Trying to move to nasal/pillow mask. Leaks?

[tedgreen]

mouth breathing tends to lead to OSA and snoring

You have the causation backwards.  Sleep disordered breathing tends to lead to mouth breathing and snoring.

From what I have read, mouth breathing increases the chance of snoring and obstruction.

[holden4th]

I got a nasal mask initially because I am a side sleeper and a FFM was never going to be an option for this reason. I am (was?) a mouth breather and read early on about the tongue suck procedure and think I now do it automatically unless I lie on my back. I try and nose breathe during the day to reinforce the habit.

The biggest change for me was ditching the chin strap for the cervical collar.

[Sleepster]

I wear the same full face mask as you and sleep on my side or stomach. I use the Papillow. If sleeping on your back was making your OSA worse you'd see a higher AHI. I don't believe that a full face mask increases mouth breathing for the reasons I stated, but that is just my opinion.

To answer your original question, mouth-leaking for me showed up on my leak rate graph as chunks of time (10 to 20 minutes or so) when the leak rate was elevated by 15 to 20 L/min or so above the baseline. I also experienced fragmented sleep.