(07-30-2015, 06:37 PM)DariaVader Wrote: It looks like Flow limitations are a 0 to 1 scale. Flow limitations that are less than 50% seem to be the dominating feature of the majority of my nights. My AHI is low with CPAP - even if I set the pressure to a constant 7 (a 1 night experiment) the AHI is low, but the flow limitations were constant and I felt almost like i had slept without my cpap. Last night I set the min pressure to 8 and knocked out all FL for the first half of the night, and greatly reduced for second half. going to leave it that way for a couple nights to see how it works out... the higher pressure caused my water retention level to raise again, but i slept so well.
I am still not really clear on how flow limitations become obstructions... Did not see a 1 on the FL when an OA was scored, for instance. Would welcome some insight on the entire subject
BTW - saw my sleep doc yesterday and finally got my whole sleep study report. Seems the majority of my AHI was H in the study (for which I barely slept, unfortunately and it was a home study so they cannot tell) I think that FL = H at a certain level???
Conventional wisdom says there are multiple stages of your airway's compromise:
1) When your airflow rate starts decreasing, it shows as flow limitation.
2) it reduces further and typically causes a RERA in most individuals.
3) if RERA is not induced to correct the airway patency, it becomes a hypopnea.
4) If it collapses further, it will become an obstructive event.
You machine (S9) reports all of stage 1 and 2 as flow limitations. Why it doesn't show an FL of 1 before an O event is beyond my level of competence.
The potential reason why you feel like crap at pressure of 7cm is that you are having a bunch of RERAs which correct your airway patency thus avoiding H or O event (so keeping your AHI low). But these RERAs harm your sleep architecture by knocking you out of a deeper sleep stage to a shallower one. When this happens multiple times in the night, you end up spending more time in shallower sleep stages than deeper ones (SWS,REM). And then you don't feel rested in the morning.
You could potentially use your FL no. as a proxy for RERAs. You probably need very little extra pressure to subdue the FL no. after AHI is in treated zone - as you experienced with pushing the pressure to 8.
My 2 cents. I am sure more experienced members will chime in soon.