Ol Mike's story reminded me. Twice in HS I had phlegm block my airway while sleeping. Once I managed to wake up somehow and get it loose. Another time my older bro dragged me out of bed and whacked scheidt out of me to loosen it up. Still needed O2 that time when the FD arrived. I honestly don't remember being dragged off the top bunk by my bro, so maybe I was on my way??
I still have a tendency to avoid sleeping flat on my back and positively hate post nasal drip crap after those events.