I never have to personal doctor experiences. But I definitely have when watching medical documentaries. I don't know all the specifics of organ transplants, but I do see that often after a patient recieves an organ transplant, she must be taken on short walks down the hall just to test and build up her stamina and such. And often, that appears to be her first time wearing a mask (pre-2020, anyway) for her immune system (though I know this isn't always the case).
One such case literally left me shaking after I went to bed that night (fetishes are a powerful thing). The cameras were on a thin, dirty blonde, bronzed upper-teen young woman who had just had a heart transplant. She was filmed in matching red shirt and pants (maybe pajamas, couldn't tell) surrounded by nurses and doctors. She was beginning to walk outside her hospital room, and for that,, she needed to wear a pleated yellow earloop surgical mask. I couldn't get to sleep until I masturbated at least a couple times.
Another such case is kind of the same thing, but the girl (a fair skinned dark haired girl), is in a purple button up shirt, black pants and a grey elastomeric respirator with pink pancake filters to protect a new set of lungs (video below). A nurse is heard urging her to walk down the hall to see how far she can walk. At this hospital, the patient wears a pleated yellow earloop before transplant, but afterwards, she is given the big grey respirator mask to wear.
https://patch.com/california/danville/srvhs-alum-talks-about-double-lung-transplant