Well, @gregromano - the reason I wouldn’t recommend taping the mouth is that it can be dangerous. Should a person vomit, the mouth would be obscured with the tape. Some people might be too sleepy to be quick enough to remove the tape, and could aspirate or breathe in the matter from the mouth into the lungs.
I do know that people do this (tape up the mouth), but I cannot say it is something safe.
Having worked on many a “Code Blue” team in hospitals, I saw the importance of keeping the mouth free of debris when quick ventilation must take place.