I've only had one panic attack in my life, it was at download festival,was watching metallica on stage and I was smack bang in the middle of thousands and thousands of people.
I was fine for twenty minutes until I started thinking about getting crushed, escape routes etc... started breathing fast and heavy, sweating and overheating so just closed my eyes and pushed to the edge to get out which must have took 5 minutes then got some water and felt fine after. Was scary at the time.