Background: Influenza virus is a common pathogen causing community-acquired pneumonia. After H1N1 infection, some patients present with rapid disease progression and various respiratory complications, especially immunocompromised patients and pregnant women. However, most patients have a favorable prognosis. Influenza viruses infect respiratory epithelial cells, leading to diffuse alveolar damage (DAD), which could induce secondary bacterial or fungal infections that could lead to serious complications, such as acute respiratory failure, severe pneumonia, pneumothorax, mediastinal emphysema, acute respiratory distress syndrome (ARDS) and post-ARDS fibrosis. Objective: The short-term mortality rate of ARDS is decreasing, and understanding survivors' posthospitalization outcomes is very important. Our aim was to evaluate the outcomes of 69 patients who survived H1N1 pneumonia with severe respiratory complications and abnormal CT findings and developed post-ARDS pulmonary fibrosis. Materials and methods: The 280 inpatients included in this trial had been diagnosed with H1N1 infection that was confirmed by pharyngeal sputum or swab tests. The data were collected from January 2018 to January 2020 in the First Affiliated Hospital of Zhengzhou University and the Sixth People's Hospital of Zhengzhou. Of these patients, 232 had CT findings indicating pulmonary fibrosis after H1N1 infection, and 69 survived and consented to participate in this study. 6°months after diagnosis, the 69 surviving patients were interviewed and underwent physical examinations, CT scans, 6°min walk tests, and quality-of-life evaluations (SF-36). We analyzed the baseline variables and six-month outcomes of post-ARDS pulmonary fibrosis in patients with H1N1 pneumonia. Results: Of the 69 surviving patients with post-ARDS pulmonary fibrosis, there were 24 females and 45 males, with a mean age of 53.7 ± 16.8°years; 18 patients (26%) had no underlying disease, and 14 (20%) patients had more than one underlying disease. The distance walked in 6°min increased from an average of 451.9°m at 3°months to 575.4°m at 6°months; the mean 36-Item Short Form Survey (SF-36) physical function score increased from an average of 75.3 at 3°months to 77.5 at 6°months; and the average CT score decreased from 31.3 at 3°months to 14.8 at 6°months. Treatment with systemic corticosteroids and the presence of an underlying disease were related to the CT score and the distance walked in 6°min. Conclusion: Among the survivors with pulmonary fibrosis after H1N1 influenza, the 6°min walk test and CT scores continued to be affected after 6°months. The 6°min walk distance and imaging findings improved during the first 6°months. The health-related QoL (HRQoL) scores of H1N1 pneumonia survivors were lower than those of sex- and age-matched controls.

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