I dont believe its possible or likely. The closest recorded accounts I've personally read are japanese samurai/sword masters projecting kiai and subduing small birds at a close range. But that also could be a complete falacy, or even just do to shock a particular breed of bird may experience under such conditions..ie: a set up.
qi projection though to knock someone down/out? nope. If I ever met anyone claiming that I would ask them to do it to me and then laugh when they couldnt.
Here is what really happens when a Kiai master /Qi projector of a high rank meets a fighter who is not a brain washed student.
http://www.youtube.com/watch?v=gEDaCIDvj6I
For whoso comes amongst many shall one day find that no one man is by so far the mightiest of all.