Pathophysiology of SvO2 and ScvO2: SvO2 level Clinical Correlate SvO2 > 75% Normal extraction O2 supply > O2 demand 75% > SvO2 > 50% Compensatory extraction Increasing O2 demand or decreasing O2 supply 50% > SvO2 > 30% Exhaustion of extraction Beginning of lactic acidosis O2 supply < O2 demand 30% < SvO2 < 25% Serve lactic acidosis SvO2 < 30% Cellular death 1.2.2.