Segmental bronchi collapsibility: computed tomography-based quantification in patients with chronic obstructive pulmonary disease and correlation with emphysema phenotype, corresponding lung volume changes and clinical parameters.
BACKGROUND
Global pulmonary function tests lack region specific differentiation that might influence therapy in severe chronic obstructive pulmonary disease (COPD) patients. Therefore, the aim of this work was to assess the degree of expiratory 3rdgeneration bronchial lumen collapsibility in patients with severe COPD using chest-computed tomography (CT), to evaluate emphysema-phenotype, lobar volumes and correlate results with pulmonary function tests.


METHODS
Thin-slice chest-CTs acquired at end-inspiration & end-expiration in 42 COPD GOLD IV patients (19 females, median-age: 65.9 y) from November 2011 to July 2014 were re-evaluated. The cross-sectional area of all segmental bronchi was measured 5 mm below the bronchial origin in both examinations. Lung lobes were semi-automatically segmented, volumes calculated at end-inspiratory and end-expiratory phase and visually defined emphysema-phenotypes defined. Results of CT densitometry were compared with lung functional tests including forced expiratory volume at 1 s (FEV1), total lung capacity (TLC), vital capacity (VC), residual volume (RV), diffusion capacity parameters and the maximal expiratory flow rates (MEFs).


RESULTS
Mean expiratory bronchial collapse was 31%, stronger in lobes with homogenous (38.5%)vs. heterogeneous emphysema-phenotype (27.8%, P=0.014). The mean lobar expiratory volume reduction was comparable in both emphysema-phenotypes (volume reduction 18.6%±8.3% in homogenousvs. 17.6%±16.5% in heterogeneous phenotype). The degree of bronchial lumen collapsibility, did not correlate with expiratory volume reduction. MEF25correlated weakly with 3rdgeneration airway collapsibility (r=0.339, P=0.03). All patients showed a concentric expiratory reduction of bronchial cross-sectional area.


CONCLUSIONS
Changes in collapsibility of 3rdgeneration bronchi in COPD grade IV patients is significantly lower than that in the trachea and the main bronchi. Collapsibility did not correlate with the reduction in lung volume but was significantly higher in lobes with homogeneousvs. heterogeneous emphysema phenotype. Changes in the 3rdgeneration bronchial calibres between inspiration and expiration are not predictive for the degree of small airway collapsibility and related airflow limitation.
Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University, 72076 Tübingen, Germany.
Christopher
C
Kloth
Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University, 72076 Tübingen, Germany.
Wolfgang Maximilian
WM
Thaiss
Siemens AG Healthcare, Imaging & Therapy Systems Computed Tomography & Radiation Oncology, HC IM CR R&D PA CA DC, 91301 Forchheim, Germany.
Hendrik
H
Ditt
Department of Internal Medicine II, Eberhard-Karls-University, 72076 Tübingen, German.
Jürgen
J
Hetzel
Department of Internal Medicine II, Eberhard-Karls-University, 72076 Tübingen, German.
Eva
E
Schülen
Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University, 72076 Tübingen, Germany.
Konstantin
K
Nikolaou
Department of Diagnostic and Interventional Radiology, Eberhard-Karls-University, 72076 Tübingen, Germany.
Marius
M
Horger
Chronic obstructive pulmonary disease (COPD); computed tomography (CT); emphysema; lung volume