A nasal cannula system includes a nasal cannula for the delivery of and collection of gases, wherein the nasal cannula is coupled to a pair of extension tubes which are slidingly received within right and left earpieces respectively for retaining and securing the extension tubes to fix the cannula in a desired position for use by a patient. Each nasal cannula includes an open recessed channel disposed between a pair of bridges for retaining the extension tube within the earpiece and an locking exit hole at its distal end for helping to secure therein the extension tube to provide a fixed distance adjustment between the nasal cannula and the ears of the patient.