I have used
CPAP for 2-3 months, there appears to be little benefit, I switched from APAP?, the automated pressure version, to a constant 12 with the machine releasing pressure when breathing out (C-flex), this was with a Respitronics machine.
There was a few weeks of data, and we changed from Autopap to Cpap with c-flex and a ramp rate on the same machine, with a nasal mask only.