The volume of air inhaled per breath (Milliliters). Average resting is 500 mL.
Number of breaths per minute. Average resting is 12-20 bpm.
Air remaining in airways not reaching alveoli (mL). Typically 150 mL for adults.
Minute Ventilation ($V_E$)
0 L/min
Total air volume moved per minute
Alveolar Ventilation ($V_A$)
0 L/min
Actual gas exchange volume per minute
function calculateVentilation() {
// 1. Get input values
var tidalVolInput = document.getElementById('tidalVolume').value;
var respRateInput = document.getElementById('respRate').value;
var deadSpaceInput = document.getElementById('deadSpace').value;
// 2. Validation
if (tidalVolInput === "" || respRateInput === "") {
alert("Please enter both Tidal Volume and Respiratory Rate.");
return;
}
// 3. Parse numbers
var vt = parseFloat(tidalVolInput); // mL
var rr = parseFloat(respRateInput); // breaths per min
var vd = parseFloat(deadSpaceInput); // mL
// Fallback for deadspace if empty or invalid, though value="150″ is set in HTML
if (isNaN(vd)) {
vd = 150;
}
// 4. Calculate Minute Ventilation (Ve)
// Formula: Ve = (Vt * RR) / 1000 to convert mL to Liters
var minuteVentilationML = vt * rr;
var minuteVentilationL = minuteVentilationML / 1000;
// 5. Calculate Alveolar Ventilation (Va)
// Formula: Va = ((Vt – Vd) * RR) / 1000
// Ensure Vt is greater than Vd to avoid negative numbers
var alveolarVentilationL = 0;
if (vt > vd) {
var alveolarVentilationML = (vt – vd) * rr;
alveolarVentilationL = alveolarVentilationML / 1000;
} else {
alveolarVentilationL = 0; // If dead space exceeds tidal volume, no effective ventilation occurs
}
// 6. Display Results
var resultSection = document.getElementById('resultsSection');
var resVe = document.getElementById('resMinuteVent');
var resVa = document.getElementById('resAlveolarVent');
resVe.innerHTML = minuteVentilationL.toFixed(2) + " L/min";
resVa.innerHTML = alveolarVentilationL.toFixed(2) + " L/min";
// Show the result container
resultSection.style.display = "block";
}
How to Calculate Ventilation Rate of a Person
Understanding respiratory ventilation rate (often called minute ventilation) is crucial for fields ranging from medical diagnostics to sports science. It measures the total volume of air entering the lungs each minute. Whether you are a student, a respiratory therapist, or an athlete tracking performance, knowing how to calculate this metric provides insight into respiratory efficiency.
The Formula: Minute Ventilation ($V_E$)
The primary calculation for the ventilation rate of a person is relatively simple. It involves two main variables: Tidal Volume and Respiratory Rate.
Formula: $V_E = V_T \times f$
$V_E$ (Minute Ventilation): The total volume of air exhaled per minute (usually in Liters/minute).
$V_T$ (Tidal Volume): The amount of air inhaled or exhaled during a single breath (usually in Milliliters).
$f$ or $RR$ (Respiratory Frequency/Rate): The number of breaths taken per minute.
Step-by-Step Calculation Example
Let's calculate the ventilation rate for a healthy adult at rest.
Determine Tidal Volume: The average adult inhales approximately 500 mL of air per breath at rest.
Determine Respiratory Rate: Count the number of breaths in one minute. A typical resting rate is 12 breaths per minute.
Apply the Math: Multiply 500 mL by 12.
500 mL × 12 = 6000 mL/minute.
Convert to Liters: Since ventilation is usually expressed in Liters, divide by 1000.
6000 / 1000 = 6.0 L/min.
Minute Ventilation vs. Alveolar Ventilation
While Minute Ventilation measures the total air moved, it does not account for the air that stays in the trachea and bronchi where no gas exchange occurs. This "unused" area is called Anatomical Dead Space ($V_D$).
To calculate the air that actually reaches the alveoli for gas exchange, we use the Alveolar Ventilation ($V_A$) formula:
Formula: $V_A = (V_T – V_D) \times f$
Using the previous example, if the anatomical dead space is 150 mL:
$V_T – V_D = 500 \text{ mL} – 150 \text{ mL} = 350 \text{ mL}$ (effective air per breath).
Clinical Assessment: In medical settings, a significant change in ventilation rate can indicate respiratory distress, acidosis, or other metabolic issues. Doctors use these calculations to adjust mechanical ventilators.
Athletic Performance: During intense exercise, Tidal Volume can increase to 2-3 Liters, and respiratory rate can exceed 40-50 breaths per minute. An elite athlete might achieve a Minute Ventilation of over 150 L/min! Monitoring these rates helps in determining aerobic capacity ($VO_2$ max) and ventilatory thresholds.