Cpap with A flex or C flex

[Meecalii]

What does these do? i looked it up and it said the same thing for both my machine does c flex or a flex. right now it is set up for a flex. so what differance between these two?

[Pugsy]

You can read about how they are different here http://aflex.respironics.com/ though to be honest it doesn't explain things very well. The difference in how they feel is very subtle. I have had a chance to use both and I prefer AFlex. It felt pretty much like my own natural breathing rhythm and was just more comfortable to me.
Using either one and whatever setting you prefer is going to be an individual thing. What works for me may not work for you.
There should be a demo available of each mode with the different settings. Just try them all to see which feels the best for you.
There is no "right" or "wrong" choice. Main thing is for you to feel comfortable with it.
I found that the higher setting of 3 in each mode made me feel like the machine was rushing me to breath and a setting of 1 seemed a bit slow but a setting of 2 seemed to match my breathing perfectly.
The relief is flow based so how much it reduces and at what timed pattern will depend on your own breathing.
Flex relief doesn't do the per cm reduction in pressure that ResMed's EPR does. So don't think that a setting of 3 will necessarily give you a 3 cm drop in pressure. What I found when viewing my reports that the reduction in pressure was so small it really didn't show up on the pressure lines. Instead think of it as more of a timing issue instead of a pressure reduction.