Abstract
BACKGROUND: The human respiratory airway undergoes dramatic growth during infancy and childhood, which induces substantial variability in air flow pattern and particle deposition. However, deposition studies have typically focused on adult subjects, the results of which cannot be readily extrapolated to children. We developed models to quantify the growth of human nasal-laryngeal airways at early ages, and to evaluate the impact of that growth on breathing resistance and aerosol deposition.
METHODS: Four image-based nasal-laryngeal models were developed from 4 children, ages 10 days, 7 months, 3 years, and 5 years, and were compared to a nasal-laryngeal model of a 53-year-old adult. The airway dimensions were quantified in terms of different parameters (volume, cross-section area, and hydraulic diameter) and of different anatomies (nose, pharynx, and larynx). Breathing resistance and aerosol deposition were computed using a high-fidelity fluid-particle transport model, and were validated against the measurements made with the 3-dimensional models fabricated from the same airway computed tomography images.
RESULTS: Significant differences in nasal morphology were observed among the 5 subjects, in both morphology and dimension. The turbinate region appeared to experience the most noticeable growth during the first 5 years of life. The nasal airway volume ratios of the 10-day, 7-month, 3-year, and 5-year-old subjects were 6.4%, 18.8%, 24.2%, and 40.3% that of the adult, respectively. Remarkable inter-group variability was observed in air flow, pressure drop, deposition fraction, and particle accumulation. The computational fluid dynamics predicted pressure drops and deposition fractions were in close agreement with in vitro measurements.
CONCLUSIONS: Age effects are significant in both breathing resistance and micrometer particle deposition. The image/computational-fluid-dynamics coupled method provides an efficient and effective approach in understanding patient-specific air flows and particle deposition, which have important implications in pediatric inhalation drug delivery and respiratory disorder diagnosis.
- nasal morphology
- child-adult discrepancy
- infants
- breathing resistance
- aerosol deposition
- pediatric drug delivery
Footnotes
- Correspondence: Jinxiang Xi PhD, Department of Mechanical and Biomedical Engineering, Central Michigan University, 1200 South Franklin Street, Mount Pleasant MI 48858. E-mail: xi1j{at}cmich.edu.
Dr Berlinski has disclosed relationships with Johnson & Johnson, MPEX Pharmaceutical, Gilead, Philips, Genentech, Vertex, Abvie, and S&T Technologies. None of their products are discussed in this paper. The other authors have disclosed no conflicts of interest.
Dr Xi presented a version of this paper at the OPEN FORUM of the AARC Congress 2012, held November 10–13, 2012, in New Orleans, Louisiana; for this research he was awarded the 2012 Monaghan-Trudell Fellowship for Aerosol Technique Development from the American Respiratory Care Foundation.
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