Calculate Systemic Oxygen Consumption (VO2) using hemodynamic variables
The volume of blood pumped by the heart per minute (L/min). Normal resting is approx 5.0 L/min.
Oxygen content in arterial blood (mL O2/L). Normal is approx 200 mL/L (or 20 vol%).
Oxygen content in mixed venous blood (mL O2/L). Normal is approx 150 mL/L (or 15 vol%).
Rate of Oxygen Consumption (VO2)
0
Arteriovenous Oxygen Difference
0
Oxygen Extraction Ratio
0
function calculateOxygenConsumption() {
// Retrieve inputs by specific ID
var qInput = document.getElementById('cardiacOutput');
var caInput = document.getElementById('arterialO2');
var cvInput = document.getElementById('venousO2');
// Parse values
var Q = parseFloat(qInput.value);
var CaO2 = parseFloat(caInput.value);
var CvO2 = parseFloat(cvInput.value);
// Validation to prevent NaN errors
if (isNaN(Q) || isNaN(CaO2) || isNaN(CvO2)) {
alert("Please enter valid numerical values for all fields.");
return;
}
if (CvO2 >= CaO2) {
alert("Venous oxygen content cannot be higher than or equal to arterial oxygen content in a physiological system.");
return;
}
// Fick Equation: VO2 = Q * (CaO2 – CvO2)
// Units: Q is L/min, Contents are mL/L. Result is mL/min.
var avDifference = CaO2 – CvO2; // mL/L
var vo2 = Q * avDifference; // mL/min
// Calculate Extraction Ratio: (CaO2 – CvO2) / CaO2
var extractionRatio = (avDifference / CaO2) * 100;
// Display Results
var resultDiv = document.getElementById('resultsArea');
var displayVO2 = document.getElementById('resultVO2');
var displayDiff = document.getElementById('resultDiff');
var displayExtraction = document.getElementById('resultExtraction');
displayVO2.innerHTML = vo2.toFixed(1) + ' mL O2/min';
displayDiff.innerHTML = avDifference.toFixed(1) + ' mL/L';
displayExtraction.innerHTML = extractionRatio.toFixed(1) + ' %';
resultDiv.style.display = "block";
}
Understanding the Rate of Oxygen Consumption
The Rate of Oxygen Consumption (VO2) is a fundamental physiological metric that quantifies the volume of oxygen the body uses to convert energy from food into Adenosine Triphosphate (ATP), the fuel for cellular processes. Accurately calculating VO2 provides insight into a person's metabolic rate, cardiovascular health, and aerobic fitness.
The Fick Principle
The most precise physiological method for calculating oxygen consumption is known as the Fick Principle. This principle states that the rate of oxygen uptake by the body is equal to the product of blood flow (Cardiac Output) and the difference in oxygen concentration between the blood leaving the heart (arterial) and the blood returning to the heart (venous).
The formula used in this calculator is:
VO2 = Q × (CaO2 – CvO2)
Q (Cardiac Output): The amount of blood the heart pumps in one minute (L/min).
CaO2 (Arterial Oxygen Content): The amount of oxygen carried in arterial blood (mL/L).
CvO2 (Mixed Venous Oxygen Content): The amount of oxygen remaining in the blood after it has passed through the body's tissues (mL/L).
Typical Values for Healthy Adults
In a healthy adult at rest, typical hemodynamic values are often cited as:
Cardiac Output: Approximately 5.0 L/min.
Arterial Oxygen Content: Approximately 200 mL/L (20 vol%).
Venous Oxygen Content: Approximately 150 mL/L (15 vol%).
Using these numbers, the resting VO2 calculation would be: 5.0 L/min × (200 mL/L – 150 mL/L) = 250 mL/min.
Clinical Significance
Arteriovenous Oxygen Difference (a-vO2 diff): The calculator also outputs this value. It represents how much oxygen the tissues have extracted from the blood. A higher difference usually indicates that tissues are metabolically active and extracting more oxygen, or that cardiac output is insufficient to meet demand, forcing tissues to extract more oxygen per unit of blood.
Oxygen Extraction Ratio (O2ER): This represents the fraction of oxygen delivered to the capillaries that is actually consumed by the tissues. Normal resting extraction is approximately 25% to 30%. In states of shock or extreme exercise, this ratio can increase significantly.