ORCID Profile
0000-0002-7715-7896
Current Organisation
Kyushu University
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Publisher: SAGE Publications
Date: 08-2016
Abstract: In vivo studies involving mammal surrogate models for toxicology studies have restrictions related to animal protection and ethics. Computer models, i.e., in silico models, have great potential to contribute towards essential understanding of heat and mass transfer phenomena in respiratory tracts in place of in vivo and in vitro studies. Here, we developed numerical upper airway models of a rat, a dog, a monkey, and two humans by using computed tomography data and then applied computational fluid dynamics analysis. Convective heat transfer coefficients were precisely analysed as a function of breathing airflow rate. Based on the computational fluid dynamics simulation results, the correlations between Nusselt ( Nu) number and the product of the Reynolds ( Re) and Prandtl ( Pr) numbers were summarized. The heat transfer efficiency (order of h c and correlation of Nu and RePr) in the upper airway of the dog seems to match those of the human models. On the other hand, the results for the rat and monkey showed clear differences compared with those of human models. The identified fundamental qualities of convective heat transfer phenomena in airways for rats, dogs, monkeys, and humans, have enabled discussions about quantitative differences of heat and mass transfer efficiency between different animals/species.
Publisher: Informa UK Limited
Date: 02-04-2020
Publisher: Elsevier BV
Date: 2023
DOI: 10.1016/J.CMPB.2022.107243
Abstract: Brachycephalic obstructive airway syndrome (BOAS) susceptible dogs (e.g., French bulldog), suffer health complications related to deficient breathing primarily due to anatomical airway geometry. Surgical interventions are known to provide acceptable functional and cosmetic results however, the long-term post-surgery outcome is not well known. In silico analysis provides an objective measure to quantify the respiratory function in postoperative dogs which is critical for successful long-term outcomes. A virtual surgery to open the airway can explore the ability for improved breathing in an obstructed airway of a patient dog, thus supporting surgeons in pre-surgery planning using computational fluid dynamics. In this study five surgical interventions were generated with a gradual increment of decongested levels in a bulldog based on computed tomography images. The effects of the decongested airways on the breathing function of a patient bulldog, i.e., airflow characteristics, pressure drop, wall shear stress, and air-conditioning capacity, were quantified by benchmarking against a clinically healthy bulldog using computational fluid dynamics (CFD) method. Our findings demonstrated a promising decrease in excessive airstream velocity, pressure drop, and wall shear stress in virtual surgical scenarios, while constantly preserving adequate air-conditioning efficiency. A linear fit curve was proposed to correlate the reduction in the pressure drop and decongested level. The in silico analysis is a viable tool providing visual and quantitative insight into new unexplored surgical techniques.
Publisher: Wiley
Date: 04-08-2022
Abstract: Particles longer than 5 μm and with a length/diameter ratio are defined as fibers. Asbestos or other fibers are still identified in residential environments due to the emission from asbestos‐used building materials. The respiratory system is the primary route of asbestos exposure under a longer residence time, asbestos‐related adverse health effects are inevitable. Currently, asbestos fibers have been replaced with man‐made vitreous fibers (MMVFs) however, studies have revealed some similar biological effects of MMVFs with asbestos. Therefore, MMVFs‐induced diseases need to be determined by analyzing their deposition characteristics and foci in human respiratory tracts. In this study, we used computational fluid dynamics method to investigate fibers' airflow and deposition patterns in two realistic human respiratory models. Two drag models were used to predict the deposition of uniform 1 μm (asbestos) and 3.66 μm (carbon fiber‐CF) diameter, 15–300 μm long fibers. Two drag models provided comparable results with the experimental data. Comparatively, asbestos deposition was independent of fiber length, while CF deposition increased proportionally to fiber length. The highest level of local deposition was detected in the anterior nasal cavity. The results obtained from this study can extend current knowledge of human vitreous fiber exposure‐related lung diseases.
Publisher: Wiley
Date: 03-01-2021
DOI: 10.1002/CNM.3414
Publisher: Informa UK Limited
Date: 15-10-2018
DOI: 10.1080/08958378.2018.1545810
Abstract: Regional deposition of inhaled aerosols is essential for assessing health risks from toxic exposure. Upper airway physiology plays a significant role in respiratory defense by filtering micrometer particles, whose deposition mechanism is predominantly inertial impaction and is mainly controlled by airflow characteristics. The monkey is commonly used in tests that study inhalation toxicity as well as in preclinical tests as human surrogates due to their anatomical similarities to humans. Therefore, accurate predictions and an understanding of the inhaled particles and their distribution in monkeys are essential for extrapolating laboratory animal data to humans. The study goals were as follows: (1) to predict the particle deposition based on aerodynamic diameters (1-10 µm) and various steady inspiratory flow rates in computational models of monkey and human upper airways and (2) to investigate potential differences in inhalation flow and particle deposition between humans and monkeys by comparing numerical simulation results with similar in-vitro and in-vivo measurements from recent literature. The deposition fractions of the monkey's numerical airway model agreed well with in-vitro and human model data when equivalent Stokes numbers were compared, based on the minimum cross-sectional area as representative of length scale. Vestibule removal efficiencies were predicted to be higher in the monkey model compared with the human model. Our results revealed that the particle transportations were sensitive to the anatomical structure, airway geometry, airflow rates, inflow boundary conditions and particle size.
No related grants have been discovered for Kazuhide Ito.