Source : Webster's Revised Unabridged Dictionary (1913)

Respiratory \Re*spir"a*to*ry\ (r?*sp?r"?*t?*r? or r?s"p?*r?-),
   a. (Physiol.)
   Of or pertaining to respiration; serving for respiration; as,
   the respiratory organs; respiratory nerves; the respiratory
   function; respiratory changes.

   {Respiratory foods}. (Physiol.) See 2d Note under {Food}, n.,
      1.

   {Respiratory tree} (Zo["o]l.), the branched internal gill of
      certain holothurians.

Source : WordNet®

respiratory
     adj : pertaining to respiration; "respiratory assistance"