Anesthetic Ethyl Chloride Spray is first sprayed in the mask, as it is pleasant and potent, it produces unconsciousness in 1-2 minutes.
Ether is then introduced till the patient is anaesthetized to Guedel ‘s stage III and plane H when respiration is regular, eye movements cease, pupils are in mid position and reflexes absent (eyelid, comeal, conjunctival, swallowing).
Anesthetic Ethyl Chloride Spray is the plane of surgical anaesthesia. In stage IV (which should be avoided) the respiration stops, pupils are central and dilated. This stage can be reversed by cutting off ether due to its high therapeutic ratio, i.e., the dose required for surgical anaesthesia and severe cardiac depression is high. (Ether has also been used in semi-closed and closed anaesthesia circuits.)