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      3D-measurement of tracheobronchial angles on inspiratory and expiratory chest CT in COPD: respiratory changes and correlation with airflow limitation

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          To assess tracheobronchial angles and their changes on combined inspiratory and expiratory thoracic computed tomography (CT) scans and to determine correlations between tracheobronchial angles and several indices of chronic obstructive pulmonary disease (COPD).

          Materials and methods

          A total of 80 smokers underwent combined inspiratory and expiratory CT scans. Of these, 65 subjects also performed spirometry and 55 patients were diagnosed with COPD. On CT scans, 3-dimensinal tracheobronchial angles (trachea–right main bronchus [RMB], trachea–left main bronchus [LMB], and RMB–LMB) were automatically measured by software. Lung volumes at inspiration and expiration were also automatically calculated. Changes in tracheobronchial angles between inspiration and expiration were assessed by the Mann–Whitney test. Correlations of the angles with lung volume, airflow limitation, and CT-based emphysema index were evaluated by Spearman rank correlation.


          The trachea–LMB angle was significantly smaller and the RMB–LMB angle was significantly larger at expiration than inspiration ( P<0.0001). The trachea–LMB and RMB–LMB angles were significantly correlated with lung volume, particularly at expiration. The RMB–LMB angle was significantly correlated with airflow limitation and CT emphysema index ( P<0.001–0.05) at inspiration and expiration, suggesting that narrowed RMB–LMB angle indicates more severe airflow limitation and larger extent of emphysema.


          Tracheobronchial angles change during respiration and are correlated with severity of COPD and emphysema.

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          Most cited references 27

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          Standardisation of lung function testing: helpful guidance from the ATS/ERS Task Force.

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            Dimensions of the normal human trachea.

            The coronal and sagittal diameters of the tracheal air column were measured on posteroanterior and lateral chest radiographs of 808 patients with no clinical or radiographic evidence of respiratory disease. The 430 male and 378 female subjects were 10-79 years of age. Assuming a normative range that encompasses three standard deviations from the mean or 99.7% of the normal population, the upper limits of normal for coronal and sagittal diameters, respectively, in men aged 20-79, are 25 mm and 27 mm; in women, they are 21 mm and 23 mm, respectively. The lower limit of normal for both dimensions is 13 mm in men and 10 mm in women. Deviation from these figures reflects pathologic widening or narrowing of the tracheal air column. No statistically significant correlation was found between tracheal caliber and body weight or body height.
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              Collapsibility of lung volume by paired inspiratory and expiratory CT scans: correlations with lung function and mean lung density.

              To evaluate the relationship between measurements of lung volume (LV) on inspiratory/expiratory computed tomography (CT) scans, pulmonary function tests (PFT), and CT measurements of emphysema in individuals with chronic obstructive pulmonary disease. Forty-six smokers (20 females and 26 males; age range 46-81 years), enrolled in the Lung Tissue Research Consortium, underwent PFT and chest CT at full inspiration and expiration. Inspiratory and expiratory LV values were automatically measured by open-source software, and the expiratory/inspiratory (E/I) ratio of LV was calculated. Mean lung density (MLD) and low attenuation area percent (<-950 HU) were also measured. Correlations of LV measurements with lung function and other CT indices were evaluated by the Spearman rank correlation test. LV E/I ratio significantly correlated with the following: the percentage of predicted value of forced expiratory volume in the first second (FEV(1)), the ratio of FEV(1) to forced vital capacity (FVC), and the ratio of residual volume (RV) to total lung capacity (TLC) (FEV(1)%P, R = -0.56, P < .0001; FEV(1)/FVC, r = -0.59, P < .0001; RV/TLC, r = 0.57, P < .0001, respectively). A higher correlation coefficient was observed between expiratory LV and expiratory MLD (r = -0.73, P < .0001) than between inspiratory LV and inspiratory MLD (r = -0.46, P < .01). LV E/I ratio showed a very strong correlation to MLD E/I ratio (r = 0.95, P < .0001). LV E/I ratio can be considered to be equivalent to MLD E/I ratio and to reflect airflow limitation and air-trapping. Higher collapsibility of lung volume, observed by inspiratory/expiratory CT, indicates less severe conditions in chronic obstructive pulmonary disease. Copyright 2010 AUR. Published by Elsevier Inc. All rights reserved.

                Author and article information

                Int J Chron Obstruct Pulmon Dis
                Int J Chron Obstruct Pulmon Dis
                International Journal of COPD
                International Journal of Chronic Obstructive Pulmonary Disease
                Dove Medical Press
                10 August 2018
                : 13
                : 2399-2407
                [1 ]Division of Respiratory Medicine, Department of Internal Medicine, St Marianna University School of Medicine, Kawasaki, Japan
                [2 ]Department of Radiology, St Marianna University School of Medicine, Kawasaki, Japan, clatsune@
                [3 ]Department of Radiology, Graduate School of Medical Science, University of the Ryukyus, Nishihara, Japan, clatsune@
                Author notes
                Correspondence: Tsuneo Yamashiro, Department of Radiology, Graduate School of Medical Science, University of the Ryukyus, 207 Uehara, Nishihara, Okinawa 903-0215, Japan, Tel +81 98 895 1162, Fax +81 98 895 1420, Email clatsune@
                © 2018 Onoe et al. This work is published and licensed by Dove Medical Press Limited

                The full terms of this license are available at and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed.

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