A breathing assistance device, capable of operating according to several respiratory modes forming a list of possible modes. The device is equipped with a mechanism for selecting a desired mode from a group of modes that can be selected. The device also includes a mechanism for realizing a configuration diagnostic of the device, a mechanism for associating with authorization level with each possible mode, according to the results of the diagnostic, with the lowest authorization level corresponding to unauthorized modes, a mechanism for authorizing only the selection of authorized modes, in such a way that selecting unauthorized modes is impossible.