High Flow Nasal Cannula Oxygen Therapy (HFNCT) for Infants and Children (not for use in NICU)

• Indications for the use of HFNCT
• Special Considerations in the use of HFNCT
• Contraindications to the use of HFNCT
• How it works
• Advantages
• Potential disadvantages
• Set up
• Management
• Monitoring
• Assessment
• Assessment flow chart
• If HFNCT is failing
• Discontinuation of HFNCT
• Equipment and personnel requirements
• Transfer of children on HFNCT from PICU to ward
• Transfer of children on HFNCT between children's wards
• Complex patients
• Top Tips for Vapotherm use
• Appendix

Children may require respiratory support for many reasons.
Non-invasive respiratory support may reduce the frequency with which children require mechanical ventilation. Two modes are readily available:

• Continuous Positive Airway Pressure (CPAP)
• High Flow Nasal Cannula Oxygen Therapy (HFNCT)

HFNCT was introduced to paediatric practice with no evidence to support its use. There are now several randomized controlled trials (RCTs) supporting the use of HFNCT in small children with moderate to severe bronchiolitis 8,9. Note these studies do not support the concept that HFNCT is a therapeutic modality, it is simply another way of supporting breathing. Further the evidence supports the use of HFNCT, but there is still debate over whether it is “better” than low flow oxygen or CPAP. There is some evidence from early studies in infants to suggest that HFNCT may be as effective as CPAP whilst being simpler to administer1, 2 . Research is on-going and will inform our future practice.

The above is important to understand as inappropriate use of HFNCT may lead to deferred escalation of care and worse outcomes. Inappropriate use of oxygen therapy can also be detrimental to the patient. There are a limited number of high flow devices and so it is important that they are used appropriately. The machines and consumables come at a cost. The decision to start HFNCT should be by a senior decision maker (ST4 or above, or trained ANP) needs to be informed.

The following is a guide aimed predominantly at the use of HFNCT for the management of infants and children with acute respiratory illness, WITHOUT pre-existing co-morbidity. There is a section at the end of the document for the management of children with pre-existing co-morbidity who may require a different approach. This approach should be discussed with the child’s named Consultant. This guide is not for use on the Neonatal Unit.

Vapotherm is the form of HFNCT predominantly used in Leeds Childrens Hospital, and in this document “Vapotherm” and “HFNCT” are used interchangeably. A device called Airvo by Fisher & Paykel is sometimes used, and other forms of HFNCT are available. Different devices have advantages and disadvantages and the settings on one device are not directly comparable with another. The settings used in this document refer to Vapotherm as this is still the most commonly used device. If Airvo is used in the acute management of a child, the same starting settings may be used, but will require closer observation and more frequent adjustment to ensure the child is getting adequate support. This advice may change as Airvo becomes more widely used.

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Indications for the use of HFNCT

Consider additional respiratory support with HFNCT if, despite optimising treatment/other manoeuvres to optimise respiratory condition, two or more of the following are present:

• Respiratory rate scoring 3 (amber) or more on PAWS
• Apnoeas in infants less than 6 months of age with probable bronchiolitis
• Bradypnoea or cyanotic episodes (with or without bradycardia) despite supplemental O₂
• Significantly increased respiratory effort including recession
• Need for high oxygen flow rate via nasal prongs (max 2-4L/min depending on comfort and age of child), facemask (8-10L/min), or headbox (consider if requiring 50-60%)
• Inability to achieve target saturations with, or to tolerate, other modes of oxygen delivery
• PaCO₂ 8.5 kPa or more (in children without pre-existing chronic lung disease) on a capillary blood gas.
• Rising PaCO² (more than 2kPa from baseline)
• Respiratory acidosis (pH 7.2 – 7.28, if pH less than 7.20 consider ventilation)

HFNCT should not be used as a routine oxygen delivery system for children due to its cost and the scarcity of machines.

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Special Considerations in the use of HFNCT

Patients in this group must be discussed with the Paediatric Consultant responsible for the patient before HFNCT is started as other options may be preferable.

