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  1. Article ; Online: What is "functional small airway disease" in inspiratory and expiratory CT images?

    Kitaoka, Hiroko / Kijima, Takashi

    Respiratory investigation

    2020  Volume 59, Issue 1, Page(s) 157–158

    MeSH term(s) Humans ; Pulmonary Disease, Chronic Obstructive ; Tomography, X-Ray Computed/methods
    Language English
    Publishing date 2020-10-11
    Publishing country Netherlands
    Document type Letter
    ZDB-ID 2660821-2
    ISSN 2212-5353 ; 2212-5345
    ISSN (online) 2212-5353
    ISSN 2212-5345
    DOI 10.1016/j.resinv.2020.08.010
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  2. Article ; Online: Proposal of selective wedge instillation of pulmonary surfactant for COVID-19 pneumonia based on computational fluid dynamics simulation.

    Kitaoka, Hiroko / Kobayashi, Hisato / Takimoto, Takayuki / Kijima, Takashi

    BMC pulmonary medicine

    2021  Volume 21, Issue 1, Page(s) 62

    Abstract: Background: The most important target cell of SARS-CoV-2 is Type II pneumocyte which produces and secretes pulmonary surfactant (PS) that prevents alveolar collapse. PS instillation therapy is dramatically effective for infant respiratory distress ... ...

    Abstract Background: The most important target cell of SARS-CoV-2 is Type II pneumocyte which produces and secretes pulmonary surfactant (PS) that prevents alveolar collapse. PS instillation therapy is dramatically effective for infant respiratory distress syndrome but has been clinically ineffective for ARDS. Nowadays, ARDS is regarded as non-cardiogenic pulmonary edema with vascular hyper-permeability regardless of direct relation to PS dysfunction. However, there is a possibility that this ineffectiveness of PS instillation for ARDS is caused by insufficient delivery. Then, we performed PS instillation simulation with realistic human airway models by the use of computational fluid dynamics, and investigated how instilled PS would move in the liquid layer covering the airway wall and reach to alveolar regions.
    Methods: Two types of 3D human airway models were prepared: one was from the trachea to the lobular bronchi and the other was from a subsegmental bronchus to respiratory bronchioles. The thickness of the liquid layer covering the airway was assigned as 14 % of the inner radius of the airway segment. The liquid layer was assumed to be replaced by an instilled PS. The flow rate of the instilled PS was assigned a constant value, which was determined by the total amount and instillation time in clinical use. The PS concentration of the liquid layer during instillation was computed by solving the advective-diffusion equation.
    Results: The driving pressure from the trachea to respiratory bronchioles was calculated at 317 cmH
    Conclusions: The simulation study has revealed that selective wedge instillation under bronchoscopic observation should be tried for COVID-19 pneumonia before the onset of ARDS. It will be also useful for preventing secondary lung fibrosis.
    MeSH term(s) Bronchi/physiology ; Bronchioles/physiology ; Bronchoscopy ; COVID-19/drug therapy ; Computer Simulation ; Humans ; Hydrodynamics ; Instillation, Drug ; Pressure ; Pulmonary Surfactants/administration & dosage ; Respiration, Artificial ; SARS-CoV-2 ; Trachea/physiology
    Chemical Substances Pulmonary Surfactants
    Language English
    Publishing date 2021-02-22
    Publishing country England
    Document type Journal Article
    ZDB-ID 2059871-3
    ISSN 1471-2466 ; 1471-2466
    ISSN (online) 1471-2466
    ISSN 1471-2466
    DOI 10.1186/s12890-021-01435-4
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  3. Article ; Online: Static end-tidal expiratory computed tomography visualizes only a static type of expiratory central airway collapse.

    Kitaoka, Hiroko / Takimoto, Takayuki / Kijima, Takashi

    Respiratory investigation

    2021  Volume 60, Issue 1, Page(s) 182–183

    MeSH term(s) Exhalation ; Humans ; Lung ; Tidal Volume ; Tomography, X-Ray Computed
    Language English
    Publishing date 2021-09-10
    Publishing country Netherlands
    Document type Letter
    ZDB-ID 2660821-2
    ISSN 2212-5353 ; 2212-5345
    ISSN (online) 2212-5353
    ISSN 2212-5345
    DOI 10.1016/j.resinv.2021.08.004
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  4. Article ; Online: What Is Tracheobronchomalacia in Obstructive Lung Disease?

