We brought our cat in (same day) because he asked to go out, and instead lay down on the threshold, panting. Not sure if that fits in the 'trouble breathing' category or 'behavior changes' category. I think we did the right thing as he ended up having a urinary tract infection.

Thanks for doing this. it is very helpful. Do yo offer your clients 'pet 101'? Not knowing about purring would seem to indicate a need.