Inclusion Criteria:  Age ≥18 years. Severe hypoxemic respiratory failure (partial pressure of arterial oxygen/ fraction of inspired oxygen < 250 mmHg). Confirmed SARS-Cov2 infection. Radiological images compatible with pneumonia covid.  Exclusion Criteria:  Hypoxemic respiratory failure secondary to a cause other than SARS-Cov2 pneumonia. Hypercapnic respiratory failure. Patient with criteria of orotracheal intubation at admission. Glasgow < 15 Haemodynamic instability that needs drugs treatment Patients with swallowing problems that conditioned an aspiration pneumonia risk.