Associations of small airway dysfunction assessed by impulse oscillometry with lung function decline and exacerbations in participants with chronic obstructive pulmonary disease: A prospective cohort study in China

Abstract

Introduction

Small airway dysfunction (SAD) assessed by impulse oscillometry (IOS) was common in patients with chronic obstructive pulmonary disease (COPD). However, little is known about the associations between IOS-defined small airway dysfunction (SAD) and the long-term prognosis of COPD. This study aimed to explore the associations between IOS-defined SAD, lung function decline and exacerbations in patients with COPD.

Methods

We analyzed baseline and 2-year follow-up data from the prospective cohort study in China. We defined SAD using IOS parameters Z-score greater than the 1.645 or less than −1.645. Subsequently, these patients were divided into three groups based on the different criteria defined SAD using IOS (normal group [none IOS parameters abnormalities], inconsistent SAD [any IOS parameters abnormalities, but not all], consistent SAD [all of IOS parameters abnormalities]). Negative binomial regression was conducted to analyze the associations between SAD and exacerbations, while a multivariable linear regression model was utilized to identify associations between SAD and lung function decline.

Results

833 patients with COPD were enrolled in our study. SAD (defined by X5, AX, and Fres z-score) was associated with a faster decline in lung function and higher risk of exacerbation. Meanwhile, for inconsistent diagnosis of SAD, we observed that patients with consistent SAD and inconsistent SAD experienced a faster decline in FEV₁ and higher risk of exacerbations than those with normal group.

Conclusions

IOS-defined SAD was associated with worse outcomes in patients with COPD, and further clinical trials are needed to clarify whether early intervention to reduce the severity of small airway lesions can delay the progress of COPD.

Trial registration

Chinese Clinical Trial Registry, ChiCTR1900024643. Registered on 19 July 2019.