Changes in the airway lumen and surrounding parenchyma in chronic obstructive pulmonary disease

Kazuyoshi Kurashima,¹ Toshiko Hoshi,² Yotaro Takaku,¹ Tetsu Kanauchi,² Keitaro Nakamoto,¹ Miyuki Ueda,² Noboru Takayanagi,¹ Thomas V Colby,⁴ Yutaka Sugita,¹ Yoshinori Kawabata<sup>3

1</sup>Department of Respiratory Medicine, ²Department of Radiology, ³Department of Pathology, Saitama Cardiovascular and Respiratory Center, Kumagaya City, Saitama, Japan; ⁴Department of Laboratory Medicine and Pathology, Mayo Clinic, Scottsdale, AZ, USA

Background: The purpose of this study was to examine changes in the airway lumen and parenchyma in relation to lung function in patients with chronic obstructive pulmonary disease (COPD) compared with controls.
Methods: We studied 70 patients with COPD and 15 normal subjects. Using reconstructed computed tomography (CT) images, we traced the bronchial trees and reconstructed 3 cm circle images around the airways exactly perpendicular to the airway axis at the peripheral, middle, and central zones of the bronchi. We measured the number of airways and vessels, the airway inner diameter, and the area of emphysema in the circles, and analyzed the relationship of these image parameters to lung function.
Results: Reduced airway numbers and increased upper lobe emphysema were observed even in early spirometric stages in patients with COPD compared with controls. Other findings included decreased airway inner diameter in advanced spirometric stages. The numbers of peripheral zone bronchi, the extent of the middle zone emphysematous area, and the mean airway inner diameter of the airways were the best predictors of spirometric parameters. A portion of the airways in patients with COPD showed a loss of airway patency at middle or central zone bronchi predominantly in the late spirometric stages. Lumen-obliterated bronchial trees could be traced into emphysematous areas showing air trapping.
Conclusion: Compared with controls, our CT observations in patients with COPD showed that airway lumen and lung parenchyma changes along airways differed by spirometric stage, and these changes were associated with decreased lung function. A portion of CT-identified emphysema in patients with COPD appeared to be due to lumen-obliterated airways in the bronchial tree.

Keywords: airway dimension, computed tomography, emphysema, pulmonary functions