Technical note An idealized branching airway geometry that mimics average aerosol deposition in pediatric central conducting airways Azadeh A.T. Borojeni n , Michelle L. Noga, Andrew R. Martin, Warren H. Finlay n Department of Mechanical Engineering, University of Alberta, Edmonton, Alberta, Canada T6G 2G8 article info Article history: Received 14 November 2014 Received in revised form 25 February 2015 Accepted 14 March 2015 Available online 23 March 2015 Keywords: Idealized child central conducting airways Tracheobronchial (TB) airways Children Pediatric bifurcation model in vitro abstract The objective of this work was to design an idealized pediatric central conducting airway model that mimics average total particle deposition in the airways of 4–8 year old children. Dimensions of the idealized model were selected based on analytical prediction of deposition in scaled versions of existing adult airway geometries. Validation experi- ments were then conducted using steady inhalation air flow rate to measure the deposition of monodisperse particles with mass median diameters (MMD) of 3.5, 4.5, 5 and 5.2 mm in the idealized pediatric model. The total deposition of particles was measured using gravimetry. Experimental data confirmed that aerosol deposition in the idealized pediatric central conducting airway geometry was consistent with the average deposition previously measured in 10 realistic airway replicas for children 4–8 years old. & 2015 Elsevier Ltd. All rights reserved. 1. Introduction The use of idealized, representative upper airways geometries that mimic average aerosol deposition in various populations has proven indispensable in the development and assessment of devices used to deliver inhaled pharmaceutical aerosols (Below, Bickmann, & Breitkreutz, 2013; Bickmann, Wachtel, Kroger, & Langguth, 2008; Byron et al., 2010; Delvadia, Longest, & Byron, 2012; Golshahi & Finlay, 2012; Longest, Tian, Walenga, & Hindle, 2012; Oldham, Mannix, & Phalen, 1997; Wachtel, Bickmann, Breitkreutz, & Langguth, 2010). Such idealized geometries exist as a result of extensive fundamental investigation of air flow and aerosol deposition in the upper airways (Grgic, Finlay, & Heenan, 2004; Heenan, Finlay, Matida, & Pollard, 2003; Zhang, Gilbertson, & Finlay, 2007; Zhou, Sun, & Cheng, 2011). For many pharmaceutical aerosol delivery devices, physical phenomena that can influence upper airways deposition are sufficiently complex to model that in vitro testing on the bench top remains commonplace in research and development. Such phenomena include fluidization and deagglomeration of multi-component powders used in dry powder inhalers (DPIs) and rapid deceleration and evaporation of propellant droplet sprays emitted from pressurized metered-dose inhalers (pMDIs). When evaluating aerosol delivery in vitro using upper airways geometries, the fraction of active drug penetrating the geometry is commonly interpreted as the lung dose (Borgstrom, Olsson, & Thorsson, 2006). For the vast majority of inhalers in use and in development, the fraction of drug inhaled into the lung and subsequently exhaled is negligible, such that this interpretation is acceptable. Accordingly, current in vitro methods using idealized upper airways geometries permit average in vivo total lung dose to be predicted Contents lists available at ScienceDirect journal homepage: www.elsevier.com/locate/jaerosci Journal of Aerosol Science http://dx.doi.org/10.1016/j.jaerosci.2015.03.002 0021-8502/& 2015 Elsevier Ltd. All rights reserved. n Corresponding authors at: Aerosol Research Laboratory Department of Mechanical Engineering 4-9 Mechanical Engineering Building University of Alberta Edmonton, Alberta Canada T6G 2G8. Tel.: þ780 492 4707; fax: þ780 492 2200. E-mail addresses: akhavant@ualberta.ca (A.A.T. Borojeni), warren.finlay@ualberta.ca (W.H. Finlay). Journal of Aerosol Science 85 (2015) 10–16