How does ResMed S9 initiate breathing after an apnea event

[KC2684]

Ok, I downloaded SleepyHead (thanks for the recommendation).
It shows that with a therapeutic pressure on 10cmH20, the mask pressure (not readily available in ResMed) varies from 10 inhale to 7 exhale giving an average of, let me calculate this, less than the 10 I am supposed to get.
Furthermore, unlike the S8 (which used to boost the EPR pressure back up if I didn't spontaneously inhale) the S9 mask pressure stays at 7 until I start to gasp. (I suppose that's good thing otherwise I would not wake up at all...ever...)
So I turned off the EPR and slept soundly through the night.
With the EPR ON at 3 my AHI ranged from 9 to 13. With the EPR OFF it was 3.1.
I have attache the two graphs produced by SleepyHead that shoe the differences.
I am also trying to get an appointment with the CPAP provider to"help" then understand my problem of modify their firmware so that people who NEED 10 get 10 and not 7 as was my case.
It was the technician from the provider who suggested the EPR!

Thanks to all those who helped me understand what was happening.

Footnote: The ResMed S8 (mine anyway) definitely automatically reverts to the therapeutic pressure after the exhale, the S9 does not!

[KC2684]

The "Patient" setting means allow the patient to adjust the setting.

OK. I see what you mean. Thanks.

[Regular Joe]

Huh? If your S9 is set to 10, you're getting 10. The EPR just allows it to drop down a bit to make your exhale a little easier. Turn off the EPR off if you want to. You shouldn't "average" your 7 and 10 to calculate your therapeutic pressure. That mask pressure graph looks ragged too. Mine is much more smooth and regular.

[KC2684]

Huh? If your S9 is set to 10, you're getting 10. The EPR just allows it to drop down a bit to make your exhale a little easier. Turn off the EPR off if you want to. You shouldn't "average" your 7 and 10 to calculate your therapeutic pressure. That mask pressure graph looks ragged too. Mine is much more smooth and regular.

My point is that when I NEED the pressure to be 10 at the beginning of the inhale, its only 7, not 10.

[Regular Joe]

So, turn off EPR. Think of it this way, you're exhaling against 7 cm, not 0. That 7 along with your own "exhale pressure" will keep your airway open.

[KC2684]

I have both ResScan and SleepyHead now. March 16.
ResScan does not show mask pressure but SleepyHead does.
S9 Elite DOES NOT INCREASE PRESSURE during EPR, but sets up a low pressure bias pressure to differentiate between OA and CA and hypogea events.

I have confirmed that with EPR ON the S8 Elite does indeed increase the pressure back to the set point. I also verified this by building a simple water manometer to show the increase in pressure. I talked to a ResMed technical person who confirmed this change in operation between the S8 and S9.

He gave the following explanation:
1) The S8 Elite pressure increase would move the sleeper out of REM sleep (if indeed she was in REM sleep) which ResMed determined was not a good thing.
2) He also said that once in an apnea event, it takes more pressure than the proscribed pressure to open the airways.

Item "2" may indeed be correct, but item "1" actually raised questions (which I did not clarify in the phone call). That is, certainly in an apnea event, the sleeper would eventually be moved out of rem sleep if she had to gasp for air, given she was not breathing. So which is worse?
I thought the increase of pressure helped me.

The S9 Elite definitely does not increase pressure. the VPAP models may do this. I am investigating...

I have now turned EPR off, as suggested and have set up an appointment with my resirologist to see what he knows.

I do have some summary data from my old data card (thanks to the ResMed store) that I shall compare to new data once i have a few months to see if there is any difference in the AHI components.

Thanks for all the help.
Barry

[archangle]

I have both ResScan and SleepyHead now. March 16.
ResScan does not show mask pressure but SleepyHead does.
S9 Elite DOES NOT INCREASE PRESSURE during EPR, but sets up a low pressure bias pressure to differentiate between OA and CA and hypogea events.

