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+--- Thread: Expiry Pressure Relief - Does it really work? (/Thread-Expiry-Pressure-Relief-Does-it-really-work)
Expiry Pressure Relief - Does it really work? - Ron AKA - 05-03-2018
Some time ago I initiated a thread called Can EPR use cause Central Apnea Events? In that thread I asked for comments on another thread in another forum titled Not Understand EPR Setting. I got some feedback from posters here that if I can summarize briefly would be that in some individuals EPR can cause an increase in CA events, but in others it offers some advantages.
With some personal experience and some further research I have started to question the value of EPR in treating apena in general. I tried two treatment methods over a period of several days. I found that to get similar AHI results my 95% IPAP pressure had to be about 2.5 cm higher when I used 3 cm of EPR. In other words the IPAP therapy pressure to control apnea increased almost one for one by the amount of EPR used. Said another way, apnea events were controlled by EPAP pressure not IPAP. I then have wondered if my experience was unique or if it reflected that of the typical apnea sufferer. I found one very interesting article written by two sleep specialists from the University of Southern Florida Sleep Apnea Treatment Unit. They concluded somewhat surprisingly that the point in the inspiration and expiration cycle where apnea was most likely to occur was near the very end of the expiration cycle, and that if anything pressure should be maintained higher during expiration compared to inspiration. They even suggested that therapy could be improved if BiPAP machines would allow setting a negative pressure support, rather than a positive pressure support. I take this as a validation to my own conclusion that the EPAP pressure is the one that is most important in treating apnea, not the IPAP. And with a ResMed APAP the only way you can compensate for EPR use is to allow a higher IPAP therapy pressure. In other words the price you pay for EPR is increased IPAP pressure. In any case here is a link to the article. Warning. It is a bit of a tough read...
Expiratory and Inspiratory Positive Airway Pressures in Obstructive Sleep Apnea: How Much Pressure is Necessary? A Different Point of View
With respect to EPR and pressure causing increased central apnea, I'm having trouble finding a way to justify that this is a significant effect. Why? Well lets take the case of using EPR first. Lets say that by using an EPR of 3 cm you empty the lungs to a level 3 cm lower in pressure, and to compensate for that you pressurize the lungs to a level 3 cm higher. That adds about 6 cm of pressure effect oxygen which is said to be the cause of the centrals. However this needs to be put into context. Atmospheric pressure at sea level in our CPAP units of cm of water is about 1030 cm. 6 cm in comparison is an increase of about 0.1%. Not very much. And as another comparison when we go from a low pressure weather condition to a high pressure condition this is an increase of about 35 cm pressure. If 6 cm is significant, then changes in weather should have an effect that is about 6 times worse. And then there is the issue of traveling from say Denver Colorado to sea level. This is a pressure increase of about 155 cm of water. This should have a huge effect in increasing centrals. I recently traveled to an area about 1300 feet lower than where we live. I had the best AHI's I have ever had. There was a large reduction in centrals, no increase.
The same argument could be made for simply running higher pressure such as 20 cm vs 14 cm. 6 cm is just as insignificant as the 6 cm one could attribute to EPR. Bottom line is that I am having a hard time accepting that in the small pressures involved in CPAP that it really can have that big of an effect on oxygen levels and central apnea. That said, I do know that it is at least claimed that titration tests for treatment pressure frequently report increased centrals with increased pressure. I wonder if it is possible that due to the short duration of a titration test ( an hour or so at each pressure?), what is seen is a transient increase, that is not sustained when the pressure is used for days, months, and years?
So, my answer to the question of whether or not EPR works, my thoughts are: No, it doesn't really help with treatment, and it results in a requirement to increase treatment pressure almost one for one for the amount of EPR that you select. You pay for using EPR with an increased mask pressure and the effects that can have on leaks and comfort. And on the other hand, I find it hard to believe that it has any significant detrimental effects on central apnea frequency.
Comments?
RE: Expiry Pressure Relief - Does it really work? - pholynyk - 05-03-2018
RonAKA is speaking from his personal experience.
In my experience, EPR set to 3 gives me the lowest AHI that I have seen. Typically I have zero obstructives, clear airway in the tenths, and hypotneas in the range of one to two. Once, when my EPR was left at zero after a calibration test, I had my worst AHI ever, at over eight. Undoubtedly I would benefit from a bi-level machine.
