Does EPR reduce therapy effectiveness?

Hi everyone! I'm at work right now but can't wait to download ResScan tonight and take a look at my first night's data!
In the meantime, I was wondering today - does the changing pressure of EPR have the potential to reduce the effectiveness of CPAP therapy?

No. If it did PAP manufacturers would not be allowed to offer it. Most of us end up turning it off, and turning Ramp off too eventually as we get acclimated to and comfortable w/our PAP therapy. The important issue is COMPLIANCE, using that PAP every time we sleep, even for naps. And if EPR, Ramp, C- or A-Flex or Bi-Flex encourages and improves compliance those options are viable and important.

Since EPR stands for expiratory pressure relief, I cannot see how it would have a deleterious effect on therapy since it's the pressure on inhalation that keeps your airway open. On the other hand, I think the beneficial effect goes without saying...especially for those whose tolerance for exhaling against a "wind storm" is low.

Yes......potentially.
As has been discussed many times before, EPR drops the pressure on exhale in the number of centimeters according to which setting you select......1 drops 1 cm......2 drops 2 cm......3 drops 3 cm.......for the full exhale period. If the user is prone to having apneas at the point of "end-of-exhale"/"beginning-of-inhale", then you either need to reduce the EPR number or compensate for that with a higher set pressure if you're using CPAP mode or higher minimum pressures if you're using APAP mode.


Den

Amigo wrote:Since EPR stands for expiratory pressure relief, I cannot see how it would have a deleterious effect on therapy since it's the pressure on inhalation that keeps your airway open.

I wasn't sure how intelligent the machines are at detecting just when you start exhaling, so I guess I was worried about it dropping the pressure when you aren't really exhaling. Because yeah, like you said, it's inhalation that counts...

joeattardi wrote:

Amigo wrote:Since EPR stands for expiratory pressure relief, I cannot see how it would have a deleterious effect on therapy since it's the pressure on inhalation that keeps your airway open.

I wasn't sure how intelligent the machines are at detecting just when you start exhaling, so I guess I was worried about it dropping the pressure when you aren't really exhaling. Because yeah, like you said, it's inhalation that counts...

Not really so. The airway could collapse if/when the exhalation pressure falls below what the individual needs to keep their airway open.

So at a set pressure of say 10 cm an EPR of 1 may have no effect while EPR of 2 or 3 could increase the number of events. This is more pronounced with a BiPap but has the same effect with a CPAP with Cflex/Afelx or EPR.

GumbyCT wrote: So at a set pressure of say 10 cm an EPR of 1 may have no effect while EPR of 2 or 3 could increase the number of events. This is more pronounced with a BiPap but has the same effect with a CPAP with Cflex/Afelx or EPR.

Hmm, interesting. My current pressure is 9 cm and I believe my EPR is set to 3.

Den is correct, but only careful monitoring of your statistics will give you a clue if changing your settings might make a difference in your therapy.

My advice is to not go looking for problems just yet.

joeattardi wrote:

GumbyCT wrote: So at a set pressure of say 10 cm an EPR of 1 may have no effect while EPR of 2 or 3 could increase the number of events. This is more pronounced with a BiPap but has the same effect with a CPAP with Cflex/Afelx or EPR.

Hmm, interesting. My current pressure is 9 cm and I believe my EPR is set to 3.

Then your "effective" pressure at the point of exhale/inhale is 6 cm. If that isn't enough to keep your airway open, then you need to compensate for it in one of the two ways I mentioned before. It's been noted before that ResMed's EPR is sort of like a mini Bi-Level......but, with Bi-Level therapy, you need to set the EPAP pressure to the point where you eliminate the Apneas.


Den

Nestled inside a thread about C-flex was this work of art from RG about EPR . . .

viewtopic.php?p=436272#p436272

jnk wrote:Nestled inside a thread about C-flex was this work of art from RG about EPR . . .

viewtopic.php?p=436272#p436272

Thanks for the link! That was a really good read.

She's a gem.

If you want to go deeper, you may enjoy the discussion between two other gems in this forum, -SWS and jdm2857, which encompasses Easy-Breathe and its interaction with EPR . . .

viewtopic.php?f=1&t=44898&p=402793#p402785

There was a doctor who spoke to the NY AWAKE group recently (on YouTube, but I am too lazy to figure out his name or the site right now) who was explaining EPR and one thing I seem to remember is that the effective pressure drop from EPR is not as much as it would seem because there is also the pressure from the exhalation itself.

