Cathy, I think it is possible that both Flow Limitations and/or APAP could disturb sleep. Pictured above is representative of my flow limitations with and with out a soft neck brace.
This is what I've found: In the Auto mode, my S9 will drive the pressure up in response to FL, neck brace or no, although for any given min-max settings the average pressure over night will be lower when a brace is used.
For me, relatively little pressure is needed to eliminate obstructive apneas, around 7, yet in the auto mode set at 7-10, flow limitations will drive the average pressure up to over 9. The resulting AHI is low, around 1.0, but made up primarily of CA's which I believe are really arousals caused by pressure variations, mask leaks or a combination.
Decreasing the spread, say to 9-10, maintains the AHI, decreasing the CAI slightly, but increases the leak rate.
Now, going to a fixed CPAP of 8 and adding a neck brace slighty lowers the AHI, with AI lower, CAI lower, and HI a little higher.
But the real telling of this story is in the Zeo results.
At 7-10, Zeo reports 4% deep and 7% Wake
At 9-10, Zeo reports 6% deep and 10% Wake
At 8 fixed, Zeo reports 12% deep and 3% Wake, a dramatic improvement.
All the above stats are averages derived from data gathered over several days in each condition. Last night, at 8 fixed with brace, my AHI was 1.28 with an HI of 0.51. Zeo reported 17% deep, 1.4% wake and a total sleep time of 7 hours 40 minutes. And, and I feel pretty darned good. My average sleep time in the past has been less than 6.5 hours.
So, I think in overcoming the Flow Limitations, the S9 auto therapy disturbs my sleep. But by using the neck brace, I can reduce the Flow Limitations (which if unchecked could be disturbing) allowing me to use the less disturbing CPAP mode. In fact, in a discussion of this yesterday, my sleep doctor who had previously recommended the 7-10 auto, suggested I try reducing the pressure from fixed 8 to 7 while using the brace.
If you want to try a neck brace, mine is pretty simple. It's about a 3" x 8" piece of one inch foam wrapped in handkerchief, with a hair band pinned to the front. I slip it over my head so that the foam piece is under my chin. It's a lot more comfortable than the commercial ones since there is no bulk around the sides and back of the neck.