To our knowledge, there is no data oil the effect of tiotropium on pulmonary gas exchange in healthy subjects. The aim of this study was to assess the effects of tiotropium on pulmonary diffusing capacity. Twenty-one healthy volunteers were enrolled for a prospective, randomized, double-blind, placebo-controlled study. Spirometric Measurements, including pulmonary-diffusing capacity, were obtained before and after inhalation of drug at placebo. There was a significant decrease in forced vital capacity (FVC) and, consequently, an increase in,the forced expiratory volume in one second (FEVI) to FVC ratio after placebo inhalation (p < 0.05), bill no changes were found for percent-predicted FVC, FEVI, percent-predicted FEVI, percent-predicted forced expiratory flow, (FEF25%-75%), percent-predicted peak expiratory flow (PEF), diffusing capacity of the lung for carbon monoxide (DLCO), single-breath alveolar volume (VA) and DLCO/VA ratio when compared with the baseline. Tiotropium inhalation caused a significant increase in FVC, percent-predicted FEVI, FEVI/FVC and percent-predicted FEF25%-75%, although the decrease in DLCO was insignificant (12.4 +/- 0.9 to 11.4 +/- 0.9). In conclusion, tiotropium does not change the pulmonary-diffusing capacity in healthy volunteers. (C) 2007 Prous Science. All rights reserved.