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Lung deposition and respirable mass during wet nebulization
Sanjay Sangwan1, Rany Condos, Gerald C Smaldone
1Division of Pulmonary and Critical Care Medicine, Department of Medicine, State University of New York, Stony Brook, New York 11794-8172, USA.
Summary
This study found that low-flow cascade impaction during simulated breathing accurately predicts aerosol deposition in the lungs for nebulizers. This method is crucial for assessing the fine particle fraction of inhaled medications delivered via nebulizers.
Area of Science:
- Respiratory Drug Delivery
- Inhalation Aerosol Technology
- Pharmacokinetics and Drug Metabolism
Background:
- Accurate in vitro assessment of aerosol deposition is critical for optimizing nebulizer performance.
- Existing methods for metered dose inhalers (MDIs) do not directly translate to nebulizer characterization.
- There is a need for validated in vitro models to predict in vivo lung deposition from nebulizers.
Purpose of the Study:
- To compare in vitro aerosol deposition using low-flow cascade impaction with in vivo deposition in human subjects for two nebulizers.
- To establish reliable in vitro standards for evaluating nebulizer performance and predicting lung deposition.
Main Methods:
- A 10-stage low-flow (1 L/min) cascade impactor was used to measure aerodynamic particle distributions of aerosolized interferon-gamma (IFN-gamma) from Misty-Neb and AeroEclipse nebulizers.
- Aerosol characterization was performed under two conditions: static (standing cloud) and dynamic (simulated breathing with a piston pump).
- In vivo oropharyngeal deposition was measured in three human subjects, with (99m)Tc-DTPA used as a radiolabel.
Main Results:
- Nebulizer performance, indicated by mass median aerodynamic diameter (MMAD), was significantly affected by simulated ventilation, with smaller MMADs observed during breathing.
- Oropharyngeal deposition varied significantly between nebulizers in vivo, with Misty-Neb showing higher deposition (68.1%) compared to AeroEclipse (30.9%).
- In vitro measurements under simulated breathing conditions indicated that particles below 2.5 microm are necessary for lung penetration (fine particle fraction) during wet nebulization.
Conclusions:
- Low-flow cascade impaction under simulated tidal breathing conditions provides a relevant in vitro method for predicting in vivo aerosol deposition from nebulizers.
- The fine particle fraction for wet nebulization is reliably predicted by in vitro methods when aerosol distribution is measured during simulated breathing.
- This approach allows for better assessment of nebulizer efficacy in delivering medication to the lungs.