1-year follow-up of pulmonary CT and function in patients recovering from ARDS induced by H1N1 influenza

Abstract

Background Patients recovering from pneumonia-induced acute respiratory distress syndrome (ARDS) may demonstrate persistent lung abnormalities and declining pulmonary function. However, a comprehensive assessment of long-term outcomes in survivors of influenza A (H1N1) remains insufficiently explored. This study was to identify and characterize pulmonary radiological and functional impairments in patients with ARDS caused by H1N1 pneumonia during 1 year of follow-up after discharge.Methods We conducted a prospective, single-center, longitudinal cohort study on patients admitted to intensive care unit (ICU) due to H1N1 pneumonia complicated by ARDS from March 2016 to December 2020. Serial chest CT scans were obtained from admission to 1 year after discharge and longitudinally analyzed. The extent of CT abnormalities was semi-quantitatively scored in detail. Multiple linear regression analysis was performed to identify factors associated with CT score and diffusing capacity of the lung for carbon monoxide (DLCO) at follow-up.Results Among 345 patients diagnosed with ARDS, 92 individuals (26.7%) were diagnosed with laboratory-confirmed H1N1 pneumonia, 59 survivors (mean age, 47.2 years ± 13.2 [SD]; 43 men) completed follow-up and were included in the final analysis. At 1-year follow-up, 29/32 patients (90.6%) exhibited CT abnormalities and more than 80% were characterized by parenchymal bands and reticular lesions. In the multiple linear regression model, age and duration of ICU stay demonstrated a correlation with 1-year CT score (R2 = 0.574). Furthermore, smoking status and CT scores of reticular lesions were correlated with 1-year DLCO percent predicted (R2 = 0.386).Conclusions Over 90% of patients with H1N1-ARDS exhibited pulmonary parenchymal abnormalities 1 year following discharge, predominantly characterized by pulmonary fibrotic lesions, which were associated with a decline in pulmonary diffusion capacity.