1.Serious basic diseases affecting survival, including: uncontrolled malignant tumor with multiple metastases that cannot be removed, hematological diseases, cachexia, active hemorrhage, severe malnutrition, AIDS, etc., 2.Obstructive pneumonia, severe pulmonary interstitial fibrosis, alveolar proteinosis and allergic alveolitis caused by lung tumor, 3.Use in vitro life support (ECMO, ECCO2R), 4.Patients with bronchial asthma, peptic ulcer, and patients allergic to acetylcysteine, 5.Any potential violation of test compliance or any other circumstance affecting safety and effectiveness evaluation that may exist, which the researchers believe is not suitable for patients participating in the study.

1.Serious basic diseases affecting survival, including: uncontrolled malignant tumor with multiple metastases that cannot be removed, hematological diseases, cachexia, active hemorrhage, severe malnutrition, AIDS, etc., 2.Obstructive pneumonia, severe pulmonary interstitial fibrosis, alveolar proteinosis and allergic alveolitis caused by lung tumor, 3.Use in vitro life support (ECMO, ECCO2R), 4.Patients with bronchial asthma, peptic ulcer, and patients allergic to acetylcysteine, 5.Any potential violation of test compliance or any other circumstance affecting safety and effectiveness evaluation that may exist, which the researchers believe is not suitable for patients participating in the study.