They don't wear the masks in every public setting they visit. They wear the masks during surgery because there are open wounds that are easily infected. Also they don't wear the same masks day afer day after day.
They wear them for many hours every work day.
Also they don't wear the same masks day afer day after day.
Which would have no affect on the concentration of CO2, which is the basis for this paper's claims.
Face it, if this paper were accurate we would have a mental health crisis affecting most of our healthcare workers.
I think I read somewhere that do something in operating rooms to put more oxygen into the air, or otherwise improve air quality to make up for the masks.