Humidified High Flow Nasal Cannulae (HHFNC) Delivered by - Precision Flow (Vapotherm), Optiflow (Fisher & Paykel) or Fabian (Inspiration Medical)
This guideline is applicable to all medical and nursing staff caring for babies in neonatal intensive care units in West of Scotland neonatal services. All staff using these devices must ensure they have received instruction in the safe use of these devices.
Humidified High-flow nasal cannulae (HHFNC) are small, tapered cannulae that are used to deliver heated, humidified high-flow air and blended oxygen. HFNC may deliver positive end expiratory pressure. They are usually less than 1cm long and should occlude less than 50% of the area of nares 1. Flow rates used are >1L/min.
The use of HHFNC in the UK and around the world in neonatal units is high 2,3. It is common in both term and preterm infants 3,4..
HHFNC are being used as an alternative to CPAP, weaning from CPAP, for apnoea of prematurity and post extubation 2,5,7. Reported advantages of HHFNC over CPAP are: less trauma to the nares, simple application, easier to care for and access the baby, including for skin-to-skin and feeding 1,2,3,6.
Reported benefits include a reduction in both ventilation days and re-intubations 5. As it is non-invasive, HHFNC also helps to reduce ventilator-associated pneumonia and other lung injuries 5. HHFNC reduce the discomfort, mucosal damage and drying of secretions seen with non-humidified gases 3.
Flows used vary from 1-6L/min, up to 8L/min max. Some units report starting around 5L/min and adjust accordingly. It is recommended that small calibre cannulae are used (obstructing less than 50% of nares) to allow for leak around the nares and thus reduce risk of pressure build-up in the airways 3. The level of pressure generated in each individual is variable and not fully predictable 3
Consider HHFNC when CPAP 4-6 cmH20 and oxygen requirements <0.4
Change to low flow pernasal oxygen if HHFNC <2-3L and Fi02 <0.3
- Vapotherm /Fabian - The same cannulae are compatible with the Vapotherm and Fabian HHFNC devices. Company though recommends to use ONLY Vapotherm cannulae with Precision Flow devices.
The following sizes are a guide but the diameter of nares vary.
Weight | Cannula Type | Outer diameter |
< 1.4 Kg | Premature | 0.14 cm |
1.4 to 2.6 Kg | Neonatal | 0.19 cm |
> 2.6 Kg | Infant | 0.27 cam |
From Vapotherm GUIDE (19):
- Optiflow - The following is a guide for Optiflow cannulae with Wigglepad. The cannulae can be used for up to 7 days as per manufacturer. The Wigglepads may be changed independently of the cannulae. The following link contains a demonstration of fitting the cannulae: https://www.fphcare.co.uk/products/optiflow-junior-nasal-cannula
Nasal Cannulae | Item Code | Approx Weight | Wigglepad code |
Premature Size | OPT 312 | Up to 3kg | OPT010 |
Neonatal Size | OPT 314 | 2-8kg | OPT012 |
Consider pneumothorax if baby develops increased respiratory distress and oxygen requirement
Weaning strategies may vary from individual to individual and the following recommendations are a guide only. Weaning strategies fall into two main groups: firstly, those babies with acute respiratory illnesses who may be expected to wean over a shorter timescales and; secondly, infants with chronic lung disease in whom the requirement for respiratory support and supplementary oxygen may be more prolonged.
