IV. Statistical analysis. T-Student, Mann-Whitney and chi-square test for between-groups comparisons. Relationship analysis using Pearson correlation and multivariate regression models. Intention-to-treat evaluation of the main objective with imputation of missing data by a regression model. The effect of the intervention will be evaluated by the difference of change for each variable between the two groups using general linear models. The crude effect (only adjusted for baseline values) and the adjusted effect for several confounders (sex, age, BMI, smoking, treatment and FEV1%) will be determined.