Respiratory

Arterial Oxygen Content (CaO₂) Calculator

Oxygen carried in each dL of arterial blood from hemoglobin, saturation and dissolved O2; shows whether anemia or hypoxemia limits delivery.

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

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Formula

(1.34 * Hgb * (SaO2/100)) + (0.003 * PaO2)

Reference: Normal 17–20

How it is used

• Normal CaO₂ is 17 to 20 mL/dL.
• CaO₂ reflects the total amount of oxygen carried in the blood, combining both hemoglobin-bound oxygen and dissolved oxygen.

• Hemoglobin is the primary driver of oxygen content. If a patient is hypoxic and anemic, transfusing PRBCs will increase CaO₂ much more significantly than increasing the FiO₂.

Same formula as the app. Open it in the web app.

Related one-pagers

• ABG Interpretation in 6 StepsCaO₂ = (1.34 × Hb × SaO₂) + (0.003 × PaO₂): Hb 15, SaO₂ 0.98 and PaO₂ 100 give 19.7 + 0.3 = 20 mL/dL (sources use 1.34 to 1.39). DO₂ = cardiac output × CaO₂ × 10, about 1,000 mL/min, against a VO₂ of about 250, so extraction is about 25% and SvO₂ 65–75%. With Hb 8, SaO₂ 0.90 and PaO₂ 60, CaO₂ is 9.8. Raising PaO₂ to 100 (SaO₂ 0.98) gives 10.8, a 10% gain; raising Hb to 10 gives 12.2, a 25% gain; a 20% rise in cardiac output raises DO₂ by 20%.
• Hemodynamic NormalsCaO2 = 1.34 × Hb × SaO2 (decimal) + 0.003 × PaO2 (17–20 mL/dL)
• Shock Types at a GlanceDO₂ = CO × CaO₂ × 10; hemoglobin and CO are the biggest levers, dissolved oxygen the smallest.
• Blood Products and TransfusionRed cells restore oxygen delivery: DO₂ = cardiac output × CaO₂ × 10, with CaO₂ = (1.34 × Hgb × SaO₂) + (0.003 × PaO₂). At Hgb 15 g/dL, SaO₂ 98% and cardiac output 5 L/min, DO₂ is about 1,000 mL/min against a resting VO₂ of 250 mL/min, an extraction of 25%. Anemia is tolerated by raising cardiac output and extraction: resting volunteers hemodiluted to Hgb 5 g/dL had no rise in lactate (Weiskopf, JAMA 1998). The heart already extracts 70–75% at rest and can meet more demand only with more coronary flow, which a stenosis limits, so thresholds are higher in coronary disease.

Related calculators

• A-a Gradient
• Alveolar Gas Equation (PAO₂)
• Dead Space Fraction (Bohr)
• Driving Pressure
• Dynamic Compliance
• Minute Ventilation
• O₂ Extraction Ratio
• Oxygen Consumption (VO₂)

For education and exam preparation only. Follow your institution’s protocols. For education and exam preparation only. Verify results independently and follow your institution’s protocols. Not a substitute for clinical judgment.