Comparing spirometry, impulse oscillometry with computed tomography for assessing small airway dysfunction in...

Area of Science:

• Pulmonary Medicine
• Respiratory Physiology
• Medical Imaging

Background:

• Small airway dysfunction (SAD) detection methods like spirometry and impulse oscillometry (IOS) lack established consistency with histological assessments.
• Lung histopathology is invasive, necessitating non-invasive comparative studies for SAD detection.

Purpose of the Study:

• To compare spirometry and IOS with chest computed tomography (CT) for diagnosing small airway dysfunction (SAD).
• To evaluate the clinical characteristics of subjects identified with SAD by these three techniques.

Main Methods:

• Utilized baseline data from the Early COPD (ECOPD) study, including 2055 subjects.
• Defined CT-defined SAD using parametric response mapping (PRM^fSAD ≥ 15%).
• Defined spirometry-defined SAD by specific flow rate criteria (MMEF, FEF50, FEF75 < 65% predicted).
• Defined IOS-defined SAD by peripheral airway resistance (R5 - R20 > 0.07 kPa/L/s).
• Assessed consistency using Kappa coefficients and correlations using Spearman analysis.

Main Results:

• Low agreement was observed between spirometry and CT (Kappa=0.126), IOS and CT (Kappa=0.266), and all three methods (Kappa=0.056).
• Moderate correlation existed between spirometry and CT parameters, while the correlation was weak between IOS and CT parameters.
• Spirometry-defined SAD correlated with lower lung function and increased airway wall thickness; IOS-defined SAD correlated with better lung function, less emphysema, and thicker airway walls compared to CT-defined SAD.

Conclusions:

• There is low consistency in assessing small airway dysfunction (SAD) when comparing spirometry and CT, and IOS and CT.
• The findings highlight significant discrepancies in SAD detection across these common pulmonary function testing methods.