I also use an oxygen concentrator at night (because I live close to 7,000') and where I'm having surgery is about 3,000'...so that should help, too. At least having the O2 handy will make me feel like I'm getting some help during the night.
49er, I will ask my surgeon to clarify his reasons. My pressure is "set" at 8 and that doesn't seem like it's going to blow my stitches apart. I haven't slept one night without CPAP since I got it about three years ago. Well, maybe I'll be so "loopy" after surgery, I'll fall asleep and do OK.
Thanks everyone for your very helpful suggestions! Hugs to you all from the high desert of Nevada.