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Nursing guidelines

High flow nasal prong (HFNP) therapy

  • Introduction

    Aim

    Definition of Terms

    Indications

    Contraindications 

    Initiation 

    Management: Acute

         Flow rate

         Humidification

         Complications

         Supplemental Oxygen

         Patient Monitoring

         Documentation 

         Nursing Care

         Transfers

         Ceasing HFNP therapy

    Special Considerations 

         Cleaning

    Companion Documents

    Links

    Evidence Table

    References

    Introduction

    Humidified high flow nasal prong (HFNP) therapy is a form of non-invasive respiratory support. HFNP may act as a bridge between low flow oxygen therapies and CPAP, reducing the need for CPAP/intubation. At high flows of 2 litres per kilogram per minute, using appropriate nasal prongs, a positive distending pressure may be achieved. The high flows and humidification improve functional residual capacity and mucocililary clearance of secretions thereby reducing work of breathing. The high flows may also affect pulmonary and systemic circulation which is an important consideration when applying HFNP therapy to children with cardiac disease.
    Please Note: HFNP therapy is an aerosol generating procedure (AGP), a patient’s clinical requirement for HFNP should be balanced against the risk of aerosolization. When HFNP therapy is required for a SCOVID or COVID patient, this should be carried out in a negative pressure room using Airborne Precautions which include personal protective equipment (PPE): P2 respirator (N95 mask); Eye protection (e.g. Eyewear, face shield); Long-sleeved gown; Gloves (non-sterile). If a negative pressure room is unavailable, AGPs may be performed in a single room without negative pressure ventilation with the door closed. Airborne precautions should be maintained for 30minutes after an AGP has been performed. The patient should be transferred to a negative pressure room as soon as possible. PPE including P2/N95 masks should be discarded following an aerosol generating procedure or discarded and replaced if contaminated with blood or body fluids. 

    Aim

    The aim of this guideline is to describe the indications and procedure for the use of High Flow Nasal Prong (HFNP) therapy within paediatrics. 

    This guideline does not refer to the management of HFNP in the neonatal patient.  Please refer to the Newborn Intensive Care Unit

    Definition of terms

    • CPAP: Continuous Positive Airway Pressure
    • FiO2: Fraction of inspired oxygen (%). 
    • PaCO2: The partial pressure of CO2 in arterial blood. It is used to assess the adequacy of ventilation. 
    • PaO2: The partial pressure of oxygen in arterial blood. It is used to assess the adequacy of oxygenation. 
    • SaO2: Arterial oxygen saturation measured from blood specimen. 
    • SpO2: Arterial oxygen saturation measured via pulse oximetry. 
    • High flow: High flow systems are specific devices that deliver the patient's entire ventilatory demand, meeting, or exceeding the patients Peak Inspiratory Flow Rate (PIFR), thereby providing an accurate FiO2. Where the total flow delivered to the patient meets or exceeds their Peak Inspiratory Flow Rate the FiO2 delivered to the patient will be accurate.  High flow in approved areas only. Consult your NUM if unsure.  
    • Humidification is the addition of heat and moisture to a gas. The amount of water vapour that a gas can carry increases with temperature. 
    • Hypercapnea: Increased amounts of carbon dioxide in the blood. 
    • Hypoxaemia: Low arterial oxygen tension (in the blood.) 
    • Hypoxia: Low oxygen level at the tissues. 
    • Low flow: Low flow systems are specific devices that do not provide the patient's entire ventilatory requirements, room air is entrained with the oxygen, diluting the FiO2. 
    • Peak Inspiratory Flow Rate (PIFR): The fastest flow rate of air during inspiration, measured in litres per second. 
    • Tidal Volume: The amount of gas that moves in, and out, of the lungs with each breath, measured in millilitres (6-10 ml/kg). 
    • Ventilation - Perfusion (VQ) mismatch: An imbalance between alveolar ventilation and pulmonary capillary blood flow.

    Indications 

    Patients requiring respiratory support.