More mature babies recovering from acute respiratory illness
NB – At the discretion of a senior clinician, HHFNC therapy may be discontinued more rapidly than described above if the symptoms of respiratory distress have resolved
Preterm infants with developing chronic lung disease
Babies developing Chronic Lung Disease and higher FiO2 requirements may be prone to atelectasis or apnoeas if the flow is reduced prematurely. They may benefit from a more prolonged period of high flow until their oxygen requirements start to decline with better growth and maturity. Once weaning commences they may benefit from slower rates of weaning than those described above e.g 48hly
After any reduction in the high flow therapy, which results in an increase in the work of breathing or increase in Fi02 by >0.1, consider going back to previous settings
Estimated Inspired Oxygen Concentration (%) when using nasal cannulae
Flow |
Weight |
|||||||
0.7 |
1.0 |
1.25 |
1.5 |
2 |
2.5 |
3 |
3.5 |
|
0.01 |
22 |
22 |
22 |
22 |
22 |
21 |
21 |
21 |
0.03 |
24 |
23 |
23 |
23 |
23 |
22 |
22 |
22 |
0.06 |
28 |
26 |
25 |
24 |
23 |
23 |
23 |
23 |
0.125 |
35 |
30 |
29 |
27 |
26 |
24 |
24 |
24 |
0.15 |
38 |
33 |
30 |
29 |
27 |
26 |
25 |
24 |
0.25 |
49 |
41 |
37 |
34 |
31 |
29 |
27 |
26 |
0.5 |
77 |
60 |
53 |
47 |
41 |
37 |
34 |
31 |
0.75 |
100 |
80 |
68 |
60 |
51 |
45 |
41 |
36 |
1.0 |
100 |
100 |
84 |
74 |
60 |
53 |
47 |
41 |
1.25 |
100 |
100 |
100 |
87 |
71 |
60 |
54 |
47 |
1.5 |
100 |
100 |
100 |
100 |
77 |
68 |
60 |
51 |
It is possible to deliver nebulized medications in patients receiving HHFNC via Vapotherm Precision Flow. An interface consists of 3 essential parts: Aeroneb ® Pro-X controller, Aeroneb Solo nebulizer (single patient use) and Vapotherm Aerosol Adapter (single use).
Data on efficiency is very limited. It is claimed that in vitro testing demonstrated the inhaled efficiency ranging form 4.5-9.1% at flows 1-8L/min. Another study showed the inspired dose (percent of nominal dose) of 0.6%, 0.6%, and 0.5% for the infant cannula at 3, 5, and 8 L/min, respectively. (Influences of cannula size and flow rate on aerosol drug delivery through the Vapotherm humidified high-flow nasal cannula system Pediatr Crit Care Med. 2013 Jun;14(5):e250-6.)
The use of inhaled nitric oxide (iNO) in combination with HHFNC is becoming topical and of interest. In newborn infants presenting with hypoxic respiratory failure with hypoxemia without hypercarbia, respiratory distress, or evidence of parenchymal lung disease, iNO in combination with HHFNC may reduce exposure to high levels of inspired oxygen and avoid mechanical ventilation. Randomized and double blinded trials evaluating this therapeutic modality are warranted.
The evidence for inhaled nitric oxide via nasal cannula is limited but neonatal case reports 13 exist, detailing the successful use of inhaled nitric oxide with HHFNC in infants with severe hypoxia and pulmonary hypertension, avoiding the need for mechanical ventilation. It has been postulated that term neonates with idiopathic persistent pulmonary hypertension (PPHN) and adequate respiratory drive without any parenchymal lung disease may benefit from non-invasive methods of iNO delivery to treat the condition without the complications associated with mechanical ventilation. Infants with PPHN suffer from long-term morbidity such as chronic lung disease, neurological morbidity, and sensorineural deafness. Some of these long-term consequences may be secondary to mechanical ventilation. Barotrauma and volutrauma are often associated with prolonged mechanical ventilation in newborn infants. The case of a young infant with primary pulmonary hypertension, who was treated with nasal nitric oxide for several weeks until approved for enrollment into a long-term intravenous prostacyclin therapy program has been reported 13. iNO via a nasopharyngeal tube was used in a 145-day-old infant with a severely hypoplastic lung and end-stage pulmonary hypertension, in whom clinical improvement was maintained for 7 days 13. Premature infants received iNO therapy through continuous positive airway pressure and nasal cannula in the weaning phase in the Nitric Oxide to Prevent Chronic Lung Disease (NO-CLD) trial for prevention of bronchopulmonary dysplasia without any negative consequences 13. Non- invasive delivery of iNO therapy has also been reported for late pulmonary hypertension in newborn infants with congenital diaphragmatic hernia 13. In a case series, patients who had suprasystemic pulmonary hypertension when iNO was discontinued before extubation were treated with iNO through a nasal cannula 13. A large paediatric cardiac intensive care centre in America reports having used inhaled nitric oxide with HHFNC for two years successfully on their patients with pulmonary hypertension and cardiac dysfunction, either avoiding ventilation or facilitating weaning from ventilation and aiding post-op recovery. They have found it to be safe and efficient 12. Furthermore case reports also exist in adult practice detailing the successful use of inhaled nitric oxide and HHFNC is patients with severe pulmonary hypertension and cardiac dysfunction that has improved
oxygenation and haemodynamics thus either avoiding ventilation or allowing weaning from mechanical ventilation 14,15.
