I started BiPAP a couple of years ago and haven’t experienced increased gas. If you’re swallowing air perhaps a chin strap would be worth a try. I can think of two possible causes of the nighttime accidents: the increased gas or the deeper (and better!) sleep. Do you take a bowel slower (Imodium or Lomotil) at bedtime? I’ve found Lomotil to be helpful. A small, fatty meal (like a spoonful of peanut butter) at bedtime can also slow things down. Good luck!