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Appendix 2: Clinical Pathway for Initiation and Management of HHFNC

Indications for Starting Heated High Flow Nasal Cannula (HHFNC)

  • Moderate (score 6 to 10) to severe (score 11 or higher) work of breathing despite nasopharyngeal suctioning and repositioning to optimize respiratory status.
  • SpO2 consistently below 90% despite supplemental oxygen at 4 L/min by conventional nasal cannula (FiO2 1.0).

Exclusion Criteria - Consider PICU Consult

  • Congenital heart disease requiring medications.
  • Anatomical airway anomalies.
  • Neuromuscular diseases.
  • Chronic lung disease with home oxygen.
  • Pulmonary hypertension requiring medications.
  • Immunodeficiencies.
  • History of prior intubation for respiratory failure.
  • Prematurity younger than 32 weeks gestational age.

Step 1: Start HHFNC

  • If moderate (score 6 to 10): Start flow at 0.5 to 1 L/min/kg.
  • If severe (score 11 or higher): Start flow at 2 L/min/kg.
  • Adjust FiO2 to keep oxygen saturation above 90%.

Step 2: Assess Whether the Patient Is Stabilized or Improving

If yes: Begin the weaning pathway.

If no: Escalate care.

Step 3: Escalation of Care

  • Increase flow by 2 L/min increments to a maximum flow of 2 L/min/kg.
  • Consider obtaining a capillary blood gas.
  • Consider placing a peripheral IV (PIV) and making the patient NPO.

Step 4: Reassess After Escalation

Determine whether the patient is stabilized or improving.

If yes: Begin the weaning pathway.

If no: Consult PICU for transfer.

Transfer Criteria

Consult PICU for transfer if any of the following are present:

  • No improvement and still severe or worsening after 1 hour at 2 L/min/kg.
  • Significant hypercarbia.
  • FiO2 greater than 60% is required to maintain saturation.
  • Need for higher respiratory support.

Weaning Pathway

  • Wean FiO2 as tolerated to maintain SpO2 above 90%.
  • Wean flow by 2 L/min every 2 hours as tolerated.
  • For patients with bronchiolitis on HFNC who are 30 days of age or older, follow the High Flow Holiday guidance in Appendix 3.