RE: Expiry Pressure Relief - Does it really work? - DeepBreathing - 05-03-2018
Interesting concept Ron, but I found it hard to follow your argument (and sorry I didn't have time to read the papers you linked to). The experience of many members here, over a period of many years, is that EPR does indeed offer more comfort for people who experience difficulty exhaling against pressure. Experience also shows that in some people a reduction in pressure-induced central apnea can be achieved by lowering EPR or turning it off. It's quite likely that pressure changes may be required to compensate for the pressure reduction, but that's all part of the ongoing titration and adaptation we as users go through.
Perhaps when you've had some more CPAP nights under your belt you will have enough personal data to expand (or retract) aspects of your theory.
RE: Expiry Pressure Relief - Does it really work? - SarcasticDave94 - 05-04-2018
IMO it seems that EPR can be beneficial to some. (Please note that I have never used it myself, and this is based on noting others comments only. When it applies to myself, since I've never used it, I cannot state if I'd benefit or not.) To others it is not helping, but actually EPR becomes a hindrance, where it causes as mentioned Central episodes or other negatives.
My observation is that with all the various settings on the PAP machines, and external influencers AKA pillows, collars, etc., the therapy is extremely an individual focused set of criteria that combine to give that individual optimal treatment. It's what I call anti-cookie cutter treatment. An example of the opposite of anti-cookie cutter is a doc or DME that says "everyone" will be treated via a CPAP set to 12.
Happy Friday!
RE: Expiry Pressure Relief - Does it really work? - Ron AKA - 05-04-2018
(05-04-2018, 08:09 AM)SarcasticDave94 Wrote: An example of the opposite of anti-cookie cutter is a doc or DME that says "everyone" will be treated via a CPAP set to 12.
Actually, I strongly suspect that if I replaced my AirSense 10 AutoSet with a dumb brick set at a fixed 12 cm, I would get just as good results as I am now getting. I must fit the standard cookie cutter!
RE: Expiry Pressure Relief - Does it really work? - SarcasticDave94 - 05-04-2018
Which type of cookie shall you call yourself?
RE: Expiry Pressure Relief - Does it really work? - Ron AKA - 05-04-2018
(05-03-2018, 11:05 PM)DeepBreathing Wrote: I found it hard to follow your argument (and sorry I didn't have time to read the papers you linked to). The experience of many members here, over a period of many years, is that EPR does indeed offer more comfort for people who experience difficulty exhaling against pressure.
If you take a simple example of a fixed 7 cm of pressure giving good apena treatment results and introduce an EPR of 3 cm, then you have to increase the fixed pressure to 10 cm to get the same apnea mitigation. That keeps EPAP at 7 cm, and you are still exhaling against 7 cm. You have gained nothing in expiry relief, and in the process you now have to put up with a mask pressure of 10 cm instead of 7 cm. I would call that a net negative in comfort, not an improvement. Yes, if you just put an EPR of 3 in place and leave the fixed pressure at 7 cm, you will get expiry relief, but your treatment effectiveness suffers.
RE: Expiry Pressure Relief - Does it really work? - Ron AKA - 05-04-2018
(05-04-2018, 09:01 AM)SarcasticDave94 Wrote:
Which type of cookie shall you call yourself?
Well 12 cm would be a fairly large cookie!
RE: Expiry Pressure Relief - Does it really work? - Rcgop - 05-04-2018
Here is my take on EPR. My idea revolves around 3 and only 3 pressure “settings” and in order of importance.
- EPR setting. I consider it to be a comfort setting and treat it as such. However it can affect AHI. I determine my comfort setting first.
- Minimum IPAP setting. Setting this second is to find the minimum EPAP pressure that will control obstructive apneas. Since xPAP has a built in minimum IPAP/EPAP of 4, you need to start the minimum IPAP setting to 4 plus the EPR setting. In my case, my most comfortable EPR is 2. My minimum IPAP is set to 6 which makes my EPAP pressure start at 4. Now I can slowly raise my minimum pressure setting to a level that controls OAs. Fortunately the setting that accomplished this for me was 6.2.
- Maximum IPAP pressure. Now I can adjust my maximum setting in order to control the rest of the events. If I raise EPR I must raise the minimum pressure setting in order to maintain the control of OAs.
Good luck on finding your sweet spot.
RE: Expiry Pressure Relief - Does it really work? - SarcasticDave94 - 05-04-2018
That applies more to me then.Despite my off topic injections, EPR is an interesting aspect of treatment for discussion. I have to learn about it via others that have/use it. Since I'm on the ASV, and had a BiPAP DreamStation prior, I did not encounter EPR. Kudos on bringing the subject up.