasn't prevented be a further complicating factor?

Are there many well-documented cases of specific patients who were served well by one auto machine and not served well by another machine? And wouldn't applying that further than that one patient then require a very costly study attempting to get a representative cross-section of population and then weeks inside a fully-equipped PSG lab to make meaningful comparisons based on a standard that would lead to useful conclusions?

Doesn't the AASM consider UPPP to be a contraindication for using an auto at all? If so, is Mar's example applicable to the discussion at hand other than as a graphical demonstration of someone who may not be well served by any brand's auto?

This is very interesting, and I look forward to further discussion on it.

carbonman · Post by **carbonman** » Mon May 11, 2009 1:34 pm

jnk wrote:This is an interesting discussion. But it raises questions in my mind.

Are there many well-documented cases of specific patients who were served well by one auto machine and not served well by another machine? And wouldn't applying that further than that one patient then require a very costly study attempting to get a representative cross-section of population and then weeks inside a fully-equipped PSG lab to make meaningful comparisons based on a standard that would lead to useful conclusions?

See, now this has been on my mind all am.
Provided these questions you pose could be answered w/meaningful data,
are we, cpap users, being perscribed/given/forced to take machines,
for all the wrong reasons.

The sleep labs/docs/DME are passing out machines to make money.
It blows air up their nose, cha-ching, good to go.

We, cpap users, are considering machines because:
they don't have bricks,
we think they are more quiet,
have a bigger HH tank,
are easier to travel with
or we like the foot print,
not because their specific, defined
mode of operation fits our particular event needs,
as diagnosed from our sleep study results.

I am thinking about trying a different machine because I'm:
curious, like a cat.....just want to know if it
will be easier to breath,
promote better therapy,
help me feel better than I already do.
.....see if it is that much better without a brick.

I am enjoying this discussion, but the bottom line maybe,
I have to try it before I will be satisfied, one way or the other.

...ah....still standing by, Houston.

robertmarilyn · Post by **robertmarilyn** » Mon May 11, 2009 2:44 pm

carbonman wrote: See, now this has been on my mind all am.
Provided these questions you pose could be answered w/meaningful data,
are we, cpap users, being perscribed/given/forced to take machines,
for all the wrong reasons.
The sleep labs/docs/DME are passing out machines to make money.
It blows air up their nose, cha-ching, good to go.

I think my first sleep doctor/dme (I think he own/runs the dme show connected with his practice) prescribes ResMeds only...as far as I know, in fact, he only prescribes the Resmed Escape II and the Resmed Autoset II. From what I could tell, he had no intention of prescribing me anything else, no matter what the data said. What I would like to own is a machine that works for ME. I seem to have a bunch of issues, including having had an UPPP, and a host of other 'stuff'. I have a new sleep doctor now and will be having a another titration test (more than for just titration...she wants to get a picture of everything that is going on with me) and a MLST.

We, cpap users, are considering machines because:
they don't have bricks,
we think they are more quiet,
have a bigger HH tank,
are easier to travel with
or we like the foot print,
not because their specific, defined
mode of operation fits our particular event needs,
as diagnosed from our sleep study results.

I don't care about any of the above except what I need for my specific, defined mode of operation that fits my particular event needs, as diagnosed from my sleep study results.

I was handed the Escape II CPAP, set on a pressure of 14 with no epr, by my former sleep doctor's dme and that was it. No mention of ever being seen by the sleep doctor (after two sleep tests even) and no mention of any kind of follow-up. I initiated 3 office visits with the sleep doctor and exchanged the Escape for the Autoset. That was as far as I was ever going to get from what I could see. The doctor did decide to do another sleep test and MLST and had me get pulmonary function tests and chest xrays (he is also a pulmonary doctor) but he said my sleep test was going to be done with my autoset II...he also was not going to release any more info to me or my referring doctor than a three page summary report.

I decided, based on a lot of things, including the above, that I wanted to see a new doctor. I feel like I am going to get the help I need with this new doctor, whatever that help may be.

I am thinking about trying a different machine because I'm:
curious, like a cat.....just want to know if it
will be easier to breath,
promote better therapy,
help me feel better than I already do.
.....see if it is that much better without a brick.

I am enjoying this discussion, but the bottom line maybe,
I have to try it before I will be satisfied, one way or the other.

I'd love to have the liberty of picking a machine based on a lot of things but I know I need to find the machine/machines that will work with my body. It can't be based on the only brand a doctor will dispense and it can't be based on aesthetics.

I'm enjoying this discussion also. And there is nothing wrong in owning several machines if you can afford them. It is understandable that some of us would like to try different ones out and collect a variety of masks and other equipment. And the more folks like you learn about the various machines the more help you may be able to give the rest of us. Rested gal sure does have a very good grasp of how different machines are made to handle our various problems. Someday, if we pin down exactly what is going on with me, we may be able to use that knowledge to filter out certain machines that may or may not work with my body. But first I would like to find the best machine for my condition (if possible) and then I might look at others as a second choice. For now I own the Redmed Autoset II no matter how it works with my body. Hopefully now that I have a doctor that wants to get a thorough sleep and day study done and wants make decisions based on those results, I will be able to find what machine will work the best for me.

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