On the final day of RDD Europe 2011 in Berlin, most of the focus turned to the abbreviated impactor method (AIM) and efficient data analysis (EDA), but the first session of the morning was devoted to advanced imaging methods for understanding drug delivery.
The first speaker, Henk Versteeg of Loughborough University, described his method for studying transport of nasal sprays to the nasal cavity in his talk titled, “Nasal Film Formation and Deposition – Flow Visualization and Modeling of Nasal Delivery in Constrained Geometries.” He demonstrated his technique for using an MRI scan to create a model of the nasal passages that could then be converted into a mesh for computational fluid dynamics (CFD) modeling and a full-scale transparent resin model for use in high speed visualization.
According to the models, says Versteeg, only a tiny percentage of any aqueous nasal spray is deposited in the nasal cavity itself; the majority deposits in the nasal vestibule, where it creates a pool of liquid. When the patient inhales sharply, the resulting shear draws a film of liquid into the nasal cavity through the nasal valve. Further distribution in the nasal cavity then results from air drag and gravity.
Jan de Backer of FluidDa was scheduled to follow Versteeg’s talk, but technical problems with his slides led to a switch in the order of presentation, so Michael Oldham went next, speaking about “CFD Deposition Modeling: Debating the Human Metrics Controlling Oropharyngeal Aerosol Deposition.” The talk covered various parameters in laryngeal growth in pediatric patients the importance of those factors to predictions of aerosol deposition in the airways.
According to Oldham, measurements of 37 dimension taken from cadavers of patients ranging from birth to 20 years demonstrate that height is a more important predictor of laryngeal growth than age. Mouth-throat models were generated scaled for body height of a live 5-year-old and a 10-year-old, and CFD simulations showed little difference in deposition between the models. His work concluded that the Stokes number based on mouth-throat geometry provided good predictions of deposition and that possibly a Stokes number based on flow rate and glottic diameter alone could predict deposition for patients of all ages.
Jan de Backer’s presentation, once the technicians got it working properly, generated strong interest in the audience. De Backer’s work involves tomographic airway imaging, in which CT scans are used to create models of individual patients that are then used for individualized CFD calculations of airway resistance, airway volume, and deposition, providing more sensitive parameters than FEV1 and allowing for clinical trials using fewer patients.
The second morning session consisted of a series of AIM and EDA talks, part of the IPAC-RS and EPAG efforts to introduce these topics to the industry. Previous sessions on these topics have taken place at the most recent DDL and IPAC-RS conferences, and AIM/EDA was also the subject of the optional satellite conference held by IPAC-RS in the afternoon of Day 3 of RDD Europe.
The RDD conference proper, however, ended with a prize draw in which organizers gave away a camera, an iPod Nano, a portable dvd player, and a copy of Steve Newman’s book, RDD: Essential Theory & Practice. Peter Byron appeared to have a good time presiding over the prize draw and inviting the crowd to meet up once again at RDD 2012 in Phoenix, Arizona before officially closing the meeting.
