Pharyngeal pressure with high-flow nasal cannulae in premature infants

The Role of Heated Humidified High-flow Nasal Cannula as Noninvasive Respiratory Support in Neonates

Recently, heated humidified high-flow nasal cannula (HHHFNC) has been introduced and applied as a noninvasive respiratory support in neonates. Although HHHFNC is widely used in neonates presenting with respiratory distress, the efficiency and safety when compared with nasal continuous positive airway pressure or noninvasive positive pressure ventilation are still controversial. This review aims to evaluate the performance and applications of HHHFNC in neonates.

Carbon dioxide washout during high flow nasal cannula versus nasal CPAP support: An in vitro study

OBJECTIVE

To compare CO₂ washout time at different levels of HFNC versus NCPAP in a premature infant lung model with simulated mouth-closed and mouth-open conditions using two sizes of nasal cannula and full- and half-prong HFNC insertion depths.

DESIGN/METHODS

A piston-cylinder lung simulator, having a fixed volume of 30 ml and a 4.8 ml dead space, simulated spontaneous breathing (6.5 ml tidal volume, 50 br/min, Ti = 0.5 sec). Two Fisher & Paykel™ cannulas (Fisher & Paykel Healthcare Ltd., Auckland, New Zealand) (2.8 and 3.2 mm O.D.) and two Infant-Flow™ (CareFusion, Yorba Linda, CA) NCPAP cannulas (3.4 and 4.1 mm O.D.) were applied to simulated airways having either 3.5 or 4.5 mm I.D. nares. Simulated mouth opening was a 5 mm I.D. side tap below the nasal interface. The lung was primed with 5% CO₂ . Washout times were determined at HFNC settings of 3, 4, 5, 6, and 8 L/min and NCPAP at 3, 4, 5, 6, and 8 cm H₂ O with simulated open and closed-mouth conditions and full- and half-inserted HFNC prongs.

RESULTS

Overall combined mean washout times for NCPAP with mouth-closed were significantly longer than HFNC over all five pressure and flow device settings by 16.2% (P < 0.001). CO₂ washout times decreased as flow or pressure device settings were increased. There were negligible differences in washout times between NCPAP and HFNC with mouth-open. Mouth-open washout times were significantly less than mouth-closed for all conditions. Overall closed-mouth washout times for HFNC half-prong insertion were longer than for full-prong insertion by 5.3% (P < 0.022).

CONCLUSIONS

Significantly improved CO₂ elimination using HFNC versus NCPAP should be a particularly important consideration in premature infants having very high dead space-to-tidal volume ratio compared to larger infants. Pediatr Pulmonol. 2017;52:792-798. © 2017 Wiley Periodicals, Inc.

Heated Humidified High-Flow Nasal Cannula for Prevention of Extubation Failure in Preterm Infants

OBJECTIVES

To compare extubation failure rate between the heated humidified high-flow nasal cannula (HHHFNC) and continuous positive airway pressure (CPAP) groups.

METHODS

Intubated infants with gestational age (GA) <32 wk, who were ready to extubate, were randomized to receive respiratory support with either CPAP or HHHFNC after extubation. In CPAP group, nasal mask CPAP with preset pressure and fraction of inspired oxygen (FiO₂) equal to positive end-expiratory pressure (PEEP) and FiO₂ of ventilator before extubation was applied. In the HHHFNC group, predefined flow rate according to the protocol was applied. Primary outcome was extubation failure within 72 h after endotracheal tube removal.

RESULTS

Forty-nine infants were enrolled; 24 in the HHHFNC and 25 in the CPAP group. Baseline demographic and respiratory conditions before extubation were similar. There was no difference in infants who met failed extubation criteria between the two groups [8 (33%) in HHHFNC vs. 6 (24%) in CPAP group (p = 0.47)]. However, 6 infants (75%) in HHHFNC and 4 infants (66%) in CPAP group who met failed extubation criteria could be rescued by bilevel CPAP. Therefore, the reintubation rate was comparable [2 infants (8.3%) in HHHFNC vs. 2 infants (8%) in CPAP group]. Morbidities or related complications were not different but infants in the HHHFNC group had significantly less nasal trauma (16.7% vs. 44%; p = 0.03).

CONCLUSIONS

In the index study, the extubation failure rate was not statistically different between infants who were on HHHFNC or CPAP support.

