What are the different methods of respiratory oxygen delivery, including Nasal Cannula (NC), masks, BiPAP (Bilevel Positive Airway Pressure), and intubation?

Respiratory Oxygen Delivery Methods: From Low-Flow to Invasive Ventilation

The most appropriate respiratory oxygen delivery method should be selected based on the patient's clinical condition, oxygen requirements, and risk of respiratory failure, progressing from nasal cannula to masks, non-invasive ventilation, and finally intubation as respiratory status deteriorates.

Low-Flow Oxygen Delivery Systems

Nasal Cannula

• Delivers oxygen flow rates of 1-6 L/min, providing approximately 24-50% FiO2 1, 2
• Advantages include:
  • Greater patient comfort compared to masks 1
  • Can be worn during meals and speech 1
  • Less likely to be removed by patients 1
  • Lower inspiratory resistance than face masks 1
  • No risk of carbon dioxide rebreathing 1
  • More cost-effective than other oxygen delivery systems 1
• Disadvantages include:
  • May cause nasal irritation or soreness, especially at higher flow rates 1
  • May not be effective with severe nasal congestion 1
  • Actual FiO2 cannot be precisely predicted 1, 2
  • Flow rates above 4 L/min can cause discomfort in some patients 1
• Clinical applications:
  • Preferred for medium-concentration oxygen therapy over simple face masks 1, 3
  • Can substitute for 24-28% Venturi masks at 1-2 L/min flow rates 1
  • Flow rates should be adjusted based on oximetry measurements and blood gas results 1

High-Flow Nasal Cannula (HFNC)

• Delivers warmed, humidified oxygen at flow rates of 30-70 L/min 1, 4
• Provides more predictable FiO2 and modest positive airway pressure (CPAP effect) 1, 4
• Clinical applications:
  • Acute hypoxemic respiratory failure (preferred over non-invasive ventilation) 1
  • Post-extubation respiratory support 1, 5
  • During intubation procedures to maintain oxygenation 1, 6
  • Preoxygenation before intubation in critically ill patients 1
• Contraindications include severe facial trauma and suspected skull base fractures 1

Mask Oxygen Delivery Systems

Simple Face Mask

• Delivers 40-60% FiO2 at flow rates of 5-10 L/min 3
• Should never be used at flow rates below 5 L/min due to risk of CO2 rebreathing 1, 3
• Suitable for patients with type 1 respiratory failure without risk of CO2 retention 3
• Less preferred than nasal cannula for medium-concentration oxygen therapy due to patient comfort issues 1, 3

Venturi Mask

• Provides precise control of oxygen concentration (24%, 28%, 31%, 35%, 40%, and 60%) 3
• Recommended for patients requiring accurate FiO2 delivery, particularly those at risk of hypercapnic respiratory failure 1, 3
• Particularly useful for COPD patients requiring controlled oxygen therapy 1, 3

High-Concentration Reservoir Mask (Non-rebreather)

• Delivers 60-90% FiO2 at a flow rate of 15 L/min 3
• Preferred for critically ill patients requiring high-concentration oxygen until reliable pulse oximetry monitoring is established 1, 3
• Most suitable for trauma and emergency situations in patients without risk of CO2 retention 3

Non-Invasive Positive Pressure Ventilation

Continuous Positive Airway Pressure (CPAP)

• Delivers constant positive pressure throughout the respiratory cycle 1
• Applications:
  • Preoxygenation before intubation (5-10 cm H2O) 1
  • Between intubation attempts to prevent hypoxemia 1
  • For patients with impaired oxygenation 1

Bilevel Positive Airway Pressure (BiPAP)

• Provides two levels of positive pressure: higher during inspiration (IPAP) and lower during expiration (EPAP) 5
• More effective than HFNC in preventing reintubation in high-risk patients 5
• Applications:
  • Post-extubation support in high-risk patients 5
  • Acute hypercapnic respiratory failure 1

Invasive Ventilation

Endotracheal Intubation

• Indicated when non-invasive methods fail to maintain adequate oxygenation or ventilation 1
• Provides definitive airway protection and control 1
• Requires rapid sequence induction with preoxygenation, positioning, intravenous induction, and neuromuscular blockade 1
• Confirmation of successful placement requires waveform capnography 1
• Patients receiving NIV, CPAP, or HFNC should be intubated promptly when these modalities are failing to prevent profound hypoxemia 1

Clinical Decision-Making Algorithm

1. Initial oxygen therapy for mild hypoxemia:

   • Start with nasal cannula at 1-4 L/min (24-40% FiO2) 1, 2
   • If precise FiO2 control needed (e.g., COPD patients): Use Venturi mask (24-28%) 1, 3

2. Escalation for moderate hypoxemia:

   • Increase nasal cannula to 5-6 L/min (up to 50% FiO2) 1, 2
   • Or switch to simple face mask (5-10 L/min) for 40-60% FiO2 3
   • Consider HFNC if available and patient has increasing oxygen requirements 1, 4

3. Severe hypoxemia:

   • High-concentration reservoir mask at 15 L/min (60-90% FiO2) 1, 3
   • Or HFNC at 30-70 L/min 1
   • Consider CPAP/BiPAP if patient showing signs of respiratory distress despite high FiO2 1, 5

4. Respiratory failure despite non-invasive support:

   • Prepare for endotracheal intubation 1
   • Use HFNC or nasal cannula at 15 L/min during intubation attempts to prevent desaturation 1, 6
   • Consider facemask ventilation with CPAP between intubation attempts 1

Important Considerations and Pitfalls

• Mouth breathing may actually increase oxygen delivery with nasal cannula, which is important in patients with acute breathlessness 1, 7
• Supplemental nasal cannula oxygen during preoxygenation with masks can improve oxygenation, especially when mask leaks are present 8
• The actual FiO2 delivered by nasal cannula varies widely between patients, so titration based on oximetry and blood gases is essential 1, 7
• For patients requiring precise oxygen control (e.g., COPD patients), Venturi masks provide more reliable FiO2 than simple masks or nasal cannula 3
• HFNC should be considered early in patients with acute hypoxemic respiratory failure to potentially avoid intubation 1, 4