The Collaborative International Dictionary of English v.0.48:

Eupnaea \Eup*n[ae]"a\, n. [NL., fr. gr. ? easy breathing; e'y^
   well + ? to breathe.] (Physiol.)
   Normal breathing where arterialization of the blood is
   normal, in distinction from dyspn[ae]a, in which the blood
   is insufficiently arterialized. --Foster.
   [1913 Webster]