Earlier quoted context omitted.
Wouldn't you already be super dead with a true reading of 80? Or at least unable to cognitively interpret the reading?
That's definitely a danger zone for healthy people but interestingly enough people with things like COPD may have a blood oxygen level in the 80s and while that is indicative of the disease, they may be totally stable and may not even need oxygen [1]. [1] https://www.drugs.com/medical-answers/normal-oxygen-level-so...
[0]: https://en.wikipedia.org/wiki/Effects_of_high_altitude_on_hu...