Abstract
Bronchodilators, including long‐acting muscarinic antagonists (LAMAs), improve airflow limitation and lung hyperinflation in patients with chronic obstructive pulmonary disease (COPD). While bronchodilators increase airway caliber and deflate the lungs, little is known about the effects of the local interaction between airway dilation and lung deflation on functional improvements resulting from bronchodilator therapy. This study aimed to explore whether lung deflation with increased airway volume in the upper and lower lung regions would produce different physiological responses to LAMA therapy. Using the clinical data of 41 patients with COPD who underwent spirometry and inspiratory computed tomography (CT) before and 1 year after LAMA treatment, we measured the 1‐year change in the airway tree to lung volume percentage ratio (AWV%) for the right upper, middle, and lower lobes (RUL, RML, and RLL) and the left upper and lower lobes (LUL and LLL), and total airway count (TAC) identifiable on CT in relation to the forced expiratory volume in 1 s (FEV1). The results showed that LAMA treatment significantly increased the FEV1 and AWV% of the RUL, RML, RLL, LUL, and LLL. Increased AWV% in the RLL and LLL, but not in the RUL and LUL, was correlated with increased FEV1. In the multivariate analysis, the increased AWV% in the RLL was associated with the increased FEV1 independent of the change in TAC in the RLL after treatment. This is the first study to show that the physiological improvements after bronchodilator treatment in COPD could be mainly due to the combination of regional deflation and increased airway volume of the lower lobes.
Highlights
Chronic obstructive pulmonary disease (COPD) is characterized by chronic airflow limitation and lung hyperinflation induced by a combination of increased airway resistance due to luminal narrowing and decreased elastic recoil of the parenchyma due to emphysema (Vogelmeier et al, 2017)
This study aimed to investigate whether increases in the AWV% in the right upper, middle, and lower lobes (RUL, right middle lobe (RML), and right lower lobe. LUL (RLL)) and the left upper and lower lobes (LUL and left lower lobe (LLL)) had different associations with the change in forced expiratory volume in 1 s (FEV1) that occurs in response to standard long-acting muscarinic antagonists (LAMAs) treatment by using the clinical data of a prospective cohort, including patients with COPD who underwent computed tomography (CT) scans before and 1 year after LAMA treatment
This study showed that LAMA treatment increased the FEV1 and AWV% in the right upper lobe (RUL), RML, RLL, LUL, and LLL in patients with COPD
Summary
Chronic obstructive pulmonary disease (COPD) is characterized by chronic airflow limitation and lung hyperinflation induced by a combination of increased airway resistance due to luminal narrowing and decreased elastic recoil of the parenchyma due to emphysema (Vogelmeier et al, 2017). Other measurements regarding lung hyperinflation, such as residual volume (RV), functional residual capacity (FRC), and ratio of RV to total lung capacity (TLC), are used to detect lung deflation (Hohlfeld et al, 2018; Kostikas & Siafakas, 2016). These physiological measures assess only the entire lung, including both the airway and lung. The underlying local structural responses to bronchodilators are still not fully understood
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