Prone position and APRV for severe hypoxemia in COVID-19 patients: The role of perfusion

There have been confusion and contradiction on how to best manage patients with acute respiratory failure secondary to Corona virus disease-2019 (COVID-19). Recent report suggested two different phenotypes of patho-physiology (type L and type H). Type L is characterized by low elastance and low ventilation-perfusion mismatch ratio (V/Q), while type H is more consistent with the classic acute respiratory distress syndrome (ARDS) characterized by high elastance, and increased right to left shunt. The role of perfusion deficits has been clearer with the discovery of micro and macro vascular thrombi in the lung vascular endothelium. Prone position has gained interest in research and guidelines as a maneuver capable of improving ventilation and perfusion. Airway pressure release ventilation (APRV) can theoretically improve hypoxemia due to ventilation/perfusion mismatch in patients with COVID-19 compared to other conventional strategies. From this perspective, we may have to consider perfusion as the major problem in the disease process more than just ventilation. More studies are required to explore the role of perfusion and the different ventilatory strategies to best manage those patients. Key Words: airway pressure release ventilation; APRV; prone position; COVID-19; SARS-CoV-2.