Heated Humidified High Flow Nasal Cannula versus Nasal Continuous Positive Airway Pressure as Primary Mode of Respiratory Support for Respiratory Distress in Preterm Infants

OBJECTIVE

To compare the outcomes of preterm infants with respiratory distress initiated on either Heated Humidified High Flow Nasal Cannula or Nasal Continuous Positive Airway Pressure as a primary mode of respiratory support.

STUDY DESIGN

Prospective observational cohort study.

SETTING

Tertiary care level III neonatal intensive care unit.

PARTICIPANTS

88 preterm infants between 28 to 34 weeks of gestation with mild to moderate respiratory distress within 6 hours of birth.

INTERVENTION

Eligible infants were treated either with Heated Humidified High Flow Nasal Cannula (n=46) or Nasal Continuous Positive Airway Pressure (n=42).

PRIMARY OUTCOME

Need for mechanical ventilation within 72 hrs of initiating support.

RESULTS

Baseline demographic characteristics were comparable between the two groups. There was no difference in the requirement of mechanical ventilation between Heated Humidified High Flow Nasal Cannula (19.5%) and Nasal Continuous Positive Airway Pressure (26.2%) groups [RD-0.74 (95% CI 0.34-1.62; P =0.46)]. Moderate or severe nasal trauma occurred less frequently with Heated Humidified High Flow Nasal Cannula (10.9%) in comparison to Nasal Continuous Positive Airway Pressure (40.5%) (P= 0.004).

CONCLUSIONS

Heated Humidified High Flow Nasal Cannula was comparable to Nasal Continuous Positive Airway Pressure as a primary respiratory support for preterm infants with respiratory distress, with lesser incidence of nasal trauma.

Evidence Support and Guidelines for Using Heated, Humidified, High-Flow Nasal Cannulae in Neonatology: Oxford Nasal High-Flow Therapy Meeting, 2015

Nasal high-flow therapy (nHFT) has become a popular form of noninvasive respiratory support in neonatal intensive care units. A meeting held in Oxford, UK, in June 2015 examined the evidence base and proposed a consensus statement. In summary, nHFT is effective for support of preterm infants following extubation. There is growing evidence evaluating its use in the primary treatment of respiratory distress. Further study is needed to assess which clinical conditions are most amenable to nHFT support, the most effective flow rates, and escalation and weaning strategies. Its suitability as first-line treatment needs to be further evaluated.

Nasal High-Flow Therapy for Primary Respiratory Support in Preterm Infants

BACKGROUND

Treatment with nasal high-flow therapy has efficacy similar to that of nasal continuous positive airway pressure (CPAP) when used as postextubation support in neonates. The efficacy of high-flow therapy as the primary means of respiratory support for preterm infants with respiratory distress has not been proved.

METHODS

In this international, multicenter, randomized, noninferiority trial, we assigned 564 preterm infants (gestational age, ≥28 weeks 0 days) with early respiratory distress who had not received surfactant replacement to treatment with either nasal high-flow therapy or nasal CPAP. The primary outcome was treatment failure within 72 hours after randomization. Noninferiority was determined by calculating the absolute difference in the risk of the primary outcome; the chosen margin of noninferiority was 10 percentage points. Infants in whom high-flow therapy failed could receive rescue CPAP; infants in whom CPAP failed were intubated and mechanically ventilated.

RESULTS

Trial recruitment stopped early at the recommendation of the independent data and safety monitoring committee because of a significant difference in the primary outcome between treatment groups. Treatment failure occurred in 71 of 278 infants (25.5%) in the high-flow group and in 38 of 286 infants (13.3%) in the CPAP group (risk difference, 12.3 percentage points; 95% confidence interval [CI], 5.8 to 18.7; P<0.001). The rate of intubation within 72 hours did not differ significantly between the high-flow and CPAP groups (15.5% and 11.5%, respectively; risk difference, 3.9 percentage points; 95% CI, -1.7 to 9.6; P=0.17), nor did the rate of adverse events.

CONCLUSIONS

When used as primary support for preterm infants with respiratory distress, high-flow therapy resulted in a significantly higher rate of treatment failure than did CPAP. (Funded by the National Health and Medical Research Council and others; Australian New Zealand Clinical Trials Registry number, ACTRN12613000303741 .).

Work of breathing during CPAP and heated humidified high-flow nasal cannula

OBJECTIVE

To determine whether continuous positive airway pressure (CPAP) compared with heated humidified, high-flow nasal cannula (HHFNC) in infants with evolving or established bronchopulmonary dysplasia (BPD) reduced the work of breathing (WOB) and thoracoabdominal asynchrony (TAA) and improved oxygen saturation (SaO2).