    • Acute respiratory distress associated with respiratory illness, hypoxaemia (SpO2<90%) and/ or moderate to severe work of breathing
    • Respiratory distress in association with non-respiratory issues e.g., congestive cardiac failure, fluid overload
    • Post-operative respiratory support e.g., tonsillectomy & adenectomy (Ts&As)
    • Respiratory support to infants and children with chronic lung disease.
    • Weaning therapy from mask CPAP or BPAP

    Contraindications 

    • Critically ill infants and children requiring immediate higher level of respiratory support i.e. NIV or invasive ventilation or decreased level of consciousness.
    • Upper airway obstruction
    • Central apnoea
    • Blocked nasal passages/choanal atresia 
    • Trauma/surgery to nasopharynx
    • Pneumothorax

    Initiation 

    • The decision to initiate HFNP therapy must be made in consultation with the bed card Consultant
    • Medical order placed within EMR
    • HFNP can be initiated in wards if clinically indicated
    • Any patient who does not exhibit signs of clinical stabilization, as described below, within 2 hours of commencement of HFNP therapy should be reviewed by PICU outreach service.
    • Any patient who does not exhibit signs of clinical stabilization with 4 hours of commencement of HFNP should be considered for transfer to the PICU.
    • The RCH Nursing Guideline: Oxygen Delivery should be consulted with regards to equipment, set up, FiO2 delivered and target SpO2 ranges. 

    Management: Acute

    • Equipment and set up, check device settings match the EMR order
    • Secure nasal cannula on patients using supplied “Wiggle pads,” ensuring the prongs sit well into the nares. Nasal prongs should not completely occupy the nares. 
    • Start the high flow nasal cannula system in room air ie. 21% oxygen
    • Once prescribed flow rate is reached assess requirement for supplemental oxygen.

    Flow rate

    Flow rate for HFNP Therapy is the same for all patients regardless of medical condition

    • ≤12Kg: 2 L/kg/minute
    • >12Kg: 2 L/kg/minute for the first 12kg + 0.5L/kg/minute for each kg thereafter (max flow 50 L/min)
    • Increase flow to the prescribed rate over a few minutes, or as tolerated.

    Humidification

    • Water humidification is necessary to avoid drying of respiratory secretions and for maintaining nasal cilia function due to the high flow rate
    • Airvo humidifier setting at 34° C non-invasive setting. 

    Complications 

    • Abdominal distension. 
    • Pressure areas. 
    • Blocked HFNP due to secretions. 
    • Pneumothorax. 
    • Possible hypotension 

    Supplemental Oxygen

    When HFNP therapy is commenced to provide respiratory support for children with non-respiratory issues, supplemental oxygen should be used cautiously with a FiO2 not greater than 0.3

    In children with cyanotic congenital heart disease and balanced circulation, HFNP therapy is generally used with an FiO2 of 0.21 (air) or a low increased fraction of oxygen (≤30%) The addition of supplemental oxygen requires approval from Cardiac or PICU Consultant

    In children with clinical signs of upper airway obstruction (noisy breathing, tracheal tug, subcostal retractions, absence of tachypnoea) or potential obstruction e.g., post-op Ts & As on HFNP therapy should only receive FiO2 0.21 (air).  The addition of supplemental oxygen requires approval from ENT or PICU Consultant.

    Supplemental Oxygen therapy should be commenced for patients on HFNP who display hypoxaemia 

    • SpO2 is persistently less than 90% (PaO2 less than 80mmHg) in patients without cyanotic heart disease
    • SpO2 is persistently less than patient’s acceptable limit in the patient with cyanotic heart disease, generally <70% (PaO2 less than 37mmHg)

    Where supplemental oxygen is required, titrate FiO2 to the minimum amount required to maintain target SpO2.

    Oxygen therapy should be reduced or ceased if: 

    • SpO2 is ≥ 90% in patients without cyanotic heart disease.
    • Child with cyanotic heart disease reaches their baseline SpO2

    Patient monitoring

    Observation, patient clinical assessment and documentation should occur hourly at a minimum. Adjustment of frequency of patient observation and assessment should occur in response to clinical condition.

    • Continuous monitoring of SpO2 and HR until clinically stable 
    • Monitor patient for response in 
      • Respiratory rate 
      • Heart rate 
      • Respiratory Distress (Work of Breathing) 
      • SpO2
    • Within 2 hours it should be possible to reduce the FiO2 (where required) and signs of clinical stabilization should be seen 
      • Heart rate should reduce by 20% or to within normal range. 
      • Respiratory rate should reduce by 20% or to within normal range. 
      • Signs of respiratory distress should improve. 
      • FiO2 required to maintain SpO2 in the target range should decrease to <40%.
    • Seek medical / Outreach / After-hours review if any of the following occurs: 
      • Patient is not stabilizing as described above  
      • Degree of respiratory distress remains unchanged or worsens. 
      • Hypoxaemia persists despite oxygen therapy. 
      • Requirement for >40% oxygen in respiratory patients 
      • Requirement for >30% oxygen in non-respiratory patients 

    Documentation

    • Document hourly: 
    • RR, HR, SpO2 & WOB. 
    • Flow rate, FiO2 & humidifier temp.
    • Water level, rainout.

