For diffusion hypoxia to occur during emergence from an anesthetic in which nitrous oxide is used, the

  1. anesthetic must have contained more than 50% nitrous oxide
  2. patient must breathe spontaneously
  3. anesthetic must have lasted more than 45 minutes
  4. patient must breathe room air at the end of the anesthetic

Any and/or all of the answers may be correct

All discussion re: this question is welcomed... even if you don't wanna commit to an answer! No pressure here