The Collaborative International Dictionary
Orthopnoea
Orthopnoea \Or`thop*n[oe]"a\, Orthopny \Or*thop"ny\, n. [L. orthopnoea, Gr. ?; 'orqo`sstraight, right + pnei^n to breathe: cf. F. orthopn['e]e.] (Med.) Specifically, a morbid condition in which respiration can be performed only in an erect posture; by extension, any difficulty of breathing.
Wiktionary
orthopnoea
n. Shortness of breath when lying flat.
orthopnœa
n. (alt form of orthopnoea English)