How do you set 30% FiO2 using nitrous oxide (N2O) and air on a Mindray ventilator?

Setting 30% FiO2 on a Mindray Ventilator Using Nitrous Oxide and Air

To achieve 30% FiO2 on a Mindray ventilator when using nitrous oxide (N2O) and air, you should add oxygen at 4 L/min close to the ventilator side of the circuit.

Understanding FiO2 Control on Mechanical Ventilators

When using a mechanical ventilator like Mindray, achieving a precise FiO2 of 30% requires careful adjustment of gas flows. Standard ventilators typically use air (21% oxygen) as the base gas, with supplemental oxygen added to reach the desired concentration.

Key Principles for Setting FiO2:

1. Oxygen Delivery Location:

   • Connect oxygen closest to the ventilator side of the circuit (near the exhaust port) for the highest and most consistent FiO2 1
   • This positioning provides better mixing and more reliable oxygen delivery

2. Flow Rate Requirements:

   • To achieve approximately 30% FiO2, use an oxygen flow rate of 4 L/min 1
   • Lower flow rates may not achieve 30% concentration
   • Higher flow rates will exceed 30% concentration

3. Pressure Considerations:

   • Higher inspiratory positive airway pressure (IPAP) settings will decrease the delivered FiO2 1
   • If using IPAP levels >12 cmH2O, you may need to increase oxygen flow above 4 L/min

Practical Steps for Setting 30% FiO2:

1. Connect the nitrous oxide source to the ventilator according to manufacturer specifications
2. Connect supplemental oxygen at the ventilator side of the circuit
3. Set oxygen flow to 4 L/min
4. Verify FiO2 with an oxygen analyzer placed near the patient connection
5. Adjust flow rate as needed to maintain 30% FiO2

Important Monitoring Considerations:

• Use continuous oxygen saturation monitoring to ensure adequate oxygenation 2
• Target SpO2 of 88-92% for patients with risk of hypercapnic respiratory failure or 94-96% for patients with normal respiratory drive 3
• Monitor for signs of inadequate oxygenation despite set FiO2

Common Pitfalls to Avoid:

• Incorrect oxygen connection point: Connecting oxygen further from the ventilator will result in lower and less predictable FiO2 1
• Inadequate flow rate: Using less than 4 L/min may not achieve 30% FiO2 1
• Failure to verify actual FiO2: Always verify the delivered concentration with an oxygen analyzer rather than relying solely on flow settings
• Overlooking circuit leaks: Significant leaks can alter the delivered FiO2

By following these guidelines, you can reliably achieve a 30% FiO2 when using nitrous oxide and air on a Mindray ventilator, ensuring appropriate oxygenation while avoiding the risks associated with higher oxygen concentrations.