Lung function
All patients underwent lung function tests by using Spirolab II system(Medical International Research, Rome, Italy). It was performed by a trained operatör, and the equipment was calibrated daily. Measured parameters were the prebronchodilator forced expiratory volume in 1st second(FEV1), the forced vital capacity(FVC), the FEV1 to FVC ratio(FEV1/FVC) and the forced expiratory flow between 25% and 75% of vital capacity(FEF25%-75%). Results were reported as percentage of the predicted value according to references.23