Certainly go to the ER if it goes low but you can still function; if not, call 911. I can usually function reasonably well until my 02 goes quite low, but I wouldn't hesitate to call 911 if I was really in trouble. Usually it won't just drop like a rock; it will just go a bit lower over time. I came home from Baltimore with a nasty cold, and my 02 dropped quite slowly over a couple of days until I had to increase my usage and settings.

Hello Karen If you don't have oxygen and can't breathe please go to the ER Be safe

Thanks, I had bronchitis which caused drop & had to go to ER, in hospital 4 days, hospital would not release me without getting ox at home.
Now my pulmonologist says I do not need the home ox, have not used it at all. So that is why I ask if ER, which was a terrible ordeal, is only solution. Any other ways to raise ox level? I am new to COPD, moderate.