• Pre-existing lung disease/ Cardiac conditions
• Neuromuscular disorders
• Thoracic abnormalities
• Patients with an initial pH< 7.2 who don’t meet other indications, (i.e. could this be something else such as a metabolic acidosis/sepsis)
• Small neonates with apnoeas (consider sepsis)
• Asthma – NOT standard therapy, therefore would need a discussion with PICU. If started, it should be in parallel with and not delay standard asthma therapy, such as IV bronchodilators. Standard nebulisers should not be used at the same time as HFNCT as this is not an efficient form of drug delivery. A device called an Aerogen nebuliser is required to enable nebulised drug delivery with HFNCT. Currently it is recommended that asthmatics on HFNCT requiring nebulised therapy should also be on IV bronchodilators and in a critical care setting. Note Aerogen is sometimes used on the general wards on stable patients such as those with chronic lung disease of prematurity or cystic fibrosis, and represents a different clinical situation.
• Croup - NOT standard therapy, therefore would need a discussion with PICU. If started, it should be in parallel with and not delay standard croup and airway management.

When starting a child on HFNCT, an appropriate clinical risk assessment needs to be made. Consider whether the child needs HDU/PICU/stabilization area or high dependency bed. Please consider staffing and equipment availability.

Standard nebulisers should not be used at the same time as HFNCT as it will prevent drug delivery. A device called an Aerogen nebuliser is required to enable drug delivery with HFNCT.

COVID19 is not a contraindication to HFNCT. The RCPCH and PICCs organisations have put out statements to the effect that if a child has or is suspected to have COVID19 HFNCT can be used if the child is hypoxic despite low flow oxygen, with appropriate PPE. It has been used without an increased risk of health care worker infection in adult centres both nationally and internationally. Please see guidance on PPE (insert link here)

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Contraindications to the use of HFNCT

• The need for intubation and/or mechanical ventilation as evidenced by the presence of:
• Severe respiratory or cardiovascular instability and impending arrest
• pH less than 7.20 and not improving with initial support
• SpO₂ less than 88% in maximal effective oxygen therapy
• Exhaustion (decreasing respiratory rate, desaturations, apnoea and increasing heart rate or bradycardia may indicate fatigue)
• Upper airway abnormalities that may make HFNCT, NCPAP, or Nasal Mask (NM)-CPAP ineffective or potentially dangerous (e.g., choanal atresia, cleft palate, tracheoesophageal fistula)
• Pneumothorax
• Burns to the face/ chest

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How it works

HFNCT is a system by which warmed and humidified high flow oxygen/air mixture is administered via nasal cannulae at flow rates more than 2 l/min 3. It can be used by trained staff to provide respiratory support for infants who would be considered for CPAP therapy.

HFNCT delivery systems work by producing gas flows that exceed patient inspiratory flow rates. This ensures that the patient inspires the intended gas composition and may provide other physiological benefits including:

• Washout of nasopharyngeal dead space
• Reduction in inspiratory resistance associated with gas flow through the nasopharynx
• Improvement in respiratory mechanical parameters associated with gas temperature and state of humidification, such as ciliary function.
• Reduction in metabolic work associated with heating and humidification of gas
• Provision of mild distending pressures3,4

It is not intended for use as a continuous positive airway pressure device, but rather as a high flow system to deliver conditioned (i.e. warmed and humidified) breathing gases.³

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Advantages

• More comfortable, with less risk of nasal trauma than with CPAP
• Less nursing time required as easier to use than CPAP, not dependent on seal
• Easier access to child than CPAP (and head box oxygen in infants)
• Easier parental interaction with their child

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Potential Disadvantages

• Unpredictable delivery pressures which are not measured (however the circuit pressure will always be significantly greater than pressure within the nasopharynx), 3 and there have been case reports of barotrauma. 5
• The Vapotherm unit needs wall oxygen to operate and cannot therefore be used to transfer patients on a normal trolley. A specially adapted trolley is available in LCH and can be obtained through Theatres or PICU should transfer be required.
• The Vapotherm unit has very limited battery and so should not be used in situations where power supply is unreliable.
• Due to the above limitations the patient needs to be in a room with oxygen and it can make interventions such as radiological investigations challenging.
• Standard nebulisers should not be used at the same time as HFNCT as it will prevent drug delivery. A device called an Aerogen nebuliser is required to enable drug delivery with HFNCT.
• Vapotherm cannot be used as an oxygen home delivery device as it is driven by oxygen. Airvo is driven by air so can be used at home. However, it uses cylinder or concentrator oxygen and so maximal oxygen delivery is limited.

