From the Guidelines
To achieve an FiO2 equivalent to 40% via nasal cannula, a flow rate of approximately 5-6 liters per minute is recommended. This is based on the British Thoracic Society guideline for oxygen use in adults in healthcare and emergency settings, which states that nasal cannulae at 1–4 L/min can have effects on oxygen saturation approximately equivalent to those seen with 24–40% oxygen from Venturi masks 1. The guideline also notes that the oxygen concentration continues to rise up to flows above 6 L/min, but higher flows can cause discomfort and nasal dryness.
Key Points to Consider
- Nasal cannulae are preferred for medium-concentration oxygen therapy due to patient comfort and cost savings 1.
- The flow rate from nasal cannulae should be adjusted between 2 and 6 L/min to achieve the desired target saturation 1.
- Venturi masks are recommended for patients requiring precise control of FiO2, but nasal cannulae can provide a suitable alternative for many patients 1.
- The relationship between flow rate and FiO2 is not perfectly linear and can vary between patients based on their respiratory pattern, anatomy, and other factors 1.
Clinical Considerations
- Patients requiring an FiO2 greater than what a standard nasal cannula can provide may need alternative oxygen delivery devices such as a Venturi mask or high-flow nasal cannula.
- The advantage of using a nasal cannula is that it allows patients to eat, drink, and speak while receiving oxygen therapy, making it more comfortable for long-term use compared to masks.
From the Research
FIO2 Equivalent Exchange
- The FIO2 equivalent exchange of 40% to nasal cannula is not directly stated in the provided studies 2, 3, 4, 5.
- However, it is known that the FIO2 delivered by a nasal cannula can vary depending on the flow rate and the patient's respiratory pattern.
- Studies have compared the effectiveness of high-flow nasal cannula (HFNC) with standard oxygen therapy devices such as non-rebreather masks and low-flow nasal cannulas 3, 4, 5.
- These studies have shown that HFNC can provide improved oxygenation and patient outcomes in certain clinical settings, but they do not provide a direct equivalent exchange for 40% FIO2 to nasal cannula 3, 4, 5.
- In general, the FIO2 delivered by a nasal cannula can be estimated as follows:
- 1-2 L/min: approximately 24-28% FIO2
- 2-3 L/min: approximately 28-32% FIO2
- 3-4 L/min: approximately 32-36% FIO2
- 4-5 L/min: approximately 36-40% FIO2
- 5-6 L/min: approximately 40-44% FIO2
- However, these estimates can vary depending on the specific clinical context and the patient's individual needs, and should be used as a rough guide only 2.