[maxton]

The article you linked is littered with misinformation. I would not recommend that anyone read it.

It asserts "facts", like the false statement that wearing a mask lowers blood oxygen concentration by 20%, using citations of Facebook videos and conspiracy theory "news" websites as sources.

[coldtea]

I don't know about 20%, but here's an earlier non-partisan research on medical staff wearing masks:

http://scielo.isciii.es/pdf/neuro/v19n2/3.pdf

Some rebuttals on the current concerns I've seen are just some doctors on their own doing a self-test (under god knows what standards and not peer reviewed).