A system and method for delivering a flow of breathing gas to an airway of a patient. A characteristic that varies based on variations of the flow of the breathing gas is monitored and used to determine a Target Flow for the gas delivered to the patient. The Target Flow is set to a level sufficient to treat Cheyne-Stokes respiration or a sleep disordered breathing event. The Target Flow is altered if the patient experiences a sleep disordered breathing event. In a further embodiment, the system determines an apnea detection time (Tapnea) as Tinsp plus a constant, and delivers a machine triggered breath if an amount since the start of inspiration reaches Tapnea. Yet another embodiment monitors the characteristic during an inspiratory phase of a respiratory cycle, and controls the flow of gas during the inspiratory phase of the respiratory cycle based on a result of this comparison.
