Whipits are fairly benign, so I wouldn't attribute your incident to that. Think about it, when you get a tooth pulled or filled, your dentist gives 70% Nitrous Oxide (whipit) and 30% oxygen (the same amount that is in the atmosphere) for an extended period of time. It can cause b12 deficiency, but not one or two.
I think I know exactly what happened...you had a panic attack.
Feeling like you have depersonalized or seeing your self in the third person is typical of a grade A freak out, as is hyperventilating and going pale and tingly. Don't dwell on it, odds are you got light headed, then you tried to get air by hyper or hypo ventilating, which caused you to feel more light headed, maybe even like you were going to pass out. Trust me, this was a panic attack, nothing more. If you are worried, go see your doc and tell him you are worried about your hear and/or lungs, he'll do a chest x-ray and an EKG and they'll both come back completely normal.
Seriously, don't sweat it man.