Back when I was fininshing my pregrad, had a patient come in with COPD/chest pain, possibly pneumonia (don't recall details exactly.) Of course, she was a smoker. After Ventolin q. 4 h. around the clock, she was starting to feel a bit better. It was the end of a reaaaallly long night shift, and with the previous mask, I found I had to keep an eye on her to keep her from removing it. Well, 6 am. rolled around, and sure enough, I came back to check on her after finishing my med pass, and the mask was on the floor. I tried to put it back on her, and she said: "Don't bother. I don't want it." I tried to explain why she needed it, and she got nasty with me, then tuned me out.
One of the few times I recall swearing at a patient while still within their hearing....

The other patient in the room heard me, too.