High Flow Nasal Cannula Therapy
T Townend Christchurch Hospital
Ra9onale
• Non-‐invasive respiratory support • Delivery of prescribed FiO2
– ↓air entrainment (dilu9on) • Humidifica9on (≥95%) • Comfortable nasal interface • Low-‐level CPAP
• Easier applica9on and beNer facial access than nasal CPAP
Mechanisms of ac9on
• Washout of nasopharyngeal deadspace • Reduced WOB
• Improved mechanics • Reduced metabolic expense • Distending pressure
Dysart et al, Respiratory Medicine 2009; 103:1400-‐1405
Applica9ons
• High O2 requirements or WOB • Need for humidifica9on (secre9ons) • Poor tolerance of mask
Paucity of evidence
• Cochrane review 2014 – To determine whether HFNC therapy is more effec9ve than other forms of non-‐invasive therapy in paediatric pa9ents who require respiratory support
– Content to 1st April 2013 – No study matched inclusion criteria
• Neonatal evidence not much beNer
Neonates • Most studies have focused on respiratory support during post-‐
extuba9on period in premature infants
• RCT of 432 infants 28-‐42 weeks gesta9on comparing nCPAP and HFNC – Primary therapy or post-‐extuba9on – Primary outcome: need for intuba9on within 72hrs of applied non-‐invasive
therapy
• No difference in: – Early failure HFNC vs nCPAP – Subsequent need for any intuba9on – Dura9on on oxygen – Rates of BPD
Bradley et al, Pediatrics 2013;131;e1482
of bronchopulmonary dysplasia (BPD)at 36 weeks’ gestational age for infantsborn at ,32 weeks’ gestation wassimilar between study groups, as wasthe proportion of infants dischargedfrom the hospital on oxygen (Table 4).
After study entry, several potentialadverse outcomes were closely mon-itored. As shown in Table 5, the over-all adverse event rate was similar
between infants randomly assignedto nCPAP compared with HHHFNC.Importantly, the rate of any form of airleak occurring on study mode sup-port was quite low and not differentbetween groups. There were also nodifferences in the occurrence of in-creased apnea or sepsis, frequency ofdelayed intubation, or time to full oralfeedings between study groups. The
only difference in measured adverseoutcomes was a small but statisticallysigni!cant higher rate for any nasaltrauma during nCPAP support (Table 5).
We compared infants successfullymanaged by either study mode withthose with early study failure to de-termine if there were identi!ablecharacteristics that might help to pre-dict early failure. We did not !nd anydifferences in prestudy characteristics(Table 6). Speci!cally, gestational age,birth weight, surfactant therapy, pre-study respiratory support mode, re-spiratory support pressure, and FIO2were similar for infants experiencingearly failure compared with thosesuccessfully managed by either nCPAPor HHHFNC.
Rates for early failure were not signif-icantly different between devices (P =.521): Fisher and Paykel (16 of 143;11%), Vapotherm (4 of 52; 8%), andHudson Comfort-Flo (3 of 17; 18%).Likert scale assessments from thebedside nurse and respiratory thera-pist related to ease of care and patientcomfort revealed no differences be-tween the 2 study modes.
DISCUSSION
In this multicenter randomized trialinvolving neonates $28 weeks’ gesta-tional age undergoing planned non-invasive respiratory support, we foundno signi!cant difference betweenHHHFNC and nCPAP with regard to theprimary outcome of intubation withinthe initial 72 hours of support. In ad-dition, we found no differences be-tween infants randomly assigned tonCPAP compared with HHHFNC forseveral respiratory outcomes, includ-ing duration of oxygen supplementation,diagnosis of BPD, or discharge fromthe hospital on oxygen. Despite con-cerns over unregulated/unmonitoredpressure delivery during HHHFNC sup-port, we found no differences in theoccurrence rate for any form of air
TABLE 2 Demographic Characteristics of Infants Randomly Assigned to nCPAP or HHHFNC
nCPAP (n = 220) HHHFNC (n = 212)
Gestational age, mean 6 SD, wk 33.2 6 3.2 33.5 6 3.6,32 wk, n (%) 75 (34) 75 (35)
Birth weight, mean 6 SD, g 2108 6 782 2201 6 816,2000 g, n (%) 111 (50) 100 (47)
Male, n (%) 137 (62) 137 (65)Antenatal steroids, n (%) 71 (32) 80 (38)Respiratory distress syndrome, n (%) 162 (74) 156 (74)Study start age, median (25%–75%), h 20 (7–54) 24 (8–62)Start age ,7 d, n (%) 201 (91) 194 (92)Prestudy support mode, n (%)Ventilator 145 (66) 146 (69)nCPAP 46 (21) 39 (18)Other (NC, hood O2, room air) 29 (13) 27 (13)
Prestudy surfactant, n (%) 129 (59) 142 (67)Prestudy nitric oxide, n (%) 18 (8) 13 (6)Prestudy caffeine, n (%) 66 (30) 58 (27)
P . .05 for all comparisons.