    Takimoto, Takayuki / Kitaoka, Hiroko / Kijima, Takashi

    Chest

    2021  Volume 159, Issue 1, Page(s) 442–443

    MeSH term(s) Adrenal Cortex Hormones ; Humans ; Lung Diseases, Obstructive ; Tracheobronchomalacia/diagnosis ; Tracheobronchomalacia/diagnostic imaging
    Chemical Substances Adrenal Cortex Hormones
    Language English
    Publishing date 2021-01-06
    Publishing country United States
    Document type Letter ; Comment
    ZDB-ID 1032552-9
    ISSN 1931-3543 ; 0012-3692
    ISSN (online) 1931-3543
    ISSN 0012-3692
    DOI 10.1016/j.chest.2020.07.085
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  5. Article ; Online: The origin of frequency dependence of respiratory resistance: an airflow simulation study using a 4D pulmonary lobule model.

    Kitaoka, Hiroko

    Respirology (Carlton, Vic.)

    2011  Volume 16, Issue 3, Page(s) 517–522

    Abstract: Background and objective: The origin of frequency dependence of respiratory resistance has been explained by ventilation inhomogeneity; however, it is unclear which components in the respiratory system generate the frequency dependence. The author ... ...

    Abstract Background and objective: The origin of frequency dependence of respiratory resistance has been explained by ventilation inhomogeneity; however, it is unclear which components in the respiratory system generate the frequency dependence. The author constructed a 4D pulmonary lobule model and analysed relationships between airflow rate, pressure and airway resistance by the use of computational fluid dynamics.
    Methods: The lobule model contained bifurcated bronchioles with two adjacent acini in which deformable inter-acinar septa and alveolar duct walls were designed. Constrictive conditions of respective bronchioles were designed, too. 4D finite element models for computational fluid dynamics were generated and airflow simulations were performed under moving boundary conditions of the arbitrary Lagrangean-Eulerean method. From the simulation results, airway resistances for various conditions were calculated.
    Results: Tissue resistance emerged under the condition of different acinar pressures caused by unequal airway resistances. If the inter-acinar septum was shifted so as to cancel the pressure difference, the acinar pressures were equal in spite of unequal airway resistances, and hence, tissue resistances did not emerge. Therefore, the tissue resistance in the former case is thought to be an index of alveolar pressure inequality (which could be cancelled by mechanical interaction of lung parenchyma), rather than a material property of the tissue itself.
    Conclusions: Inequality of alveolar pressure decreases as the input oscillatory frequency increases. Therefore, frequency dependence of the respiratory resistance should be regarded as a conditional index of the alveolar pressure inequality caused by heterogeneous changes in the intra-pulmonary airway and/or the lung parenchyma.
    MeSH term(s) Airway Resistance/physiology ; Bronchioles/physiology ; Computer Simulation ; Finite Element Analysis ; Humans ; Lung/physiology ; Lung Compliance/physiology ; Models, Biological
    Language English
    Publishing date 2011-04
    Publishing country Australia
    Document type Journal Article
    ZDB-ID 1435849-9
    ISSN 1440-1843 ; 1323-7799
    ISSN (online) 1440-1843
    ISSN 1323-7799
    DOI 10.1111/j.1440-1843.2011.01925.x
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  6. Article: [The origin of frequency dependence of respiratory resistance: airflow simulation study by the use of a 4D pulmonary lobule model].

    Kitaoka, Hiroko

    Nihon Kokyuki Gakkai zasshi = the journal of the Japanese Respiratory Society

    2011  Volume 49, Issue 9, Page(s) 629–635

    Abstract: Background and objective: The origin of frequency dependence of respiratory resistance has been explained by ventilation inhomogeneity, however it is unclear which components in the respiratory system generate the frequency dependence. The author ... ...