    Nursing care

    • Patients on HFNP therapy should have a strict fluid balance
    • Patients on HFNP should have a NGT for air decompression (unless contraindicated e.g. post op Ts&As)
    • Method of nutrition/ hydration should be based on severity of respiratory distress
    • Do not feed during the initial 2 hours following commencement of HFNP therapy.
    • Once stable the child should be assessed as to whether they can tolerate oral feeds.
    • Oral feed should be ceased if child clinically deteriorates during feeding.
    • If oral feeding is not tolerated, commence 2 hourly NG bolus feeds with EBM or formula as appropriate, reduce total volume to 2/3 maintenance.
    • Consider continuous NG feeds if not tolerating bolus feeds. 
    • Infants who do not clinically stabilize within 2 hours or who do not tolerate NGT feeds should have an I.V. inserted to receive hydration. 
    • Aspirate the NGT for air 2-4 hourly. 
    • Oral and nasal care must be performed 4 hourly. 
    • Check for pressure areas, nasal prongs are in correct position and saturation probe moved regularly
    • Gentle suction as required to keep nares clear. 
    • Monitor for abdominal distention and aspirate NGT as clinically indicated
    • Cluster cares and minimal handling

    Notes

    • For the patient with cardiac disease, heart failure and respiratory failure have similar clinical manifestations. HFNP therapy may mask signs of heart failure, therefore consider other tests, such as ECHO, ECG to understand child’s cardiac function.
    • If a high FiO2 is used, oxygen saturation may be maintained in an infant despite the development of hypercarbic respiratory failure. 
    • If there is rapid deterioration of oxygen saturation or marked increased work of breathing, a chest x-ray should be done to exclude a pneumothorax. 
    • Do blood gas analysis when clinically indicated but remember that blood taking can further upset an infant.  If in doubt discuss with Consultant or PICU
    • Sometimes an infant commenced on HFNP will be more distressed because of the discomfort of the therapy.  This is sometimes interpreted as indicating a deterioration requiring escalation of therapy.  However sometimes such infants will be just as stable, or even more settled, simply on standard low flow 100% oxygen.  Deciding which children require escalation and which children would be better changed to standard flow 100% oxygen therapy requires judgement and sometimes a trial of standard oxygen.  This decision is best made by a doctor and nurse who have observed the child consistently since commencement of HFNP therapy.  Contact the Consultant, PICU Outreach or After-hours if unsure.

    Transfers

    The Airvo requires main power and is not portable. Patients receiving HFNP therapy who require transfer must be escorted by a nurse or doctor. Patients on HFNP with oxygen therapy, can be transferred on low flow oxygen therapy with HFNP re-established as soon as possible. If unstable off HFNP, patients require escalation of care prior to transport. 

    Ceasing HFNP therapy 

    When the child's clinical condition is improving as indicated by: 

    • Decreased work of breathing 
    • Normal or improved respiratory rate 
    • Return to normal cardiovascular parameters

    Wean FiO2 to 21% then cease HFNP therapy. HFNP therapy should not be routinely weaned, just stopped.

    Consider transfer to low flow nasal prong oxygen therapy where HFNP is no longer required but clinical requirement for oxygen persists.  Consult section on weaning oxygen on the Oxygen Nursing Clinical Guideline.

    Continue pulse oximetry monitoring for 30 minutes post cessation of HFNP therapy, perform vital sign observation, intermittent SpO2 monitoring 30 minutes later, then hourly for 2 hours.

    Where cessation of HFNP therapy is successful – usually known within 2 hours of stopping - continuous pulse oximetry monitoring may be discontinued.

    Unless contraindicated, an attempt to wean oxygen or cease HFNP flow should be made at least once per shift.

    Special Considerations

    Cleaning 

    • The AIRVO 2 Humidifier requires cleaning and disinfection between patients. 
    • Follow the instructions in the disinfection kit manual. 

    Companion documents

    Links

    Evidence table

    Click here to view the evidence table.  


    Please remember to read the disclaimer.

    The development of this clinical guideline was coordinated by John Kemp, Clinical Support Nurse and Respiratory CNC, Sugar Glider and the coordination of making this guideline hospital wide was done by Sophie Linton, CNC, Nursing Innovation; and approved by the Nursing Clinical Effectiveness Committee. Updated November 2021.