DESIGN

Randomised crossover study.

SETTING

Tertiary neonatal unit.

PATIENTS

20 infants (median gestational age of 27.6 weeks (range 24.6-31.9 weeks)) were studied at a median postnatal age of 30.9 weeks (range 28.1-39.1 weeks).

INTERVENTIONS

Infants were studied on 2 consecutive days. On the first study day, they were randomised to either CPAP or HHFNC each for 2 h, the order being reversed on the second day.

MAIN OUTCOME MEASURES

The WOB was assessed by measuring the pressure time product of the diaphragm (PTPdi). PTPdi, TAA and SaO2 were assessed during the final 5 min of each 2 h period and the results on the two study days were meaned.

RESULTS

There were no significant differences in the results on CPAP versus HHFNC: mean PTPdi 226 (range 126-294) versus 224 cm H2O/s/min (95% CI for difference: -27 to 22; p=0.85) (range 170-318) (p=0.82), mean TAA 13.4° (range 4.51°-23.32°) versus 14.01° (range 4.25°-23.86°) (95% CI for difference: -3.9 to 2.8: p=0.73) (p=0.63) and mean SaO2 95% (range 93%-100%) versus 95% (94%-99%), (95% CI for difference -1.8 to 0.5; p=0.25) (p=0.45).

CONCLUSION

In infants with evolving or established BPD, CPAP compared with HHFNC offered no significant advantage with regard to the WOB, degree of asynchrony or oxygen saturation.

High-flow nasal cannula: Mechanisms, evidence and recommendations

The use of high-flow nasal cannula (HF) therapy as respiratory support for preterm infants is rapidly increasing, due to its perceived ease of use and other potential benefits over the standard 'non-invasive' respiratory support, continuous positive airway pressure (CPAP). The evidence from randomized trials suggests that HF is an alternative to CPAP for post-extubation support of preterm infants. Limited data are available from randomized trials comparing HF with CPAP as primary support, and few trials have included extremely preterm infants. This review discusses the proposed mechanisms of action of HF, the evidence from clinical trials of HF use in preterm infants, and proposes recommendations for evidence-based practice.

High flow nasal cannula for respiratory support in preterm infants

BACKGROUND

High flow nasal cannulae (HFNC) are small, thin, tapered binasal tubes that deliver oxygen or blended oxygen/air at gas flows of more than 1 L/min. HFNC are increasingly being used as a form of non-invasive respiratory support for preterm infants.

OBJECTIVES

To compare the safety and efficacy of HFNC with other forms of non-invasive respiratory support in preterm infants.

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 1), MEDLINE via PubMed (1966 to 1 January 2016), EMBASE (1980 to 1 January 2016), and CINAHL (1982 to 1 January 2016). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised or quasi-randomised trials comparing HFNC with other non-invasive forms of respiratory support in preterm infants immediately after birth or following extubation.

DATA COLLECTION AND ANALYSIS

The authors extracted and analysed data, and calculated risk ratio, risk difference and number needed to treat for an additional beneficial outcome.

