1. A method for controlling the delivery of a breathing gas to a patient, the method including: regulating the delivery of the breathing gas delivered to the patient; determining a value of a first ventilation parameter, the first ventilation parameter comprising a physiologic parameter of the patient; comparing the determined value of the physiologic parameter of the patient to a pre-determined target value for the first ventilation parameter; automatically adjusting the breathing gas delivered to the patient in response to the comparison between the determined value of the first ventilation parameter of the patient and the pre-determined target value for the first ventilation parameter; and automatically determining a new target value for the first ventilation parameter based at least in part on the determined value of the first ventilation parameter of the patient.