Should oxygen be administered via mask or nasal cannula (NC)?

Oxygen Delivery Method Selection: Nasal Cannula vs. Mask

For most patients requiring oxygen therapy, nasal cannulae should be used rather than face masks as the initial delivery method due to better patient comfort, tolerance during meals, and equivalent clinical efficacy. 1

Initial Oxygen Therapy Decision Algorithm

For patients with severe hypoxemia (SpO2 < 85%):

• Start with a reservoir mask at 15 L/min initially 1
• Once stabilized, adjust downward to nasal cannulae (1-6 L/min) or simple face mask (5-10 L/min) to maintain target saturation of 94-98% 1

For patients with mild to moderate hypoxemia without critical illness:

• Begin with nasal cannulae with flow rate adjusted to achieve target saturation of 94-98% 1
• If nasal cannulae are not tolerated or ineffective, switch to a simple face mask 1

For patients at risk of hypercapnic respiratory failure:

• Use a 24% or 28% Venturi mask or nasal cannulae at low flow rates (1-2 L/min) 1
• Target lower oxygen saturation (88-92%) for this specific patient group 1

Advantages of Nasal Cannulae

• Greater patient comfort compared to face masks 1
• Can be worn during meals and speech 2
• Less likely to be removed by patients 1
• Adjustable flow (1-6 L/min) provides wide oxygen concentration range (approximately 24-50% FiO2) 1
• Lower inspiratory resistance than face masks 2
• No risk of carbon dioxide rebreathing 2

Advantages of Face Masks

Simple Face Mask:

• Delivers 40-60% oxygen at flow rates of 5-10 L/min 3
• Should never be used below 5 L/min due to risk of carbon dioxide rebreathing 3

Venturi Mask:

• Provides precise control of oxygen concentration (24%, 28%, 31%, 35%, 40%, 60%) 3
• Recommended for patients requiring accurate FiO2 delivery, particularly those at risk of hypercapnic respiratory failure 3
• Less likelihood of dilution by room air if patient's inspiratory flow exceeds mask flow rate 1

High-Concentration Reservoir Mask:

• Delivers 60-90% oxygen at 15 L/min 3
• Most suitable for trauma and emergency situations 3
• Must always be used with flow rates of 15 L/min to avoid carbon dioxide rebreathing 4, 5

Important Clinical Considerations

• If medium-concentration therapy with nasal cannulae or simple face mask fails to achieve desired saturation, change to a reservoir mask and seek senior or specialist advice 1
• For patients with COPD with respiratory rate >30 breaths/min, increase flow rate above the minimum specified for Venturi masks 1
• High-flow nasal cannulae (HFNC) are well tolerated and may be used as an alternative for patients requiring medium to high-concentration oxygen who are not at risk of hypercapnia 1
• Compared to non-rebreather masks, HFNC has shown better oxygenation, higher success rates, and greater patient satisfaction in some studies 6

Common Pitfalls to Avoid

• Using simple face masks or non-rebreather masks with inadequate flow rates (below 5 L/min for simple masks, below 15 L/min for non-rebreather masks) can cause carbon dioxide rebreathing 5
• Failure to monitor patients receiving oxygen therapy with pulse oximetry and, when necessary, arterial blood gas measurements 3
• Not recognizing that higher flow rates generally produce greater aerosol generation, which may be relevant in infectious disease settings 7
• Overlooking the importance of proper mask fit - effectiveness is greatly reduced if masks are not properly positioned 3

Flow Rate Adjustments

• Nasal cannulae: 1-6 L/min (adjust to achieve target saturation) 1
• Simple face mask: 5-10 L/min (never below 5 L/min) 1
• Venturi mask: Flow rate specified for each concentration setting (higher flow needed if respiratory rate >30) 1
• Reservoir mask: 15 L/min 1