Bi level is probably not the answer.
If you have central Sleep apnea then the ASV machine would be the best.
I don't know enough about just using O2 but my doctor would not try it.
Its a very complicated system with all kinds of feed back loops. Loop gain etc.
With me, everything would be going good, nice in and out flow and then something would disturb it (?? leg movement??) and a big breath would come in and the system would over react then over react to that so you end up with big overshoots up and down and finally, stop breathing all together. eventually, one of the back up systems kick in and you start breathing again, but possibly back into the cycle again. Thats what happens with Cheynes Stockes pattern. The ASV machine watches you and then trys to predict when you are going to overshoot and intercept it. Its pretty wild to see what it tries to do. I have good insurance but I would buy an O2 concentrator if it would help. Insurance would only pay if O2 drops to like 75 or someting.