Oxygen Content Calculator (CaO₂ & Oxygen Delivery DO₂)

How it works

CaO₂ (mL O₂/dL) = 1.34 × Hb (g/dL) × SaO₂ + 0.0031 × PaO₂ (mmHg) · DO₂ (mL/min) = CaO₂ × cardiac output (L/min) × 10 · CvO₂ ≈ 1.34 × Hb × SvO₂ · VO₂ = (CaO₂ − CvO₂) × CO × 10 · O₂ extraction = (CaO₂ − CvO₂) ÷ CaO₂ · 1 kPa = 7.5 mmHg, Hb g/L ÷ 10 = g/dL

Almost all the oxygen in arterial blood travels bound to hemoglobin: each gram of fully saturated hemoglobin carries about 1.34 mL of oxygen (Hüfner’s constant as used clinically). Only 0.0031 mL per dL dissolves for each mmHg of PaO₂, which is why anemia or low saturation reduces oxygen content far more than a low PaO₂ on its own. Multiplying content by cardiac output gives oxygen delivery (normally about 900–1,100 mL/min in an adult at rest); adding a mixed venous saturation gives venous content, oxygen consumption by the Fick principle and the extraction ratio (normally about 20–30%).

Worked example

Hemoglobin 140 g/L (14 g/dL), SaO₂ 98% and PaO₂ 12.7 kPa (95 mmHg): bound O₂ = 1.34 × 14 × 0.98 = 18.38 mL/dL and dissolved O₂ = 0.0031 × 95.3 = 0.30 mL/dL, so CaO₂ = 18.7 mL O₂/dL. With a cardiac output of 5 L/min, DO₂ = 18.7 × 5 × 10 = 934 mL O₂/min. With SvO₂ 70%, CvO₂ = 13.1 mL/dL, the extraction ratio is 30% and VO₂ = 277 mL O₂/min.

Sources: Dunn JO et al. Physiology of oxygen transport. BJA Education 2016;16:341–8 · StatPearls: Physiology, Oxygen Transport

Frequently asked questions