The delivery rate of O₂ to the tissues (DO₂) can be calculated by multiplying the arterial O₂ content (C_aO₂ = 200 mL/L) and the cardiac output (CO = 5 L/min):

DO₂ = C_aO₂ x CO

       = 200 x 5

       = 1000 mL/min

The rate of O₂ consumption (VO₂) at rest is only 25% of this
(250 mL/min), leaving venous blood 75% saturated with a content of 150 mL/L (Fig 1).