Inhalation of terbutaline spray through an extended mouthpiece: effect on central and peripheral airways

In a cross-over experiment, 16 adult asthmatics slowly inhaled, at functional residual capacity, cumulative doses of terbutaline spray with and without extension of the mouthpiece of the aerosol canister by a cylindrical tube (length 10.0 cm, diameter 3.2 cm). No difference was found between the two modes of treatment with regard to the bronchodilator response assessed by measurement of specific airway conductance, registration of expiratory flow-volume curves and determination of helium response. The results suggest that the use of an extension tube may not promote a more extensive nor a more peripheral deposition in the bronchial tree of a properly inhaled pressurized aerosol drug.