Well that's some interesting information.

Anyway, all I really knew was it fatigued and got exhausted, didn't know about the oxygen part

With the monster exp, I believe Little Nepents should be higher than Dire Wolf. Little Nepents (not that little) are level 3's, Kirito 1hko a Dire wolf at level 1, (at least that's what it looked like at the end of episode 1)
If something is wrong with that information please correct me.