There's already a pretty gaping issue here.
There's nothing 'rational' per say about mental/personality disorders. It's like sitting there, watching someone have a panic attack and saying. "What your doing is irrational." It's not going to magically snap someone out of it. They usually know it's irrational but that's how a disorder works.
The focus is not on snapping them out of the panic attack, but rather in preventing and minimizing the panic attack, and also doing so for the after effects of the attack (shame, fear, guilt, etc). The impact of the irrational thinking is felt at every turn; before, during and after the attack, and can therefore be challenged/disputed at every turn as well.
A common problem for a person who suffers from panic attacks is that they so fear the actual panic attack that they bring it on themselves. Their thinking may go something like this, "I can't stand to have another panic attack, it was so horrible, I was so embarrassed, it must not happen!"
If I tell someone, "you must not look to your left" most will instinctively look to their left. I think a similar principle works with this type of thinking as well.
I don't know why, but when someone demands that something "must not happen" they add a certain gravity to the happening or not happening, and therefore distort the reality of the situation. Then, if it does happen, it is "horrible," after all, we "couldn't stand it" happening, so it must be really bad!
Then, when a panic attack hits them they tell themselves, "Dammit, I shouldn't have these panic attacks, I am weak and defective, and people think that of me too." REBT refers to this as a "secondary disturbance" or being upset about being upset.
So what you do is help the person realize that the panic attack is inconvenient, not "horrible" or "unbearable." After all, the person has survived many before, right? Once they rationally consider that the attack is merely inconvenient, they can demystify the whole thing and take much of the power out of it.
You can also help them cope with the attack, but that is different than addressing the underlying causes- irrational thinking.
The therapist will also want to strongly challenge the self-downing, such as when a person suffers and attack and then tells themselves "I am defective for having panic attacks" or something of the sort. This further takes the power and gravity out of the situation.
The therapist will also look for deeply rooted beliefs, such as "in public I am in danger" and the like, which may act as specific triggers of panic attacks, and challenge those irrational beliefs as well.