Impaired exercise capacity in individuals with non-obstructive small airway dysfunction

Zhishan Deng; Xiaochen Li; Chenglong Li; Youlan Zheng; Fan Wu; Zihui Wang; Sha Liu; Heshen Tian; Jinzhen Zheng; Jieqi Peng; Peiyu Huang; Huajing Yang; Shan Xiao; Xiang Wen; Changli Yang; Xiangwen Luo; Gongyong Peng; Bing Li; Yumin Zhou; Pixin Ran

doi:10.21037/jtd-22-1328

Impaired exercise capacity in individuals with non-obstructive small airway dysfunction

J Thorac Dis. 2023 Feb 28;15(2):472-483. doi: 10.21037/jtd-22-1328. Epub 2023 Feb 15.

Authors

Zhishan Deng^#¹, Xiaochen Li^#¹, Chenglong Li^#¹, Youlan Zheng¹, Fan Wu^{1

2}, Zihui Wang¹, Sha Liu¹, Heshen Tian¹, Jinzhen Zheng¹, Jieqi Peng¹, Peiyu Huang¹, Huajing Yang¹, Shan Xiao¹, Xiang Wen¹, Changli Yang³, Xiangwen Luo⁴, Gongyong Peng¹, Bing Li^{1

5}, Yumin Zhou^{1

2}, Pixin Ran^{1

2}

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, the First Affiliated Hospital of Guangzhou Medical University, Guangzhou Medical University, Guangzhou, China.
² Guangzhou Laboratory, Bioland, Guangzhou, China.
³ Department of Pulmonary and Critical Care Medicine, Wengyuan County People's Hospital, Shaoguan, China.
⁴ Department of Internal Medicine, Lianping County People's Hospital, Heyuan, China.
⁵ GMU-GIBH Joint School of Life Sciences, Guangzhou Medical University, Guangzhou, China.

^# Contributed equally.

Abstract

Background: Whether individuals with non-obstructive spirometry-defined small airway dysfunction (SAD) have impaired exercise capacity is unclear, particularly in never-smokers. This study clarifies the degree of impaired exercise capacity and its potential cause in individuals with non-obstructive SAD.

Methods: This community-based, multiyear cross-sectional study analyzed data collected in Guangdong, China from 2012-2019 by the National Science and Technology Support Plan Program. Measurements of exercise capacity [peak work rate and peak oxygen uptake ( $\dot{V} O_{2peak}$ )] in participants with non-obstructive spirometry-defined SAD (n=157) were compared with those in controls (n=85) and Global Initiative for Chronic Obstructive Lung Disease (GOLD) I patients (n=239). Subgroup analyses were performed by smoking status.

Results: The risk of impaired exercise capacity was significantly higher in participants with non-obstructive SAD [ $\dot{V} O_{2peak}$ <84%predicted, adjusted odds ratio (aOR) =2.53; 95% confidence interval (CI): 1.42-4.52] than in controls but was not significantly different from that in GOLD I patients. Results were consistent within subgroups of smoking status (ever-smokers: non-obstructive SAD vs. controls, aOR =2.44; 95% CI: 1.08-5.51; never-smokers: non-obstructive SAD vs. controls, aOR =2.38, 95% CI: 1.02-5.58). Participants with non-obstructive SAD had a significantly lower peak work rate (β=-10.5; 95% CI: -16.3 to -4.7) and $\dot{V} O_{2peak}$ (%predicted, β=-4.0; 95% CI: -7.7 to -0.2) and tended to have higher ventilatory equivalents for carbon dioxide at the ventilatory threshold ( ${\dot{V}}_{E} / \dot{V} {CO}_{2AT}$ , β=1.1; 95% CI: -0.1 to 2.3) when compared with controls. Both peak work rate and $\dot{V} O_{2peak}$ were negatively correlated with ${\dot{V}}_{E} / \dot{V} {CO}_{2AT}$ .

Conclusions: Although not meeting the current criteria for chronic obstructive pulmonary disease, individuals with non-obstructive SAD have impaired exercise capacity that may be associated with ventilatory inefficiency regardless of smoking status.

Keywords: Exercise tolerance; chronic obstructive pulmonary disease (COPD); ventilatory inefficiency.