Aerosol performance of the Pulmospray® soft-mist inhaler for inhalation of high amounts of liquid formulations

Liquid formulations are popular for drug delivery in inhalation products. Many compounds are available as liquid formulation and delivery devices as soft-mist-inhalers (SMI) or smart nebulizers have been employed to improve the delivery efficiency and usability. However, SMI are limited to small dosages and nebulizers require electricity, which is often not in-line with the target treatment setting, were single use or energy independent on-the-go devices are required (e.g. COVID-19, rescue). In this study, we assessed the aerosol performance of the mechanical and disposable Pulmospray inhaler, that is designed for application of a liquid volume of up to 1mL. To assess the aerosol characteristics, cascade impaction testing (NGI) was performed (3 repetitions, 1mL of 5.85% NaCl). Four device variants with different nozzle pore sizes were tested. The content sampled on impactor stages and the UIP was assessed by Conductivity. Mass Median Aerodynamic Diameter (MMAD) and the Geometric Standard Deviation (GSD) were calculated. The delivery rate was assessed by using a spray time of 10 sec per actuation. With pore sizes of 1.6, 1.7, 1.8 and 1.9 μm, MMAD was 5.12, 5.73, 5.90 and 6.70 μm, and GSD was 1.46, 1.49. 1.48, 1.56, respectively. The drug flow rate during actuation was 7.26, 8.17, 8.60, 11.25 μL/sec for the different pore sizes, respectively, which corresponds to an administration time for 1mL between 1.5 to 2.3min. Results from this study indicate that the Pulmospray allows a fast administration of 1mL within ∼2min. The combined results from narrow size distribution (GSD), the MMAD results (smaller pore size) and the built-in flow limitation of the device allows efficient delivery to the lungs as indicated by other publications.