Cardiac Output by Fick Principle (CO)

Cardiac Output by Fick Principle (CO) | Online Free Tool | Elysia Tools

Tool usage guide

Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Category: Health
Input types: number
Output type: json
Sample coverage: 4
API ready: Yes

Overview

The Cardiac Output by Fick Principle calculator estimates cardiac output in L/min from hemoglobin, arterial and mixed venous oxygen measurements, and oxygen consumption. It uses the Fick equation and requires mixed venous samples obtained through a pulmonary artery catheter. This tool is not medical advice.

When to use

Estimate cardiac output when arterial and pulmonary-artery mixed venous oxygen data are available.
Review the arterial–venous oxygen difference alongside the calculated Fick cardiac output.
Use a measured VO₂ value when available, or use the default estimate of 250 mL/min for a resting adult.

How it works

1Enter hemoglobin, SaO₂, PaO₂, SvO₂, and PvO₂ values using the specified units and fractional saturation format.
2The calculator derives arterial oxygen content with CaO₂ = 1.34 × Hb × SaO₂ + 0.003 × PaO₂.
3It derives mixed venous oxygen content with CvO₂ = 1.34 × Hb × SvO₂ + 0.003 × PvO₂.
4It calculates cardiac output as CO = VO₂ ÷ (CaO₂ − CvO₂) ÷ 10 and rounds the result to the selected decimal places.

Use cases

A critical care clinician can estimate cardiac output from pulmonary artery catheter data and arterial blood gas measurements.
A cardiology trainee can check each component of the Fick calculation, including CaO₂, CvO₂, and the oxygen difference.
A hemodynamics review can compare a resting estimate with a calculation using directly measured oxygen consumption.

Examples

1. Normal resting cardiac output

Cardiology trainee

Background

A resting adult has hemoglobin of 15 g/dL, arterial saturation of 0.97, arterial PO₂ of 100 mmHg, mixed venous saturation of 0.75, and mixed venous PO₂ of 40 mmHg.

Problem

Calculate cardiac output and review the oxygen content difference.

How to use

Enter the five measurements and leave VO₂ at its default of 250 mL/min.

Hemoglobin: 15 g/dL; SaO₂: 0.97; PaO₂: 100 mmHg; SvO₂: 0.75; PvO₂: 40 mmHg; VO₂: 250 mL/min; decimal places: 2.

Outcome

CaO₂ is 19.80 mL O₂/dL, CvO₂ is 15.20 mL O₂/dL, and the arterial–venous difference is 4.60 mL O₂/dL. Calculated cardiac output is approximately 5.43 L/min.

2. Low-output cardiogenic shock example

Critical care clinician

Background

A patient has hemoglobin of 12 g/dL, arterial saturation of 0.92, arterial PO₂ of 60 mmHg, mixed venous saturation of 0.50, and mixed venous PO₂ of 30 mmHg.

Problem

Estimate cardiac output using the available oxygen measurements.

How to use

Enter the arterial and mixed venous values, then use VO₂ of 250 mL/min or replace it with a measured value if available.

FAQ

What inputs are required?

Hemoglobin, SaO₂, PaO₂, SvO₂, and PvO₂ are required. VO₂ is optional.

What does the default VO₂ value mean?

VO₂ defaults to 250 mL/min, an estimate for a 70 kg adult at rest.

Can I enter a measured VO₂?

Yes. Enter the measured whole-body oxygen consumption in mL/min to replace the default estimate.

What type of venous sample is needed?

SvO₂ and PvO₂ should come from mixed venous blood obtained through a pulmonary artery catheter, not a peripheral venous sample.

What does the result include?

The JSON result includes cardiac output, arterial and venous oxygen content, the arterial–venous oxygen difference, and the VO₂ source.

Hemoglobin: 12 g/dL; SaO₂: 0.92; PaO₂: 60 mmHg; SvO₂: 0.50; PvO₂: 30 mmHg; VO₂: 250 mL/min; decimal places: 2.

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Learn when to use this tool, what it supports, and how real users apply it.

Key facts

Overview

When to use

How it works

Use cases

Examples

1. Normal resting cardiac output

2. Low-output cardiogenic shock example

FAQ

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