The Collaborative International Dictionary of English v.0.48:

Dyspnoea \Dysp*n[oe]"a\, n. [L., fr. Gr. ?, fr. ? short of
   breath; pref. dys- ill, hard + ?, ?, breathing, ? to blow,
   breathe: cf. F. dyspn['e]e.] (Med.)
   Difficulty of breathing.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dyspnoea
    n 1: difficult or labored respiration [syn: dyspnea,
         dyspnoea]