Inclusion Criteria:  > 18 years positive PCR for Sars-Cov-2 Rna on any respiratory samples within 7 days from enrollment imaging positive for pulmonary involvement or clinical evidence of respiratory involvement ( new onest of hypoxemia with 02 <80mmHg or SpO2 < 94% in air or need for oxygen therapy in oreder to mantaine SpO2 > 93%. need of hospitalization  Exclusion Criteria:  start of prone-positioning cycles before being enrolled in the study SpO2/FiO2 <200 need of high-flow oxygen therapy (HFNC) or need of non-invasive ventilation and/or CPAP or indications for intubation and mechanical ventilation relative or absolute contraindications for prone positioning (eg facial fractures, advanced pregnancy, mental status alterations, spinal instability...)