Ca-vO2, C(a-v)O2 and a-vDO2 are used indistinctly.
This formula assumes that Hb carries 1.36 mL of O2.
Some formulas use the constant 0.003, MediCalculator™ uses 0.0031.

Ca-vO2 depends on SaO2, SvO2 and hemoglobin, 1 g of hemoglobin carries 1.36 mL of O2 (1.34mL - 1.39mL).
See also Ca-vO2 equation from 5 inputs.