I took your wise advice and increased my pressures, in two steps, most recently (last 7 nights) auto-EPAP 11-13, pressure support 5-10.
The increased pressures have reduced my AHI even further (average AHI, excluding these occasional bad nights, of 0.5), even two zero AHIs since I last posted (of a total of 3 ever). But I continue to have the same pattern as for months on ASV in that every 7 to 12 days my numbers escape noticeably - one night last week an AHI of 2.3, & last night 4.6, and the events always come in bunches in a periodic breathing pattern towards the end of the night. But I am sure I was asleep at the time on each occasion so I very much doubt they are sleep-wake junk. I'm not taking any drugs (prescription or illicit) that affect sleep and alcohol intake is just a couple of beers a week. I don't take any caffeine drinks or caffeine-rich food.
Last night is at: http://imgur.com/a/ZqYE1
In general my fatigue is much better on ASV compared to CPAP or APAP but it's unchanged I think from now compared to when I had much lower ASV pressures (e.g. fixed EPAP 10, PS 1-7). And yet again, with typical luck, last night was not the once-a-week night when I wear an oximeter (my O2 parameters have always been excellent on ASV). Leaks have been very well controlled during these poor nights and as far as I am aware I have slept very well during these nights.
My current pressure settings are acceptable for comfort, but I was even more comfortable at lower ASV pressures.
If you were me, would you keep on increasing the EPAP and/or PS until these events cease completely? or just ignore them as something that happens sometimes. I can see myself reaching maximum pressures of 25, 26, and upwards, and *still* not abolishing these bunches of events. One night I might just find myself floating towards the ceiling... (I'm joking - I know the pressures wouldn't even inflate a balloon).
And why are they happening? I have no idea other than (not sure) they may be during REM sleep (I've never had a sleep-lab study so I have no data as to what I do in REM compared to other sleep stages), or perhaps I am having one of my paralytic events (genetic muscle disorder) during sleep - this would weaken my throat and chest muscles for an hour or so, so perhaps collapsing the airway further. I don't think I am spending much time, if any, on my back or left side (sleeping on my right side was much better than back or left-side during my home diagnostic test).
P.S. My Sleepyhead has somehow got 'stuck' in French, so for the attached screenshots: Flux = flow. Fuite = leak. Ronflement = snore. Evènement utilisateur #2 = user flag #2, 50% flow reduction.
I'd very much appreciate your input, thank you.