How to adjust high flow nasal cannula (HFNC) settings?

Adjusting High Flow Nasal Cannula Settings

High flow nasal cannula (HFNC) settings should be adjusted based on flow rate (35-60 L/min), temperature (34-37°C), and FiO2 titration to achieve target oxygen saturation, with flow rate titrated to patient comfort and respiratory effort.

Initial Settings and Titration

Flow Rate

• Start with flow rates between 35-60 L/min for adults, titrated to patient comfort and respiratory effort 1
• Higher flow rates (50-60 L/min) may provide greater physiological benefits including PEEP effect and dead space washout 1
• Adjust flow to patient tolerance - some patients may experience discomfort at higher flows 1

Temperature

• Set temperature between 34-37°C according to patient preference 1
• Higher temperatures (37°C) provide optimal humidification but some patients find lower temperatures (34°C) more comfortable 1

FiO2 Adjustment

• Titrate FiO2 to achieve target oxygen saturation 1
• For patients without risk of hypercapnia: target SpO2 of 94-98% 1
• For patients at risk of hypercapnic respiratory failure (e.g., COPD): target SpO2 of 88-92% 1
• FiO2 can be precisely controlled with air/oxygen blending 1

Monitoring and Assessment

Parameters to Monitor

• Respiratory rate - should decrease with effective HFNC therapy 1
• Work of breathing - assess for accessory muscle use and patient comfort 1
• Oxygen saturation - continuous monitoring with pulse oximetry 1
• Arterial blood gases - when necessary to assess response to therapy 1

Signs of HFNC Success

• Decreased respiratory rate 1
• Improved oxygenation 1
• Reduced work of breathing 1
• Patient comfort and tolerance 1

Signs of HFNC Failure

• Persistent tachypnea despite optimal settings 1
• Worsening hypoxemia 1
• Increased work of breathing 1
• Deteriorating mental status 1

Special Considerations

Hypoxemic Respiratory Failure

• Higher initial flow rates (50-60 L/min) may be more beneficial 1
• FiO2 should be titrated to maintain SpO2 targets 1
• Consider early escalation to NIV or intubation if no improvement within 1-2 hours 1

Post-Extubation Support

• Flow rates of 35-50 L/min are typically sufficient 1
• FiO2 should be titrated to maintain SpO2 targets 1
• Consider for patients at low or moderate risk of extubation failure 1

Hypercapnic Respiratory Failure

• Consider a trial of NIV first before transitioning to HFNC 1
• HFNC may be used during breaks from NIV 1
• Target SpO2 of 88-92% to avoid worsening hypercapnia 1

Practical Adjustments Algorithm

1. Initial Setup:

   • Start with flow rate 40-50 L/min 1
   • Set temperature to 37°C (adjust to 34°C if patient discomfort) 1
   • Set initial FiO2 to achieve target SpO2 1

2. Flow Rate Adjustment:

   • If increased work of breathing: increase flow by 5-10 L/min 1
   • If patient discomfort: decrease flow by 5-10 L/min 1
   • Maximum flow typically 60 L/min 1

3. FiO2 Adjustment:

   • Titrate in 5-10% increments to maintain target SpO2 1
   • For non-hypercapnic patients: maintain SpO2 94-98% 1
   • For hypercapnic risk patients: maintain SpO2 88-92% 1

4. Reassessment:

   • Evaluate response after 30-60 minutes 1
   • If no improvement, consider escalation to NIV or intubation 1
   • If improved, continue therapy and reassess regularly 1

Common Pitfalls to Avoid

• Inadequate flow rate: Flow rates that are too low may not provide sufficient PEEP effect or dead space washout 1
• Excessive oxygen: Targeting SpO2 >98% may lead to oxygen toxicity and potential harm 1
• Delayed escalation: Failure to recognize HFNC failure can lead to delayed intubation and worse outcomes 1
• Poor interface fit: Ensure proper cannula size to avoid air leaks that reduce effectiveness 1
• Insufficient humidification: Inadequate humidification can lead to airway dryness and patient discomfort 1