Most of the machines sold now are continuous, but not at constant pressure. Mine's set to detect apnea events and adjust between 5-15 for pressure and to adjust that further based on exhalation.
Mine can do all that, but I actually have it all turned off...I find I have a much easier time getting and staying comfortable that way...every time the pressure changes my mask would shift...at a constant pressure I can get it "just right" and it doesn't leak at all and I find it easier to fall asleep as the pressure points don't shift around.