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

ABSTRACT

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 FiO₂ 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 FiO₂ protocols to achieve SpO₂ 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 FiO₂ strategy (p < 0.05) selected. The PaO₂/FiO₂ deteriorated, PA-aO₂ increased and Pa/AO₂ decreased significantly when using FiO₂ to achieve SpO₂ 96%. Conversely, the functional shunt fraction was reduced. Respiratory mechanics were not affected by the FiO₂ 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 FiO₂ strategy.

Clinical Trials Register: NCT04486729.

Keywords:
COVID-19; Respiratory distress syndrome; Respiration; artificial; Oxygenation; Pulmonary gas exchange; Respiratory mechanics