This same exact thing happens to me, especially when I am driving. And I can't even get a yawn to happen. I start feeling disconnected, like I can't feel my face. I try to explain it like this; you know this cheap halloween masks with the rubber band that holds them on your head? If you were to put one on, and pull it off your face about an inch or 2 and trying to see the world from that perspective.
The only thing that comes close to working for me is having the cold air conditioner full blast in my face. Every once in a while I will catch a full breath and feel like I can go on for a few more miles before I start panicking again that I will faint from lack of oxygen. Sometimes I just have to pull into a parking lot and collect my senses. Maybe call someone to get my mind off my situation.
I had it severely over the weekend. I had woken up at 3:30 in the morning, my usual wake up time, but it being Saturday morning I went to bed late - I could not catch my breath for anything. I found that giving a little cough after the futile inhale seemed to alleviate it just slightly. Eventually I turned my hemi-sync MP3 and listened through my headphones from my iPhone - and that seemed to do the trick. Maybe it's mental and somehow I have it reasoned in my mind that that relaxation technique is some sort of "safe zone" for me. I ended up getting out of bed at 9 that morning - which is unheard for me, being an early morning person.
So, i can sympathize. And regardless of my therapist asking, "well, have you ever passed out", and being no; it still does not put my mind at ease. I figure, there is always a first time for everything. and then the therapist said, which is true; that, "if you did pass out; it is just your mind re-regulating your normal function because you are not capable on the conscious level at the time". Which is a little soothing, if I am at home on the couch when that regulation happened, and not driving, or in the middle of a store, or business meeting.
Essentially, before I go to a business meeting, I have to take at least 1mg of Xanax about an hour before in order to cope with it - then a few hours later, after the meeting, fight the urge to go to sleep gazing at my computer, trying to be creative on the heels of a stressful situation.