Starting Formula for High Flow Nasal Cannula (HFNC) Therapy
The recommended starting flow rate for high flow nasal cannula therapy is 35-60 L/min for adults, titrated to patient tolerance, with temperature set at 34-37°C according to patient preference, and FiO2 adjusted to achieve SpO2 between 88-92%. 1
Initial HFNC Settings for Adults
Flow Rate
- Start at 35-60 L/min for adults 1
- Titrate flow as tolerated by the patient
- Higher flows (50-60 L/min) are preferred when possible as they:
- Better meet peak inspiratory flow demands
- Improve oxygenation
- Reduce work of breathing
- Enhance CO2 washout 2
Temperature
- Set between 34-37°C based on patient comfort 1
- Heated humidification is essential for all HFNC therapy
Oxygen Concentration (FiO2)
- Adjust to achieve target SpO2 of 88-92% 1
- Start with FiO2 of 0.45 (45%) for high-risk patients 3
- Titrate based on continuous SpO2 monitoring
Pediatric HFNC Settings
For pediatric patients, flow rates are weight-based:
- ≥1 L/kg/min for patients up to 10 kg
- ≥10 L/min for patients above 10 kg 1
- For infants with bronchiolitis, approximately 2 L/kg/min is more effective than 1 L/kg/min 4
Monitoring During HFNC Therapy
- Continuous SpO2 monitoring
- Monitor at least every 4 hours, more frequently during titration 5
- Obtain arterial blood gas within 30-60 minutes in patients at risk of hypercapnic respiratory failure 1
- Monitor for signs of treatment failure:
- Persistent hypoxemia
- Increased work of breathing
- Respiratory rate
- Patient comfort
Advantages of HFNC Over Conventional Oxygen Therapy
HFNC provides several physiological benefits compared to conventional oxygen therapy:
- Delivers higher and more stable FiO2
- Generates positive airway pressure
- Reduces anatomical dead space
- Decreases work of breathing
- Improves mucociliary clearance through humidification 6
Common Pitfalls and How to Avoid Them
- Insufficient flow rate: Ensure flow exceeds patient's peak inspiratory flow to maximize benefits
- Inadequate humidification: Always use heated humidification to prevent airway dryness
- Improper sizing: Select appropriate cannula size (should occupy no more than 50% of nares)
- Delayed escalation: Monitor closely for treatment failure and escalate to NIV or intubation if needed
- Overlooking patient comfort: Adjust temperature and flow based on patient tolerance
When to Consider Alternative Respiratory Support
Consider escalation to NIV or intubation if:
- Persistent hypoxemia despite HFNC
- Increasing work of breathing
- Development of hypercapnia
- Clinical deterioration
HFNC is increasingly recognized as an effective form of respiratory support that can reduce treatment failure compared to conventional oxygen therapy 6, but should be used with appropriate monitoring and clear criteria for escalation of care.