An oral mask like the oracle will not inflate your ears once you learn how to use it. They can be tough to use, though. Especially due to dryness and having the oral interface in your mouth.
There is a valve at the back of your nose. Imaging blowing up a balloon. You don't have to pinch your nostrils shut, but no air comes out of your nose despite pressure in your mouth. This is the way you use an oral mask.
When I tried one, I would put it on, and act like I was trying to blow air back into the machine. I would get the feel of how the back of my nose felt, and then try to relax my throat. The pressure in my mouth would tend to hold the valve/flap at the back of the nose closed.
It's hard to describe, but becomes somewhat automatic after a while. They supply some nose plugs for "training," but you want to learn how to do it without the plugs.
When you do this right, there is no air pressure in your nose, or in your ears.
While I was able to stay sealed with the oral mask, I never got the hang of sleeping with it. The feeling was just too odd, and it dried my throat and mouth out a lot. There was also some discomfort and strange situation due to there being no airflow in my nose.
I was just experimenting with it, so I went back to my nasal mask.
An oral mask could be a lifesaver for people with certain nose/ear/eye problems.
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