ATS 2025: Exploring Small Airway Dysfunction in Pre-COPD: Insights from Parametric Response Mapping, Impulse Oscillometry, and Airway Inflammatory Profiles - A Prospective Cohort Study in an East Asian Population

Introduction:

Small airway dysfunction (SAD) or emphysema are crucial features and early indicators of chronic obstructive pulmonary disease (COPD). In the pre-COPD stage, SAD or emphysema can be detected via computed tomography (CT) even in the absence of airflow obstruction. While Impulse Oscillometry (IOS) and Parametric Response Mapping (PRM) have shown promise in detecting SAD, their correlation and diagnostic accuracy remain unclear.

Aim:

To assess the ability of IOS and PRM to detect SAD in pre-COPD patients compared with smokers and COPD patients with varying disease severity.

Methods:

1. Study Design: Prospective cohort study conducted in Taiwan
2. Participants: 164 individuals were included.

• Pre-COPD: 46 patients (FEV₁/FVC >7, FEV₁ < 80%, and/or emphysema ≥ 5%)
• Mild COPD: 27 patients
• Moderate-to-severe COPD: 43 patients
• Smoker controls (>10 pack-years): 48 (FEV₁/FVC >7, FEV₁ > 80%, emphysema < 5%)

3. Assessments:
   1. Spirometry and Impulse Oscillometry
   2. High-resolution computed tomography (HRCT) with parametric response mapping for emphysema (PRM_Emp) and function SAD (PRM_fSAD).
   3. Bronchoalveolar lavage (BAL) for airway cytokine analysis (IL-6, IL-8, MCP-1)

Results:

Discriminatory Ability:

• PRM_Emp and PRM_fSAD differentiated smokers from pre-COPD:
1. PRM_Emp AUC: 0.84 (cutoff 1.18%)
2. PRMf_SAD AUC: 0.73 (cutoff 6.98%)

• PRM_fSAD and Fres from IOS were most effective in distinguishing pre-COPD from COPD:
1. PRM_fSAD AUC: 0.72 (cutoff 23.07%)
2. IOS Fres AUC: 0.69 (cutoff 17.1 Hz)

• PRM_fSAD and AX (IOS) showed weak but significant correlation (Pearson’s r = 0.237, p = 0.03).
• Cytokine levels increased progressively with disease severity.  
• IL-8 demonstrated a robust correlation with PRM and all IOS parameters associated with SAD.

Conclusion:

Impulse oscillometry and parametric response mapping effectively detected small airway dysfunction in pre-COPD, differentiating it from both smoker controls and COPD patients. A modest but significant association between PRM and IOS, along with progressively elevated airway cytokines, supports early identification of SAD. These findings could enable timely management in individuals at risk of developing COPD.

Am J Respir Crit Care Med 2025; 211: A7936

ATS 2025, 18-21 May, San Francisco