Discordant Spirometry and Impulse Oscillometry Assessments in the Diagnosis of Small Airway Dysfunction

Lifei Lu; Jieqi Peng; Ningning Zhao; Fan Wu; Heshen Tian; Huajing Yang; Zhishan Deng; Zihui Wang; Shan Xiao; Xiang Wen; Youlan Zheng; Cuiqiong Dai; Xiaohui Wu; Kunning Zhou; Pixin Ran; Yumin Zhou

doi:10.3389/fphys.2022.892448

Discordant Spirometry and Impulse Oscillometry Assessments in the Diagnosis of Small Airway Dysfunction

Front Physiol. 2022 Jun 22:13:892448. doi: 10.3389/fphys.2022.892448. eCollection 2022.

Authors

Lifei Lu¹, Jieqi Peng¹, Ningning Zhao¹, Fan Wu^{1

2}, Heshen Tian¹, Huajing Yang¹, Zhishan Deng¹, Zihui Wang¹, Shan Xiao¹, Xiang Wen¹, Youlan Zheng¹, Cuiqiong Dai¹, Xiaohui Wu¹, Kunning Zhou¹, Pixin Ran^{1

2}, Yumin Zhou^{1

2}

Affiliations

¹ National Center for Respiratory Medicine, 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, Guangzhou, China.
² Guangzhou Laboratory, Guangzhou, China.

Abstract

Background and objective: Spirometry is commonly used to assess small airway dysfunction (SAD). Impulse oscillometry (IOS) can complement spirometry. However, discordant spirometry and IOS in the diagnosis of SAD were not uncommon. We examined the association between spirometry and IOS within a large cohort of subjects to identify variables that may explain discordant spirometry and IOS findings. Methods: 1,836 subjects from the ECOPD cohort underwent questionnaires, symptom scores, spirometry, and IOS, and 1,318 subjects were examined by CT. We assessed SAD with R₅-R₂₀ > the upper limit of normal (ULN) by IOS and two of the three spirometry indexes (maximal mid-expiratory flow (MMEF), forced expiratory flow (FEF)_50%, and FEF_75%) < 65% predicted. Multivariate regression analysis was used to analyze factors associated with SAD diagnosed by only spirometry but not IOS (spirometry-only SAD) and only IOS but not spirometry (IOS-only SAD), and line regression was used to assess CT imaging differences. Results: There was a slight agreement between spirometry and IOS in the diagnosis of SAD (kappa 0.322, p < 0.001). Smoking status, phlegm, drug treatment, and family history of respiratory disease were factors leading to spirometry-only SAD. Spirometry-only SAD had more severe emphysema and gas-trapping than IOS-only SAD in abnormal lung function. However, in normal lung function subjects, there was no statistical difference in emphysema and gas-trapping between discordant groups. The number of IOS-only SAD was nearly twice than that of spirometry. Conclusion: IOS may be more sensitive than spirometry in the diagnosis of SAD in normal lung function subjects. But in patients with abnormal lung function, spirometry may be more sensitive than IOS to detect SAD patients with clinical symptoms and CT lesions.

Keywords: COPD; computed tomography; impulse oscillometry; small airway dysfunction; spirometry.

Grants and funding

This study was supported by the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01S155), the National Key Research and Development Program (2016YFC1304101), the National Natural Science Foundation of China (81970045), and Zhongnanshan Medical Foundation of Guangdong Province (ZNSA-2020003, ZNSA-2020012, and ZNSA-2020013).