The invention relates to a method which is carried out by means of a device for dispensing a gaseous mixture, including a gaseous mixture outlet connected to a first gas source including oxygen O2 as well as to a second gas source including, for example, nitrous oxide N2O, via means for mixing gases and means for monitoring the gaseous mixture. A step of initialising (61) the dispensing of the gaseous mixture is carried out by activating a first parametrisable program controlling the monitoring means such as to follow a predetermined rising curve (64) of variation over time of the concentration of N2O in the mixture.
