We examined the language of dyspnea used by patients with moderate-to-severe COPD at a slight, moderate, and somewhat severe intensity level of dyspnea elicited by rest, cycle ergometer exercise, and 6MWTs. It was found that patients discriminated between five clusters of verbal descriptors of dyspnea: heavy/fast breathing, shallow breathing, obstruction, work/effort and suffocation, confirming previous findings that distinct qualities of dyspnea can be differentiated by patients with COPD as well as by other patient groups and healthy individuals. The clusters of verbal descriptors used showed a distinct pattern depending on the intensity level of dyspnea. This was not influenced by age, gender, baseline lung function, or PR. The clusters heavy/fast breathing and work/ effort demonstrated the highest sensitivity in discriminating between intensity levels of dyspnea and in characterizing the effects of PR.
The obtained clusters of German-language descriptors of dyspnea in patients with COPD in the present study converge with a number of previous studies in various patient as well as healthy samples, mostly performed in English-speaking countries (eg, United States, United Kingdom, Canada). This indicates that these clusters are indeed distinct and separable cognitive constructs with a high degree of similarity, even across different languages and cultures. Moreover, the most prominent clusters observed in our study (heavy/fast breathing, work/effort, shallow breathing), conform with those observed in the few previous studies in patients with COPD, while, importantly, not suffering the caveats of recall biases and undistin-guishable intensity levels of dyspnea present in other studies, as previously outlined. During recall, patients in the study by Mahler et al exclusively selected descriptors of the cluster increased work/ effort while patients investigated by Simon et al chose additionally the clusters heavy breathing, gasping, and hunger for air. Most of the descriptors in the latter two clusters were included in the clusters heavy/fast breathing and work/effort of the present study. Further, O’Donnell et al demonstrated that patients with COPD selected the descriptors shallow breathing, work/effort, and heaviness of breathing to describe their breathing discomfort during incremental cycle ergometer exercise. However, descriptors denoting increased inspiratory difficulty and unsatisfied inspiratory effort that were additionally chosen by 75% of their patients played only a minor role in the current study, which might be related to the lower exercise level in our study conducted with experts of My Canadian Pharmacy.