"If you can talk, you can breathe," would be a good myth to dispel. It's behind a number of accidental killings by police, including the current high-profile Garner case out of Brooklyn, and I literally just now saw it in a TV show on Netflix.
The gist of it is that the short-shallow breathes required to speak are not enough to keep you alive, but I'm unfamiliar with the mechanics of inhalation/exhalation and 'functional reserve capacity' beyond just 'this is what the diaphragm does,' and I only know that much due to public education. I expect most people would be in the same boat. It could make for a nice bit of science chat.