Reversibility of inspiratory lung function parameters after short-term bronchodilators in COPD

Background: The responsiveness of short-term bronchodilator use on inspiratory lung function parameters (ILPs), including Forced Inspiratory Volume in one second (FIV1), Inspiratory Capacity (IC), Forced Inspiratory Flow at 50% of the vital capacity (FIF50), Peak Inspiratory Flow (PIF) and on the relationship between these values and dyspnea in COPD subjects has been examined only sparsely in past studies. The aim of this study was to assess the effects of inhaled salbutamol 400mcg, ipratropium 80mcg and a placebo on ILP and FEV1 and their relationship to dyspnea, as measured with a Visual Analogue Scale (VAS). Methods: A total of 85 subjects with stable COPD participated in a crossover, randomized, double-blind, placebo-controlled study. Spirometry was performed before and after inhalation of salbutamol, ipratropium or a placebo. The primary analysis was performed using 63 participants with absent reversibility. Results: All ILP and FEV1 values improved significantly after bronchodilator administration except for FIF50 after ipratropium administration. After administration of both bronchodilators, the mean percent changes from initial values did not significantly differ between the various ILPs and FEV1. The mean VAS score showed significant improvements after bronchodilator and placebo inhalation but did not significantly correlate with changes in lung function parameters. For each lung function parameter, patients were further classified as responders if the amount of change was greater than the coefficient of repeatability of the test. Response rates did not differ significantly between the various ILPs. Moreover, no significant differences were found between responders and non-responders with respect to dyspnea after bronchodilator inhalation. This finding applied to all ILP and FEV1 values. Conclusions: In subjects with COPD, all ILP, FEV1 values and VAS scores showed significant improvements after bronchodilator use as well as with placebo. However, ILPs were not more sensitive than FEV1 for detecting responders after bronchodilator use or changes in the VAS score.

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