https://orcid.org/0000-0003-0720-4674
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Abstract
Background
It has been found that the degree of terminal bronchiole destruction is associated with the severity of COPD. However, total airway count (TAC) of CT-visible and its relationship with COPD lung function severity and pulmonary function decline remains controversial. The present study aimed to determine whether TAC is significantly reduced in early-stage COPD (GOLD stage I–II) compared with healthy control subjects and whether TAC is associated with annual decline in pulmonary function in Chinese patients with early-stage COPD.
Methods
A total of 176 participants were enrolled in this study, of which 139 participants had undergone at least two spirometry measurements within 7 years (average 5.5 [standard deviation 0.8] years) after baseline data acquisition. CT-visible TAC was measured by summing all airway segments using semi-automated software. Average lumen diameter, average inner area, emphysema index, air trapping, and inspiratory Pi10 were also measured. Multivariable linear analysis was performed to evaluate variables that were significantly related to pulmonary function parameters and to evaluate the correlation between TAC and annual decline in longitudinal pulmonary function.
Results
Compared with healthy control subjects, CT-visible TAC was significantly reduced by 51% in GOLD II and by 31% in GOLD I after adjustment. TAC had the greatest impact on pre-bronchodilator FEV1, pre-bronchodilator FVC, post-bronchodilator FEV1, and post-bronchodilator FEV1/FVC (both p<0.001) among all CT indicators measured. TAC has the best correlation with inspiratory Pi10 (ρ=−0.751, p<0.001), an evaluation indicator of the degree of airway remodeling. TAC was independently associated with annual decline in pre-bronchodilator FEV1 (p=0.023), post-bronchodilator FEV1 (p=0.018), and post-bronchodilator FEV1/FVC (p<0.001).
Conclusion
This finding suggests that CT-visible TAC may be an evaluation indicator of the degree of airway remodeling, and was diminished in greater COPD lung function severity, and independently associated with disease progression. Early-stage COPD patients have already occurred lung structural changes and early intervention may be needed to ameliorate the progression of disease.
Clinical Trial Registration
ChiCTR-OO-14004264.
Abbreviations
COPD, chronic obstructive pulmonary disease; micro-CT, micro-computed tomography; CT, computer tomography; TAC, total airway count; FEV1, forced expiratory volume in 1 second; FVC, forced vital capacity; HRCT, High resolution computer tomography; VIDA, Volumetric Information Display and Analysis; HU, Hounsfield units; LAA−950, low-attenuation area of the lung with attenuation values below −950 Hounsfield units on full-inspiration computed tomography; Perc15, the HU at which 15% of the voxels fall below at full inspiration; LAA−856, low-attenuation area of the lung with attenuation values below −856 Hounsfield units on full-expiration computed tomography; Pi10, the square root of the airway wall area for a theoretical airway with 10-mm internal perimeter; GOLD, Global Initiative for Chronic Obstructive Lung Disease; SD, standard deviation; IQR, interquartile range; ANCOVA, analysis of covariance; BMI, body mass index; CI, confidence interval; SE, standard error.
Data Sharing Statement
With the permission of the corresponding authors, we can provide participant data without names and identifiers. The corresponding authors have the right to decide whether to share the data based on the research objectives and plan provided. Data will be immediately available after publication. No end date. Please contact correspondence author for data requests.
Ethics Approval and Informed Consent
This study was approved by the Ethics Committee of the First Affiliated Hospital of Guangzhou Medical University (No. 2013-37), and all of the participants received information regarding radiation exposure and all provided written informed consent in advance of their participation in the study.
Acknowledgment
We thank Lianping County People’s Hospital and Wengyuan County People’s Hospital for providing us with the research follow-up site. We also thank all subjects and their families who agreed to donate their data for analysis. We thank Bijia Lin, Peiyu Huang, Shaodan Wei, Xiaopeng Lin (State Key Laboratory of Respiratory Disease, National Clinical Research Center for Respiratory Disease, Guangzhou Institute of Respiratory Health, The First Affiliated Hospital of Guangzhou Medical University, Nanshan Medicine Innovation Institute of Guangdong Province), for their efforts in collecting the information and verification.
Author Contributions
All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.
Disclosure
The authors have no conflicts of interest to declare.