[MysticCat]

What Dionysus said.

My wife used to have them. While it's happening, back off some -- he feels like the world is closing in on him, so you don't want to add to the feeling that it is.

Best thing you can do is make sure he knows you don't think he's crazy and that you want to be helpful and supportive. But the bottom line is he's going to have to do the work himself (1) to figure out what's at the root of the anxiety and (2) what works for him in preventing them.