Consistent and reproducible dosing is critical in aerosol-mediated drug delivery during mechanical ventilation. Aerosol dosing is typically single dose or continuous dosing over several hours. The objective of this study was to evaluate dose to dose consistency and cumulative dose delivered over a continuous 6-hour treatment period during simulated mechanical ventilation.
This study incorporated a continuous nebulisation tube set with a standard syringe pump in conjunction with a vibrating mesh nebuliser. A ventilator was used to generate adult breath in line with a humidified heated wire circuit attached to a 5-mm inner-diameter endo-tracheal tube. Consistency of dosing and cumulative dose were evaluated by laser diffraction, gravimetric analysis and by characterising the delivered dose. Albuterol sulphate (5 mg/2.5 mL) was nebulised at 6 and 12 mL/hour feed rates and delivered dose recorded every 30 minutes. Drug was quantified using UV spectrophotometry (276 nm).
Results indicate consistent dose delivery (2.58 ± 0.37 mg/30min at 6 mL/hr), (4.49 ± 0.38 mg/30min at 12 mL/hr) along with reproducible average droplet size (4.66 ± 0.02 µm at 6 mL/hr), (4.51 ± 0.04 µm at 12 mL/hr) and droplet volume (0.04 mL ± 0.00 at 6 mL/hr) & (0.04 mL ± 0.00 at 12 mL/hr) independent of input rate. Additionally, significant delivered dose across the two input rates were recorded; 30.96 mg at 6 mL/hr input rate and 53.83 mg at 12 mL/hr input rate. This study suggests continuous nebulisation therapy is an efficient and reproducible means of aerosol delivery.
For the first time, the reproducibility and consistency of continuous nebulisation has been characterised with a vibrating mesh nebuliser. The results of this study indicate that across two commonly used drug feed rates, vibrating mesh nebulisation was capable of producing consistent droplet sizes and delivered doses.