What is the comparison between High Flow Nasal Cannula (HFNC) and Non-Invasive Ventilation (NIV) in the treatment of hypoxemia?

From the Guidelines

High-Flow Nasal Cannula (HFNC) is recommended over Non-Invasive Ventilation (NIV) as the first-line treatment for acute hypoxaemic respiratory failure, due to its better comfort, ease of use, and similar efficacy to NIV, as suggested by the European Respiratory Society task force 1.

Key Considerations

• The selection between HFNC and NIV should be based on the severity of hypoxemia and patient-specific factors.
• For mild to moderate hypoxemia (PaO2/FiO2 ratio >150), HFNC is generally recommended as first-line therapy.
• Start HFNC at 30-60 L/min with FiO2 titrated to maintain SpO2 >92%.
• For more severe hypoxemia (PaO2/FiO2 ratio <150), particularly in patients with COPD exacerbation or cardiogenic pulmonary edema, NIV may be more appropriate.

Comparison of HFNC and NIV

• HFNC works by providing high flow rates that wash out anatomical dead space and create mild positive pressure.
• NIV delivers set inspiratory and expiratory pressures that more actively recruit alveoli and reduce work of breathing.
• The choice between these modalities should consider patient comfort, as NIV masks can cause claustrophobia and skin breakdown, while HFNC is generally better tolerated for longer periods.

Monitoring and Escalation

• Close monitoring is essential with either modality, and patients should be reassessed within 1-2 hours of initiation.
• If oxygenation doesn't improve or deteriorates, consider switching between modalities or escalating to intubation.

Evidence-Based Recommendations

• The European Respiratory Society task force suggests the use of HFNC over NIV in acute hypoxaemic respiratory failure (conditional recommendation, very low certainty of evidence) 1.
• The task force also suggests the use of HFNC over conventional oxygen therapy (COT) in patients with acute hypoxaemic respiratory failure (conditional recommendation, moderate certainty of evidence) 1.

From the Research

Comparison of High Flow Nasal Cannula (HFNC) and Non-Invasive Ventilation (NIV)

• HFNC and NIV are both used in the treatment of hypoxemia, but they have different effects on patients with acute hypoxemic respiratory failure 2, 3, 4.
• A study comparing HFNC and helmet NIV found that helmet NIV improved oxygenation, reduced dyspnea, inspiratory effort, and simplified pressure-time product, with similar transpulmonary pressure swings, PaCO2, and comfort 2.
• Another study suggested that HFNC may be superior to conventional oxygen therapy (COT) in avoiding intubation and may be used as a first-line noninvasive respiratory support in patients requiring more than 6 L/min of oxygen or PaO2/FiO2 ≤ 200 mm Hg and a respiratory rate above 25 breaths/minute or clinical signs of respiratory distress 3.
• HFNC has been shown to be better tolerated than NIV, delivers high fraction of inspired oxygen (FiO2), generates a low level of positive pressure, and provides washout of dead space in the upper airways, thereby improving mechanical pulmonary properties and unloading inspiratory muscles during acute respiratory failure (ARF) 4.

Effects of HFNC on Dyspnea and Hypoxemia

• HFNC has been found to reduce the risk of requiring more advanced ventilation support and relieve dyspnea better than conventional oxygen therapy (COT) in patients with dyspnea and hypoxemia before hospitalization 5, 6.
• A study investigating the physiologic effects of HFNC compared with COT in subjects with acute dyspnea and hypoxemia in the emergency room found that HFNC significantly improved dyspnea and subject comfort compared with COT 6.
• HFNC has been associated with a lower rate of requiring more advanced ventilation, reduced the rate of dyspnea, lowered the dyspnea scale score, and decreased patients' respiratory rate significantly 5.

Comparison of HFNC and NIV in Clinical Practice

• The choice between HFNC and NIV may depend on the individual patient's needs and the availability of resources, with HFNC being a simpler and more comfortable option for some patients 3, 4.
• Further studies are needed to assess the potential benefits of CPAP, NIV through a helmet, and awake prone position in patients with acute hypoxemic respiratory failure not related to COVID-19 3.
• HFNC may be considered as a first-line therapy even before making a clear diagnosis for dyspnea, due to its undeniable short-term effects in reducing the risk of requiring more advanced ventilation and relieving dyspnea 5.