TABLE 3 Early Respiratory Failure in Infants Managed With nCPAP and in Those Managed WithHHHFNC
nCPAP (n = 220) HHHFNC (n = 212) OR (95% CI)a
Early failure, all 18 (8.2) 23 (10.8) 1.37 (0.71–2.61),32 weeks’ gestational age 5/75 (6.7) 3/75 (4.0) 0.58 (0.13–2.53)Prestudy ventilator 9/145 (6.2) 17/146 (11.6) 1.89 (0.86–4.63)Start age ,7 d 16/201 (8.0) 23/194 (11.9) 1.56 (0.80–3.04)
Data are shown as n (%). Data in rows 3–5 are also shown as number of failures/number of infants (%). CI, con!denceinterval; OR, odds ratio.a Unadjusted.
TABLE 4 Respiratory Support Outcomes Among Infants Randomly Assigned to nCPAP ComparedWith HHHFNC
nCPAP (n = 216) HHHFNC (n = 211) P
Days on study mode 2 (1–4) 4 (2–7) ,.001Delayed use of other study mode, n (%) 31 (14) 19 (9) .096Days ventilated 2 (1–4) 2 (1–5) .476Days any positive pressure support 4 (2–8) 6 (3–11) ,.001Days supplemental O2 8 (5–24) 10 (5–27) .357BPD,a n (%) 12/73 (16) 15/75 (20) .575Home oxygen, n (%) 38 (18) 40 (19) .698Age at discharge 25 (13–47) 25 (14–49) .756
Data are shown as medians (25%–75%) unless otherwise indicated.a Only surviving infants ,32 weeks’ gestational age at birth.
e1486 YODER et al at Canterbury Medical Library on August 13, 2014pediatrics.aappublications.orgDownloaded from
Bradley et al, Pediatrics 2013;131;e1482
leak. The outcome results from thisrelatively large randomized trial in-dicate that the use of HHHFNC, as de-scribed in this report, appears to be aseffective and as safe as nCPAP in thispopulation of infants.
The actual approach to “high-!ow”nasal cannula must be carefully con-sidered in evaluating all studies. Someinvestigators have described “high-!ow” in the presence of !ow limited to1 to 2 lpm and in the absence of a well-heated, humidi"ed gas source for !ow.
Flow limitation has been based on ear-lier studies from Locke et al5 andSreenan et al6 suggesting the potentialfor high, unregulated positive airwaypressure. Over the past decade, sys-tems have been designed to allowmuchhigher !ow rates (2–8 lpm for neonatesand up to 50 lpm in adults) accompa-nied by optimal heating (37°C) andhumidi"cation (100%) of the deliveredgas. We, and others, have de"ned thissystem of NC therapy as heated, hu-midi"ed high-!ow nasal cannula or
HHHFNC.19 Recent studies have reportedmuch lower airway pressures usingHHHFNC, both indirectly via pharyngealor esophageal pressure measurementand, in an animal model of neonatalrespiratory distress, directly via intra-tracheal pressure monitor.20–23 Theimportance of the NC interface in thepotential delivery of airway pressureshould not be minimized. In recentneonatal studies, external NC diame-ters were typically limited to ,3 mm.This size appears to be a critical di-mension for neonatal HHHFNC, becauseLocke et al5 demonstrated that highairway pressures were measurablewith a cannula diameter of 3 mm butnot when the cannula was 2 mm in di-ameter. All infants in our study weremanaged with NC having an externaldiameter of ,3 mm, with 95% mea-suring ,2.0 mm.
Several retrospective and observa-tional studies have been publishedsuggestingthatHHHFNCmaybeeffectiveand safe in managing preterm infantswith respiratory dysfunction.8,12–14 Itis important to differentiate "ndingsfrom these reports from those of otherinvestigations in which high-!ow nasalcannula has been applied with the useof inadequately heated/humidi"ed gasat signi"cantly lower !ow rates. Abdel-Hady et al24 reported that weaningfrom nCPAP to high-!ow NC limited to 2lpm was associated with longer dura-tion of oxygen and respiratory supportcompared with infants maintained onnCPAP until weaned directly to roomair. In their study, not only was NC !owrate limited but the gas conditioningmay have been inadequate. Campbellet al25 reported in 40 infants that “HF-CPAP” [high-!ow CPAP], administeredvia standard NC, was less effective atpreventing reintubation than nCPAP.There were limitations in NC !ow rate(range: 1.4–1.7 lpm) and gas condi-tioning similar to those in the Abdel-Hady et al study, and “HF-CPAP”
FIGURE 2Infants randomly assigned to nCPAP (black line) had signi"cantly shorter duration of study supportmode compared with infants randomly assigned to HHHFNC (gray line); P , .01. There were no sig-ni"cant differences between study groups for duration of ventilator support (dotted lines) or time towean to room air (dashed lines) in the 7 days after study entry. RA, room air.