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Set up

• HFNCT is applied to children via nasal cannulae, and is attached to a continuous flow of warm, humidified air and oxygen.
• It is intended as an open system, which allows for flushing of nasopharyngeal dead space.
• Select appropriate sized nasal cannula for that child. These must not occlude more than 50% of the child’s nostrils
• The mouth must not be held closed
• Select appropriate circuit
• There are 2 circuits available for HFNCT:
• High flow circuit can deliver 5-40L flow
• Low flow circuit can deliver 1-8L flow
• Infant and Intermediate Infant cannulae can only be used with the low flow circuit which can be sourced from NICU or PICU.
• Select the initial flow rate using the table below (higher flow rates may be used in babies younger than 2 months of age following PICU advice).
• Stop feeds initially (See Fluid Management below)
• See equipment and personnel requirements below

Nasogastric tubes:

• Insert if required for feeding
• Observe the child for gastric distension and pass an NG tube if it occurs. Leave on free drainage
• Please use the LHP for NG feeding (insert link here)

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Management

Start with FiO₂ 0.6 (60%) and the starting flow rate – weight related. (See table below).
Set target SpO₂ for child (normally 92 -95%) may need to be lower in children with chronic lung disease or congenital heart disease.

Ensure nares are not occluded by more than 50%. They cannula can be sat below the nostrils.

Weight	Minimum Flow Rates	Starting Flow	Maximum Flow	Equipment
Less than 3kg	5	6	8*	Paediatric Small Cannula (infant or intermediate cannula can be used) Low flow circuit
Greater than or equal to 3kgs but less than 4kgs	5	8	12	Paediatric Small Cannula High flow circuit
Greater than or equal to 4kgs but less than 8kgs	8	10	15	Paediatric small cannula High flow circuit
Greater than or equal to 8kgs but less than 12kgs	10	15	20	Paediatric small cannula High flow circuit
Greater than or equal to 12kgs but less than 20kgs	12	20	25	Paediatric/Adult small cannula High Flow Circuit
Greater than or equal to 20kgs but less than 30kgs	16	25	40	Paediatric/Adult small cannula High Flow Circuit
Greater than or equal to 30kgs	20	30	40	Adult small cannula High Flow Circuit

*For PICU review

Blood gases

• Check a capillary gas before starting HFNCT
• If pH less than 7.20 – consider if invasive ventilation/ PICU admission is required
• pH 7.20 – 7.25 – start HFNCT. Observe closely. Repeat the gas within 1 hour and contact the on duty Consultant with the result
• pH more than 7.25 and clinically improving on HFNCT – no need to repeat gas unless there is a change in the patient’s condition.

Supportive Care

• Stop feeds initially; Start 80% maintenance IV fluids as per the fluids guideline
• Consider prone positioning
• Consider chloral hydrate 25mg/kg (max 1 gram four times a day), initially 6 hourly, in unsettled babies as chloral does not cause apnoeas in the majority of patients. Only use in children with normal or improving blood gases.
• If the child is irritable then consider other causes e.g. hypoxia, hypercapnia, meningitis.
• Do not administer chloral hydrate in small babies with apnoeas/ those with poor muscle tone or those with any other contra-indication to Chloral hydrate
• Once stable/improving:
• Consider nasogastric feeds after 4 hours of therapy if the patient is stable
• Oral feeds can be considered in patients who have mild - moderate respiratory distress and are improving after discussion with the consultant.

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Monitoring

• Continuous HR and SpO₂ monitoring
• Half hourly recording of RR, HR, SpO₂, PAWS for the first 2 hours, with 4 hourly temperature, BP and AVPU score
• 4 hourly observations once stable/improving
• Fluid balance
• Daily U&E if on IV fluids

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Assessment (see flowchart)

If SpO₂ more than 95% or prescribed target range

• Reduce FiO₂ in 10% increments as tolerated until SpO₂ in target range or greater than 95%. (Note once FiO₂ is 40% (0.4) then consider reducing flow)
• Review FiO₂ with every set of observations at least (i.e. every 4 hours or more frequently if possible) and reduce accordingly.
• If following reduction in FiO₂ to 40%, SpO₂ remains more than target range or greater than 95% and clinical observations and PAWS are stable after at least 2 hours of HFNCT, reduce flow by 2 litres per minute increments as tolerated, until SpO₂ is in target range. Consider weaning at every set of observations.
• If SpO₂ remains more than target range or greater than 95% and flow rate has reached minimum weight-appropriate thresholds (see table), the child should have a trial off HFNCT on low flow oxygen (unless it was started for apnoeas or airway obstruction).
• If target saturations are not maintained after flow or FiO₂ are reduced then go back to previous settings.

