Inclusion Criteria:  age > 18 years; diagnosis of SARS-CoV-2 infection confirmed by means of RT-PCR on specimen from nasopharyngeal swab; bilateral interstitial pneumonia at CT scan; hypoxemic respiratory failure defined as PaO2/FiO2 < 200 at blood gas analyses.  Exclusion Criteria:  type 2 respiratory failure; hemodynamic instability requiring vasopressors and/or inotropes support; CT evidence of pneumothorax/pneumomediastinum; concomitant acute medical disease (stroke; myocardial infarction; septic shock; gastrointestinal bleeding; acute renal failure requiring dialysis)