Abstract: A system for delivering a humidified gas to a patient is disclosed. The system includes a supply tube having a first supply tube end and a second supply tube end. The supply tube has a first inner diameter. The system also includes an apparatus for delivering heated and humidified gas to the first end of the supply tube and a single lumen having a first lumen end and a second lumen end. The single lumen has a second inner diameter, smaller than the first diameter. The first lumen end is in fluid flow communication with the second supply tube end. The system also includes a nasal cannula in fluid flow communication with the second lumen end. A method of delivering heated and humidified gas to a patient is also disclosed.