Help with settings - Min Pressure and Flow Limits

[TimboSlice]

Hey all, been on CPAP therapy for about a year. Had a mild AHI of 7 and was put on the usual 4cm-20cm auto regime and EPR 3 with an Airsense 10. It helped a lot for awhile, but unfortunately I still have daytime fatigue and restless sleep. Basically feel like I wake up often and my Oura ring says I move a lot and don't get much deep sleep. My AHI is low, usually around 1, but I know that doesn't tell the full story.

I started looking at the CPAP data in OSAR and noticed I am having spikes in respiratory rate that correlate with flow limits and increased pressure. I think this increased breathing rate is what is waking me up but I'm not sure how to resolve the issue. At first I thought maybe I was fighting the increased pressure so capping the pressure off would help but after doing some googling on what flow limits are (precursor to hypopneas/OA's if I understand correctly) it seems more likely I'm sensitive to the FLs and breathing faster afterwards to get more air.

I did some reading on this forum on FLs and EPR and it seemed like the consensus was that using EPR at 3 helps with FLs. I'm still somewhat confused on why, but as long as that's right I can read more on it later once I'm sleeping better. So it seems like the way to go is increasing my minimum pressure. 

My questions are;
1. Is my interpretation of EPR helping FLs correct? Or would lowering the EPR and increasing minimum pressure have the same effect if I tolerate the lower EPR ok?
2. Is the increased respiratory rate like I have typical with FLs or can it indicate some other issue?
3. With no max pressure set, my 95% pressure is usually around 7, should that be my min pressure?


Overview from last night:
   

Zoomed in on flow limit. The Flow rate graph definitely indicates some issue.
   

Any input is appreciated! Thanks!

[Sleeprider]

We view the Resmed Autoset machines as being like a bilevel (BiPAP) machine with distinct inhale (IPAP) and exhale (EPAP) pressure, but with the difference between IPAP/EPAP being limited to 3-cm.  The bilevel pressure works identically to the VPAP (Aircurve) machines except you are limited to 3-cm and 1-cm increments.  This wiki article probably explains it better http://www.apneaboard.com/wiki/index.php...limitation

EPR is equivalent to pressure support (PS), and that is what treats flow limitation.  As you begin inhale, pressure starts to rise, following your spontaneous effort. In a normal breath the pressure continues to rise, even as inspiratory flow slows and approaches zero. The machine cycles to EPAP pressure as you start exhaling. This Oscar chart shows that transition to exhale with a black line comparing respiratory flow rate at zero and mask pressure at its peak.  That is how flow limitation is treated by both the Airsense and Aircurve machines.  The chart comes from a bilevel with PS 4, but you can look at the mask pressure chart in Oscar for your own data and see similar respiratory flow to mask pressure.  Just move mask pressure up to where you are showing pressure on your zoomed shot.  You can also add a dotted line at zero flow to the flow rate chart by right-clicking near the title of that chart and adding a dotted line at zero.

[sunsaffron]

As far as I understand from the advice I was given here, EPR 3 with a minimum pressure of 4 does nothing, since EPR requires lowering the pressure on exhale and the machine can't go lower than 4. You'd need to set your minimum pressure to at least 7 to get the effects of EPR 3 (7 - 3 = 4).

[TimboSlice]

 Just move mask pressure up to where you are showing pressure on your zoomed shot.

Thanks for the info! Do you mean move min mask pressure up to that spot including EPR or no? So if it is 6cm, should min pressure go to 6cm or 8cm if the EPR is at 2?

[Gideon]

7 is a reasonable starting pressure for anyone so
set min pressure = 7, this will accommodate any level of EPR, 1,2, or 3

Should your charts sho the need the min pressure can easily be adjusted based on results.

[TimboSlice]

Ok, I will give 7cm with 3cm EPR a try.

At 6cm and 2cm EPR I felt like I slept better and had less movement during the night. Flow limits and increased RR were pretty much the same.

[TimboSlice]

7cm of pressure minimum definitely helped keep the FLs to a minimum. Felt like I didn't sleep quite as well and have had more CA's, but it's been a pretty big pressure increase over the last few nights so I think I just need to get used to it. Might need to keep bumping it up a bit over time.
   

I did find some weird patterns though. Do the spots where the flow rate flatlines look like mini centrals? They last a few secondsThere weren't any flow limits or leaks around that time.
   

[Gideon]

I would hold at these settings and turn the ramp off. You are at the device minimums so the Ramp is doing nothing for you.
Adjustments should be made mostly based on how you feel.

[TimboSlice]

Kept at 7cm min/3cm EPR and the data shows a pretty good night. Centrals went down compared to the night before and the pressure at ~7 is limiting the FLs. I felt like I slept poorly still though with a lot of wake-ups and tossing/turning. Can't quite tell how I'll feel during the day yet, but I woke up without an alarm after ~9 hours and felt more refreshed than I have in the past weeks. Going to ride it out for a few days with these settings and see if the sleep quality improves.

Thanks for the help Sleeprider and Gideon!

[Gideon]

It's the EPR that is limiting the flow limits, not the pressure.
You should turn off your ramp. Your pressures are minimal, EPAP is stable near 4 and IPAP is stable near 7 and you are missing 1.5 hours of reporting and nearly that of effective therapy.