Combined inhaled treatment with long acting adrenergics and steroids in an unique inhaler plays an important role in the management of non-mild asthma. Some studies have demonstrated that the use of spacers achieve better lung deposition and decrease the number of side effects. Recently a new combined treatment for asthma has been developed (extrafine formoterol plus beclomethasone dipropionate). The small size of the extrafine particles of this new combination get the small airway and theorically improve their positive effect. Some authors have stated that the use of a spacer with extrafine particle could decrease the effectiveness of this treatment due to the adhesion of particles on the walls of the spacer because of the electrostatic characteristics of plastic spacers.

However, there are no clinical or functional studies demonstrating the role of this phenomena in the control of asthmatic patients. The investigators' hypothesis is that the benefit of using spacers with this new treatment is at least equal in magnitude than the loss of efficacy because of the adhesion of particles on the wall of the spacer and then the investigators hypothesized that the use of spacer with extrafine formoterol-beclomethasone do not suppose a decrease in clinical or functional control in stable moderate-severe asthma patients.