Administration
The gas is self administered through a demand valve, using a mouthpiece, bite block or face mask. Self-administration of Entonox remains safe because if enough is inhaled to start to induce anaesthesia, the patient becomes unable to hold the valve, and so will drop it and soon exhale the residual gas. This means, that unlike with other anesthetic gases, it does not require the presence of an anaesthetist for administration. The 50% oxygen in Entonox ensures the patient will have sufficient oxygen in their system for a short period of apnoea to be safe.
Read more about this topic: Nitrous Oxide And Oxygen