Cardiac Output by the Fick Principle
Cardiac output and cardiac index by the Fick principle: VO₂ ÷ (arteriovenous O₂ content difference), with VO₂ either measured or estimated (LaFarge/Miettinen) from age, sex, and heart rate.
Open the calculator → Runs in your browser. Data leaves only if you deliberately send a problem report from the interactive tool.
Example
- VO₂ source
- Measured VO₂
- Measured VO₂
- 280 mL/min
- Hemoglobin
- 15 g/dL
- Arterial O₂ saturation SaO₂
- 98 %
- Mixed-venous O₂ saturation SvO₂
- 70 %
- Body surface area
- 1.9 m²
Result: Cardiac output 4.9 L/min; cardiac index 2.58 L/min/m².
The tool opens with these values already filled in. Replace them with your own.
What the result means
- Cardiac index
- Normal 2.5–4.0 L/min/m²; below is low output, above is high output.
What you enter
- VO₂ source
- Measured VO₂
- Age (for estimate)
- Sex (for estimate)
- Heart rate (for estimate)
- Hemoglobin
- Arterial O₂ saturation SaO₂
- Mixed-venous O₂ saturation SvO₂
- Body surface area
How this is calculated
- Formula
- CO (L/min) = VO₂ / [1.36·Hb·(SaO₂ − SvO₂)·10]; cardiac index = CO / BSA.
Fick A. Über die Messung des Blutquantums in den Herzventrikeln. Sitzungsber Phys Med Ges Würzburg. 1870. Estimated VO₂: LaFarge CG, Miettinen OS. The estimation of oxygen consumption. Cardiovasc Res. 1970;4(1):23-30. Read the source ↗
A reference and educational tool. Not medical, legal, or financial advice, and not a substitute for clinician judgment.