[Symptoms] Aircurve 10 ASV - spO2 Desat during REM, leading to awakening?

[d95p]

Background: very bad sleeper, awful onset insomnia and early awakenings, plus a messed up sleep schedule. Diagnosed with AHI=20 and was given an Airsense 10 Autoset a year ago. I got pretty comfortable using the machine and had good compliance with residue AHI hovering around 3, but no improvements on any of the symptoms. Still tired all day with brain fog.

A few months ago I discovered and started analyzing my sleep with OSCAR, and learned that almost all of my events are Clear Airways while also getting plenty of flow limits. Scheduled an appointment with my sleep doctor and finally talked with her over the phone last month. She said she did not receive any data from my DME, would like me to call her again in 2 months after receiving the data, and hung up on me in 3 minutes.

I figured I'm probably on my own, bought a second hand ASV and an O2Ring for more data. The ASV got my AHI down to nearly 0, though O2Ring revealed that I'm getting a lot of desaturations during REM sleep, with me waking up during my third REM sleep almost every night. To determine that whether this pattern is caused by ASV, I wore the O2Ring for a few nights with my old Autoset, and indeed I still get the desaturations during REM. Which I guess partially explains the early awakenings? How do I address this?

The zoomed in screenshot shows my first REM of that night. The amplitude of flow rate is noticeably lower during REM, and the target minute vent according to ResMed's ASV algorithm is lower as well.

[d95p]

I am guessing that the variable at play here is PS max, since EPAP min/max address OSA which is already taken care of, PS min addresses comfort/flow limits but matters little since ASV adjust PS on the fly.
I adjusted the PS range to 2~7 for the night shown in screenshots after I got awaken by a pressure surge at 2~15. Maybe I should increase PS max a bit?

[d95p]

Here's the night with PS range 2~10.
The machine turned itself off for some reason, or maybe I pulled the tube which I don't remember doing nor reattaching the tube. I will try disabling auto start/auto off and see if it was me or the machine.
The spO2 during the first REM is somewhat better, but judging from the heart rate variations, I don't think it's restful. Desat index went down from 7.57/h to 4.91/h.
I also removed the mouth tape for this night, which I've been using for the past month.
Minute vent and target minute vent went up significantly, not sure what caused it. Tidal volume stayed the same but resp. rate went up from 13 to 15.

Increase PS max further?

[d95p]

New night, still getting a lot of awakenings and desat during REM.

[d95p]

Here's the zoomed in graphs during the second REM. The spiking heart rate, minute vent and tidal volume don't look good.

[d95p]

While the ASV algorithm does a great job during NREM at preventing centrals, it destabilizes my breathing and wakes up during REM. The forced minimum PS of 5 cm H2O is actually detrimental, I think.

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I am going to put the machine in ASV rather than ASVAuto, with PS range 0-5 and see how that goes.