EPR: just a comfort feature or affects AHI

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

So where does the pressure drop come from?

Any thoughts on Ozij's question?

FOT pulsations occur 4 seconds after exhalation toward apnea differentiation. The EPR decision to suspend takes longer:
1) if the patient’s breathing drops 75% below the baseline for 10 seconds or more, or
2) if exhalation lasts 15 seconds or longer

Note the first of those two EPR-suspension criteria allows for FOT to occur immediately after hypopneas and hence while EPR is already suspended. So FOT can occur at the prescribed CPAP pressure as well as at the lower EPR pressure.

SWS apparently has mind-reading capabilities. I was posting a question about what pressure FOT operates at and boom. There's my answer!

Well kind of. Would I be correct to think, then, that FOT can occur at any pressure between min - EPR and max in auto mode?

BernieRay wrote: Would I be correct to think, then, that FOT can occur at any pressure between min - EPR and max in auto mode?

That's my take as well.

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?

jnk wrote:"It differentiates closed-airway from open-airway, which is actually much more relevant to moment-to-moment treatment-pressure decisions for an APAP."

Agreed. IMO it would have been nice if Resmed had also published genuine central-apnea detection sensitivity/specificity/accuracy scores for their Central Sleep Apnea Detection (CSAD) method. Instead, the above superb scores simply relate to whether the airway was really open after all. Open-airway detection is an imperfect proxy for central-apnea detection as scored by PSG.

And I also agree those superb scores at least support/validate S9 pressure increases---which is the intended purpose of Resmed's CSAD feature.

-SWS wrote:

BernieRay wrote: Would I be correct to think, then, that FOT can occur at any pressure between min - EPR and max in auto mode?

That's my take as well.

Yep, i just confirmed FOT at several points between my range of 10-13. I rarely have any events at sleep onset, though, so I didn't find any when EPR clearly was in effect (7-10 range). When I first mask up and go to sleep is the only time my pressure is ever below 10.

Oh, one other thought. I have never seen fluctuations in the pressure graph to indicate EPR activity. I wonder if pressure changes due to EPR are ignored as far as that graph is concerned. If that's true, we may not have a way to deduce it's activity nor effect using the data collected by the S9.

BernieRay wrote: I have never seen fluctuations in the pressure graph to indicate EPR activity. I wonder if pressure changes due to EPR are ignored as far as that graph is concerned.

I agree...

While running mine at 10cm w/ EPR=3, for instance, my pressure graph stays pegged at 10cm--- despite a 10-second resolution on the graph.

You can see here drops in the pressure graph due to EPR:

http://www.apneasupport.org/post-4953.html

I have to agree with Bernie Ray. Due to severe jaw drop and mouthleaks I was forced to switch from the Swift FX nasal pillow to a Full Face mask. My DME did not have the HYBRID that is supposed to be a good choice for mouth breathers so I picked up a Quattro FX.

I just used my new Quattro FX for the 2nd night and on night one I had the EPR off and a pressure setting of 9. Like Bernie Ray ....I felt like I was breathing against the machine. In fact, it was so very uncomfortable to not be able to fully exhale. It felt like I was short of breath. I ended up falling asaleep but waking up 3 hours later and had to take it off. On night two, I set the EPR to 3 and it was so much easier to exhale and I slept through the night.

I also feel like others have posted, that it is best to loosen the FX mask as much as possible so as not to get leakage and let it "float" on your face. For some reason with the Quattro FX , the more I tightened it up the more difficult it was to breathe out and exhale.

Will have to see how things go over the next few weeks.

avi123 wrote:You can see here drops in the pressure graph due to EPR:

http://www.apneasupport.org/post-4953.html

Good link, AVI. You probably noticed NotMuffy had linked to that same post and graphs earlier in the current thread:
viewtopic.php?f=1&t=61788&st=0&sk=t&sd= ... 15#p579206

The author of that older post and those NPSG graphs, sleepydave, is no other than our knowledgeable poster, NotMuffy. Surprise!

wally13 wrote: Will have to see how things go over the next few weeks.

Good luck!

jnk wrote:

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

So where does the pressure drop come from?

Any thoughts on Ozij's question?

Each of those points need to be confirmed.

For instance, does EPR, in fact, suspend when FOT is running a scout?

Looking at NotMuffy's patient flow graph above:
-Exhalation ends a little after t=7 seconds
-FOT pulsation or "FOT scout" begins in the flow signal a little after t=11 seconds (4 seconds after exhalation according to Resmed spec)
-FOT pulsation continues right up until around t=29 seconds---which is the very peak of that first inhalation immediately after the above apnea

Now looking at NotMuffy's mask pressure graph above:
-EPR is in effect when the apnea begins
-EPR stays in effect the duration of the apnea
-Therefore EPR does not suspend in the middle of a detected apnea

Thanks, NotMuffy and ozij!

And a big thank you to you, -SWS, NotMuffy and jnk.

Next question:
NofMuffy, did you see EPR suspend at all on the S9?
And - does it suspend when an apnea is tagged as open airway?

And some comments:
I can's see images on imageshack, I get this instead:

http://imageshack.us/img/blocked_login.jpg


I don't think I would have been able to raise my pressure to where it is now (9.2) if it were not for the comfort of EPR.

-SWS wrote:Now looking at NotMuffy's mask pressure graph above:
-EPR is in effect when the apnea begins
-EPR stays in effect the duration of the apnea
-Therefore EPR does not suspend in the middle of a detected apnea

The question of how would the machine know that an apnea (as distinct from something else, possibly undefined) was in progress, purely from data that can be determined from the air circuit, would appear to be germane here?

If the machine was unable to definitely score an apnea, then it would have no cause to cease EPR.

Did the machine formally score an event, and if so what class of event did it score it as?

Cheers,

Bill

Here ya go, ozij.

This is the graph that appears above in NotMuffy's post where he said --

"For instance, does EPR, in fact, suspend when FOT is running a scout?"