What are the guidelines for using high flow nasal oxygen (HFNO) therapy in patients with respiratory distress?

Guidelines for High Flow Nasal Oxygen (HFNO) Therapy in Respiratory Distress

The American College of Physicians (ACP) recommends high-flow nasal oxygen over conventional oxygen therapy for hospitalized adults with postextubation acute hypoxemic respiratory failure, and suggests HFNO over noninvasive ventilation for management of acute hypoxemic respiratory failure. 1

Indications for HFNO Therapy

HFNO is indicated in the following clinical scenarios:

• Acute hypoxemic respiratory failure (SpO₂ < 92% despite conventional oxygen therapy)
• Postextubation respiratory support, especially in high-risk patients
• Patients with increased work of breathing and compensatory tachypnea
• Patients requiring respiratory support but with good tolerance for HFNO

Contraindications

• Severe nasal obstruction
• Patients requiring immediate intubation
• Severe hypercapnic respiratory failure (NIV may be preferred initially in COPD patients) 2

Physiological Benefits of HFNO

HFNO provides several advantages over conventional oxygen therapy:

• Improved oxygenation (increases PaO₂ by approximately 16.72 mmHg) 2
• Reduced work of breathing (decreases respiratory rate by about 2.25 breaths/min) 2
• Enhanced patient comfort compared to conventional oxygen and NIV 2
• Provision of low-level PEEP (approximately 7 cm H₂O at 50 L/min flow) 2
• Reduced anatomical dead space 3
• Improved secretion clearance through heated humidification 2

Initial HFNO Settings

When initiating HFNO therapy:

• Flow rate: 40-50 L/min
• FiO₂: Titrate to maintain SpO₂ ≥ 92%
• Temperature: 37°C for adequate humidification 2

Monitoring and Assessment

Patients on HFNO require close monitoring:

• Continuous monitoring of respiratory rate and oxygen saturation
• Evaluation of work of breathing and signs of respiratory muscle fatigue
• Assessment of level of consciousness
• Serial arterial blood gases as needed
• Reevaluation within 1-2 hours to determine response to therapy 2

HFNO vs. Alternative Respiratory Support

HFNO vs. Conventional Oxygen Therapy

• HFNO is preferred over conventional oxygen therapy for postextubation acute hypoxemic respiratory failure 1
• HFNO provides more stable FiO₂ delivery and improved patient comfort 2

HFNO vs. Noninvasive Ventilation (NIV)

• HFNO is suggested over NIV for management of acute hypoxemic respiratory failure 1
• HFNO may reduce mortality (RR 0.77) and need for intubation (RR 0.84) compared to NIV 2
• HFNO improves patient comfort compared to NIV 2
• NIV may be preferred in patients with significant respiratory muscle fatigue, congestive heart failure, or severe metabolic acidosis 2

When to Escalate Respiratory Support

Consider escalation to NIV or intubation if:

• Persistent or worsening hypoxemia despite HFNO
• Increasing work of breathing or respiratory fatigue
• Deteriorating mental status
• Inability to maintain airway protection

Weaning from HFNO

While optimal weaning strategies are still being investigated 4, consider:

• Gradual reduction of FiO₂ to 0.3 and flow to 20 L/min before transitioning to conventional oxygen therapy
• Continued monitoring during the weaning process
• Reassessment of respiratory parameters during each step of weaning

Special Considerations

• HFNO may be particularly beneficial in patients with COPD, congestive heart failure, hypercapnia, or older age 2
• HFNO should be applied immediately after extubation in high-risk patients to realize outcome benefits 2
• In patients with "do not intubate" status, HFNO may provide respiratory support while maintaining comfort 5

Common Pitfalls and Caveats

• Delaying intubation when indicated can worsen patient outcomes 2, 6
• HFNO may not work effectively if the nose is severely congested or blocked 2
• Nasal irritation or soreness may occur but is generally well-tolerated 2
• HFNO requires specific equipment and higher oxygen flow rates, though avoiding intubation may offset these costs 2

HFNO represents an innovative and effective respiratory support modality for adults with respiratory failure from diverse causes 3. The evidence supporting its use continues to grow, with guidelines now recommending it over conventional oxygen therapy in many scenarios of acute respiratory failure.