    Abstract Background and objective: The origin of frequency dependence of respiratory resistance has been explained by ventilation inhomogeneity, however it is unclear which components in the respiratory system generate the frequency dependence. The author constructed a 4D pulmonary lobule model and analyzed relationships between airflow rate, pressure and airway resistance by the use of computational fluid dynamics (CFD).
    Methods: The lobule model contained bifurcated bronchioles with two adjacent acini in which deformable inter-acinar septa and alveolar duct walls were designed. Constrictive conditions of respective bronchioles were designed, too. 4D finite element models for CFD were generated and airflow simulations were performed under moving boundary conditions of the arbitrary Lagrangean-Eulerean method. From the simulation results, airway resistances for various conditions were calculated.
    Results: Tissue resistance emerged under the condition of different acinar pressures caused by unequal airway resistances. If the inter-acinar septum was shifted so as to cancel the pressure difference, the acinar pressures were equal in spite of unequal airway resistances, and hence, tissue resistances did not emerge. Therefore, the tissue resistance in the former case is thought to be an index of alveolar pressure inequality (which could be canceled by mechanical interaction of lung parenchyma), rather than a material property of the tissue itself.
    Conclusions: Inequality of alveolar pressure decreases as the input oscillatory frequency increases. Therefore, frequency dependence of the respiratory resistance should be regarded as a conditional index of the alveolar pressure inequality caused by heterogeneous changes in the intra-pulmonary airway and/or the lung parenchyma.
    MeSH term(s) Airway Resistance/physiology ; Bronchioles/physiology ; Humans ; Models, Biological ; Pulmonary Alveoli/physiology ; Pulmonary Ventilation/physiology
    Language Japanese
    Publishing date 2011-09
    Publishing country Japan
    Document type English Abstract ; Journal Article
    ZDB-ID 1456536-5
    ISSN 1345-9538 ; 1343-3490
    ISSN (online) 1345-9538
    ISSN 1343-3490
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  7. Article ; Online: Micrometer aerosol deposition in normal and emphysematous subacinar models.

    Xi, Jinxiang / Talaat, Mohamed / Si, Xiuhua April / Kitaoka, Hiroko

    Respiratory physiology & neurobiology

    2020  Volume 283, Page(s) 103556

    Abstract: Emphysema is a chronic respiratory disease characterized by interalveolar septa destruction and enlarged air sacs. How the inhalation dosimetry in the pulmonary acini varies in the time course of emphysema is still unclear. The aim of this study is to ... ...

    Abstract Emphysema is a chronic respiratory disease characterized by interalveolar septa destruction and enlarged air sacs. How the inhalation dosimetry in the pulmonary acini varies in the time course of emphysema is still unclear. The aim of this study is to numerically evaluate the impact of septal destructions on particle deposition in a pyramid-shape subacinar model that is composed of 496 alveoli. Four emphysematous models were generated by progressively removing the inter-alveolar septa from the normal geometry. Spatial distribution and temporal evolution of particle deposition were quantified in expanding/contracting subacinar models on both total and regional basis using a well-validated discrete-phase Lagrangian model. Airflow fields in the subacinar cavities are sensitive to the septal raptures, with regular, radial streamlines in the proximal alveoli in the normal geometry in contrast to unsymmetrical and recirculating flows in the emphysematous subacini. Intensified collateral ventilation and significantly increased doses in the outer wall and base are observed in disease than heath. The deposition rate of small particles (1-1.5 μm) is more sensitive to the level of septal rapture than large particles (2.5-3 μm). Unexpectedly, more particles per unit area deposit on the outer wall and at the base of the subacinus than on the inner septal walls. The subacinus-averaged doses increase with progressing septal destructions, suggesting an escalating risk factor to the acinar health at the late stages of emphysema.
    MeSH term(s) Aerosols ; Emphysema ; Humans ; Models, Biological ; Pulmonary Alveoli ; Respiratory Physiological Phenomena
    Chemical Substances Aerosols
    Language English
    Publishing date 2020-09-30
    Publishing country Netherlands
    Document type Journal Article ; Research Support, Non-U.S. Gov't
    ZDB-ID 2077867-3
    ISSN 1878-1519 ; 1569-9048
    ISSN (online) 1878-1519
    ISSN 1569-9048
    DOI 10.1016/j.resp.2020.103556
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    Zs.A 519: Show issues Location:
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  8. Article ; Online: Aerosol Spread with Use of High-Flow Nasal Cannula: A Computational Fluid Dynamics Analysis

    Kobayashi, Hisato / Takimoto, Takayuki / Kitaoka, Hiroko / Kijima, Takashi

    J Hosp Infect

    Keywords covid19
    Publisher Elsevier; PMC; WHO
    Document type Article ; Online
    Note WHO #Covidence: #597953
    DOI 10.1016/j.jhin.2020.06.010
    Database COVID19

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  9. Article ; Online: Estimation of the site of wheezes in pulmonary emphysema: airflow simulation study by the use of A 4D lung model.

