Reliability of verbal descriptors of dyspnea and their relationship with perceived intensity and unpleasantness

Verbal descriptors of dyspnea have been suggested as being useful in providing information on the underlying pathophysiology. However, little is known about the reliability of these descriptors. The present study examined the reliability of a German language list of respiratory symptom descriptors and studied the association of these descriptors with the intensity and unpleasantness of perceived dyspnea. Fourteen healthy volunteers performed cycle-ergometer exercise and voluntary breath-holding during which they rated the perceived intensity (VAS-I) and unpleasantness (VAS-U) of dyspnea on visual analog scales. Following this, they judged their sensations of dyspnea using the list of symptom descriptors. Both conditions were repeated in reverse order on a subsequent occasion 10 days apart. Ventilatory measures, heart rate, blood lactate, VAS-I and VAS-U during cycle-exercise as well as breath-holding time, VAS-I and VAS-U during breath-holding showed no differences between both occasions. Separate hierarchical cluster analyses identified four clusters of verbal descriptors of dyspnea which were widely comparable between both occasions: effort, speed, obstruction and suffocation. Separate multidimensional scaling analyses (MDS) confirmed these four clusters for each occasion. On both days, perceived unpleasantness of dyspnea was correlated with all four clusters during cycle-exercise, while perceived intensity showed only correlations with effort or speed, respectively. No such correlations were obtained for breath-holding. The results suggest that separable clusters of German language descriptors of dyspnea are reliably used by healthy volunteers. The obtained clusters are widely comparable to previously described clusters in other languages and are differently related to the intensity and unpleasantness of perceived dyspnea.