I went for a sleep study recently. I was using a pressure range of 12-18 and went back to a pressure of 12 last night and felt better as Derek did. The doc is considered the best in the area and this is what he had to say.
When an apnea occurs, the machine senses this and increases the pressure to compensate for the cessation in breathing. This occurrence then has the effect of causing a partial arousal, thereby disturbing one’s sleep rhythm. By leaving the pressure at a fixed psi, the sleep rhythm is not disturbed and one is able to get into successive stages of REM sleep sooner.
Hope this info helps someone else.