Inhalation requires muscle action--contraction of the diaphragm and other accessory muscles, but in most of us (some lung pathologies interfere with exhalation) exhalation is mostly passive (as the diaphragm relaxes, it pushes the air out) and exerts its own pressure on the airway--sort of like when you let go of the balloon, the opening will not collapse until all or most of the air is expelled. So even though the EPR may reduce the pressure 1, 2, or 3 cm respectively going in, the actual pressure in the airway does not drop that much since there is also pressure coming out from the exhalation itself.

I may be all wet about this, but I do recall a rather lengthy explanation about that.

Slinky wrote:Most of us end up turning it off, and turning Ramp off too eventually as we get acclimated to and comfortable w/our PAP therapy.

That would be some, not most.

Cheers,

Bill

Janknitz wrote:There was a doctor who spoke to the NY AWAKE group recently (on YouTube, but I am too lazy to figure out his name or the site right now) who was explaining EPR and one thing I seem to remember is that the effective pressure drop from EPR is not as much as it would seem because there is also the pressure from the exhalation itself.

Inhalation requires muscle action--contraction of the diaphragm and other accessory muscles, but in most of us (some lung pathologies interfere with exhalation) exhalation is mostly passive (as the diaphragm relaxes, it pushes the air out) and exerts its own pressure on the airway--sort of like when you let go of the balloon, the opening will not collapse until all or most of the air is expelled. So even though the EPR may reduce the pressure 1, 2, or 3 cm respectively going in, the actual pressure in the airway does not drop that much since there is also pressure coming out from the exhalation itself.

I may be all wet about this, but I do recall a rather lengthy explanation about that.

Janknitz

Your logic seems ok to me. In fact, if we place a dial manometer at the machine end of the airhose & another at the mask end, the pressure data becomes quite interesting esp when observing EPR and then EPR turned off.

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EPR OFF

With EPR turned off, the machine is basically in cpap mode (lets ignore Auto mode for this discussion). But as you breathe in and out the dial manometer at the mask end will vary around 1-2 even 3 CMs (depending on how fast & forcefully the person breathes) but the dial manometer at the machine end will vary very little.

To go deeper, if the machine is delivering say 10 CMs then as we breathe out the back pressure down the air hose can be seen at the machine end as a very minor pressure increase & if you could hear the blower (they are so quiet these days it is hard to) you would hear it slow a bit as the machine drops speed in order to maintain the 10 CMs pressure delivered at the machine end of the hose.

As we breathe in, the blower will speed up again to make up for any 'potential' drop in pressure created by the suction of breathing in. Put simply the machine will always adjust its blower to keep the delivered pressure at 10 CMs and the act of breathing in an out has the natural effect of increasing & decreasing the back pressure from the mask to the machine.

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EPR ON

With EPR on the EasyBreathe kicks in. Put simply, easy breathe is the way the blower varies its speed as the pressure is dropped on exhale and raised on inhale for EPR. This variation is called the 'shark fin' wave form & the blower speed is adjusted in this pattern which tends to closely mimic normal breathing. Normal breathing in starts quickly & then slows towards full breath in then accelerates out quickly on breathing out. Looking at a time graph, that pattern of pressure rise & fall from the sleeping person looks just like a shark fin hence the original descriptions of it. Early Bilevels tended to drop & raise the ipap=>epap=>ipap=>epap airflow more like a square wave which felt unnatural to the sleeper. EasyBreathe became possible because the blowers used in these new generation of machines, can adjust pressure so quickly & quietly that the designers were able to adjust the speed to exactly match normal breathing patterns.

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My way of getting better benefit from EPR.

When I used EPR myself, I found that to get the best benefit I raised my cpap pressure 1 CMs above my titration pressure & then set EPR to 3 & that worked really well. Many people have commented that if they stay with their titration pressure then set EPR = 3, they don't feel as good as when they turn EPR off or to a lower setting & I believe Wulfman explained this point pretty well.

I used EPR as I found that it reduced aerophagia for me compared to using the machine in straight cpap or auto mode (I was originally on 15 CMs and aerophagia was an issue at the pressure).


DSM