As nitrous oxide diffuses out of the body, it reduces the amount of oxygen within the airways, and there is a relative diffusion hypoxia. Because of this, it is sometimes recommended that after the procedure is finished, that the person be placed on 100% oxygen to help diminish this diffusion hypoxia. I find that it is not necessary to do that when using nitrous oxide for conscious sedation/analgesia for outpatient procedures in healthy patients.
