Systemic Oxygen Utilization in Severe COVID-19 Respiratory Failure-A Case Series

Background: Management of hypoxemia in patients with severe COVID-19 respiratory failure is based on the guideline recommendations for specific SpO(2) targets. However, limited data exist on systemic O-2 utilization. The objective of this study was to examine systemic O-2 utilization in a case series of patients with this disease. Patients and methods: Between March 24, and April 9, 2020, 8 patients intubated for severe COVID-19 respiratory failure had near-simultaneous drawings of arterial blood gas (ABG), central venous blood gas (cVBG), and central venous oxygen saturation (ScvO(2)) at a mean of 6.1 days into hospitalization. Three patients were managed with indirect cardiac output (CO) monitoring by FloTrac sensor and Vigileo monitor (Edwards Lifesciences, Irvine, CA). The oxygen extraction index (OEI; SaO(2)-ScvO(2)/SaO(2)) and oxygen extraction fraction (OEF; CaO2-CvO(2)/CaO2 x 100) were calculated. Values for hyperoxia (ScvO(2) >= 90%), normoxia (ScvO(2) 71-89%), and hypoxia (ScvO(2) <= 70%) were based on the literature. Mean values were calculated. Results: The mean partial pressure of oxygen (PaO2) was 102 with a mean fraction of inspired O-2 (FiO2) of 44%. One patient was hyperoxic with a reduced OEI (17%). Five patients were normoxic, but 2 had a reduced OEF (mean 15.9%). Two patients were hypoxic but had increased systemic O-2 utilization based on OEF or OEI. Conclusions: In select patients with severe COVID-19 respiratory failure, O-2 delivery (DO2) was found to exceed O-2 utilization. SpO(2) targets based on systemic O-2 utilization may help in reducing oxygen toxicity, especially in the absence of anaerobic metabolism. Further data are needed on the prevalence of systemic O-2 utilization in COVID-19.