A system for delivering a flow of breathing gas to an airway of a patient, the apparatus comprising: a gas flow/pressure generating system for generating a flow of breathing gas; a patient circuit coupled to the gas flow/pressure generating system and adapted to communicate the flow of breathing gas to an airway of a patient; monitoring means for monitoring a characteristic that varies based on variations of the flow of the breathing gas, wherein said characteristic includes the flow of gas at the patient (Q patient); a controller configured to determine a Target Flow to be delivered to the patient based on the monitored characteristic, wherein the Target Flow is set to a level sufficient to treat Cheyne-Stokes Respiration or a sleep disordered breathing event, wherein the controller is configured to determine whether such a patient is experiencing a sleep disordered breathing event by analyzing the flow of gas at the patient (Q patient), wherein the controller is configured to alter the Target Flow based on a determination that such a patient is experiencing a sleep disordered breathing event, characterized in that the controller is configured to determine an Instantaneous Average Inspiratory Flow (Qave(t)) during an inspiratory cycle based on the instantaneous flow of gas at the patient (Q patient), wherein the Qave(t) is the summation of inspiratory patient flows over a period of time divided by the number of samples taken during the period of time, and wherein the controller is configured to determine a Maximum Average Inspiratory Flow (Qave(max)) as the maximum value of the Qave(t) that occurred during the inspiratory cycle of one breath, wherein the controller is configured to compare the Qave(max) to the Target Flow, and wherein the controller is configured to control the gas flow/pressure generating system based ona result of this comparison. a gas flow/pressure generating system for generating a flow of breathing gas; a patient circuit coupled to the gas flow/pressure generating system and adapted to communicate the flow of breathing gas to an airway of a patient; monitoring means for monitoring a characteristic that varies based on variations of the flow of the breathing gas, wherein said characteristic includes the flow of gas at the patient (Q patient); a controller configured to determine a Target Flow to be delivered to the patient based on the monitored characteristic, wherein the Target Flow is set to a level sufficient to treat Cheyne-Stokes Respiration or a sleep disordered breathing event, wherein the controller is configured to determine whether such a patient is experiencing a sleep disordered breathing event by analyzing the flow of gas at the patient (Q patient), wherein the controller is configured to alter the Target Flow based on a determination that such a patient is experiencing a sleep disordered breathing event, characterized in that the controller is configured to determine an Instantaneous Average Inspiratory Flow (Qave(t)) during an inspiratory cycle based on the instantaneous flow of gas at the patient (Q patient), wherein the Qave(t) is the summation of inspiratory patient flows over a period of time divided by the number of samples taken during the period of time, and wherein the controller is configured to determine a Maximum Average Inspiratory Flow (Qave(max)) as the maximum value of the Qave(t) that occurred during the inspiratory cycle of one breath, wherein the controller is configured to compare the Qave(max) to the Target Flow, and wherein the controller is configured to control the gas flow/pressure generating system based ona result of this comparison.