Fig. 4:  The etymology of “dyspnea” goes back to two Greek words, referring to a bad breeze or to difficulty breathing.  As a condition it certainly is subjective, but although it is subjective it can certainly be measured, because it relates to breathing discomfort that consists of qualitatively different sensations that vary in intensity. 

This is the definition of dyspnea from a statement issued by the American Thoracic Society (ATS).^[1]  Dyspnea has three major qualities (although there are more).  First, there is the sense of respiratory work or effort.  This concept of a perception of increased work or effort goes back to the 1980s, when it was probably thought of as the major etiology of dyspnea and chronic lung disease, and it probably still is the overriding basis for dyspnea. 

There is a also a qualitative sensation of tightness, which as one might guess may be associated with bronchospasm and “air hunger” or unsatisfied breathing, a perception of not getting enough air in, or the unpleasant urge to breathe. 

These three major qualities overlap, and there are others.  For a while people were trying to determine the major quality of dyspnea, to see if that might be useful in the differential diagnosis of the etiology of dyspnea, but I am not sure that has been all that successful, and as I said, dyspnea is the primary disturbing symptom in COPD.