Please do not try this at home. Repeat: DO NOT TRY THIS AT HOME.
Even though that scientist appears to be drinking liquid nitrogen, it seems that all he’s doing is swallowing the condensed vapor, blowing it out through his mouth and nostrils. In any case, this strikes me as a very bad idea. Oh, maybe the Leidenfrost Effect could protect you for a short while in case you swallow some liquid by mistake, but I wouldn’t really count on that for the benefit of your continued health and comfort.