Slitter

grabcad

This doesn't work. It will leak oxygen and cause a fire hazard but it's kinda cool. I don't see any other submission that works either, so throwing this in the hat. You have threads that can't be printed and crimping of the cannula tubes. If I were a patient I wouldn't want to know that someone is crimping my oxygen supply line with no regard for short/long term deformation. This contest was a great feasibility study on FDM solutions for this application.