    Kitaoka, Hiroko / Cok, Salim

    Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE Engineering in Medicine and Biology Society. Annual International Conference

    2013  Volume 2013, Page(s) 449–452

    Abstract: Adventitious lung sounds in pulmonary emphysema, wheezes, are continuous musical sounds during expiration with 400 Hz or more. The textbook tells that expiratory airflow limitation in emphysema occurs at the peripheral airways and that wheezes are ... ...

    Abstract Adventitious lung sounds in pulmonary emphysema, wheezes, are continuous musical sounds during expiration with 400 Hz or more. The textbook tells that expiratory airflow limitation in emphysema occurs at the peripheral airways and that wheezes are generated there. We have recently proposed a novel hypothesis based on image analysis and theoretical consideration that expiratory airflow limitation in emphysema occurs at the intra-mediastinal airway (trachea, main bronchi, and right lobar bronchi) due to compression by overinflated lungs. We performed expiratory airflow simulation by the use of a 4D finite element lung model, and found periodical vortex release with 300-900 Hz at the end of protrusion of the the tracheal posterior wall. Relationship between the peak frequency of pressure fluctuation and airflow velocity was in agreement with Strahal's law either in normal or emphysematous condition. Contrarily, airflow simulation in a small bronchus (1.5 mm in diameter) indicated no apparent periodic vortex release.
    MeSH term(s) Bronchi/physiopathology ; Computer Simulation ; Humans ; Lung/physiopathology ; Male ; Middle Aged ; Models, Anatomic ; Phenotype ; Pulmonary Disease, Chronic Obstructive/physiopathology ; Pulmonary Emphysema/physiopathology ; Pulmonary Ventilation ; Respiration ; Respiratory Sounds ; Signal Processing, Computer-Assisted ; Tomography, X-Ray Computed ; Trachea/physiopathology
    Language English
    Publishing date 2013-10-07
    Publishing country United States
    Document type Journal Article
    ISSN 2694-0604
    ISSN (online) 2694-0604
    DOI 10.1109/EMBC.2013.6609533
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  10. Article: [Pneumodynamics: Respiratory Physiology Related to Anesthesiology].

    Kitaoka, Hiroko / Hirata, Haruhiko / Kijima, Takashi

    Masui. The Japanese journal of anesthesiology

    2016  Volume 65, Issue 5, Page(s) 452–460

    Abstract: Although pneumodynamics is the most basic research field in the respiratory management, the number of the researchers is rapidly decreasing in this century. This is not because of the maturing of pneumodynamics but because the conventional theory has ... ...

    Abstract Although pneumodynamics is the most basic research field in the respiratory management, the number of the researchers is rapidly decreasing in this century. This is not because of the maturing of pneumodynamics but because the conventional theory has been wrong. The authors have been investigating this area theoretically and experimentally for more than ten years and propsed novel pneumodynamics based on dynamic imaging technique during breathing and computational fluid dynamics. In this paper, we first indicate the dynamic collapse of the intra-mediastinal airway during maximum forced expiration in emphysematous patients visualized by 4D-CT images, and explain its mechanism in terms of fluid dynamics where the turbulence of airflow in the large airway plays an important role. Although conventional pneumodynamics is based on electric circuit analogy, it has a crucial defect that the turbulence of airflow is never contained. Then, we will introduce a 4D alveolar model which explains how the alveolar shape changes during breathing based on experimental images, and indicate that the essential morphological change in diffuse alveolar damage (DAD) is the alveolar collapse, which has been misrecognized as "thickening of the alveolar wall". The new era of respiratory physiology has just begun in Japan.
    MeSH term(s) Anesthesiology ; Four-Dimensional Computed Tomography ; Humans ; Japan ; Pulmonary Alveoli/physiology ; Respiration
    Language Japanese
    Publishing date 2016-05
    Publishing country Japan
    Document type English Abstract ; Journal Article ; Review
    ZDB-ID 391878-6
    ISSN 0021-4892
    ISSN 0021-4892
    Database MEDical Literature Analysis and Retrieval System OnLINE

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