Abstract: A patient interface system for delivering a gas to a patient includes a patient interface device that includes at least one inhalation valve and at least one exhalation valve. The system also includes a venturi device that has at least one port for connection to a gas source. The venturi device has at least one primary air entrainment window and at least one secondary air entrainment window which is downstream of the at least one primary air entrainment window. The inhalation valve is disposed between: (1) the main body and (2) the primary and secondary air entrainment windows of the venturi device. At least one of the primary air entrainment window and secondary air entrainment window includes a means for closing the respective window, thereby changing a degree at which the respective window is open and changing a flow rate of the air flowing through the respective window.

Abstract: A venturi connector includes a housing having a mixing chamber defined therein and at least one window that is in fluid communication with the mixing chamber and is open to atmosphere to allow air to be entrained into the mixing chamber. The connector includes a nozzle actuator member includes a body having a plurality of discrete nozzles formed therein. The nozzles are defined by different sized venturi orifices through which gas flows, thereby allowing the concentration of the gas delivered to the patient to be varied. The nozzle actuator member is disposed within one window formed in the housing between the gas port and the mixing chamber such that the position of the nozzle actuator member within the housing can be adjusted so as to position one of the discrete nozzles into the gas flow path, thereby controlling the flow rate of the gas into the mixing chamber and ultimately the concentration of gas delivered to the patient.