Vapotherm offers a Precision Flow Disposable Patient Circuit (DPC) designed for non-invasive nitric oxide delivery via high flow nasal cannula 16. In collaboration with Ikaria®, Vapotherm developed a DPC that is compatible with the INOmax DS & DSIR systems (PF-NODPC-LOW, Nitric Oxide Disposable patient Circuit Low).
It should be noted that increasing the NO setting will increase the NO flow rate, which may cause a bolus of NO2 to be delivered to the patient. This is due to residual NO2 build-up within the INOvent system at very low flow rates. If the NO setting is increased by more than 5ppm in a 5 minute period, a quick purge of the INOvent system should be performed. To perform a quick purge, disconnect the cannula from the sample tee and increase the oxygen flow to 15L/min at the desired NO setting for 1 minute then reconnect at the desired O2 flow setting 17.
HHFNC systems appears to have similar effectiveness to nCPAP in improving clinical parameters in infants, but at flow rates above 2 L/min. HHFNC are thought to be more comfortable for preterm infants and to cause less nasal septal trauma than NCPAP. From the studies that have reported adverse outcomes, none found a significant increase or difference between HHFNC use vs CPAP use in risk of NEC, pneumothorax, BPD, IVH, ROP, days in hospital or on O2, sepsis or death 2. The use of HHFNC as a primary therapy from birth requires further research.
It is recommend only heated, humidified HFNC systems with flow rates >2 litres/min, up to the maximum flow rate recommended by the manufacturer are used 2. Prongs should not completely occlude the nares. Manufacturers recommend that the prong outer diameter occupy <50% of the nares internal diameter 9. When setting the flow rate, the infant’s weight must be considered as pressure generation increases with decreasing infant size 2. A starting flow rate of 4–6 L/min in newly born preterm infants appears to be a reasonable balance between efficacy and safety based upon the available evidence and current clinical practices.
The majority of units report weaning HHFNC by a gradual reduction in flow rate. Yoder et al 9 recommended increasing the flow rate in 1 L/min increments if (1) FiO2 increased by 0.1 above the starting FiO2, (2) pCO2 increased by 10 mm Hg (equivalent to 1.3kPa) above the baseline value, (3) increased distress or recession noted, or (4) decreased lung expansion noted on CXR. They recommended decreasing the flow rate by 0.5- to 1.0 L/min increments if all of the following were sustained for at least a 4-hour period: (1) FIO2 <0.3 and oxygen saturation within ordered parameters, (2) pCO2 was maintained within ordered parameters, (3) no signs of significant distress were noted, and (4) lung expansion was deemed adequate, if CXR was obtained.
Postulated mechanisms of action
Proposed mechanisms of action include elimination of dead space, reduction in work of breathing, improvement in lung compliance and delivering some degree of CPAP 2, 3.
This is thought to be the primary mechanism, reducing the overall dead space and contributing to more effective CO2 elimination. Studies of comparable tracheal gas insufflation demonstrated reduced tidal volume and immediate effect on respiratory rate.
HHFNC reduction of the dead space also has an effect on oxygenation – due to reduced entrainment of room air, the airway oxygen concentration is higher when compared to use of non-rebreathing masks and in patients with mouth opened.
HHFNC matches/exceeds the patient’s inspiratory flow and eliminates increasing nasopharyngeal resistance caused by its inspiratory distendability.
Breathing cold, non-humidified gas for only five minutes decreases lung compliance and conductance. Cold, dry gas elicits bronchoconstriction (nasal mucosa receptors, muscarinic effect).
The nasopharyngeal cavity provides effective warming and humidification to inspiratory gas but this requires a significant amount of energy. Babies on HHFNC have been shown to gain weight quicker than on CPAP.
High gas flow generates positive airway pressure (although very unreliably and depending on factors like body weight, mouth leaks, etc). It appears that larger babies require higher gas flow in order to maintain effective dead space washout and support inspiratory effort.
