A ventilator or fluid delivery system that provides a flow of gas to an airway ofa user. The ventilator includes a source of gas (30, 32), a conduit (63, 65, 42)that carries the flow of gas to the airway of a patient, a first valve (38, 40) thatcontrols a pressure, flow, or volume, of the flow of gas, a pressure sensor (46)operatively coupled to the conduit between the valve and the patient and adaptedto monitor a pressure of the gas in the conduit, and a controller (50) adapted tocontrol the valve based on an output of the pressure sensor. The ventilator furtherincludes a restrictor (62) provided in the conduit between the pressure sensorand the patient. The restrictor, in essence, divides the fluid delivery systemsuch that a first volume is defined in the conduit between the valve and the restrictorand a second volume is defined in the conduit between the patient and the restrictor,wherein the first volume is less than the second volume. The control system controlsthe pressure, flow, or volume relative to the first volume so that an accurate,fast, and stable control of the pressure, flow, or volume is achieved.
