The purpose of this study is to monitor short-term changes in tissue oxygen saturation and local blood flow as results of changing from supine to prone position in ARDS COVID-19 patients

After obtaining consent to participate in the study, the subjects included in the study will undergo a baseline 15-minute measurement of tissue oxygen saturation (StO2) measured non-invasively on the forearm by means of near-infrared spectroscopy (NIRS). Once a baseline stable StO2 value is obtained, a provocative test, consisting of a transient vascular occlusion, will be performed. The test will allow the obtention of a local metabolic rate, and a StO2 recovery rate after the ischemic stimulus.

Tissue oxygenation measurements will be performed in supine position, immediately before changing to prone positioning, and repeated after 20 minutes of stabilization, once in prone position.

Inclusion Criteria:

• COVID-19 patients admitted in the ICU receiving invasive mechanical ventilation and requiring prone positioning for severe hypoxemia management, as decided by the medical team

Exclusion Criteria:

• Severe peripheral vasculopathy
• Raynaud's syndrome
• Skin lesions/trauma in upper limbs interfering the placement of the NIRS probe and/or the occlusion tourniquet
• Deep venous thrombosis in the upper limbs

COVID-19 patients with severe hypoxemia, under mechanical ventilation, and requiring prone positioning as a rescue therapy for hypoxemia management