i have had them and they are awful, but cannot harm you! i also work in a dept that teaches people how to avoid them ...
if it is a true panic attack then it is too much carbon-dioxide in the blood, bringing on muscular changes and the feeling of panic! overbreathing can cause it, so don't take deep breaths to conquer them; the paper bag trick works just as well as cupping your hands over your nose and mouth, though!
BUT some panic attacks are more psychologically based, and can be avoided by not dwelling on things that make you anxious, esp. the thought of a panic attack!
i would go to the GP surgery to check there isn't an underlying lung problem first, and then try to become less anxious!
http://www.anxietyuk....ZSJnK8CFcYOfAodj2azbg
plus sites like this may help!