This is a complicated issue for me, as I can see it is for many. First, I have a deviated septum, and a pretty deviated nose, too, from my youth, when I not only played sports (football, wrestling, track), but I also was involved in several accidents where I had skull, neck, head, and/or facial injuries. So, my nose has been broken more than ten times, and my cheekbones/eye sockets/skull, neck, etc., too. Also, at the age of twenty, I had oral surgery where they cut my jaw muscles, which never healed back correctly. Then, I had my neck broken twice, skull fractured multiple times, and also rib and hip fractures, as well as arms and legs, etc. I also drank like a fish, raced cars and motorcycles, and worked extreme jobs where I was exposed to things that tried to off me, like the time I was salting cow hides in a hide pit and the floor man set up the bug fogger aimed at the pit I was in, not realizing I was there. I woke up in the hospital in dire condition. But I survived all this mayhem, and a lot more later as an adult. I've been thrown from a cutting horse 15 times in one day, been in more than 30 serious accidents (I also drove a big truck for 40 odd years), and so on. Just your typical active young life. To make a short story long, I don't breathe well through my nose at all. I also cannot sleep on my back at all. Can't breathe in that position at all.
So, I sleep on my stomach, with my face and torso turned somewhat to the left. So, my left shoulder is up a bit, my right arm straight up under the pillow towards the wall, my left arm bent and on top of the pillow, with my head resting on my hand. I've slept this way since my twenties, and cannot sleep any other way and breathe. I am also now barrel-chested due to lung expansion from C02 build-up. I sleep with my cannula on at 3 lpm. I sleep for 3-4 hours at a time, no more, and it is not very high-quality sleep. So, I am up for approval for a home ventilator, though still waiting. I do take naps some days.