Isn't Resmed's Expiratory Pressure Relief really Inspiratory Pressure Support??

[Shin Ryoku]

Second, I want clarify something here.  I'm not telling you my opinion or "expert opinions."  I'm telling you what the American Academy of Sleep Medicine and the American Academy of Sleep Technologists believe.  The publications that I referenced are the titration protocols that those organizations have published.  So, this isn't my "expert opinion," it is evidence-based science.

You misunderstood me.  I never suggested you might be telling me your opinion.

When guidelines and protocols are published by professional societies like AASM, it is common for each recommendation to be accompanied by a grade based on strength of evidence.  For example, these:




The AASM guidelines use these:




Also note this paragraph from the end of the AASM guidelines "Methods" section:

It is important to note that the recommendations published in this report are not practice parameters, since the majority of these recommendations do not achieve the evidence level of typical practice parameters. Instead, all recommendations were developed using the consensus process and the evidence grading was used only to indicate the level of evidence available to support the recommendations. AASM levels of recommendations (Table 2) are indicated in parentheses after recommendations that are based on published practice parameters; those recommendations that were not based on published parameters are labeled as “(Consensus).”

In other words, when there was a lack of sufficient evidence from published data, they took a vote amongst experts to provide a "Consensus", aka "expert opinion".


Now look at the actual recommendations and their strength of evidence from the AASM guidelines:



With regards to titrating IPAP and EPAP to prevent apnea events (4.3.2.2), they specify that this was based on Consensus (expert opinion) and do not assign a Level of Recommendation.  The only rationale provided is not that the timing of the pressure increase needed is different for apneas vs other events, but rather that it takes less pressure to prevent apneas than it takes to prevent other events.

They cite one level II study and one level V study that used increases in both IPAP and EPAP to eliminate apneas.  They do not make any claim that, for a given IPAP, further increases in EPAP have no effect on OAs, nor are there data in the cited studies to support such a claim.

With regards to further increases in IPAP based on hypopneas, RERAs, and/or snoring (4.3.2.3-5), they do not cite any studies at all.  Those recommendations are stated to be based on consensus agreement (expert opinion) only.


The bottom line is that there is a dearth of high quality scientific data to support these guidelines.  So much so that they had to explicitly state at the outset that these are not practice parameters.  And again, there is nothing in these guidelines which explicitly states that an increasing pressure during inspiration (transition from IPAP to EPAP) has no effect on OAs.  As far as I can tell, there are no high quality studies addressing that question one way or another.

[S.L. Ping Beauty]

I cannot add anything substantial to this thread and am only commenting to say thank you to all who are participating in the discussion.  

In reading the comments and replies I probably have learned more from this one thread than any other in the year that I have been here.  If there is a term or word that I do not understand I have to look it up and then the gist of what is being said is more fully understood.... it is forcing me to learn and understand.

A lot of what is being discussed here is WAY over my head, but in re-reading it I am picking up more and more little snippets of understanding.

Carry on.

[Reznik]

You misunderstood me.  I never suggested you might be telling me your opinion.

Hi Shin,

Thanks again for responding, and for your contribution.

After I wrote my last message, I read it and was unhappy with the tone of it for a variety of reasons.  I wrote it right before I left on an errand.  When I got back, I re-wrote much of it, but apparently the 90 minute "edit window" allowed by the board expired before I clicked "save", and so the original version become the final version.  I totally get how you could view my message as a bit reactionary, and I apologize for that.  That was not my intention, and had I edited the message in time, it wouldn't have been. 

I both appreciate and agree entirely with your latest message.  Some of what's in the guidelines is consensus based and some is evidence based.  Some of what the machines do is based upon the guidelines, and some is cutting edge speculation by ResMed and Respironics about what they think works.  Time will tell...

Going back to my original point, ResMed's implementation of EPR should really be called inspiratory pressure support, or perhaps "mini-VPAP."  

Rather, than offering pressure relief during expiration only, what it actually does is change the operation of the machine so that the pressure on the display is only delivered in the middle of inspiration (IPAP), and the rest of the time, i.e. during expirations, transitions, and apneas, the machine delivers an EPAP that is computed by taking the displayed pressure and subtracting the EPR level.

Stated another way, I believe that the pressures delivered at the mask by a ResMed AirSense 10 machine with EPR enabled and set to 1, 2, or 3 are indistinguishable from a ResMed AirCurve 10 machine in S mode (with Easy-Breathe enabled) or in VAUTO Mode, as long as the Pressure Support is set to 1.0, 2.0, or 3.0.

[Reznik]

I cannot add anything substantial to this thread and am only commenting to say thank you to all who are participating in the discussion.  

In reading the comments and replies I probably have learned more from this one thread than any other in the year that I have been here.  If there is a term or word that I do not understand I have to look it up and then the gist of what is being said is more fully understood.... it is forcing me to learn and understand.

A lot of what is being discussed here is WAY over my head, but in re-reading it I am picking up more and more little snippets of understanding.

Carry on.

Hi S.L.,

Thank you very much for this message.  One of the reasons why I'm having this discussion is because I'm considering writing a FAQ/Wiki Article that discusses the various machines, what they do, and the theory behind what they do.  Obviously, before I do that, I need to make absolutely sure that I really understand what I'm reading.  That's why I started the discussion.  In the process, I've also learned a lot about what other people think about these issues, all of which I intend to include if I ever get around to writing something up! 

[yrnkrn]

ReznikStated another way, I believe that the pressures delivered at the mask by a ResMed AirSense 10 machine with EPR enabled and set to 1, 2, or 3 are indistinguishable from a ResMed AirCurve 10 machine in S mode (with Easy-Breathe enabled) or in VAUTO Mode, as long as the Pressure Support is set to 1.0, 2.0, or 3.0.

