AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
Variability of Lung Targeted Aerosol Delivery during High Flow Nasal Cannula Therapy
ROSS WALENGA, Geng Tian, Michael Hindle, Worth Longest, Virginia Commonwealth University
Abstract Number: 218 Working Group: Health Related Aerosols
Abstract Patients that receive high flow nasal cannula (HFNC) therapy may benefit from lung targeted pharmaceutical aerosol administration, but results in the literature indicate that drug deposition and variability are likely to be high in both the delivery system and the nasal cavity. For this study, conventional and enhanced excipient growth (EEG) aerosol delivery methods were assessed with respect to variability of delivery through a nasal cannula interface. Adult nasal cavity dimensions from CT scan measurements and previously published data were compiled and used to select four models that represent a physiological range of nasal surface area-to-volume ratios (SA/V). Predictions at a steady state flow rate of 30 L/min through a streamlined cannula and the four nasal models were produced using validated computational fluid dynamics (CFD) methods. Conventional and EEG approaches were assessed with droplets (initial 5 micrometer aerodynamic diameter) and solid particles (0.9 micrometer and 1.5 micrometer), respectively. While the use of a conventional approach with 5 µm droplets showed a range of aerosol deposition efficiency of 15.5-64.1% (95% confidence interval (CI)) in the four geometries, the range of deposition for the EEG method with 0.9 µm particles was 2.3-3.1% (95% CI). Delivered dose, as expressed by penetration fraction (PF) through the nasopharynx, was predicted to be improved by a factor of four when using EEG as opposed to the control case. Additionally, the use of EEG as compared with a conventional aerosol reduced variability of PF by a factor of five, as expressed by the coefficient of variation. Surface area-to-volume ratio (SA/V) showed a strong correlation with PF for larger aerosols, but PF for smaller aerosols showed some dependence on nasopharyngeal exit hydraulic diameter. In summary, predictions using four newly created nasal airway models showed that lung targeted aerosol delivery was greatly improved by use of the EEG technique, while variability was significantly reduced.