Children should be weaned from HFNCT to other modes of oxygen therapy as soon as safely possible to ensure a supply of machines for other children who need them.

If SpO₂ less than 92% or below prescribed target range

• Temporarily increase FiO₂ to 80% (0.8) and increase the flow by increments of 2 litres/minute up to the maximum (see table).
• Urgent medical review
• If SpO₂ is still less than 92%, increase FiO₂ to 1 (100%)
• Urgent review of ABC and intervention as necessary
• Check circuit and the position of the cannula
• Exclude causes for failure including: nasal obstruction, pneumothorax, gastric distension leading to diaphragmatic splinting
• If the situation is not resolved, discuss with consultant and call PICU for referral.
• Some patients may be managed with high settings on a general ward with PICU supervision if duty paediatric consultant agrees.

Once condition stabilizes wean FiO₂ as tolerated.

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Success of treatment can be gauged by:

• Reduction in frequency or severity of apnoea
• Reduction in oxygen requirement
• Reduction in heart rate and respiratory rate within the first hour (but beware of fatigue!)
• Improvement in respiratory acidosis
• Reduction in work of breathing

Failure of treatment can be gauged by:

• Increasing oxygen requirement
• Unchanged / rising heart rate and respiratory rate
• Failure to improve respiratory acidosis (pH <7.2)
• An unchanged or increased work of breathing
• SpO₂ less than 92% at FiO₂ more than 60% (0.6) and maximal weight-appropriate flow rate
• Fatigue (falling respiratory rate with increasing heart rate; apnoeas; bradycardias; desaturations)

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If HFNCT is failing:

(pH less than 7.2, unable to maintain saturations in target range or increase in work of breathing):

• Urgent review of ABC and intervention as necessary. Consider calling 2222.
• Check, equipment, circuit and nasal cannulae position
• Consider repeat chest X-ray [Please link to CXR guidelines]
• Consider complications:
• Barotrauma; pneumothorax or subcutaneous emphysema
• Sudden deterioration requiring immediate ventilation
• Aspiration
• Gastric distension and diaphragmatic splinting
• Obstruction or irritation due to improper sizing of nasal cannulae
• Review diagnosis, consider:
• Nasal obstruction
• Lung collapse/secretions (consider physiotherapy)
• Pneumothorax
• Gastric distension
• Sepsis
• Metabolic
• Cardiac causes
• Undiagnosed neuromuscular disorder
• Consultant Paediatrician review
• PICU referral for further management
• Consider calling 2222 for medical emergency

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Discontinuation of HFNCT

• Need for IPPV
• Intractable gastric distension and diaphragmatic splinting
• Improvement, therefore able to wean
• If no progress by day 3 (48 - 72hours):
• Discuss with Consultant
• Review diagnosis / co-morbidity
• Consider other therapies

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Equipment and personnel requirements

• Commercially available nasal prongs
• Continuous flow air & oxygen gas source
• HFNCT delivery device
• Continuous pulse oximetry, with audible alarm settings
• Suction source, suction regulator, and suction catheters
• Resuscitation apparatus and masks of appropriate size

HFNCT can be used in Paediatric units where:

• Nursing staffing levels are adequate to ensure initial 1 nurse to 2 patient ratio until the patient is stable.
• Nursing staff have received training and are competent to care for patients with HFNCT
• Adequate medical staff cover exists to ensure frequent review of patients on HFNCT

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Transfer of children on HFNCT from PICU to ward

When the decision has been made that a child is stable on HFNCT and well enough for discharge from PICU, then transfer to another ward within the hospital should be possible. The child will require respiratory support with PEEP for transfer, or on the adapted trolley which has Vapotherm. The trolley is found either in L51 or C Floor theatres, recovery ward. A minimum of Nurse trained to use the transport trolley and an APLS trained Doctor or ANP escort is necessary with appropriate PPE.
Once a child has arrived on the ward, the PICU Nurse and Doctor will stay with the child until HFNCT has re-commenced and the ward staff are happy with the child’s clinical condition.

