Variations in Predicted Regional Lung Deposition of Salbutamol Sulphate Between 19 Nebulizer Types

Abstract

Regional lung dosages are estimated for 19 different nebulizer types, and variations in these dosages within each nebulizer type are given. Experimental methods are used to characterize the aerosols inhaled in vitro (inhalation flow rate = 300 mL/s, tidal volume = 750 mL) from nebulizers filled with 2.5 mL of Ventolin (1 mg/mL of salbutamol sulphate in normal saline) under ambient conditions of 50% ± 3% relative humidity (RH), 22°C ± 1°C. These data are input into a hygroscopic, mathematical lung deposition model to estimate regional lung dosages for a scaled Weibel A lung. The deposition model is a two-way coupled model (i.e., it includes the effects of droplet heat and mass transfer on the surrounding environment and vice versa). As a percentage of normal dose placed in the nebulizer, regional dosages differed significantly between the different nebulizer types (P < 0.01) and varied from 3.1% to 23.4%, 1.6% to 10.6%, 1.6% to 12.8%, and 1.8% to 9.5% for lung, tracheobronchial, alveolar, and extrathoracic deposition, respectively. Variations in regional dosages between nebulizers of each type had standard deviations that were, on average, less than 2% of the nominal dose. Of the three nebulizer classes tested (ultrasonic, conventional, and vented), no class consistently gave higher regional dosages than the other two classes. Good agreement with published in vivo scintigraphic data was found (P > 0.01) in lung dosages.