The perception of dyspnea in patients with mild asthma

Background: Airway function, as assessed by standard spirometry, and the intensity of dyspnea reported by asthmatic patients correlate poorly. Objective: This study tests the following two hypotheses: (1) that measures of the tendency of a patient to somatize will reduce the variation in the report of dyspnea not explained by airway function; and (2) that plethysmography is a better tool with which to estimate the degree of dyspnea associated with asthma. Design: A prospective laboratory study carried out over one study session. Participants: Forty asthmatic subjects who had withheld bronchodilator (BD) therapy overnight. Interventions: We performed spirometry, plethysmography, and an assessment of dyspnea (ie, modified Borg scale) on all subjects before and after they received BD therapy. Standard questionnaires pertaining to psychological state and trait were administered as well. Results: The change in specific airway conductance with BD therapy correlated with a decline in the Borg score (r = 0.47; p = 0.007). By contrast, neither spirographic measures nor measures of static lung volumes correlated. Correlation with the Borg scale score was not improved by adding indexes of either somatization or psychological state or trait. Conclusion: The relief of dyspnea reported by patients with mild asthma after BD therapy is related to dilatation of the central airways.