Inclusion Criteria:  Hypoxemic respiratory failure in COVID-19 patients during intensive care unit hospitalization Age> 18 years Weaning by mechanical ventilation  Exclusion Criteria:  tracheostomy, unstable clinical conditions; agitation (Richmond Agitation-Sedation Scale (RASS)≥ + 2) or non-cooperation (Kelly Matthay scale ≥5); more than two organ failure consent refusal