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NotMuffy wrote: I believe the end result is that the ResMed central identification algorithm is flawlessly specific but horrid in it's sensitivity

Check out Resmed's interesting S9 Central Sleep Apnea Detection (CSAD) estimates:

CSAD Sensitivity Estimate=99%
CSAD Specificity Estimate=89%
CSAD Accuracy Estimate=95%
http://www.resmed.com/us/assets/documen ... -paper.pdf

jnk wrote:So shouldn't specificity and sensitivity be judged only on how well it does at determining the state of the airway and not the presence or absense of effort?

Resmed based their sensitivity/specificity estimates against the current gold-standard for central-apnea detection: PSG methodology.

Bear in mind those are manufacturer estimates and not yet validated/disputed after peer review...

Thanks for the info/discussion...

I guess it's moot in my case, at least for now; I met with my doctor and apparently have "failed" xpap treatment.

The news/discussion is still sinking in, and I'm not sure what I'll do next, though there's a couple options I'm considering.

-SWS wrote:

NotMuffy wrote: I believe the end result is that the ResMed central identification algorithm is flawlessly specific but horrid in it's sensitivity

Check out Resmed's interesting S9 Central Sleep Apnea Detection (CSAD) estimates:

CSAD Sensitivity Estimate=99%
CSAD Specificity Estimate=89%
CSAD Accuracy Estimate=95%
http://www.resmed.com/us/assets/documen ... -paper.pdf

EPR 3.0 cmH2O utilization seen in their study.

However, let's send 'em bandnuts' *.rlk file and let 'em average them in.

deleted, OT

avi123 wrote:the possibility of CPAPs to control the timing of responses that far.

I assume you mean APAPs. And I assume you assume that APAPs are designed mostly with the idea of attacking events as they happen. That is not my understanding.

"By measuring upper airway resistance . . . the algorithm can determine whether the apnea is associated with a closed or open airway and can determine whether it is appropriate to increase the pressure or to make no response. This is not quite the same as determining whether the apnea is central or obstructive. By definition, all obstructive apneas are associated with a closed upper airway, but some central apneas can be associated with a closed airway if the pressure is below the airway closing pressure. If the airway is closed during a central apnea the appropriate algorithmic response is to increase the therapeutic pressure."

http://www.resmed.com/us/assets/documen ... -paper.pdf

I read the part that I marked in red as describing a choice of whether or not to raise overall pressure for the purpose of preventing future apneas that night--not a choice of whether or not to attack the apnea that is in progress.

But I'm pretty new to this stuff, not like -SWS and NotMuffy who have been around long enough to know what they are talking about, even when they don't agree 100%. Many of us here on the board learn a lot when the two of them talk such things out between them.

jnk wrote: -SWS and NotMuffy who have been around long enough to know what they are talking about, even when they don't agree 100%.

Seems both of those silly characters doubt the above manufacturer estimates.

One thing I don't understand:
EPR suspends on apnea.
FOT happens during an apnea.

So where does the pressure drop come from?

-SWS wrote:

jnk wrote: -SWS and NotMuffy who have been around long enough to know what they are talking about, even when they don't agree 100%.

Seems both of those silly characters doubt the above manufacturer estimates.

Well, then, can you at least pretend to disagree just a little so that I can learn something, darnit?

When I used the EPR on Resmeds, I simply did not wake up feeling well rested. Even on my original Resmed which worked like a charm when EPR was disabled. I think its a useless feature unless you have something like sinus surgery or an ear ache or something. Then you might be better off with a wide open APAP IMO than with EPR.

I think EPR is a totally useless feature and I dont care what the software says or shows or the company literature says about EPR...it waters down your therapy. Straight air is best for most folks.

Eric

[quote="avi123"][quote="jnk"]
I question all these discussions about the possibility of CPAPs to control the timing of responses that far. The distance from the Flow Generator to the lungs is about 7'. So a response from the end of exhalation to a start of inhalation has to travel 14' in air to comply with the timing of movements, sounds to me as a bobe-meise. Even if you connect the parts with metal rods such as in a race car engine.

[quote]

Avi, I'm way out of my league here but I do love your reference to "bobe-meise". Loosely translated it means "old wives' tale".

