Differentiation between dyspnea and its affective components.

This study investigated whether people with chronic obstructive pulmonary disease (COPD) can differentiate distress and anxiety associated with dyspnea from the intensity of dyspnea and the perceived effort of breathing. Fifty-two subjects with COPD rated their perception of the individual components of dyspnea on a 200 mm visual analog scale at rest, after a 6-min walk (6MD), and every 2 min during an incremental treadmill test (ET). Subjects differentiated among the four dyspnea components at the end of the 6MD (p < .0001) and during ET (at rest, p < 0.001; at 75% VO2 max, p < 0.0001; and at end exercise, p < 0.0001). Intensity was significantly related to perceived effort of breathing (p < .0001), as distress was to anxiety (p < .0001), suggesting that each pair measures similar components. Subjects were able to differentiate their affective response to dyspnea from the intensity of the symptom. Measurement of a patient's affective response to dyspnea may improve the selection of specific treatments and validity of outcomes.