Dry Mouth long term user

I'm 60 years old and I've been using nose pillows since I started 6-8 years ago with CPAP. I was diagnosed with 80 AHI and they set me up with a pressure of 11. My readings each year all show good levels of AHI less than 5. What I'm experiencing is that I find on my back my soft palate relaxes sometimes too much and the air blows back from the throat/sinuses back into my mouth. Moving my soft palate "slaps" the leak shut when I'm awake.

When I'm asleep though, it appears this occurs and then I wake up with dry mouth. It only happens every so often.

So here's my question(s).

Since the CPAP pressure helps force the soft palate down so the back of the throat is sealed, do I now need to have the pressure increased to help close the palate so air doesn't escape from my sinuses/throat back into my mouth?

Everything I've read indicates that if your AHI is less than 5, your pressure is adequate. So should I raise it considering the other side effects to the higher pressure?

Finally, a chin strap doesn't seem to affect my throat being closed as it can still blow back the air... So why should I use one?

I'm 68, and use the ResMed AirFit P10 nasal pillow mask and have the same issue with mouth leaks. I've tried using a full face mask (F20) but then I breathe through my mouth and my mouth is still dry in the morning. Also I find the P10 far more comfortable than the F20. I have tried about 4 different kinds of chin straps and you are correct, in that while they help they don't totally eliminate the leakage of air out of the mouth. So now I have resorted to taping my mouth shut with 1" paper medical tape. I fold over about 1/4" at one end to leave a tab to make it easy to remove in the morning or in the middle of the night if necessary. The best chin strap I have found is the Breathewear Halo. With the chin strap and tape combined, I pretty much eliminate any leaks. I run a minimum pressure of 11 cm and maximum of 12, and the tape holds.

I don't think increasing pressure is the solution to your mouth leakage problem. In fact I suspect it will make it worse. Before I started using the tape I would wake up with lots of pressure in my mouth, and simply unable to keep my lips together.

Try this maneuver: When you're ready to go to sleep and before your machine has been turned on, press your tongue against the roof of your mouth. Let the tip of your tongue rest against the backs of your upper front teeth. Relax. This should be a comfortable position. Turn on your machine. You do not have to consciously make your tongue stay where you have positioned it. Just relax and go to sleep this way. Your tongue will stay right where you left it. Somehow this seems to prevent the back flow. In the morning, you won't have dry mouth.

I agree with Sierra that raising your treatment pressures will likely make your problem worse. It's great to see that AHI under 5...and down from 80. Wow. That's great work!