# Fick Cardiac Output Calculator

Estimates the blood volume in mL per minute that the heart pumps in circulation from the left ventricle.

In the text below the form you can find the Fick equation and more information on the variables used.

The cardiac output calculator employs the Fick principle to estimate the amount of blood (in mL/min) that the heart muscle pumps in the systemic circulation from the left ventricle.

The formula used is based on the Fick principle which assumes that the rate of blood flow is correlated with oxygen consumption (in this case oxygen consumption is assumed based on approximated variable and body surface area):

Cardiac Output = O2 consumption / Arteriovenous O2 difference = (125 ml O2/min/m2 x BSA) / [13 x Hb x (SaO2 - SvO2)]

Weight & height unit system
Weight
Height
Hemoglobin
SaO2
SvO2
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Steps on how to print your input & results:

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.

## Variables and formula

Cardiac output is a hemodynamic measure of cardiac function which defines the volume of blood pumped by the left ventricle during one minute.

The variables used in the calculation are described in the following table:

 Cardiac output variable Description Hemoglobin Hemoglobin is a complex protein, found in the red blood cells, which carries oxygen through the bloodstream.Normal values are 13.8 - 17.2 g/dL for men and 12.1 - 15.1 g/dL for women. SaO2 Arterial blood-oxygen saturation, determined during pulse oximetry, is a measure of the amount of hemoglobin saturated with oxygen.Normal range is between 95 and 100%. SvO2 Venous blood-oxygen saturation with normal range between 60 and 80%. Weight Weight and height values are used to compute the body surface area which is used to estimate oxygen consumption as part of Fick equation. Height

The equation used in the above calculator is based on the Fick principle which assumes that the rate of blood flow is correlated with oxygen consumption.

Oxygen consumption cannot, however, be determined routinely, therefore a simplified estimation method, accounting for oxygen content in arteries and veins, has been devised.

The arterial and venous oxygen content (or saturation) is estimated though hemoglobin levels (obtained from blood test)

Therefore, the Fick based estimation becomes:

Cardiac Output = O2 consumption / Arteriovenous O2 difference = (125 ml O2/min/m2 x BSA) / [13 x Hb x (SaO2 - SvO2)]

Where BSA is calculated through Haycock’s formula:

Body Surface Area (BSA) = 0.024265 x (Height in cm)0.3964 x (Weight in kg)0.5378

## Cardiac output explained

CO is the heart rate multiplied by stroke volume, which results in a volume of blood in millilitres, pumped by the heart in one minute. Stroke volume is the amount of blood released in circulation by the hear with each contraction (beat).

The cardiac output of an individual with an average hear rate at rest of 70 beats per minute and a stroke volume of 70 mL, would be 4,900 mL/min.

Associating this with the estimate that each person has approximately 5 L of blood in the circulatory system, we can reach the conclusion that during a minute, at a resting pace, the heart can circulate almost the entire volume of blood in the body.

There is another calculation method for CO, method that is used in the Fick equation calculator:

CO = VO2 / (Ca - Cv)

Where:

■ VO2 is the oxygen consumption in ml/min of pure gaseous oxygen;

■ Ca is the oxygen concentration of oxygenated blood taken from the pulmonary vein;

■ Cv is the oxygen concentration of deoxygenated blood from an intravenous cannula.

The cardiac output depends on the regulation of both the heart rate and stroke volume.

Low CO is characteristic of heart failure and its severity can increase up to cardiogenic shock which is characterized by the following:

■ Systolic blood pressure of <90 mmHg (or a drop of >30 mmHg);

■ Urine output of <0.5 ml/kg/hour;

■ Heart rate >60 beats per minute;

■ With or without evidence of congestion.

Increases in CO can be observed during infections or inflammation, as the body’s fight reaction.

In some cases, combined cardiac output may be estimated, which is the sum of outputs from both right and left ventricle. This is used to evaluate fetal circulation because of its specific physiology.

## References

1. Wilkinson J. Haemodynamic calculations in the catheter laboratory. Heart. 2001; 85(1): 113–120.

2. LaFarge CG, Miettinen OS. The estimation of oxygen consumption. Cardiovasc Res. 1970; 4(1):23-30.

3. Fagard R, Conway J. Measurement of cardiac output: Fick principle using catheterization. Eur Heart J. 1990; 11 Suppl I:1-5.

4. Mahutte CK, Jaffe MB, Chen PA, Sasse SA, Wong DH, Sassoon CS. Oxygen Fick and modified carbon dioxide Fick cardiac outputs. Crit Care Med. 1994; 22(1):86-95.

Specialty: Cardiology

System: Cardiovascular

Objective: Determination

Type: Calculator

No. Of Variables: 5

Article By: Denise Nedea

Published On: June 5, 2017

Last Checked: June 5, 2017

Next Review: June 5, 2023