The Application of Computational Fluid Dynamics (cfd) Simulations for Nasal Drug Delivery

The Norwegian company OptiNose AS is developing a novel concept that challenges traditional nasal delivery systems. The patented bi-directional delivery system takes advantage of the posterior connection between the nasal passages persisting when the soft palate automatically closes during oral exhalation. The exhalation into the delivery device triggers the release of particles into an airflow, which enters one nostril via a sealing nozzle and exits through the other nostril. During the development process for their drug delivery concept, OptiNose is using Computational Fluid Dynamics (CFD). The simulations are used to visualize and demonstrate the basic features of the bi-directional technique and discuss how its design and functionality could be further optimised. CFD computations thus increase the efficiency of device development and reduce the need for expensive and time consuming laboratory experiments and clinical tests. The simulations are carried out by use of Fluent, using a volume grid generated by Tgrid. To perform successful CFD calculations on the nose, construction of a proper surface grid of the nasal cavity, is mandatory. A high resolution CT-scan was the first part of this process, where after the 3-dimensional surface geometry was created by a pipeline of image segmentation and geometric modification steps. The process of building the surface grid is presented in the paper. Essential for the CFD computations is thorough validation of the simulation results. This paper presents comparisons between experimental and numerical simulations. Simple numerical models are used to verify critical parameters, e.g. airflow and particle size, in the design process, together with in vitro experiments in a human nasal airway model.