Panic attacks and fainting are not the same thing, but apparently in your situation Mark, they are intertwined. Fainting involves blood vessels relaxing to the point where blood rushes towards your feet. It doesn't take long at this point before you lose consciousness, especially if you are already breathing improperly (not saying that you are). All the air in the world won't help you at this point, the only thing that can help is to get the blood back up to your head (bend over, then sit/lie down and elevate your feet).
If what you are experiencing S.not involves feelings of dread and doom, just take a second to check your breathing to see if it has become shallow. When I was having daily panic attackes, it would get so shallow that I wasn't sure if I was breathing at all. If this turns out to be the case for you, you should know that a large part of the anatomy of a panic attack involves rises in CO2 levels in your bloodstream as well as sitting in your lungs.
Hope this is of help.
Guilt and shame have never done any of us any good at all.