MAIN RESULTS

We identified 15 studies for inclusion in the review. The studies differed in the interventions compared (nasal continuous positive airway pressure (CPAP), nasal intermittent positive pressure ventilation (NIPPV), non-humidified HFNC, models for delivering HFNC), the gas flows used and the indications for respiratory support (primary support from soon after birth, post-extubation support, weaning from CPAP support). When used as primary respiratory support after birth compared to CPAP (4 studies, 439 infants), there were no differences in the primary outcomes of death (typical risk ratio (RR) 0.36, 95% CI 0.01 to 8.73; 4 studies, 439 infants) or chronic lung disease (CLD) (typical RR 2.07, 95% CI 0.64 to 6.64; 4 studies, 439 infants). HFNC use resulted in longer duration of respiratory support, but there were no differences in other secondary outcomes. One study (75 infants) showed no differences between HFNC and NIPPV as primary support. Following extubation (total 6 studies, 934 infants), there were no differences between HFNC and CPAP in the primary outcomes of death (typical RR 0.77, 95% CI 0.43 to 1.36; 5 studies, 896 infants) or CLD (typical RR 0.96, 95% CI 0.78 to 1.18; 5 studies, 893 infants). There was no difference in the rate of treatment failure (typical RR 1.21, 95% CI 0.95 to 1.55; 5 studies, 786 infants) or reintubation (typical RR 0.91, 95% CI 0.68 to 1.20; 6 studies, 934 infants). Infants randomised to HFNC had reduced nasal trauma (typical RR 0.64, 95% CI 0.51 to 0.79; typical risk difference (RD) -0.14, 95% CI -0.20 to -0.08; 4 studies, 645 infants). There was a small reduction in the rate of pneumothorax (typical RR 0.35, 95% CI 0.11 to 1.06; typical RD -0.02, 95% CI -0.03 to -0.00; 5 studies 896 infants) in infants treated with HFNC. Subgroup analysis found no difference in the rate of the primary outcomes between HFNC and CPAP in preterm infants in different gestational age subgroups, though there were only small numbers of extremely preterm and late preterm infants. One trial (28 infants) found similar rates of reintubation for humidified and non-humidified HFNC, and two other trials (100 infants) found no difference between different models of equipment used to deliver humidified HFNC. For infants weaning from non-invasive respiratory support (CPAP), two studies (149 infants) found that preterm infants randomised to HFNC had a reduced duration of hospitalisation compared with infants who remained on CPAP.

AUTHORS' CONCLUSIONS

HFNC has similar rates of efficacy to other forms of non-invasive respiratory support in preterm infants for preventing treatment failure, death and CLD. Most evidence is available for the use of HFNC as post-extubation support. Following extubation, HFNC is associated with less nasal trauma, and may be associated with reduced pneumothorax compared with nasal CPAP. Further adequately powered randomised controlled trials should be undertaken in preterm infants comparing HFNC with other forms of primary non-invasive support after birth and for weaning from non-invasive support. Further evidence is also required for evaluating the safety and efficacy of HFNC in extremely preterm and mildly preterm subgroups, and for comparing different HFNC devices.

Heated Humidified High-Flow Nasal Cannula for Weaning from Continuous Positive Airway Pressure in Preterm Infants: A Randomized Controlled Trial

BACKGROUND

Heated humidified high-flow nasal cannula (HHHFNC) therapy has been widely used in preterm infants. However, evidence to support its use as a continuous positive airway pressure (CPAP) weaning method is still controversial.

OBJECTIVES

We aimed to compare time to wean directly off CPAP vs. weaning by using HHHFNC.

METHODS

Infants with a gestational age (GA) of <32 weeks who met the predefined criteria for weaning off CPAP, i.e. with a CPAP of ≤6 cm H2O and a fraction of inspired oxygen (FiO2) of ≤0.3 for at least 24 h, were randomly assigned to wean by using HHHFNC or wean directly from CPAP. In the HHHFNC group, flow rate was reduced by 1 liter/min every 24 h to 2-3 liters/min depending on body weight (i.e. < or ≥1,000 g), and then HHHFNC was discontinued. In the CPAP group, pressure was reduced by 1 cm H2O every 24 h until stable on CPAP 4 cm H2O and then discontinued. The primary outcome was the time it took to wean off the use of the CPAP or HHHFNC devices.

RESULTS

One-hundred and one infants were enrolled, 51 in the HHHFNC and 50 in the CPAP group. Both groups had similar demographics and respiratory conditions before enrollment. There was no difference in time to successfully wean between the 2 groups [median (IQR): 11 (4-21) days in the HHHFNC group vs. 11 (4-29) days in the CPAP group; p = 0.12]. There were no differences in morbidities or related complications. Infants in the HHHFNC group had significantly less nasal trauma (20 vs. 42%; p = 0.01).

CONCLUSIONS

In our study, the time to wean off CPAP using HHHFNC was not different from when weaning directly from CPAP.

Noninvasive Respiratory Support

Mechanical ventilation is associated with increased survival of preterm infants but is also associated with an increased incidence of chronic lung disease (bronchopulmonary dysplasia) in survivors. Nasal continuous positive airway pressure (nCPAP) is a form of noninvasive ventilation that reduces the need for mechanical ventilation and decreases the combined outcome of death or bronchopulmonary dysplasia. Other modes of noninvasive ventilation, including nasal intermittent positive pressure ventilation, biphasic positive airway pressure, and high-flow nasal cannula, have recently been introduced into the NICU setting as potential alternatives to mechanical ventilation or nCPAP. Randomized controlled trials suggest that these newer modalities may be effective alternatives to nCPAP and may offer some advantages over nCPAP, but efficacy and safety data are limited.

