The 6 minutes walk test (6MWT) proved to correlate with functional status of patients with respiratory impairments; measurement of the impact of Pulmonary Rehabilitation (PR) on 6MWT is the primary outcome of our study. Investigators expect that this kind of treatment will improve exercise tolerance expressed by the 6MWT, assessed at T0, T1, T2 and T3 in IG. Values of 6MWT in CG will be assessed at T0 and T3 (T1 only if changes in therapy have occurred).