TABLE 5 Occurrence Rates for Secondary Outcomes in the nCPAP Compared With the HHHFNCStudy Group
nCPAP (n = 220) HHHFNC (n = 212)
Any adverse event 46 (21) 52 (25)Air leak 5 (2) 1 (,1)Increased apnea 15 (7) 23 (11)Con"rmed sepsis 7 (3) 7 (3)Con"rmed NEC 4 (2) 2 (1)Reintubation, any 25 (11) 32 (15),72 hours 18 (8) 23 (11),7 days 21 (10) 23 (11)
No nasal trauma 180 (84) 187 (91)*Abdominal distention 17 (8) 21 (10)Days to full oral feedings, median (25%–75%) 17 (8–35) 18 (8–41)Death 4 (2) 1 (,1)
Data are shown as n (%) unless otherwise indicated. *P = .047. NEC, necrotizing enterocolitis.
ARTICLE
PEDIATRICS Volume 131, Number 5, May 2013 e1487 at Canterbury Medical Library on August 13, 2014pediatrics.aappublications.orgDownloaded from
Bradley et al, Pediatrics 2013;131;e1482
Paediatrics • Most studies have focused on infants with bronchioli9s • Efficacy of HFNC yet to be demonstrated in other paediatric condi9ons
• Retrospec9ve case-‐control study, Brisbane 2011 – Reduced intuba9on rates in infants with bronchioli9s when HFNC introduced in the PICU – No direct comparison with nasal CPAP – Clinical effects need to be reassessed at 60-‐90min as most improvement (in RR and HR)
will be seen in this 9me
• French study 2014, compared HFNC and nCPAP in bronchioli9s – No difference in LOS, oxygen requirement, RR, HR
Schibler et al. Intensive Care Medicine 2011; DOI 10.1007/s00134-‐2177-‐5 Metge et al. Eur J Pediatr (2014) 173;953-‐958
• HFNC use in PICU transports • Pre-‐HFNC 7% NIV 49% IV • Post-‐HFNC 33% HFNC 2% NIV 35% IV
Schlapbach et al. Intensive Care Medicine (2014) 40; 592-‐599
Physiological effect of HFNC
Pham et al. Pediatric Pulmonology 2014
Outside PICU? • Pilot study 2014, Mater Children’s, Ward seing • 61 infants
– <12m, bronchioli9s, oxygen requirement in ED – HFNC 2L/kg/min, FiO2 to keep sats >94%
• Control group low-‐flow nasal O2
• Responders iden9fied within 60min
• HFNC 4 9mes less likely to require PICU admission
Mayfield et al, Journal of Paediatrics and Child Health 50; (2014) 373-‐378
HFNC Distending Pressure • Pressure generated is inconsistent and unpredictable
• Affected by mouth opening and size of leak at nares
• Reported pressures range from 2-‐8 cmH2O
• Prospec9ve study 2013 • 21 infants <6m, RSV bronchioli9s • Flow ≥2L/kg/min achieved a clinically relevant mean pharyngeal pressure
≥4cmH2O – Associated with improved breathing paNern and rapid unloading of respiratory muscles
Milesi et al. Intensive Care Medicine 2013 39:1088-‐1094
• Study of 18 preterm infants NICU Melbourne – Median age 34/40 – Catheter 9p pressure transducer in nasopharynx
Wilkinson et al, Journal of Perinatology (2008) 28, 42–47
pressure in infants of a given weight and at a given flow rate(see above). There was some variability between infants in themeasured pharyngeal pressure, particularly at higher flow rates.Previous studies have measured oesophageal pressure and
demonstrated increases in proportion to flow rate when flows ofmore than 1 l min!1 were delivered to infants.2,3 However, there issome difference between the pressures obtained during this studyand those previously measured (Table 1). Locke et al.2 measuredchanges in oesophageal pressure from baseline in preterm infants.They showed large increases in oesophageal pressure atcomparatively low flow rates (1 to 2 l min!1), but only in a subsetof infants in whom larger diameter cannulae were used.3 They did
not assess the relationship between infant weight and oesophagealpressure. Sreenan et al.3 titrated the flow rate of nasal cannulae toachieve the same oesophageal pressure as that measured duringnasal CPAP set at 6 cm H2O. In that study the mean change frombaseline in oesophageal pressure was 4.5 cm H2O, and the flow raterequired was estimated as (0.92" 0.68 wt).3
Considerably lower pressures were measured in a more recentstudy in 18 preterm infants, where flow rates of 3 to 5 l min!1 ledto oesophageal pressures of less than 2 cm H2O.
