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.