LSJ
ον, Att. κακόπνους, ουν, (< πνοή) breathing with difficulty, Poll. 1.197.
Liddell-Scott-Jones, Greek-English Lexicon (9th ed., 1940)
Pape
zsgzn κακόπνους, schlecht, schwer atmend, Poll. 1.197.
Pape, Griechisch-deutsches Handwörterbuch (3. Aufl., 1914)