In-silico aerosol delivery to spontaneously-breathing paediatric patients via oral (south-facing) RAE endotracheal tubes

Abstract

Introduction and Aim: In order to potentially improve aerosol delivery emitted by either a pressurised metered dose inhaler or nebuliser device to paediatric patients using oral (south facing) RAE endotracheal tubes (ETTs), an in-silico solid particle computational fluid-particle dynamic model was validated.

Methods: An elbow-tube geometry, designed to mimic a paediatric oral RAE ETT was created using Python software and imported into computational fluid-dynamic software, OpenFOAM. Computationally, a single dose of aerosol was injected into the elbow-tube at each devices reported speed, superimposed on a paediatric patient inhalation sinewave. In silico, particles were deemed to deposit in the tube when within a radius width of the tube lumen. The software solved for conservation of momentum, and mass (Navier-Stokes equations), coupled with discrete particle tracking. The Pawsey Supercomputing Centre was used to process the simulation. For validation, deposition in tube was also determined in vitro, by measuring solid aerosol (drug) particles pre- and post- the RAE ETT with an optical particle sizer/counter, after artificial evaporation of any carrier liquid. Mass conversion from particle counts in vitro were cross-checked by high performance liquid chromatography.

Results: Computational simulation showed almost all the aerosol will deposit in the elbow-tube, and this is dependent on particle-size and flow rate. The simulated result was successfully validated by the laboratory result as the ratio of penetration to capture efficiency.

Conclusion: Aerosol drug delivery via RAE ETTs is poor with common aerosol generators and can be optimised by methods developed here.