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RESEARCH PRODUCT

How Can We Assess the Perception of Induced Dyspnea in Chronic Obstructive Pulmonary Disease?

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Objective TO evaluate various methods for studying the perception of dyspnea in chronic obstructive pulmonary disease (COPD) using a new parameter, the change in Borg scale rating, and others already in use: the linear regression slope and the application of Stevens' law to the response-perception curve-ie change in forced expiratory volume in 1 second (ΔFEV 1 )-change in dyspnea (Adyspnea). Patients and method A bronchial challenge test was performed on 70 patients with stable COPD and no contraindications for performing the test (European Respiratory Society criteria), during which dyspnea was measured (Borg scale) after each nebulization. Perception was analyzed using: a ) the linear regression slope of ΔFEV 1 plotted against (Adyspnea); b ) the exponent n of Stevens' law (ψ=kΨn, in which ψ is Δdyspnea and Ψis AFEV 1 , with perception being poor when n 1), and c ) change in Borg: difference between dyspnea when FEV 1 has fallen 20% and dyspnea after saline inhalation. Subjects were classified according to the slope and change in Borg as hypoperceivers, normal perceivers, or hyperperceivers. These 2 methods of classification were compared using the κ statistic. Results According to the exponent n, all patients were hypoperceivers (n Conclusions The n exponent is not valid for evaluating the perception of dyspnea induced by a bronchial challenge test in COPD. Change in Borg is at least as useful as the slope for evaluating perception of dyspnea. The percentage of patients with this disease who are hyperperceivers is high.