Having used both machines, this is correct, both look like this:

[Sleepster]

Once again, on the VAUTO machine, EPAP and IPAP are locked together.  If one goes up, the other goes up.  You cannot infer from that behavior whether the IPAP is dragging up the EPAP or the other way around.  

But what you can tell is that neither of them rises above the titrated pressure. So your claim that it's necessary to raise IPAP when raising PS has been demonstrated to be a false claim.

[Reznik]

Once again, on the VAUTO machine, EPAP and IPAP are locked together.  If one goes up, the other goes up.  You cannot infer from that behavior whether the IPAP is dragging up the EPAP or the other way around.  

But what you can tell is that neither of them rises above the titrated pressure. So your claim that it's necessary to raise IPAP when raising PS has been demonstrated to be a false claim.

By definition, pressure support is the difference between IPAP and EPAP.  So, to increase pressure support, you must either raise IPAP, or lower EPAP. In either case, on the VAUTO, EPAP and IPAP are locked together, and Pressure Support never changes unless you go into the clinician mode and change it manually.

The fact that neither EPAP nor IPAP raises above the titrated pressure is irrelevant to whether it is necessary to raise IPAP when raising PS.  And as I said (above), you can raise the pressure support either by raising IPAP or lowering EPAP.

But, I'm totally lost as to what any of this has to do with the topic of discussion.

[Shin Ryoku]

Stated another way, I believe that the pressures delivered at the mask by a ResMed AirSense 10 machine with EPR enabled and set to 1, 2, or 3 are indistinguishable from a ResMed AirCurve 10 machine in S mode (with Easy-Breathe enabled) or in VAUTO Mode, as long as the Pressure Support is set to 1.0, 2.0, or 3.0.

Agreed.

[Sleepster]

The fact that neither EPAP nor IPAP raises above the titrated pressure is irrelevant to whether it is necessary to raise IPAP when raising PS.  And as I said (above), you can raise the pressure support either by raising IPAP or lowering EPAP.

But, I'm totally lost as to what any of this has to do with the topic of discussion.

Then I guess I'm missing your entire point. I'm titrated at a pressure of 13 cm, and that pressure works for me in the sense that it gets my AHI below 5 while using a ResMed AirSense 10. After a few nights I decide to turn on EPR and set it to 3. I'm under the impression that your advice would be to raise the pressure to 16 cm to compensate.

What I'm telling you is that if I leave the pressure at 13 cm and turn EPR on to 3 I still get the same level of treatment I got before, so there is no need to raise the pressure to 16 cm.

[Reznik]

Then I guess I'm missing your entire point. I'm titrated at a pressure of 13 cm, and that pressure works for me in the sense that it gets my AHI below 5 while using a ResMed AirSense 10. After a few nights I decide to turn on EPR and set it to 3. I'm under the impression that your advice would be to raise the pressure to 16 cm to compensate.

What I'm telling you is that if I leave the pressure at 13 cm and turn EPR on to 3 I still get the same level of treatment I got before, so there is no need to raise the pressure to 16 cm.

Hi Sleepster,

Thank you for clarifying.  

Your profile indicates that you use an AirCurve 10 VAUTO with a maximum IPAP of 13.6 and a minimum EPAP of 5.2, and with a pressure support of 4.4.  That tells me that you have not been titrated to a CPAP of 13 cm.  Rather, you were titrated to an auto-adjusting bi-level with a minimum IPAP of 9.6, a maximum IPAP of 13.6, a minimum EPAP of 5.2, and a maximum EPAP of 9.2.  The machine starts out at I9.6/E5.2 and goes up and down based upon apneas, flow restrictions, etc., but will never go higher than I13.6/E9.2.

Using a ResMed Airsense 10 at 13 with EPR set to 3 should be roughly the equivalent of using your VAUTO near its maximum programmed EPAP and IPAP (IPAP 13.6 and EPAP 9.2).  Using an Airsense programmed in CPAP mode at 13.0 with EPR 3, the IPAP is 13 and EPAP is 10.  Given your actual maximum titration, I'm not surprised that using the ResMed AirSense 10 Autoset at 13 with EPR 3 works well.  It's closer to what you're titrated at then using the same machine at 13 with no EPR.  So, it should be better for you with EPR on than off.

Setting aside what's on your profile, if you actually were titrated to CPAP using an AirSense 10 Autoset at 13 with EPR Off, and then found that setting EPR to 3 was just as effective, I'd ask whether you've ever tried turning EPR off and setting your pressure at 10.  I'd expect that would be just as effective at controlling obstructive apneas as setting the machine at 13 with EPR set to 3.  It it didn't, then I'd suspect that you're doing better because you really need BiPAP at 13/10 (or close to it), as your profile indicates, and that whoever titrated you at CPAP 13.0 was wrong....

As a final thought, you could probably get roughly the same treatment from an AirSense 10 Autoset as you are getting with your AirCurve 10 VAUTO by setting the AirSense 10 to autoset mode, with the minimum pressure set to 8.2 and a maximum of 13.6.  That machine would start out at I8.2/E5.2 and then adjust based upon apneas, flow restrictions, etc., up to a maximum of I13.6/E10.6.  You wont get quite the same pressure support as with your AirCurve (3 instead of 4.4), but you've already indicated that you do just fine with 3 cm of EPR..

My statements above are all based upon my understanding of how the machines actually work.  Before you make any changes to any machine and use it, you should consult a trained medical professional.