Learn how to breath properly, deeply from the diaphram, inhaling through your nose and holding it for 10 seconds, slowly exhaling to the count of 10. Google some
Yogic breathing or places like the Mayo or Cleveland Clinics have good advice for breathing through a hyperventalation episode.
I used to have it very badly and what worked for me really good and very quickly was breathing into a small paper bag placed over both my nose and mouth.