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No need to apologize. It really was funny the next day.

On the Oracle 2 mask there is a vent at the elbow nect to the mask and another vent where the mask hose connects to the main supply hose. This second vent has a flapper valve the prevents pressure from the CPAP from escaping but lets air escape from the exhaled breath. With the mask disconnected from the main hose, and the end of the mask hose plugged, I can inhale easily but exhaling is more difficult. I think that is what eventually woke me up.

I think that when there is no pressure from the CPAP, this valve lets the patient breath air in enough to not suffocate. At least that is the way it appears to me after the fact. I think the engineers did it that way on purpose. The hose volume is too large for a person to actually survive breathing through it without additional fresh air from somewhere.

BTW my wife tells me I can sleep through just about anything so it didn't surprise me that this could go on for so long before the effort woke me up.

That second flapper is interesting. On of the first things I did with my first night on the mask was plug the hole and see if I could breath, and the answer was, not at all, or at least not much through that frit. That is a nice feature to have in a power failure. But now that I love my mask instead of fear it, I feel I would quickly wake up and either pull of the mask or breath through my mouth. Its just that first few days and month when everything is new that one is furiously thinking "what happens if?"