FiO2 Delivered by 5L Nasal Cannula
A 5L nasal cannula delivers approximately 40% FiO2 (0.40), though this can vary significantly between patients based on their breathing pattern and other physiological factors. 1
Oxygen Delivery via Nasal Cannula: Key Principles
FiO2 Ranges for Different Flow Rates
- 1-4 L/min delivers approximately 24-40% FiO2, equivalent to Venturi masks at these concentrations 1
- 5 L/min delivers approximately 40% FiO2 1
- 1-6 L/min provides an FiO2 range from approximately 24% to 50%, making nasal cannulae suitable for variable oxygen therapy 1
Factors Affecting Delivered FiO2
- Respiratory rate: Higher respiratory rates decrease the delivered FiO2 (approximately 0.012 decrease at 20 breaths/min compared to 15 breaths/min) 2
- Mouth position: Open-mouth breathing can actually increase FiO2 compared to closed-mouth breathing, particularly during rapid breathing 3
- Tidal volume: Larger tidal volumes can dilute the oxygen concentration, especially at lower flow rates 4
- Individual variation: There is significant variation between patients, with standard deviations of ±0.04-0.15 in delivered FiO2 3
Clinical Applications and Considerations
Advantages of Nasal Cannulae
- Better patient comfort compared to masks 1
- Can be worn during meals and speech 1
- Less likely to be removed by patients 1
- Less inspiratory resistance than face masks 1
- No risk of carbon dioxide rebreathing 1
- More cost-effective than other oxygen delivery systems 1
Limitations and Cautions
- The actual FiO2 cannot be precisely predicted, making it unsuitable when exact FiO2 calculation is required (e.g., for A-a gradient determination) 1
- May cause nasal irritation or soreness, especially at higher flow rates 1
- May not be effective if the patient has severe nasal congestion 1
- Flow rates above 4 L/min can cause discomfort and nasal dryness in some patients, though many tolerate it well 1
Clinical Decision Making
- For patients requiring medium-concentration oxygen therapy, nasal cannulae are preferred over simple face masks 1
- For patients requiring precise FiO2 control (particularly those at risk of hypercapnic respiratory failure), Venturi masks may be more appropriate 1
- For many patients, 24-28% Venturi masks can be substituted with nasal cannulae at 1-2 L/min to achieve the same target range 1
- Adjust flow rates based on oximetry measurements and, when necessary, blood gas results 1
High-Flow Nasal Cannula Therapy
- High-flow nasal cannula (HFNC) systems can deliver flows of 60 L/min or more with more predictable FiO2 1
- At 60 L/min flow, the measured FiO2 closely matches the set FiO2 at 0.3 and 0.5 settings 4
- HFNC provides additional benefits including CPAP effect and improved patient comfort 1
- HFNC may reduce intubation rates in patients with acute hypoxemic respiratory failure 1
Remember that while 5L nasal cannula typically delivers approximately 40% FiO2, individual patient factors significantly influence the actual oxygen concentration received, requiring monitoring and adjustment based on clinical response.