Impact of liberal versus conservative saturation targets on gas exchange indices in COVID-19 related acute respiratory distress syndrome: a physiological study

OBJECTIVE: To compare gas exchange indices behavior by using liberal versus conservative oxygenation targets in patients with moderate to severe acute respiratory distress syndrome secondary to COVID-19 under invasive mechanical ventilation. We also assessed the influence of high FiO(2) on respiratory system mechanics. METHODS: We prospectively included consecutive patients aged over 18 years old with a diagnosis of COVID-19 and moderate-severe acute respiratory distress syndrome. For each patient, we randomly applied two FiO(2) protocols to achieve SpO(2) 88% - 92% or 96%. We assessed oxygenation indices and respiratory system mechanics. RESULTS: We enrolled 15 patients. All the oxygenation indices were significantly affected by the FiO(2) strategy (p < 0.05) selected. The PaO(2)/FiO(2) deteriorated, PA-aO(2) increased and Pa/AO(2) decreased significantly when using FiO(2) to achieve SpO(2) 96%. Conversely, the functional shunt fraction was reduced. Respiratory mechanics were not affected by the FiO(2) strategy. CONCLUSION: A strategy aimed at liberal oxygenation targets significantly deteriorated gas exchange indices, except for functional shunt, in COVID-19-related acute respiratory distress syndrome. The respiratory system mechanics were not altered by the FiO(2) strategy. Clinical Trials Register: NCT04486729.