My doctor prescribed trazodone for the fragmented sleep. It helps, but I make sure I don't take it every night. Eventually all sleeping pills stop working and then you're trapped, so I am cautious. I managed to wean myself off amitriptylene. It was very difficult. I am slowly weaning myself off trazodone. After a year I've used less than half the pills prescribed and the doctor was surprised when I declined her offer to raise the dose.
It looks like you are one of the people for whom the pressure-adjusting algorithm doesn't work. And it seems you have understood why correctly. So it would seem that you do better at a fixed pressure. If I were you, though, I would still pay attention to flow limitations. They may not advance to hypopneas and apneas, but they might still be causing arousals. So, for example, if a pressure of 8.6 seems to minimize your AHI, see if raising it just a bit can lower your flow limitations without substantially raising your CA index. Even if your CA index does go up, wait and see if it goes back down on its own, because that is the more common occurrence by far.
I've spent a year of monthly tweaking. Set it at a pressure, measure a month -long average value for the indices. Adjust again, and so on. I was trying to adjust the two pressures of my bi-level machine to minimize my CA index without raising the OA and H indices. My situation is complicated by aerophagia and the fact that too high of a bi-level pressure difference (pressure support) induced CA's. I then switched to the auto bi-level machine I have now so that I can try to minimize my AHI without raising the pressure so high that I start swallowing air.
I am now committed to a diet and exercise regime to lose weight. I'm convinced it's the best way for me to lower my pressure and reduce the fragmented sleeping. Even before I started losing weight the fragmented sleep was gradually improving. Switching from a nasal mask to a full face mask to stop mouth leaking helped a lot, too.
It's long and slow journey that requires attention. But it's worth the efforts.
Apnea Board Moderator