Respiratory

Oxygen Consumption (VO₂) Calculator

Oxygen the body uses per minute, from cardiac output and the arterial-to-venous oxygen content difference.

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

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Formula

CO * (CaO2 - CvO2) * 10

Reference: Resting about 200–250 mL/min

How it is used

• Resting VO₂ is about 200–250 mL/min.
• VO₂ = CO × (CaO₂ − CvO₂) × 10, the Fick equation rearranged; CvO₂ needs a mixed venous sample from a pulmonary artery catheter.
• Fever, shivering, sepsis, agitation and the work of breathing raise demand; sedation, paralysis and cooling lower it.
• When delivery falls below a critical level, VO₂ becomes delivery-dependent and lactate rises.

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%.
• Shock Types at a GlanceEvery shock type ends in the same place: oxygen delivery (DO₂) falls below what the tissues consume (VO₂), or the cells cannot use what arrives. CaO₂ = (1.34 × Hb × SaO₂) + (0.003 × PaO₂), about 20 mL/dL. DO₂ = CO × CaO₂ × 10, about 1,000 mL/min (DO₂I 500–600 mL/min/m²). Resting VO₂ is about 250 mL/min, so the oxygen extraction ratio (O₂ER = VO₂ ÷ DO₂) is about 25% and SvO₂ sits near 70–75%.
• Hemodynamic NormalsCardiac output is heart rate times stroke volume, and stroke volume is set by preload, afterload and contractility. Output carries oxygen: DO₂ = CO × CaO₂ × 10, so a CO of 5 L/min with a CaO₂ of 20 mL/dL delivers 1,000 mL/min against a resting VO₂ of about 200–250 mL/min, an extraction near 25%. Every monitor on this page measures one of these pieces or a pressure that stands in for one.
• ECMO EssentialsVV ECMO drains blood from the IVC or SVC, saturates it and returns it to the right atrium, where it mixes with uncaptured venous return. Arterial saturation depends on the captured fraction (ECMO flow ÷ native cardiac output), recirculation, and what the lungs add. At Hb 10 g/dL and a drainage saturation of 65%, each liter of saturated return adds about 45–50 mL of oxygen, so a resting VO₂ of 250 mL/min needs 4–6 L/min; ELSO General v1.4 sizes full adult support near 60 mL/kg/min.

Related calculators

• A-a Gradient
• Alveolar Gas Equation (PAO₂)
• Arterial Oxygen Content (CaO₂)
• Dead Space Fraction (Bohr)
• Driving Pressure
• Dynamic Compliance
• Minute Ventilation
• O₂ Extraction Ratio

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.