TNF and acute respiratory distress syndrome: Many biomarkers for the diagnosis of ARDS have been found, such as the receptor for advanced glycation end-products (RAGE), angiopoietin-2 (Ang-2), surfactant protein D (SP-D) and inflammatory factors [interleukin (IL)-6, IL-8, and tumour necrosis factor-α (TNF-α)] [11, 12].