An air delivery system includes a coupling mechanism that is adapted to be connected
between a source of oxygen-enriched air and an air cannula that can be worn by
a user. The coupling mechanism includes a spool assembly for paying out and for
winding up a predetermined length of tubing coupled between the air cannula and
the source of oxygen-enriched air. The spool assembly has a sufficiently low drag
factor to allow complete mobility of a user wearing the cannula without causing
it to be dislodged during pay out of the predetermined length of tubing and without
causing it to be dislodged during take up of the predetermined length of tubing.
