The knife most certainly didn't puncture his respiratory system. It looks like a 3 and half inch blade and combined with the heavy clothing I'd bet that knife never penetrated more than a inch or two. It's remarkably hard to stab someone, despite what movies like to show. You can get lucky with a little folder like that but there is a reason dudes in the know carry daggers. Even then the guys who practice this stuff professionally don't stab. It's all a game of cutting and slashing, that way you don't eviscerate your own palms.