Annals of biomedical engineering
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As a human grows from birth to adulthood, both airway anatomy and breathing conditions vary, altering the deposition rate and pattern of inhaled aerosols. However, deposition studies have typically focused on adult subjects, results of which may not be readily extrapolated to children. This study numerically evaluated the age-related effects on the airflow and aerosol dynamics in image-based nose-throat models of a 10-day-old newborn, a 7-month-old infant, a 5-year-old child, and a 53-year-old adult. ⋯ Further, the deposition partitioning in the sub-regions of interest is different among the four models. Results of this study corroborate the use of the in vivo-based diffusion parameter (D(0.5)Q(-0.28)) over the replica-based parameter in correlating nasal-laryngeal depositions of ultrafine aerosols. Improved correlations have been developed for the four age groups by implementing this in vivo-based diffusion parameter as well as the Cunningham correction factor.
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The avascular intervertebral disc (IVD) receives nutrition via transport from surrounding vasculature; poor nutrition is believed to be a main cause of disc degeneration. In this study, we investigated the effects of mechanical deformation and anisotropy on the transport of two important nutrients--oxygen and glucose--in human annulus fibrosus (AF). The diffusivities of oxygen and glucose were measured under three levels of uniaxial confined compression--0, 10, and 20%--and in three directions--axial, circumferential, and radial. ⋯ Furthermore, diffusivity in the radial direction was lower than in the axial or circumferential directions, indicating that nutrient transport in human AF is anisotropic. This behavior is likely a consequence of the layered structure and unique collagen architecture of AF tissue. These findings are important for better understanding nutritional supply in IVD and related disc degeneration.