Potential concerns
The majority of units use HHFNC in babies of all weights and gestational age. Whilst this modality is popular, the limited evidence available does cause concern amongst clinicians about the exact pressures being delivered to these infant’s lungs and potential for overdistension and injury, particularly infants <1000g 3,4. Pharyngeal pressure delivered by HHFNC increases proportionally, in a linear fashion, when flow is increased 2,4. Pressure delivered to the baby is affected by infant’s weight (higher pressure with lower weights), size/calibre of the cannulae, proportion of nares occluded and if the mouth is open or not 1-4,6. According to more recent studies, pressures generated by HHFNC were similar to or less than those commonly set with nCPAP3. Flow rates of 8L/min have been shown to provide a distending pressure of 4-5 cmH20 7.The Vapotherm unit used in infants has a built -in pressure relief valve, will only deliver a maximal flow of 8L/min and will alarm if high pressure is detected in the circuit 4.
There was in the past a concern regarding potential for infections with Ralstonia spp and gram negative bacteria 1,2,3 which caused a recall of Vapotherm units in 2005. The Vapotherm infection control measures have since become more stringent. Vapotherm’s vapour transfer cartridges now have pores of 0.01 micrometers which are considerably smaller than bacteria (0.2-5micrometers) and thus form a barrier for these pathogens 5.
There has been a case report of a preterm infant who was receiving HHFNC at 2 L/min (device not reported) and concomitantly was found to have subcutaneous scalp emphysema and pneumo-orbitus, which resolved after discontinuation of the HHFNC 2,3. The authors noted that these complications may have been a result of nasopharyngeal trauma rather than the mode of support.
Setup Using Disposable Patient Circuit (DPC)
Refer to Precision Flow Instruction Manual- Setup should be performed by trained personnel only:
Insert disposable circuit into Vapotherm by sliding door forward, holding unit by handle slide in downwards motion until the unit is firmly in place.
When set temperature reached, attach cannula to delivery tube, then to baby.
Notes:
When discontinuing Vapotherm therapy the unit may be left on standby in case HHFNC needs to be resumed. If left standing by the cot side the Vapotherm should be set at these settings :
Flow: 1 L/min,
Temp 33°C,
FiO2 21%
This will keep circuit operational up to 30 days from first use.
Shutting down
Changing disposable circuit
Changing sterile water
Cleaning
*The vapotherm does not have an on/off switch, when plugged in to wall the battery is charged (15 minutes battery life) and the unit is on Standby/Run.
The disposable patient circuit can be used up to 30 days on single patient.
Delivering nebulised medications via the Vapotherm
Nebulised medications may be given via the Vapotherm circuit using an Aerosol adaptor (Aerogen Aeroneb ®) - Figure 1.
In-vitro studies have demonstrated an inhaled dose efficiency of 4.5 – 9.1%
|
Parts required Aeroneb control module (Fig 1 – pole mounted) These are assembled as shown in Fig 2 & 3, The T- piece being inserted between the heated circuit and the nasal prongs. The medication is placed in the nebuliser chamber which must be kept upright, as shown, for the duration of the treatment (adapter at 45°). NB. The T-Piece should be removed between uses as water may condense in the t-piece causing water retention |
Figure 2 | Figure 3 |
Nitric Oxide may be delivered via vie Vapotherm Precision Flow. This requires the following parts
Refer to Optiflow Instruction Manual- Setup should be performed by trained personnel only:
Equipment needed:
Settings
Humidification – Select Non- invasive mode on FP850 Humidifier FiO2 – Use blender to select Oxygen concentration
Flow – Use flowmeter to select required flow between 1-8 L/min
Equipment needed:
Fabian HFO 4in1 ventilator OR Fabian therapy Evolution CPAP
Non-invasive breathing circuit – Fig 1 & 2 Humidifier
Fig 1 & 2 – Circuit for High flow – Note in fig 2 an adaptor is required between the breathing circuit and the cannulae due to the different internal diameter
Fig 3 – High Flow Screen on Fabian ventilator
Settings
Humidification – Select Non-invasive mode on FP850 Humidifier Ventilator setting – ‘O2 Therapy’
FiO2 – Select Oxygen concentration via interface shown and confirm by pressing the control knob Flow – Select required flow between 1-8 L/min
Pressures generated
Clinical effectiveness
Last reviewed: 10 July 2019
Next review: 30 April 2023
Author(s): Dr Tomasz Dygas – Consultant Neonatologist PRM; Dr Jennifer Mitchell- Consultant Neonatologist QEUH
Approved By: West of Scotland Managed Clinical Network for Neonatology