9 Interestingly inthe same study, the oesophageal pressure in infants receiving nasalCPAP set at 6 cm H2O was only 1.8 cm H2O.
9
Figure 1 Measured pharyngeal pressure at variable flow rate in one infant. Compressed recording in one infant (1.398 kg) over 2 min. The rhythmical fluctuations inpharyngeal pressure are related to infant breathing. During this recording flow was increased from 2 to 4 to 6 l min!1.
Figure 2 Mean pharyngeal pressure (with 95% confidence intervals) recorded atflow rates 2 to 8 l min!1.
Figure 3 Pharyngeal pressure vs flow per kg. Linear regression with 95%confidence interval. Predicted pressure (cm water)# 0.7" 1.1$ F (F# flow perweight in l min!1 kg!1).
Pharyngeal pressure with high-flow NCDJ Wilkinson et al
44
Journal of Perinatology
• Study of 18 preterm infants NICU Melbourne – Median age 34/40 – Catheter 9p pressure transducer in nasopharynx
• Mouth leak may be less important than nasal leak
Wilkinson et al, Journal of Perinatology (2008) 28, 42–47
Contraindica9ons
• Maxillofacial trauma • Choanal atresia or nasal obstruc9on • Suspected base of skull fracture • Risk of air leak
• Noise? • Too sick for HFNC?
Complica9ons
• Case series published 2013, all with serious air leak – 2m RSV bronchioli9s – 16y cerebral palsy, post-‐surgical/extuba9on – 22m NAI, post-‐extuba9on
• Use is “off label”
Hegde and Prodhan, Pediatrics 2013;131;e939
Flow rate
• 2L/kg/min • Children >20kg 40-‐50L/min • Adult 40-‐60L/min
2L/kg/min?
Schmalisch et al. BMC Pediatrics 2005, 5:36
!"#$%&'()*+(,-!"##$%!!&'( )**+&,,---./01234536*789.512,:;<:=";':,$,'(
>8?3!(!1@!:#./)0&$1234&+$15*$65+$,(*)*(51$/2+/5-&-7
the body weight and in the widely used TB-parameterstPTEF/tE and VPTEF/VT.
The discriminative power of TB parameters between bothpatients groups was investigated by using the ROC analy-sis (Fig. 3). In Table 4 the area under the ROC curve(AUC), the optimal cut-off value for each significantly dif-
ferent TB parameter and the resulting sensitivity and spe-cificity were presented. For the best discriminatingparameters tI and RR the area under the curve was not sta-tistically different. This means that there will not be a largedifference in the diagnostic value of tI compared to themore commonly used parameter RR. The sensitivity ofboth parameters using the optimal cutoff value was the
Table 3: Comparison of TB parameters between both patient groups ordered according to the p-value of the ANOVA (Presented are group means ± SD, statistically significant p-values after Bonferroni correction (p < 0.0028) are printed in bold)
Parameter Healthy neonates (n = 48) CLD infants (n = 48) p-value CLD
tI(s) 0.65 ± 0.14 0.45 ± 0.11 p < 0.0001RR (min-1) 39.2 ± 8.6 55.4 ± 14.2 p < 0.0001(PTIF+PTEF)/VT (s-1) 0.27 ± 0.06 0.37 ± 0.09 p < 0.0001tE (s) 0.98 ± 0.24 0.72 ± 0.22 p < 0.0001VT/tI(mL·s-1·kg-1) 8.9 ± 2.2 11.6 ± 2.8 p < 0.0001V'E(mL·min-1·kg-1) 215 ± 51.7 276 ± 76.8 p < 0.0001TIF 50 (L·min-1·kg-1) 0.75 ± 0.21 0.98 ± 0.26 p < 0.0001PTIF (L·min-1·kg-1) 0.83 ± 0.20 1.05 ± 0.28 p < 0.0001PTEF/tPTEF (L·s-2·kg-1) 2.90 ± 1.68 5.25 ± 3.66 p = 0.0001PTEF (L·min-1·kg-1) 0.64 ± 0.19 0.82 ± 0.29 p = 0.0006tptef (s)*) 0.24 ± 0.09 0.18 ± 0.11 p = 0.001TEF75 (L·min-1·kg-1) 0.60 ± 0.20 0.76 ± 0.29 p = 0.003TEF50 (L·min-1·kg-1) 0.52 ± 0.17 0.66 ± 0.25 p = 0.003TEF25 (L·min-1·kg-1) 0.38 ± 0.11 0.46 ± 0.16 p = 0.006Vptef (mL/kg)*) 1.68 ± 0.52 1.37 ± 0.44 p = 0.006VT (mL·kg-1) 5.57 ± 1.06 5.15 ± 1.35 p = 0.09VPTEF/VT(%)*) 29.4 ± 6.6% 27.2 ± 6.1% p = 0.13tPTEF/tE (%)*) 25.8 ± 9.7% 23.2 ± 7.8% p = 0.20
