Guidelines for Initiating High Flow Nasal Cannula (HFNC) Therapy in Pediatric Patients
HFNC should be initiated using weight-based flow rates: ≥1 L/kg/min for patients up to 10 kg and ≥10 L/min for patients above 10 kg, with heated and humidified gas delivery. 1
Definition and Technical Requirements
HFNC is formally defined as flow delivered through a heated humidified nasal cannula circuit at specific minimum thresholds that distinguish it from conventional oxygen therapy. 1, 2
- For infants ≤10 kg: Flow must be ≥1 L/kg/min 1
- For children >10 kg: Flow must be ≥10 L/min 1
- Below these thresholds: The patient is receiving conventional oxygen therapy, not HFNC 1
The gas must be heated and humidified to qualify as HFNC therapy. 1, 2
Initial Flow Rate Selection Algorithm
Step 1: Determine Patient Weight Category
For patients ≤10 kg (typically infants):
Start with 2 L/kg/min as the initial flow rate. 3, 4 This recommendation is based on:
- A 2021 quality improvement study demonstrating that higher initial flows (median 14.5 L/min vs 10 L/min) resulted in lower HFNC failure rates (10% vs 17%, p=0.015) and shorter hospital stays 3
- A 2018 multicenter RCT showing that 3 L/kg/min did not reduce failure rates compared to 2 L/kg/min but increased discomfort (43% vs 16%, p=0.002) and PICU length of stay 5
- A 2021 study demonstrating that 2 L/kg/min meets peak inspiratory flow demands in most infants with bronchiolitis and improves respiratory mechanics 4
For patients >10 kg:
Start with ≥10 L/min as the minimum threshold, but consider initiating at higher flows (up to 40-50 L/min depending on age and size) based on disease severity. 1, 6
Step 2: Adjust Based on Disease Severity
The Paediatric Mechanical Ventilation Consensus Conference (PEMVECC) guidelines indicate HFNC applicability increases with disease severity across all respiratory conditions. 1
- Mild disease: Consider HFNC as initial therapy 1
- Moderate disease: HFNC is increasingly applicable 1
- Severe disease: HFNC has maximal applicability, though CPAP or NIV may be preferred in some contexts 1
This applies to obstructive airway disease, restrictive disease, mixed disease, and cardiac patients. 1
Monitoring Parameters During HFNC Therapy
Essential Monitoring
SpO2: Continuous pulse oximetry monitoring is mandatory 1
Respiratory rate: Should decrease with effective HFNC therapy 6
Work of breathing: Assess for accessory muscle use and patient comfort 6
Additional Monitoring in Moderate-to-Severe Disease
- Measure PCO2 in arterial or capillary blood samples 1
- Consider transcutaneous CO2 monitoring 1
- Measure pH, lactate, and central venous saturation 1
- Target pH >7.20 (normal pH for pulmonary hypertension) 1
- Target PCO2 35-45 mmHg for healthy lungs; higher PCO2 accepted for acute pulmonary/non-pulmonary patients unless contraindicated 1
Titration and Weaning Strategy
Flow Rate Adjustments
Increase flow by 5-10 L/min (or 0.5-1 L/kg/min in infants) if: 6
- Increased work of breathing persists
- Respiratory distress worsens
- SpO2 targets not met despite FiO2 adjustment
Decrease flow by 5-10 L/min (or 0.5-1 L/kg/min in infants) if: 6
- Patient discomfort develops
- Clinical improvement allows weaning
A 2021 protocol-based study showed that rapid weaning (median 4.1 L/min/h vs 2.4 L/min/h) was safe and reduced length of stay. 3
FiO2 Adjustments
Titrate FiO2 in 5-10% increments to maintain target SpO2. 6
HFNC Failure Criteria and Escalation
HFNC failure is defined as the need for escalation to NIV or invasive mechanical ventilation. 3
Prespecified Criteria for Escalation
Consider escalation to NIV or intubation if: 5
- Worsening respiratory distress despite optimal HFNC settings
- Persistent discomfort or intolerance
- Inability to maintain SpO2 targets
- Rising PCO2 with pH <7.20 (except when permissive hypercapnia is appropriate) 1
Common Pitfalls and How to Avoid Them
Starting Flow Too Low
Pitfall: Using flows <1 L/kg/min in infants or <10 L/min in children provides conventional oxygen therapy, not HFNC, missing the therapeutic benefits of dead space washout and PEEP effect. 1, 6
Solution: Always start at minimum threshold flows (1 L/kg/min for ≤10 kg; 10 L/min for >10 kg) and titrate upward based on response. 1
Starting Flow Too High
Pitfall: Using 3 L/kg/min in young infants increases discomfort without improving outcomes. 5
Solution: Start at 2 L/kg/min in infants, which meets peak inspiratory flow demands in most cases and improves respiratory mechanics. 4
Inadequate Humidification
Pitfall: Insufficient humidification causes airway dryness and patient discomfort. 6
Solution: Ensure heated humidification is functioning; target temperature 34-37°C. 6
Delayed Escalation
Pitfall: Continuing HFNC despite clear failure criteria leads to delayed intubation and worse outcomes. 6
Solution: Use objective failure criteria and escalate promptly when indicated. 5
Poor Interface Fit
Pitfall: Air leaks reduce HFNC effectiveness. 6
Solution: Ensure proper nasal cannula sizing and positioning.
Special Clinical Contexts
Post-Extubation Support
Consider NIV in neuromuscular patients and those at increased risk for post-extubation stridor. 1 HFNC may be used as an alternative when NIV is not tolerated. 6
Positioning
Maintain head of bed elevated 30-45° during HFNC therapy. 1
Bronchiolitis-Specific Considerations
HFNC can be used in moderate to severe bronchiolitis upon initial low-flow oxygen failure. 7 The 2 L/kg/min starting rate is particularly well-supported in this population. 5, 4