Fick Principle Cardiac Output Calculator

The Fick Principle Cardiac Output Calculator estimates Cardiac Output and Index based on oxygen consumption, hemoglobin, and oxygen saturation levels. This tool helps medical professionals and students assess heart pump efficiency and tissue perfusion. Whether you are diagnosing shock, monitoring ICU hemodynamics, or studying heart failure, this calculator provides accurate results. It simplifies complex hemodynamic formulas into actionable clinical data for faster decision-making.

Range: 100 - 1000 mL/min. Typical: 250.
Range: 5.0 - 20.0 g/dL. Typical: 15.0.
Range: 70 - 100 %. Typical: 98%.
Range: 10 - 99 %. Must be lower than SaO2. Typical: 75%.
Optional. Range: 0.5 - 3.0 m². Used for Cardiac Index.
Optional. Range: 30 - 220 bpm. Used for Stroke Volume.

How Cardiac Output Is Calculated

Cardiac Output represents the volume of blood the heart pumps each minute. The calculation uses the Fick Principle, which states that oxygen consumption equals blood flow multiplied by the difference in arterial and venous oxygen content.

CO = VO2 / ((Hb × 1.36 × (SaO2 - SvO2)) × 10)

Where:

  • VO2 = Oxygen consumption (mL/min)
  • Hb = Hemoglobin (g/dL)
  • 1.36 = Hüfner's constant (oxygen capacity of hemoglobin)
  • SaO2 - SvO2 = Arteriovenous oxygen difference

The process begins by determining how much oxygen is in the arterial blood versus the venous blood. The difference between these two values shows how much oxygen the body has extracted. By dividing the total oxygen consumed by this extracted amount, the calculator determines the blood flow needed to meet that demand. The Fick method is highly regarded in critical care for its direct correlation with metabolic rate.

What Your Cardiac Output Means

This number tells you if the heart is pumping enough blood to meet the body's metabolic demands. It varies based on body size, so Cardiac Index is often used for a more accurate comparison between patients.

Clinical Scenarios

  • Normal Cardiac Function: A Cardiac Index between 2.2 and 4.0 L/min/m² usually indicates adequate tissue perfusion and stable heart health in a resting adult.
  • Low Output States: An index below 2.2 L/min/m² suggests hypoperfusion, potentially signaling cardiogenic shock or severe heart failure requiring immediate intervention.
  • High Output States: An index above 4.0 L/min/m² may indicate sepsis, anemia, or hyperdynamic states where the heart works overtime to compensate.

*This tool is for educational and informational purposes only. It is not intended to replace professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider for clinical decisions.*

Pro Tip

Track trends over time rather than relying on a single reading to assess patient response to therapy.

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