.....i think its the breathing part with or w/o oxygen. while not a panic attack in the true sense my initial reaction to a hit, yrs ago, was panic and thrashing and swearing and working myself into a frenzy. it took a while but i finally figured this over the top reaction was getting me nowhere. all this to say i adopted a verrrry slow deep breathing technique when aborting with O2 that had a remarkably calming, almost meditative effect and actually used an lpm similar to yours. aborts became quicker and calmer! your breathe and hold is another favorite....try this slow/deep....maybe even w/o the O2.