Impact of baseline and induced dyspnea on the quality of life of patients with COPD

OBJECTIVE: Dyspnea is the main symptom of chronic obstructive pulmonary disease (COPD) and as such is an important determinant of health-related quality of life. It is, however, weakly correlated to severity of obstruction and there is little information available on how it exercises its effect on health-related quality of life. The aims of this study were to identify the determinants of baseline dyspnea and to ascertain how that factor influences the health-related quality of life of patients with COPD. PATIENTS AND METHODS: A total of 101 patients with COPD were studied. Tests included full lung function assessment, the bronchial provocation test (n=70), and the 6-minute walk test. The following variables were measured: Baseline dyspnea, bronchoconstriction-induced dyspnea, exertional dyspnea, health-related quality of life, and levels of anxiety and depression. RESULTS: Determinants of baseline dyspnea were anxiety (explained variance, 17%), maximal inspiratory pressure (4%), and PaO2 (4%). In patients with mild to moderate COPD (forced expiratory volume in 1 second, >50% of predicted), the main determinant of health-related quality of life was anxiety (explained variance, 43%). Other determinants were the number of meters walked in the 6-minute-walk test, age, and Baseline dyspnea (variance explained by both factors, 26%). Baseline dyspnea and bronchoconstriction-induced dyspnea were both identified as independent determinants of health-related quality of life (on the activity and impact subscales of the St George's Respiratory Questionnaire, respectively). The main determinant of health-related quality of life in patients with severe COPD (forced expiratory volume in I second, :>50% of predicted) was baseline dyspnea. Finally, the main determinants of anxiety were exertional dyspnea (variance, 42%) and baseline dyspnea (6%). CONCLUSIONS: Anxiety is the main determinant of health-related quality of life in patients with COPD, and it is triggered mainly by baseline dyspnea and exertional dyspnea.