Grubi, I haven't much time (just came to read) but I can give a quick tip to try. For a deeper explanation, look at the video on my blog about breathing in the asthma sections. The simple version is, if you overbreathe, lack of carbon dioxide stops oxygen getting into the cells (eg, the brain). It seems converse to what you'd expect to happen from overbreathing, but CO2 is needed to transport the oxygen. This sets up a cycle where all kinds of crises happen in the body. And a panic attack causes over breathing almost as bad as asthma does - that panting, big breath, shock type breathing. To avert an attack almost immediately, hold your breath. Sounds too simple, but as the CO2 builds back up in your system, your body and mind will start to relax. Cut off the loop by cutting down the breath. Then "mouse breathe" this is what we describe to children to make it fun, but it's just breathing so small that you can barely feel it when holding a finger in front of your nose (btw, NEVER mouth breathe!!!). It will feel uncomfortable, like your dying to take a deep breath or that your starving of air. Ignore it, and soldier on. Stay uncomfortably needing air for a good five minutes, then resume regular (gentle nose) breathing. Don't deprive yourself to gasping stages, that's counter productive. But do starve of air a little.

My brother, an addict and panic attack extraordinaire in his hey day, can avert a panic attack with breath alone now.