*)Loops with flow limitations, grunting or other deformations were excluded from the evaluation (6 controls, 8 CLD infants)Abbreviations: tI,E-inspiratory, expiratory time, RR-respiratory rate, PTIF, PTEF-peak tidal inspiratory and expiratory flow, VT-tidal volume, TIF 50-tidal inspiratory flow when 50% of VT is inspired, TEF 75, TEF 50, TEF 25-expiratory flow when 75%, 50% and 25% of tidal volume remains in the lung, V'E-minute ventilation, tPTEF,VPTEF-time and volume to peak tidal expiratory flow
Table 4: ROC analysis of commonly used TB parameters between CLD infants and healthy controls. If the 95% confidence interval (95% CI) of the area under the normalized ROC curve (AUC) include the 0.5 value (no discrimination) than there is no evidence that the TB parameters has the ability to distinguish between the two groups
Parameter AUC with 95%CI Optimal cut-off point Sensitivity Specificity
tI 0.879 (0.808 to 0.950) 0.48 s 70.8% 91.7%RR 0.842 (0.754 to 0.909) 49.1 min-1 70.8% 89.6%VT/tI 0.809 (0.721 to 0.896) 11.1 mL·s-1·kg-1 58.3% 89.6%V'E 0.776 (0.682 to 0.869) 250 mL·min-1·kg-1 64.6% 85.4%PTIF 0.747 (0.649 to 0.845) 0.95 L·min-1·kg-1 62.5% 79.2%PTEF/tPTEF 0.688 (0.582 to 0.794) 4.57 L·s-2·kg-1 52.8% 87.5%PTEF 0.673 (0.566 to 0.780) 0.79 L·min-1·kg-1 45.8% 83.3%TEF25 0.653 (0.544 to 0.762) 0.67 L·min-1·kg-1 43.7% 87.5%VT 0.610 (0.497 to 0.722) - - -VPTEF/VT 0.565 (0.450 – 0.620) - - -tPTEF/tE (%) .552 (0.437 – 0.670) - - -
(Abbreviation see Table 3)
• 2L/kg/min ensures flow higher than peak inspiratory flow rate (SSH)
• Alterna9ves: – 2L/kg/min up to 10kg, plus 0.5L/kg/min for each kg above 10kg to max 50L/min (RCH)
– Flow (L/min) = maintenance fluid rate (ml/hr) / 2
Op9flow Junior
Op9flow Junior
Op9flow Junior
Op9flow Junior
1-‐4kg
3-‐10kg
10-‐12.5kg
Nasal Prong sizing
• Op9flow Junior ≤12.5kg • Op9flow >12.5kg
Adult Op9flow
Prescribing
• S9pulate FiO2 and Flow Rate
Weaning (Acute Paeds)
• Titrate FiO2, weaning to 40% – Then trial Low Flow oxygen at 1-‐2L/min (wall, not mixer)
• Don’t wean flow ie. ‘High’ or ‘Low’ – No need to change cannula (Op9flow Junior)
Nebulising via HFNC
• No paediatric data of effec9veness
• In vitro study nebulised albuterol via Vapotherm: – 3 sizes cannulae
• Adult 5-‐40L/min • Pediatric 3-‐20L/min • Infant 3-‐8L/min
– Inadequate delivery to achieve a clinical response • 0-‐2.5% of nominal dose
– Delivery inversely propor9onal to flow rate – Delivery propor9onal to cannula size
Perry et al. Pediatric CriEcal Care Medicine 14(5);e250-‐e256, June 2013
• Limited adult data suggest pulmonary deposi9on of aerosol through High Flow circuit similar to level obtained by direct inhala9on from nebuliser
Dhand R. Journal of Aerosol Medicine and Pulmonary Drug Delivery 2012; 25(2): 63-‐78
Ques9ons?
Top Related