Yep, I am no doc, like doc, but Ive spent 61 nights in hospitals, (Cali to Texas, to NJ) in the last 8 years...thank goodness not in the last two years, starting with ER then ICU, Ive never worn personal clothing nor tanks, they are piped, and I have low O2 levels. After the ER, my O2 gets to normal, usually around 98. My personal internal med Dr clash with ER docs as to my O2 levels.