Apparatus for delivering pressurized gas to the airway of a patient including: a gas flow generator for providing a flow of gas, a breathing appliance for sealingly communicating with the airway of the patient, and a conduit for delivery of the gas flow to the airway of the patient, the conduit having a first end connected to the gas flow generator and a second end connected to the breathing appliance. The apparatus further includes at least one sensor in fluid communication with the conduit and located substantially at the gas flow generator for detecting conditions corresponding to breathing patterns of the patient and generating signals corresponding to the conditions, and an information processor for receiving the signals and for controlling the output of the gas flow generator responsive to the signals. The apparatus further includes a gas flow pressure filter comprising a compliant chamber to reduce unwanted pressure fluctuations in the circuit to allow for the detection of desired signals, such as snore sounds.