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Transfer of children on HFNCT between children’s wards

Children on moderate flows and in less than 50% oxygen may be moved between wards temporarily off the Vapotherm if tolerated. Patients made distressed with mask can be transferred on nasal cannula with a suction control unit adaptor to the vapotherm cannula and some oxygen tubing. Children who need more support will need a medical escort who is capable of providing bag mask ventilation including PEEP or on the adapted trolley as above.

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Complex patients

• Patients who have underlying respiratory or neuromuscular comorbidity may not wean easily from high flow. These patients should be discussed with a respiratory consultant.
• It is unreasonable to expect a child with chronic lung disease who requires oxygen at home to be weaned to less than 40% before going on to wall oxygen. It is therefore more important to wean the flow, as high flows cannot be used at home.
• The smaller the child the greater the effect of PEEP, and so will be more sensitive to flow. Large children/adolescents will be less responsive to flow rates and will require higher flow rates. See appendix and references for more physiological information.
• Therefore for chronic lung disease children, we should reduce flow but may need to tolerate higher oxygen requirements (eg 40%) when switching to low flow.
• Patients with neuromuscular problems may be receiving an unmeasurable benefit from the PEEP effect of HFNCT. These patients often benefit from NIV, if appropriate, rather than HFNCT.
• If a child cannot be weaned from HFNCT after 2 weeks, the patient should be discussed with respiratory team regarding further management and investigation.

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Top Tips for Vapotherm use

• A green light means the machine is running, an orange light means the machine is in standby. It may be necessary when you first set up, to press the run button twice, to ensure the machine starts.
• Ensure that when connecting the delivery tube to the disposable water path that it is FULLY inserted i.e. both latches must click shut to prevent leaking.
• Clamp the tube below the spike to the water bag prior to assembly. When changing the water bag when the unit is in use, there is no need to stop the machine. Just clamp the tube to the bag and switch it using non touch technique and then unclamp. (Clean the spike with 70-90% isopropyl alcohol wipe in both instances as suggested by manufacturer)
• The disposable water circuit can hold approximately 200 mls of water so may take a few minutes to fully fill initially.
• Wait until the desired temperature set (usually 37 ^oC) is reached before placing the nasal cannula on the end of the patient delivery tube. (The flashing LED becomes steady to indicate that the set temperature is reached). This allows purging of condensation out of the system. It may take up to 2 minutes to reach the set temperature.
• See suggested cannula sizes in table above, but ensure no more than 50% of nares is occluded. (If cannula are too large you can try to tape them slightly lower down face so that the prongs are sitting just below the nares.)
• If you are unable to change the settings with the dial, check that the tubes connecting to the gases are inserted correctly (e.g. if the air is not connected properly, the display will not change from 100%, and similar if O₂ not connected, it will say 21%)
• The Vapotherm machine can be put into stand-by, but there is no off/on switch. To switch off completely you must disconnect from the power supply.
• If there is a problem with the machine that you can’t seem to fix, then turning the machine off at the mains, by unplugging it until it powers off, for a minute or two and then restarting it may work! During this period the gas supply does not need to be disconnected.
• Have a bag and mask in the room while the child is on Vapotherm in case of any machine malfunction or need for urgent moving of the patient. (e.g. in the event of fire)
• If changing the circuit for any reason, assemble the circuit prior to disconnecting the machine from the patient. (The instruction manual will tell you to take the old circuit out first.)
• Clamp the water supply when the machine is in standby mode for any length of time. If you don’t, this can damage the machine and may result in it needing changing. (Circuits cost £350 per box of 5!)
• The circuits have a life of 30 days and must be replaced if still on the patient. Label the circuit with the assembly date and document in care plan.
• Only setup a Vapotherm unit if definitely being used, not “just in case.”
• If a patient is disconnected from the Vapotherm, then leave it running with the flow at 5l/min and FiO₂ set at 21% (air). If you turn the machine off completely, this will reset all the settings and the patient will need a new circuit.
• If the machine is switched off completely to trial the patient off Vapotherm, then the circuit must be changed after 12 hours. (It doesn’t need changing if the unit is left running therefore advisable to leave switched on during the trial off)
• Keep plugged in at all times (when not in use) as this ensures the machine is at full charge. Full charge takes 2 hours.
• The oxygen sensor described in the instruction manual will have already been fitted by medical physics.
• If you press the mute button when no alarms are sounding, this puts the display into night mode (the display goes from bright to dim).