My doc had spoken to me about all day O2, but I refused. He said if it went below 90 I was hitting the danger zone. I was close. I had quit smoking on 6/22/2007. In 2013, I had 2 knees replaced, anaphylactic shock, a pacemaker, breast cancer, and one of my oldest friends died. It was a stressful year. I so wanted a cigarette. With my O2 that low, I'd be an idiot. Little did I know that vaping was good for me!