I hope you're ok. Take your time. Sit down. Watch cat videos or something hilarious, that will maybe catch your attention. That happens to me once or twice a month, if I'm exhausted and start coughing.
I'm not a doctor, and these may not work but, it's worth a shot. Just remember, it's scary but, I promise you'll be okay when it's over.
It'll suck for a minute but, then you'll come out of it. One thing about panic attacks is that as much as they feel like they're going to last forever, they haven't yet.
EDIT I hope this doesn't come of as condescending. I'm trying to be reassuring.