Dyspnea (or shortness of breath) was a medical term describing a sensation of difficulty in breathing.
Dyspnea was generally considered a symptom of disease. In some species, such as Tellarites, it was considered a sign, i.e., a medical indication only detectable by a physician.
In 2365, Kareen Brianon told Dr. Selar that Ira Graves was experiencing pain, shortness of breath and irritability. (TNG: "The Schizoid Man")
Doctor Julian Bashir downloaded data about dyspnea, coughing, and other pulmonary disorders onto a PADD shortly before he left to attend a medical conference on Casperia Prime in 2374. (DS9: "Inquisition")
Later that year, Seven of Nine experienced an acute anxiety attack after being scanned by The Doctor in sickbay with symptoms including intense apprehension, shortness of breath and dizziness. (VOY: "Retrospect")
In 2376, Neelix claimed that simply thinking about the fate of the Salvoxia and its crew made him short of breath. (VOY: "The Haunting of Deck Twelve")