Oscillometrically assessed higher respiratory reactance is associated with impaired lung function and poorer prognosis in patients with fibrotic idiopathic interstitial pneumonias.

BACKGROUND: Fibrotic idiopathic interstitial pneumonias (IIPs) are progressive lung diseases with variable prognoses. Oscillometry, a non-invasive method for assessing respiratory impedance, has emerged as a potential tool for disease stratification. However, the association between standardized respiratory reactance (Xrs) measured by oscillometry and clinical outcomes in IIPs, including those other than idiopathic pulmonary fibrosis, remains unclear. Therefore, we investigated this association.

METHODS: We retrospectively analyzed 101 patients with fibrotic IIPs treated at Shizuoka General Hospital from 2017 to 2022. Fibrosis was defined by high-resolution computed tomography findings of honeycombing, traction bronchiectasis, or subpleural reticulation. Patients were categorized into high-Xrs or low-Xrs groups based on whether Xrs parameters (X5, Fres, or AX) exceeded 1.64 standard deviations above Japanese standard values. The primary outcome was mortality. Cox proportional hazards analysis identified prognostic factors.

RESULTS: Among 101 patients, 25 (24.8 %) were classified as high-Xrs. Median overall survival was significantly shorter in the high-Xrs group (21.1 months; 95 % CI, 13.2-43.3) compared to the low-Xrs group (78.7 months; 95 % CI, 56.8-not reached). A subgroup analysis of IPF and non-IPF patients showed significant survival differences between the high-Xrs and low-Xrs groups. Multivariate analysis identified low %FVC and high-Xrs classification as independent predictors of mortality.

CONCLUSIONS: High respiratory reactance measured by oscillometry was independently associated with impaired lung function and poor prognosis in patients with fibrotic IIPs. Oscillometry may be a valuable tool for risk stratification and prognostic assessment in this patient population.