Inclusion Criteria:  Age > 18 years old COVID-19 related ARDS Hospitalized in ICU Invasive mechanical ventilation  Exclusion Criteria:  Immunocompromised for previous condition transplanted patients Known pulmonary bacterial co-infection at the time of admission to the ICU Contraindication to the realization of Bronchoscopy (Itracranial Hypertension, severe hypoxaemia with P/F < 80, severe hemodynamic instability, severe arrhythmia, non correctable coagulopathy)