I have to get regular blood work because of my medication, and it never really became less trepidating.  So each time, I have a moderate panic attack, and the nurses hear my deep breathing and frantically say, "Are you okay?!  Should we stop?"  I think they're more anxious than I am at that point. 

Maybe I should say beforehand,."I'm going to have a panic attack when you do this.  Just ignore it, and it will be fine."