CaO2 calculation with Hb 12 g/dL, SaO2 95%, PaO2 60 mmHg. What is CaO2?

• A. 14.2 mL/dL
• B. 15.0 mL/dL
• C. 15.5 mL/dL
• D. 16.0 mL/dL

Answer: (C)

Oxygen content in arterial blood (CaO2) comes from two sources: the oxygen bound to hemoglobin and the small amount dissolved in plasma. Use CaO2 = (Hb × 1.34 × SaO2) + (PaO2 × 0.003).

With Hb 12 g/dL and SaO2 95% (0.95), the bound portion is 12 × 1.34 × 0.95 ≈ 15.28 mL/dL. The dissolved portion is 60 × 0.003 = 0.18 mL/dL. Total CaO2 ≈ 15.46 mL/dL, which rounds to 15.5 mL/dL.