Interpretation of EPR on Resmed machines

[EddyDee]

Resmed describes EPR as a comfort feature. If your basic pressure is 10 cm H2O, you can set EPR to reduce EPAP to 9, 8 or 7 cm H2O when the machine detects an exhale, so you don't have to push so much to breathe out. As it's a comfort feature, people seem to often recommend not using it after you got used to CPAP.

But from what I've seen round here there is an alternative interpretation.
EPR allows you effectively boost your inhale pressure. So if your basic pressure is 10 cm H2O, you would set your min pressure to 11, 12 or 13 cm H2O, and set EPR to 1, 2, or 3 accordingly. This gives you a minimum of 10 cm H2O all the time, but boosts IPAP when the machine detects an inhale.

Is this just a semantic difference? Are there guidelines on when to use EPR and what to set it to?

I couldn't find this on the wiki, but I've seen mention of EPR in the context of dealing with FL, arousals, hypopneas, but also that it can exacerbate centrals. (Not sure whether or why any of that is correct).

[Gideon]

Study how and why basic BiLevel works. That means "S" or Spontaneous mode. This corresponds to a basic CPAP in "CPAP" or constant/continuous mode but with 2 specific constant pressures vs 1 for CPAP.

There is NO official guidance for EPR other than for comfort. But with EPR a CPAP behaves similar, no identical to a BiLevel in "S" mode with Pressure Support (PS) equal to EPR and EPAP = Pressure-EPR and IPAP= Pressure.

Now the question becomes how/why do you manage pressures in a BiLevel. For that go to the Titration Guide for a BiLevel

Basically you increase EPAP until the OA events are managed, then you increase PS(EPR on ResMed CPAP/APAP devices as needed to manage Hypopneas, Flow Limitations, RERAS, and UARS. Note that RERAS and UARS are mostly about flow limitations.

Since CPAPs and EPR (which is only a comfort feature) Don't officially do this e actually increase EPR for comfort and use the hypopneas, RERA, and flow limitations as a measure of discomfort and correct that.
.
On Central Apneas, a few unlucky individuals will find that the use of a CPAP, an increase in pressure, or the use of increase of EPR (or PS) will cause Central Apneas as the improvement in breathing has increased the flushing of CO2 from our system, the need to remove CO2 is our primary drive to breathe, to below the apneic threshold resulting in a Central Apnea lasting until enough CO2 is again present to trigger breathing. Should this occur you would react to decrease the flushing of CO2 and restore normal breathing. This is not a reason not to try EPR.

[Sleeprider]

The Resmed EPR feature on Airsense machines is identical in its delivery of bilevel pressure when compared to the Aircurve S or Vauto machines, but is limited to a pressure support of 3-cm. We can interchangeably use the CPAP pressure description of 9.0 to 14 cm with EPR 3, with the bilevel notation of EPAP min 6.0, PS 3.0 Max IPAP 14. Both of these are exactly the same. The mask pressure chart for an Airsense machine looks identical to the mask pressure with an Aircurve.

[KeepSmiling]

Very informative, thank you.

My question: If 10 cm of water pressure is the prescription needed to keep airway open would the airway not close at 7cm if the EPR is set to 3 while exhaling. Maybe it is case by case.

[Sleepster]

Resmed describes EPR as a comfort feature. If your basic pressure is 10 cm H2O, you can set EPR to reduce EPAP to 9, 8 or 7 cm H2O when the machine detects an exhale, so you don't have to push so much to breathe out. As it's a comfort feature, people seem to often recommend not using it after you got used to CPAP.

I would not recommend the stopping of EPR after you get used to CPAP. You're just using the CPAP machine to breathe, so if you breathe better with EPR then why would you want to stop doing doing that?

Are there guidelines on when to use EPR and what to set it to?

Everybody's different so we have to look at the data and try different settings to see what works best.

[pholynyk]

It is definitely case by case. The lower pressure must be high enough to keep the airway open; the higher inhale pressure makes inhaling easier.

So if you've been using 10 cmw and getting zero OA, if you add in 3 cm EPR, you may start getting more OA. If you do, you should either reduce the EPR or increase the pressure setting. We would look at your flow limitations to help decide. Since EPR helps to reduce flow limitations, if they were 'high', we would increase the minimum pressure, to maintain the EPR. If flow limitations are minimal, it would depend on how comfortable you are.

So it is a matter for experimentation.

[Sleepster]

If 10 cm of water pressure is the prescription needed to keep airway open would the airway not close at 7cm if the EPR is set to 3 while exhaling.

Maybe. We would have to look at the data to find out what works best. For me personally, the answer to your question would be no because I apparently don't require the higher pressure to exhale. Maybe I do when I'm lying on my back, but I rarely sleep in that position.

[Sleeprider]

KS, that is a very good question. My approach would be to use a pressure range to cover that potential. A minimum pressure of 10 with EPR 3 would result in a pressure of 10/7 (IPAP/EPAP), so by allowing the machine a maximum pressure of 13 or 15 we can ensure that an EPAP pressure of 10 is available if needed. We typically see single pressure prescriptions are actually too high, and I don't have any qualms about suggesting self-titration to see if a lower pressure is tolerated. Most of the time it allows better comfort and is often more effective than the single higher pressure without EPR. Because EPR lets us treat flow limitation, we can often reduce RERA and hypopnea as well as OA events. We also encounter members that need lower pressure to mitigate problems like aerophagia, and we will often coach a compromise between events and comfort that is not often reflected in a prescription.

[KeepSmiling]

Sleeprider,

Thanks