Auto-Recommend (Based on Weight)
Rebreathing (Circle System)
Non-Rebreathing (Bain/T-Piece)
Recommended Settings
Calculated Oxygen Flow Rate:–
Circuit Recommendation:–
Estimated Tidal Volume:–
Reservoir Bag Size:–
Note: The calculated metabolic requirement is low, but a minimum flow rate of 0.5 L/min is applied to ensure vaporizer accuracy and prevent rebreathing.
DISCLAIMER: This tool is for educational purposes only. Always consult standard veterinary protocols and equipment specifications before administering anesthesia. Flow rates can vary based on specific vaporizer constraints.
function calculateOxygenFlow() {
var weightInput = document.getElementById('dogWeight').value;
var unit = document.getElementById('weightUnit').value;
var stage = document.getElementById('anestheticStage').value;
var circuitPref = document.getElementById('circuitType').value;
if (!weightInput || isNaN(weightInput) || weightInput <= 0) {
alert("Please enter a valid weight greater than 0.");
return;
}
// Convert to KG
var weightKg = parseFloat(weightInput);
if (unit === 'lbs') {
weightKg = weightKg * 0.453592;
}
// Logic Variables
var flowRateMl = 0;
var circuitUsed = "";
var minFlowRateL = 0.5; // Standard minimum 500ml/min for many vaporizers
// Determine Circuit
// General Rule: Dogs 10kg use Rebreathing.
var useRebreathing = false;
if (circuitPref === 'auto') {
if (weightKg >= 10) {
useRebreathing = true;
circuitUsed = "Rebreathing (Circle)";
} else {
useRebreathing = false;
circuitUsed = "Non-Rebreathing (Bain)";
}
} else if (circuitPref === 'rebreathing') {
useRebreathing = true;
circuitUsed = "Rebreathing (Circle)";
} else {
useRebreathing = false;
circuitUsed = "Non-Rebreathing (Bain)";
}
// Calculate Flow Rate
// Formula Source: Common Vet Anesthesia Guidelines
if (useRebreathing) {
// Rebreathing Logic
// Maintenance: 20-30 ml/kg/min
// Induction/Recovery: 50-100 ml/kg/min
if (stage === 'induction') {
flowRateMl = weightKg * 50; // Using conservative standard of 50ml/kg/min
} else {
flowRateMl = weightKg * 20; // Maintenance
}
} else {
// Non-Rebreathing Logic
// High flow required to flush CO2
// Formula: 200-300 ml/kg/min
flowRateMl = weightKg * 200;
}
// Convert to Liters
var flowRateL = flowRateMl / 1000;
// Apply Minimum Safety Floor
// Most vaporizers require 500ml – 1L minimum flow to function accurately
var appliedMin = false;
if (flowRateL < minFlowRateL) {
flowRateL = minFlowRateL;
appliedMin = true;
}
// Tidal Volume Calculation (approx 10-15 ml/kg)
var tidalVolMin = (weightKg * 10).toFixed(0);
var tidalVolMax = (weightKg * 15).toFixed(0);
// Reservoir Bag Calculation (6 x Tidal Volume approx)
// Or roughly 60ml/kg, rounded to nearest standard bag size (0.5L, 1L, 2L, 3L)
var bagReqMl = weightKg * 60;
var bagSizeL = "";
if (bagReqMl < 500) bagSizeL = "0.5 Liter";
else if (bagReqMl < 1000) bagSizeL = "1.0 Liter";
else if (bagReqMl < 2000) bagSizeL = "2.0 Liters";
else if (bagReqMl < 3000) bagSizeL = "3.0 Liters";
else bagSizeL = Math.ceil(bagReqMl/1000) + " Liters";
// Update UI
document.getElementById('resFlowRate').innerHTML = flowRateL.toFixed(2) + " L/min";
document.getElementById('resCircuit').innerHTML = circuitUsed;
document.getElementById('resTidal').innerHTML = tidalVolMin + " – " + tidalVolMax + " ml";
document.getElementById('resBag').innerHTML = bagSizeL;
var warningBox = document.getElementById('minFlowWarning');
if (appliedMin) {
warningBox.style.display = 'block';
document.getElementById('minFlowVal').innerHTML = minFlowRateL;
} else {
warningBox.style.display = 'none';
}
document.getElementById('resultsDisplay').style.display = 'block';
}
How to Calculate Oxygen Flow Rate for Dogs
Calculating the correct oxygen flow rate is a critical component of veterinary anesthesia safety. The flow rate determines how much oxygen (and inhalant anesthetic) is delivered to the patient and, in non-rebreathing systems, how effectively carbon dioxide is flushed from the circuit. The calculation depends heavily on the patient's weight, the type of breathing circuit used, and the stage of the anesthetic procedure.
1. Determine the Breathing System
Before calculating the flow rate, you must identify which circuit the dog will be placed on. This is usually determined by the dog's weight.
Non-Rebreathing System (Bain, T-Piece): Typically used for small patients weighing under 7kg to 10kg. These systems rely on high fresh gas flow to flush out exhaled CO2 because they lack soda lime canisters.
Rebreathing System (Circle System): Used for patients weighing over 7kg to 10kg. These systems recirculate exhaled gases through a CO2 absorbent (soda lime), allowing for lower, more economical flow rates.
2. Formulas for Calculation
Once the system is selected, use the following standard veterinary formulas to calculate the flow rate in milliliters per minute (ml/min), then convert to Liters per minute (L/min) for the flowmeter.
Note: Regardless of the calculation, a minimum flow rate of 500ml/min (0.5 L/min) to 1 L/min is usually recommended to ensure the vaporizer functions accurately.
Non-Rebreathing System Formula
Standard Rate: Weight (kg) × 200-300 ml/kg/min
Because non-rebreathing systems rely on gas flow to remove waste gas, the rates are significantly higher. Reducing the rate below the calculated requirement can lead to rebreathing of carbon dioxide.
3. Calculation Examples
Example 1: 25kg Labrador (Rebreathing)
A 25kg dog is undergoing surgery. Since the dog is >10kg, a Circle (Rebreathing) system is used.