RESUMO
BACKGROUND: The aim of this study was to evaluate the effects of increasing doses of inhaled histamine on the forced expiratory volume in one second (FEV1), inspiratory lung function parameters (ILPs) and dyspnea in subjects with mild to moderate chronic obstructive pulmonary disease (COPD) METHODS: Thirty-nine (27 males and 12 females) stable COPD patients (GOLD stages I and II) inhaled a maximum of six sequential doses of histamine according to ERS standards until one of these provocative doses produced a 20% decrease in FEV1 (PD20). The effects on the FEV1, the 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 dyspnea score by a visual analogue scale (VAS) were measured and investigated after each dose step RESULTS: After each dose of histamine, declines in all of the lung function parameters were detected; the largest decrease was observed in the FEV1. At the PD20 endpoint, more FEV1 responders than ILP responders were found. Among the ILPs, the FIV1 and IC best predicted which patients would reach the PD20 endpoint. No significant correlations were found between any of the lung function parameters and the VAS results CONCLUSIONS: In COPD patients, the FEV1 and ILPs declined after each dose of inhaled histamine. FEV1 was more sensitive to histamine than the ILPs. Of the ILPs, FIV1 and IC were the best predictors of reaching the PD20 endpoint. No statistically significant correlations were found between the lung function parameters and the degree of dyspnea.