Role of Airwave Oscillometry in Patients with Combined Fibrosis-Emphysema Syndrome (CPFE) with Preserved FEV1/FVC...

Introduction: Emphysema is frequently observed in patients with fibrosing interstitial lung diseases (f-ILDs), leading to the clinical entity known as combined pulmonary fibrosis and emphysema (CPFE). This study aimed to evaluate the utility of airwave oscillometry (AOS) in detecting small-airway dysfunction (SAD) in patients with CPFE. Due to the coexistence of both restrictive and obstructive airway disease, spirometry is comparatively less sensitive in detecting airflow limitations in this population. Methods: A cohort of 52 patients with CPFE was recruited from Monaldi Hospital, Naples, between January and September 2023. Pulmonary function tests-including spirometry, body plethysmography, and single-breath diffusing capacity for carbon monoxide (DLCO)-were performed at baseline and following bronchodilator administration. Patients with normal FEV1/FVC ratios underwent airwave oscillometry (AOS) to assess respiratory system resistance (Rrs) and reactance (Xrs), with SAD defined as an R5-R19 value greater than 0.07 kPa·s·L^-1. Results: AOS-defined SAD was present in 40.4% (21/52) of the cohort. The R5-R19 value in the SAD group was 0.13 ± 0.05 kPa·s·L^-1, which can be compared to 0.04 ± 0.02 kPa·s·L^-1 in patients without SAD. Patients with SAD were more likely to be undergoing maintenance bronchodilator therapy (16/21; 76.2%) than those without SAD (8/31; 25.8%) (p = 0.015). Fourteen CPFE patients met the criteria for bronchial responsiveness. CPFE patients who responded to bronchodilators had lower R5-R19 values than non-responders (0.04 ± 0.02 vs. 0.09 ± 0.06 kPa·s·L^-1; p = 0.04). Discussion: Although AOS parameters did not significantly change following bronchodilator administration, this study underscores the value of AOS in detecting peripheral airway dysfunction, which may be under-recognized by conventional spirometry. Conclusions: AOS shows promise as a diagnostic adjunct for identifying SAD in CPFE patients and may complement standard pulmonary function testing in clinical practice. Further multicenter studies with larger cohorts are warranted to validate these findings and investigate the longitudinal impact of SAD on disease progression and treatment outcomes in CPFE.