A pressurized flow of breathable gas is delivered to the airway of a subject to facilitate respiration by the subject. To enhance the effectiveness of the pressurized flow of breathable gas, stochastic fluctuations in the level of pressure at or near the airway of the subject are created. These stochastic fluctuations mimic similar oscillations present in so-called bubble CPAP systems. Since these stochastic fluctuations are intended to maintain the openness of the airway of the subject, and not to drive ventilation, these fluctuations tend to have a higher frequency and/or lower magnitude than changes in pressure that drive ventilation.