I think you might have awakened during or directly after dreaming when you took the break. This could be caused by interruptions (such as apnea) during the later part of the night. It is also possible that you got some restorative and REM sleep during mask use, and after you took it off, you got the benefit. You may have gotten primed during mask use, only to fall into deeper sleep thereafter. The REM sleep is supposed to be in cycles, and every lengthening thru the night. I found that I would dream both with and without the mask, and that sleeping without the mask allowed more apneas and more excursions to lowered O2 level. If I started without the mask, no dreaming remembered.
The pulse oximeter I got has an alarm feature that will alert me if my SpO2 level goes below a [user defined] limit. But, it won't make me sleep better.
Dedicated to QALity sleep.
You'll note I am listed as an Advisory Member. I am honored to be listed as such. See the fine print - Advisory Members as a group provide advice and suggestions to Apnea Board administrators and staff concerning Apnea Board operation and administrative policies. Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.