Differences in clinical characteristics and chest CT findings between severe and critical H1N1 pneumonia

INTRODUCTION: Critical H1N1 pneumonia patients usually have one of the symptoms such as respiratory failure, septic shock, multiple organ dysfunction, or other need for intensive care management, which are associated with high risk of mortality. It is essential to differentiate the severity of H1N1 pneumonia and take corresponding target treatments. OBJECTIVES: We aim to investigate the differences in clinical characteristics and chest computed tomography (CT) findings between severe and critical patients with H1N1 pneumonia. METHODS: A total of 27 patients diagnosed with H1N1 pneumonia from October 2018 to March 2019 were retrospectively analyzed, and the differences in clinical manifestations, laboratory tests, and chest CT findings between the severe group (15 patients) and the critical group (12 patients) were compared. RESULTS: Frequency of dyspnea at rest was higher in critical group than that in severe group (P = 0.019). The neutrophil percentage was higher (P = 0.014) and the lymphocyte percentage was lower (P = 0.025) in critical compared with severe group. Bilateral lung involvement was the predominant pattern in both severe and critical patients, whereas the number of involved lobes in critical patients was more than that in severe patients (P = 0.024). Peripheral distribution was the predominant pattern in severe patients (40%), whereas more diffuse involvement of the lungs was observed in critical patients (83.30%). Ground‐glass opacities and consolidation were the main CT findings in both groups, and prevalence of consolidation was higher in critical relative to severe group (83.30%). CONCLUSION: Compared with severe patients, those with critical H1N1 pneumonia were more likely to present with dyspnea at rest and decreased lymphocyte percentage. Chest CT showed that diffuse bilateral involvement and higher prevalence of consolidation are associated with critical outcomes.