What are the guidelines for using High Flow Nasal Cannula (HFNC) for oxygen therapy?

High Flow Nasal Cannula (HFNC) Guidelines

Primary Recommendations

Use HFNC over noninvasive ventilation for acute hypoxemic respiratory failure in hospitalized adults, and use HFNC over conventional oxygen therapy for postextubation hypoxemic respiratory failure. 1

Clinical Indications

Acute Hypoxemic Respiratory Failure

• HFNC is preferred over NIV for initial management of acute hypoxemic respiratory failure based on improved patient comfort, reduced intubation rates, and comparable mortality outcomes 1
• HFNC demonstrates superior tolerance compared to face masks, with better oxygenation and lower respiratory rates 1
• Higher flow rates (50-60 L/min) provide greater physiological benefits including PEEP effect (approximately 7 cm H₂O at 50 L/min) and dead space washout 1, 2

Postextubation Support

• HFNC is recommended over conventional oxygen therapy for patients with postextubation acute hypoxemic respiratory failure 1
• HFNC reduces reintubation risk within 72 hours (4.9% vs 12.2% with conventional oxygen) 1
• Flow rates of 35-50 L/min are typically sufficient for postextubation support 2

Important Contraindication

• Do not use HFNC as first-line therapy for hypercapnic respiratory failure (e.g., COPD exacerbations) - NIV should be preferred in these patients 1, 2
• HFNC may be used during breaks from NIV or if NIV is not tolerated 2

Initial Setup Protocol

Flow Rate Settings

• Start with 40-50 L/min for most adults, titrating to patient comfort and respiratory effort 2
• For hypoxemic respiratory failure, initiate at higher flows (50-60 L/min) for maximum physiological benefit 2
• Flows must be ≥60 L/min to be considered true HFNC (lower flows are conventional oxygen therapy) 1

FiO₂ Titration

• Target SpO₂ 94-98% for patients without hypercapnia risk 2
• Target SpO₂ 88-92% for patients at risk of hypercapnic respiratory failure 2
• Titrate FiO₂ in 5-10% increments to maintain target saturation 2

Temperature Settings

• Set temperature between 34-37°C based on patient preference 2
• Higher temperatures (37°C) provide optimal humidification 2

Monitoring Requirements

Essential Parameters

• Respiratory rate - should decrease with effective HFNC therapy 2
• Work of breathing - assess for accessory muscle use and patient comfort 2
• Continuous pulse oximetry to maintain target SpO₂ 2
• Arterial blood gases when necessary to assess therapy response 2

Escalation Criteria

• Ensure ability to escalate to intubation and invasive ventilation at any time, as HFNC patients are critically ill and require continuous monitoring 3
• Do not delay intubation if patient deteriorates despite HFNC optimization 2

Adjustment Algorithm

Flow Rate Modifications

• Increase by 5-10 L/min if increased work of breathing persists 2
• Decrease by 5-10 L/min if patient experiences discomfort 2
• Maximum tolerated flow is typically 60 L/min, though some patients cannot tolerate flows above 40-50 L/min 2

Managing Adverse Effects

Nasal Irritation

• Add humidification, especially for flow rates above 4 L/min 4
• Ensure proper cannula sizing and positioning to avoid excessive pressure 4
• Avoid petroleum-based products due to fire hazard with oxygen 4
• Consider high-flow humidified systems which are better tolerated than conventional cannulas 4

Bloating/Aerophagia

• Titrate flow rates downward in 5-10 L/min increments while monitoring SpO₂ 5
• Position patient with head of bed elevated 30-45 degrees 5
• Encourage proper mouth closure during therapy to minimize air swallowing 5
• Consider smaller, more frequent meals 5
• Reassess comfort 30-60 minutes after adjusting settings 5

Physiological Mechanisms

HFNC provides multiple therapeutic effects beyond simple oxygen delivery 1:

• Delivers precise FiO₂ by preventing ambient air entrainment 1
• Generates modest positive end-expiratory pressure (PEEP effect) 1
• Reduces anatomical dead space through airway washout 1
• Improves pulmonary compliance and reduces work of breathing 1
• Provides optimal humidification and warming of inspired gas 1
• Enhances secretion clearance 1

Critical Pitfalls to Avoid

• Inadequate flow rate - flows below 40 L/min may not provide sufficient PEEP effect or dead space washout 2
• Excessive oxygen - can lead to oxygen toxicity; always titrate to target SpO₂ 2
• Delayed escalation - do not persist with HFNC if patient deteriorates; delayed intubation worsens outcomes 2
• Poor interface fit - air leaks reduce effectiveness 2
• Using HFNC for hypercapnic respiratory failure - NIV is superior in this population 1, 2

Equipment Requirements

Three essential components are required 1:

• Patient interface (nasal cannula with standard dimension prongs)
• Gas delivery device (air/oxygen blender capable of 60 L/min)
• Active humidifier with heated circuit