Okay, last night I happened to wake up in the middle of the night with really, really dry mouth. On my back which is usually when I might do this. Habit I got into when sleeping with cast this summer. Working on that not because it makes OSA worse (for me doesn't really make a difference) but because it causes more back pain for me.
Here is my leak line last night. I don't know when I woke up (no clock in bedroom) so I don't know which if any of these leak spikes was when I was doing some mouth breathing. While this leak line is not perfect it is still within acceptable limits. No prolonged huge leaks. Certainly not the leak I expected to see with the amount of dry mouth I had.
So not all dry mouth will mean that leaks are bad enough to impact therapy. Respironics doesn't flag a large leak until it hits somewhere around 80 to 90 L/min. Even at my worst I was well below that line.
Yet I had major dry mouth. It doesn't take much mouth breathing to dry the mouth out.
So while dry mouth can indicate mouth breathing that might impact therapy...one should look at the leak line itself to determine how much of an impact is really occurring. Obviously, taping or full face mask is not needed here.

I may have to RISE but I refuse to SHINE.