What flow rate and FiO2 (Fraction of Inspired Oxygen) would you recommend for a High Flow Nasal Cannula (HHFNC) in a recently extubated patient?

High-Flow Nasal Cannula Settings for Post-Extubation Care

For a recently extubated patient, start with a flow rate of 40-50 L/min and FiO2 of 40-50%, then titrate the FiO2 down to maintain SpO2 94-98%. 1, 2

Initial Flow Rate Selection

Begin with 40-50 L/min as your starting flow rate. 2 The European Respiratory Society guidelines support flow rates between 35-60 L/min for adults, with the sweet spot for post-extubation patients being 40-50 L/min. 2 While higher flows (50-60 L/min) provide greater physiological benefits including PEEP effect and dead space washout 1, a recent randomized controlled trial found that starting at 40 L/min with as-needed up-titration is a reasonable alternative to automatically setting 60 L/min. 3

The key advantage of starting at 40 L/min: This approach allows for escalation if needed while avoiding unnecessary discomfort, as some patients cannot tolerate flows above 40-50 L/min despite theoretical benefits. 2 The trial showed no significant difference in reintubation or NIV use between 40 L/min and 60 L/min groups (22.1% vs 16.9%, P=0.39), though the 40 L/min group had higher rates of needing escalation (27.9% vs 9.6%, P=0.002). 3

Initial FiO2 Selection

Start with FiO2 of 40-50% to provide a safety margin while avoiding excessive oxygen exposure. 2 The goal is to achieve target SpO2 of 94-98% for patients without risk of hypercapnia. 2 This starting point allows you to:

• Ensure adequate oxygenation immediately post-extubation 1
• Avoid the risks of excessive oxygen (oxygen toxicity) 2
• Provide room for titration in either direction 2

For patients at risk of hypercapnic respiratory failure (COPD, obesity hypoventilation), target SpO2 88-92% instead. 2, 4

Titration Algorithm

Flow Rate Adjustments:

• Increase by 5-10 L/min if: Patient shows increased work of breathing, persistent tachypnea, or accessory muscle use 2
• Decrease by 5-10 L/min if: Patient reports discomfort or intolerance 2
• Maximum flow: 60 L/min for most adults 1, 2

FiO2 Adjustments:

• Titrate in 5-10% increments to maintain target SpO2 2
• Wean FiO2 first before reducing flow rate once patient stabilizes 2
• Target SpO2 94-98% for non-hypercapnic patients 2
• Target SpO2 88-92% for hypercapnic risk patients 2

Critical Monitoring Parameters

Monitor these parameters continuously in the first 1-2 hours, then every 2-4 hours:

• Respiratory rate: Should decrease from baseline with effective therapy 1, 2
• Work of breathing: Assess for accessory muscle use, retractions 2
• Oxygen saturation: Continuous pulse oximetry 2
• Patient comfort: Should improve with effective HFNC 1
• Arterial blood gases: When necessary to assess response 2

Temperature Setting

Set temperature to 37°C initially, which provides optimal humidification. 2 Adjust between 34-37°C based on patient preference. 2

Escalation Criteria - When to Increase Support

Be prepared to escalate if you observe:

• Persistent tachypnea (RR >25-30) after 1-2 hours 2
• FiO2 requirement ≥60% to maintain SpO2 targets 2
• Worsening work of breathing despite optimal settings 2
• Inability to tolerate HFNC due to interface issues 2

The evidence shows HFNC reduces reintubation rates compared to conventional oxygen therapy (risk ratio 0.62,95% CI 0.38-1.01) and reduces need for escalation to NIV (risk ratio 0.38,95% CI 0.17-0.85). 1

Common Pitfalls to Avoid

• Starting too low on flow rate: Inadequate flow (<40 L/min) may not provide sufficient PEEP effect or dead space washout 2
• Excessive oxygen administration: Using unnecessarily high FiO2 increases risk of oxygen toxicity 2
• Delayed escalation: Waiting too long to intubate when patient deteriorates leads to worse outcomes 2
• Poor interface fit: Air leaks reduce effectiveness - ensure proper nasal prong sizing 2
• Assuming precise FiO2 delivery: While HFNC provides more reliable FiO2 than standard nasal cannula, individual variation still exists based on breathing pattern 4

Evidence Quality Note

The recommendation for HFNC over conventional oxygen therapy post-extubation is supported by moderate certainty evidence from multiple guidelines. 1 The American College of Physicians, European Respiratory Society, and British Thoracic Society all conditionally recommend HFNC for post-extubation care in patients at low-to-moderate risk of extubation failure. 1