patients aged 18-50 years old, at stage 2-3 according to GINA international guidelines

patients must be free from an exacerbation from at least 2 months

patients must be on inhaled treatment (ICS alone or combination ICS/LABA) other than extrafine formulations from at least 3 months.

according to smoking habit, patients will be divided in two groups:

1. nonsmokers: patients who never smoked

2. smokers: patients with a smoking habit ranging from 10 to 20 pack/years.

Small Airways Involvement in Smoker Asthmatic Patients: a Pilot Study