Denial of the patient or physician or assistant team to participate in the study. Evident signs of ventilatory fatigue (RF greater than 30irpm, PaCO2 greater than 45mmHg, with pH less than 7.35 and use of evident accessory musculature with indication of imminent intubation # Need more than 5 EPAP and 5 IPAP in NIV. Hemodynamic instability (need for Noradrenaline above 0.3mcg per kg per min). Respiratory failure (IRPA) with estimated intubation in the next 6 hours. Cervical, sternotomy or facial surgery less than 15 days ago. Impossibility of collecting arterial blood gases. Evidence or strong suspicion of a cause of IRPA other than COVID pneumonia. Disorientation. Pregnant women with a pregnant abdomen. Have participated in the study previously. Exclusive palliative care. Any clinical impossibility of prone position such as instability or fracture of the spine, pelvis or femur, Massive hemoptysis in need of surgical intervention, Anterior thoracic drain with air leak, Presence of pacemaker installed less than 2 days ago

Denial of the patient or physician or assistant team to participate in the study. Evident signs of ventilatory fatigue (RF greater than 30irpm, PaCO2 greater than 45mmHg, with pH less than 7.35 and use of evident accessory musculature with indication of imminent intubation # Need more than 5 EPAP and 5 IPAP in NIV. Hemodynamic instability (need for Noradrenaline above 0.3mcg per kg per min). Respiratory failure (IRPA) with estimated intubation in the next 6 hours. Cervical, sternotomy or facial surgery less than 15 days ago. Impossibility of collecting arterial blood gases. Evidence or strong suspicion of a cause of IRPA other than COVID pneumonia. Disorientation. Pregnant women with a pregnant abdomen. Have participated in the study previously. Exclusive palliative care. Any clinical impossibility of prone position such as instability or fracture of the spine, pelvis or femur, Massive hemoptysis in need of surgical intervention, Anterior thoracic drain with air leak, Presence of pacemaker installed less than 2 days ago