Association between impaired diffusion capacity and small airway dysfunction: a cross-sectional study

Kunning Zhou; Fan Wu; Lifei Lu; Gaoying Tang; Zhishan Deng; Cuiqiong Dai; Ningning Zhao; Qi Wan; Jieqi Peng; Xiaohui Wu; Xianliang Zeng; Jiangyu Cui; Changli Yang; Shengtang Chen; Yongqing Huang; Shuqing Yu; Yumin Zhou; Pixin Ran

doi:10.1183/23120541.00910-2023

Association between impaired diffusion capacity and small airway dysfunction: a cross-sectional study

ERJ Open Res. 2025 Jan 13;11(1):00910-2023. doi: 10.1183/23120541.00910-2023. eCollection 2025 Jan.

Authors

Kunning Zhou^{1

2}, Fan Wu^{1

3

2}, Lifei Lu¹, Gaoying Tang¹, Zhishan Deng¹, Cuiqiong Dai¹, Ningning Zhao¹, Qi Wan¹, Jieqi Peng^{1

3}, Xiaohui Wu¹, Xianliang Zeng¹, Jiangyu Cui¹, Changli Yang⁴, Shengtang Chen⁵, Yongqing Huang⁶, Shuqing Yu⁶, Yumin Zhou^{1

3

7}, Pixin Ran^{1

3

7}

Affiliations

¹ State Key Laboratory of Respiratory Disease & National Clinical Research Center for Respiratory Disease & Guangzhou Institute of Respiratory Health & National Center for Respiratory Medicine & Department of Pulmonary and Critical Care Medicine, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou Medical University, Guangzhou, Guangdong, China.
² K. Zhou and F. Wu contributed equally as joint first authors.
³ Guangzhou National Laboratory, Guangzhou, Guangdong, China.
⁴ Department of Pulmonary and Critical Care Medicine, Wengyuan County People's Hospital, Shaoguan, China.
⁵ Medical Imaging Center, Wengyuan County People's Hospital, Shaoguan, China.
⁶ Lianping County People's Hospital, Heyuan, China.
⁷ Y. Zhou and P. Ran contributed equally as lead authors and supervised the work.

Abstract

Background: Small airway dysfunction (SAD) and impaired diffusion capacity of the lungs for carbon monoxide (D _LCO) are positively associated with a worse prognosis. Individuals with both dysfunctions have been identified in clinical practice and it is unknown whether they have worse health status or need management. We conducted this study to explore the association between SAD and impaired D _LCO, and the difference between the groups with two dysfunctions, with either one dysfunction and with no dysfunction.

Methods: This study involved subjects partly from those who had returned for the third-year follow-up (up to December 2022) of the Early Chronic Obstructive Pulmonary Disease study and those who newly participated. We assessed diffusion capacity, questionnaire, exacerbations, spirometry, impulse oscillometry (IOS) and computed tomography (CT). Impaired D _LCO was defined as D _LCO <80% predicted. Spirometry-defined SAD was defined using the percent predicted values of maximal mid-expiratory flow, and forced expiratory flow at 50% and 75% of forced vital capacity, at least two of these three values being <65% predicted after the use of a bronchodilator. IOS-defined SAD was defined when the difference in resistance at 5 and 20 Hz was >0.07 kPa·L^-1·s. CT-defined SAD was defined when the percentage of expiratory low-attenuation areas <-856 HU comprised ≥15% of the total lung volume. Covariate analyses and logistic regression were performed to assess the association between impaired D _LCO and SAD.

Results: This study involved 581 subjects. The occurrence of both spirometry- and CT-defined SAD was significantly higher in subjects with impaired D _LCO than normal D _LCO. Subjects with two dysfunctions were associated with worse preceding year's exacerbations than controls.

Conclusions: Impaired diffusion capacity is positively associated with SAD. Subjects with impaired diffusion capacity and SAD may have a worse health status and need additional management.