A clue to the theoretical nature of the info from Resmed is this statement in their above report:

Flow was measured using the output
from the pneumotachograph of the device, which provides
a more sensitive and accurate measure of flow than measurement
of mask or nasal pressure.

It tells you that in their algorithm they trusted the pneumotachograph which is located inside the CPAP box for pressures and flows, rather than measuring the actual values (at least) in the mask.

Apparently, Resmed has problems measuring pressure in the mask even if they assume so as stated in their patents.

-SWS wrote: Seems both of those silly characters doubt the above manufacturer estimates.

I wonder if this choice helped the numbers look good?:

"Mixed apneas were classified as obstructive."

Does that mean that any apnea that allowed the airway to narrow got counted as an obstructive apnea, both by the machine and by the so-called PSG-ish verification?

Some clinics have historically relegated/scored mixed apneas as obstructive. These two points seemed to stand out when I read through the document:

Resmed CSAD document wrote: A total of 232 apneas were detected by polygraphy... There were an additional 53 events [Resmed CSAD] classified as unknown (excluded from analysis).

Resmed decided not to count a significant number of apneas their CSAD method couldn't make heads or tails of. An attended PSG would have ultimately scored those. Resmed couldn't figure them out, so they decided all CSAD "head scratchers" should NOT detract from their estimates of how accurately their method can detect central apneas.

Resmed CSAD document wrote: As mentioned above, closed airway centrals are grouped with obstructive apneas [by Resmed CSAD].

Attended PSG would have scored those closed-airway central apneas as central apneas. Resmed implicitly acknowledges this, but decides to count the discrepancy in favor of their own accuracy estimates instead. The end results are some AMAZINGLY good-looking accuracy numbers.

When my nephew was only 7 he used to just beat the dickens out of my entire family at miniature golf. But as it turns out it was due to his creative score keeping.

AVI123 wrote: A clue to the theoretical nature of the info from Resmed is this statement in their above report

I'll have to disagree. Rather it reads to me like a marketing document disguised as a technical document.

After 13 years on straight CPAP, I have found that EPR = 3 does help me. I no longer have the feeling of breathing against the machine, which is what it was designed for. With my old machine, I was consciously breathing against it until I feel asleep. With EPR, that is gone. I put the mask on, breathe normally, and I fall asleep faster.

I don't really care whether it impacted my AHI because I'm sleeping better and I feel better on most mornings. As long as that is true, the rest is just a curiosity...at best.

-SWS wrote:Some clinics have historically relegated/scored mixed apneas as obstructive. These two points seemed to stand out when I read through the document:

Resmed CSAD document wrote: A total of 232 apneas were detected by polygraphy... There were an additional 53 events [Resmed CSAD] classified as unknown (excluded from analysis).

Resmed decided not to count a significant number of apneas their CSAD method couldn't make heads or tails of. An attended PSG would have ultimately scored those. Resmed couldn't figure them out, so they decided all CSAD "head scratchers" should NOT detract from their estimates of how accurately their method can detect central apneas.

Resmed CSAD document wrote: As mentioned above, closed airway centrals are grouped with obstructive apneas [by Resmed CSAD].

Attended PSG would have scored those closed-airway central apneas as central apneas. Resmed implicitly acknowledges this, but decides to count the discrepancy in favor of their own accuracy estimates instead. The end results are some AMAZINGLY good-looking accuracy numbers.

When my nephew was only 7 he used to just beat the dickens out of my entire family at miniature golf. But as it turns out it was due to his creative score keeping.

AVI123 wrote: A clue to the theoretical nature of the info from Resmed is this statement in their above report

I'll have to disagree. Rather it reads to me like a marketing document disguised as a technical document.

Thank you very much for that, -SWS. That helps.

It must be tough on the copy boys to keep everyone happy. Every doc must ask: "So does it differentiate centrals from obstructives?" The long answer would probably be: "It differentiates closed-airway from open-airway, which is actually much more relevant to moment-to-moment treatment-pressure decisions for an APAP." But, for obvious marketing reasons, it is easier to just say "yes" and then make a footnote of sorts to cover yourself technically.

Ya never market to the smartest guys in the room. Ya market to the richest guys in the room.