The Puzzle of EPR on ResMed Units. Question for all.

[Physician]

Okay. I spent three hours today with two manometers making measurements on both the ResMed S8 and S9 with specific reference to EPR aka Expiratory Pressure Relief.

EXAMPLE EXPLANATION: http://www.talkaboutsleep.com/sleep-dis ... ed-epr.htm

I was quite surprised by the testing and will explain further after many have answered the following question.

QUESTION: What specific breathing event activates EPR ?

[Wulfman]

Exhale.

That's why it's called EPR........"Exhale (or Expiratory) Pressure Relief"


Den

[echo]

Well obviously exhale, but this sounds like a trick question.... I'm just trying to figure out how you got the manometer between your mouth and your mask to test the EPR So I'm guessing the "real" answer is something else?

[Physician]

Well obviously exhale, but this sounds like a trick question.... I'm just trying to figure out how you got the manometer between your mouth and your mask to test the EPR So I'm guessing the "real" answer is something else?

You are getting warm, Echo.

[chunkyfrog]

--how about inhalation pressure tapering down prior to inhalation?

[lovecpap]

end of inspiration

[echo]

--how about inhalation pressure tapering down prior to inhalation?

I was thinking that too, but on the website it clearly says that they detect the beginning of exhalation.

When the patient exhales, the S8 flow generator detects the beginning of exhalation and reduces motor speed to drop pressure.

Maybe they're not detecting the patient's breathing pattern at all but a drop in pressure at the sensor due to the difference between the exhalation and the machine pressure that occurs when you breath out?? .. oh I don't know, but whatever it is I'm sure it's interesting

[Physician]

end of inspiration

Damn you people are good. I cannot find what i discovered today on any website. See if you can.

Today's testing was done with two manometers, both in-line, of course. Ironically, one was a Respironics and one homemade.

We reached the conclusion that EPR is NOT a good name for the feature. Even the website explanation in my start post fails to explain this feature properly. Here's why.

When the S8 or S9 is set at 10 fixed, either by CPAP mode or min 10 max 10 in Auto mode, when one holds their breath, the pressure is indeed 10. Taking in a breath caused the pressure to RISE to about 15. If one holds their breath at end inspiration, and does NOT exhale, the pressure drops to 10 and stays there after a small overshoot. If then one exhales, the pressure drops maybe to 9.5 but generally stays at 10. This surprised the DME rep and three other users. We all expected the pressure to drop on expiration. NOPE.

Thus EPR works by dropping the pressure at the end and peak of inhalation. So it should be called End Inhalation Relief, not EPR.

Here's why this feature is clinically important for at least these two reasons:

• 1. Testing. I thought my unit did not have EPR because there was no pressure drop with only expiration

• 2. Users with slow respiratory rate will experience little or no EPR despite the unit's EPR 3 setting.

You EPR users, try holding your breath a few seconds at end inspiration, then allow expiration. Then inhale and immediately exhale. Note the difference.

I have communications from ResMed and other Sleep Disorder "experts" and no one has elaborated consistent with what was demonstrated today. I have more measurements and testing with other settings, but will save them for a future thread.

Feedback please, and also see if there's a website which explains that EPR is related to the drop or end of inspiration, and NOT the act of expiration.

Happy breathing.

[-SWS]

Here's an EPR fact sheet from Resmed, physician:
http://www.resmed.com/assets/documents/ ... ow_eng.pdf

[echo]

Maybe a search on the EPR patent would help.. although we all know that what's in a patent is not necessarily what's in the product.

[Physician]

Here's an EPR fact sheet from Resmed, physician:
http://www.resmed.com/assets/documents/ ... ow_eng.pdf

Thank you.

I have seen that, and this statement contained therein is misleading: "EPR decreases the patient’s CPAP pressure during exhalation on a breath-by-breath basis. "

It may not decrease the exhalation pressure if a) there's breath holding, or b) slow respiratory rate EPR is intended to decrease expiratory pressure, but there's no guaranty of adherence to the set levels of 1, 2, or 3 because it depends upon the patient's breathing pattern.

[-SWS]

It may not decrease the exhalation pressure if a) there's breath holding, or b) slow respiratory rate EPR is intended to decrease expiratory pressure, but there's no guaranty of adherence to the set levels of 1, 2, or 3 because it depends upon the patient's breathing pattern.

EPR is intentionally suspended when apneas are perceived by the event-handling algorithm as either imminent or present. I believe that "event handling" premise (namely EPR suspension) is to avoid under-treating expiratory end-phase apneas in patients who received a CPAP titration but not a BiLevel titration.

In a BiLevel titration for obstructive apnea, EPAP ends up being CPAP-equivalent pressure. And titration protocol typically has EPAP pressure, but not IPAP pressure, address apneas. Hence the technical rationale IMO for EPR to suspend amidst either imminent or present apneas: the patient using EPR presumably had a CPAP titration, but not a BiLevel titration. At least that's my best take, Physician...

[who]

If a comfort feature, when it occurs, occurs at the time that feels most natural to the user, then it is occurring at the exact proper time.

If a user discovers that EPR, in his particular case, tends to increase his AHI, that user may choose to raise, or ask about raising, the therapy pressure to compensate for the drop in pressure that is EPR.

[-SWS]

If a user discovers that EPR, in his particular case, tends to increase his AHI, that user may choose to raise, or ask about raising, the therapy pressure to compensate for the drop in pressure that is EPR.

Good point, Who. Increased AHI while using EPR is reported to be an issue for some of our message board members. Apparently EPR's "event handling" is not proactive or responsive enough in those particular cases... I would guess those cases might be comprised of patients presenting somewhat atypical expiratory end-phase or post-phase apneas.

By contrast I have my EPR set to 3 with no discernible AHI difference compared to EPR off. However, my breath rate during sleep runs on the high side and my flow reductions tend to run in the hypopneic versus apneic range.

[Big Daddy RRT,RPSGT]

The time when the pressure is most disturbing to most patients is the point at which you begin to exhale just at the point of end inhalation but the time you need the CPAP pressure the most is at end exhalation as this is often when airway collapse occurs. This is the basis for C-flex and EPR. Less "delivered pressure" at the beginining of exhalation but back to the therapuetic pressure by end of exhalation.

However when you connect a manometer you may not get what you think. As you inhale you "draw" air out of the tube causing decrease in pressure especially when using an older CPAP machine however on the newer machines (system one, S9) "rev" up to meet your demand for air and you may see an actual increase in pressure (maybe higher than the set pressure), this is where the expiratory relief comes in, it senses the drop in demand (flow) at end inhalation and drops the "delivered pressure" at the start of exhalation but gradually raises it throughout exhalation so you are at or near your therapuetic set pressure by end exhalation. However a manomoter may not register this as you might think...

Your exertion is greatest at the start of exhalation (possibly the highest pressure in the tube) triggering the greatest drop in "delivered pressure" and the least exertion at the end of exhalation but being back to the set pressure by the end of the cycle and this effects the manometer pressure reading. This will also greatly vary patient to patient based on lung disease, upper airway anatomy, respiratory rate, and other factors.

In the sleep lab we have sometimes noticed increased snoring when using a similar pressure with resperonics c-flex vs without. We have also seen c-flex causing mild hypopneas there by causing a need for higher pressure, in my mind defeating the purpose of the pressure relief. But often we find c-flex to be a useful tool in making CPAP more tolerable for many patients. We don't have Resmed equipment in our sleep lab to test.

Don't sweat the details, more importantly....How are sleeping? How are you feeling?