Inclusion Criteria:  Within 24 hours after admission, sepsis 3.0 diagnostic criteria were met; The patients or their family members fully understand the purpose and significance of the trial, voluntarily participate in the clinical trial, and sign the informed consent.  Exclusion Criteria:  Patients with ARDS were identified at the time of admission; Patients who explicitly refused mechanical ventilation; Patients with 3 or more extrapulmonary organ injuries and organ failure(single organ SOFA score ≥ 3); Patients who need home oxygen therapy or with home mechanical ventilation (by tracheotomy or noninvasive ventilation, but excluding CPAP / BiPAP, only for patients with obstructive sleep apnea); The patient whose expected survival time was less than 48 hours; Pregnant women and lactating women; Other conditions judged by the researcher not suitable for inclusion.