I have confirmed that with EPR ON the S8 Elite does indeed increase the pressure back to the set point. I also verified this by building a simple water manometer to show the increase in pressure. I talked to a ResMed technical person who confirmed this change in operation between the S8 and S9.

He gave the following explanation:
1) The S8 Elite pressure increase would move the sleeper out of REM sleep (if indeed she was in REM sleep) which ResMed determined was not a good thing.
2) He also said that once in an apnea event, it takes more pressure than the proscribed pressure to open the airways.

Item "2" may indeed be correct, but item "1" actually raised questions (which I did not clarify in the phone call). That is, certainly in an apnea event, the sleeper would eventually be moved out of rem sleep if she had to gasp for air, given she was not breathing. So which is worse?
I thought the increase of pressure helped me.

The S9 Elite definitely does not increase pressure. the VPAP models may do this. I am investigating...

I have now turned EPR off, as suggested and have set up an appointment with my resirologist to see what he knows.

I do have some summary data from my old data card (thanks to the ResMed store) that I shall compare to new data once i have a few months to see if there is any difference in the AHI components.

Thanks for all the help.
Barry

The EPR pressure changes have nothing to do with distinguishing centrals from obstructives. ResMed S9 machines use FOT (Forced Oscillation Technique) to distinguish central (clear airway) apneas from obstructive.

FOT is a series of pulses at around 4 pulse per second. It's pressure changes, but it has nothing to do with EPR.

http://www.resmed.com/fr/assets/document...-paper.pdf

Hypopneas are determined by flow rate. As far as I know, no machine distinguishes "central" from "obstructive" hypopneas.

EPR decreases pressure when you exhale and brings it back to the set when you inhale. This is true for both S8 and S9. On an Elite machine, it will never increase above the set pressure. I believe that the waveform is different between S8 and S9 and that the S9 feels "gentler." I felt a pressure difference on my PRS1 machine with Flex, but don't feel it with my S9.

There may be some timing difference between S8 and S9, but I'm not sure. My S9 appears to not switch to the higher pressure until I start to inhale. Maybe the S8 is different.

[DKC_apnea]

I have the S9 Elite and having been using it since February.

The EPR is a "comfort" feature and allows exhale relief of up to 3 cm H2O relief. So if your set pressure is 10, and your EPR is set to 3, it will allow an exhale pressure of 7. If the unit detects an event (lasting 10 secs), it will immediately increase the pressure back to it's "set pressure" (regardless of EPR).

There is an option to allow EPR during ramp only, or allow the EPR to be full-time. Sounds like you had best results with it off entirely, and if you find that comfortable that's great.

For myself, I really prefer using the EPR, but I have noticed there is a trade-off. If the exhale pressure is allowed to drop too much, obstructive apnea events can start to occur. Essentially what happens is that once the exhale completes itself (against the reduced pressure provided by the EPR), the airway may collapse if you are relaxed and don't inhale right away. The S9 (in CPAP mode) waits 10 seconds before identifying that as an apnea event and forcing the pressure back to the set pressure.

The S9 will quickly respond, but the whole purpose of CPAP is to minimize those events or prevent them from occurring. On the other hand, if the set pressure is too high, I have a tendency to over-titrate and get central apnea events.

My sleep study resulted in a recommended pressure of 8. I would love to use an EPR of 3, but I need a minimum pressure of around 6.4 to prevent the OA's, and unfortunately a set pressure as high as 9.4 gets me back into centrals. I set my EPR to 2 and set pressure to 8.4 and that seems to work well for me. Maybe I can ween myself off EPR with time.

Of course the changes to EPR and pressure may be restricted if the CPAP is not set up to allow the patient to make their own changes. Some choose to refer to the clinician's manual and make their own adjustments. SleepHead is a very useful tool to help study your results.

Its a learning process, and best to monitor your results over time and not make too many tweaks at a time.

[KC2684]

I have the S9 Elite and having been using it since February.


Its a learning process, and best to monitor your results over time and not make too many tweaks at a time.

Thanks for your comments.
Barry

[trish6hundred]

Hi DKC_apnea,
WELCOME! to the forum.!