dreaming was more frequent and bothersome before cpap. My O2 sat would drop into the forties, which I think has a lot to do with dreaming. When I was a little guy in elementary school some friends of mine found it fun to hyperventalate then stand up quickly and pass out, I tried it once and had the most vivid adventurous dream that seemed like it lasted for more than several hours, but it was only a couple of seconds in reality. So, I know that O2 saturation has a lot to do with dreaming. As does medicine. Malaria pills if you go to jungle or someplace, cause vivid dreams, as well as some blood pressure meds.
I have been using cpap for a little over a year now. I typically only am awakened by a dream once during the night. It used to be several times before cpap treatment. I also feel that dreams are a means whereby your body tells you it needs something and you better wake up and take care of that need. Like going to pee or poop. I get lots more deep delta wave sleep with cpap, and less rem, but always some rem before I awake. The more vivid and disturbing the dream, usually the worse I need to pee, but it can also signal to me that it is simply time to get up if it is closer to the time that I arise. These are just my theories...
-nosehoser2004