Abstract
There are variations in the values reported for aerosol drug delivery across in vitro experiments throughout the published literature, and often with the same devices or similar experimental setups. Factors contributing to this variability include, but are not limited to device type, equipment settings, drug type and quantification methods. This study assessed the impact of head model choice on aerosol drug delivery using six different adults and three different paediatric head models in combination with a facemask, mouthpiece, and high-flow nasal cannula. Under controlled test conditions, the quantity of drug collected varied depending on the choice of head model. Head models vary depending on a combination of structural design differences, facial features (size and structure), internal volume measurements and airway geometries and these variations result in the differences in aerosol delivery. Of the widely available head models used in this study, only three were seen to closely predict in vivo aerosol delivery performance in adults compared with published scintigraphy data. Further, this testing identified the limited utility of some head models under certain test conditions, for example, the range reported across head models was aerosol drug delivery of 2.62 ± 2.86% to 37.79 ± 1.55% when used with a facemask. For the first time, this study highlights the impact of head model choice on reported aerosol drug delivery within a laboratory setting and contributes to explaining the differences in values reported within the literature.
Highlights
Accepted: 21 December 2021In vitro experiments play a hugely valuable role in predicting and characterizing aerosol drug delivery across a range of device and interface combinations
For High Flow Nasal Therapy (HFNT) the VMN was placed at the humidifier using the Optiflow system (AIRVO 2, Fisher and Paykel Healthcare, Auckland, New Zealand)
A one-way ANOVA was completed for each adult test series, facemask, mouthpiece, and high flow nasal cannula
Summary
In vitro experiments play a hugely valuable role in predicting and characterizing aerosol drug delivery across a range of device and interface combinations. The information and data reported are vital in the optimisation of device design, and a device’s clinical application. A wide range of head models is reported within the literature as a means to assess aerosol delivery to simulated spontaneously breathing adult and paediatric patients. Model and material is often descriptive, but limited [1,2,3]. Reported head models for benchtop experiments vary between teaching mannequins with anatomical face and upper airways [1], airway management trainer models [4], nasal cast models [5,6], and anatomically correct face/airway models derived from CT scans [7,8,9].
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