High-flow nasal cannulae are associated with increased diaphragm activation compared with nasal continuous positive airway pressure in preterm infants

AIM

High-flow nasal cannulae (HFNC) are increasingly used for respiratory management of preterm infants. However, their ability to provide support compared to nasal continuous positive airway pressure (CPAP) has been questioned. We compared the effect of HFNC versus nasal CPAP on diaphragm electrical activity (EAdi) in preterm infants.

METHODS

Preterm infants ≤1500 g were randomised in a crossover design to receive 2 hours of either Infant Flow(®) CPAP (IF-CPAP) at 5-6 cmH2 O or HFNC with the flow rate adjusted to achieve an equivalent pharyngeal pressure. A feeding catheter with miniaturised sensors was inserted for continuous EAdi measurement.

RESULTS

The study comprised ten infants. Physiologic parameters and oxygen requirements were not different between the two modes. However, seven infants demonstrated a higher EAdi peak and six showed a higher EAdi tonic on HFNC, even though the mean group data showed no difference between HFNC and IF-CPAP. Neural inspiratory time was significantly longer with HFNC than IF-CPAP (0.55 ± 0.11 versus 0.48 ± 0.06 seconds, p = 0.018).

CONCLUSION

In this cohort of preterm infants, the majority exhibited greater diaphragm activation, as assessed by neural breathing patterns, when supported with HFNC than IF-CPAP, suggesting that nasal CPAP may provide more effective respiratory support.

The effect of high flow nasal cannula therapy on the work of breathing in infants with bronchiolitis

The main physiological impact of high flow nasal cannula (HFNC) therapy is presumed to be a decrease in work of breathing (WOB). To assess this, diaphragmatic electrical activity and esophageal pressure changes were measured off then on HFNC delivered at 2 L/kg/min, in 14 infants with bronchiolitis and 14 cardiac infants. Electrical activity of the diaphragm (Edi) was measured using an Edi catheter with calculations of signal peak (EdiMAX ) and amplitude (EdiAMPL ). Pressure-rate and pressure-time products (PRP, PTP) were calculated from analyses of esophageal pressure. Changes in end-expiratory lung volume were measured using respiratory inductance plethysmography (RIPEEL ). The EdiMAX and EdiAMPL were significantly higher in infants with bronchiolitis than in cardiac infants (P < 0.05). Within the bronchiolitis group, both were significantly reduced between HFNC states from 27.9 µV [20.4, 35.4] to 21.0 µV [14.8, 27.2] and from 25.1 µV [18.0, 32.2] to 19.2 µV [13.3, 25.1], respectively (mean, 95% CI, P < 0.05). A less prominent offload of the diaphragm was observed in cardiac infants (P < 0.05). WOB decreased in both groups with a significant reduction of PRP and PTP (P < 0.05). RIPEEL increased significantly in bronchiolitis only (P < 0.05). HFNC offloads the diaphragm and reduces the WOB in bronchiolitis. A similar effect was demonstrated in cardiac infants, a group without signs of airway-obstruction.

A multicentre, randomised controlled, non-inferiority trial, comparing high flow therapy with nasal continuous positive airway pressure as primary support for preterm infants with respiratory distress (the HIPSTER trial): study protocol

INTRODUCTION

High flow (HF) therapy is an increasingly popular mode of non-invasive respiratory support for preterm infants. While there is now evidence to support the use of HF to reduce extubation failure, there have been no appropriately designed and powered studies to assess the use of HF as primary respiratory support soon after birth. Our hypothesis is that HF is non-inferior to the standard treatment--nasal continuous positive airway pressure (NCPAP)--as primary respiratory support for preterm infants.

METHODS AND ANALYSIS

The HIPSTER trial is an unblinded, international, multicentre, randomised, non-inferiority trial. Eligible infants are preterm infants of 28-36(+6) weeks' gestational age (GA) who require primary non-invasive respiratory support for respiratory distress in the first 24 h of life. Infants are randomised to treatment with either HF or NCPAP. The primary outcome is treatment failure within 72 h after randomisation, as determined by objective oxygenation, blood gas, and apnoea criteria, or the need for urgent intubation and mechanical ventilation. Secondary outcomes include the incidence of intubation, pneumothorax, bronchopulmonary dysplasia, nasal trauma, costs associated with hospital care and parental stress. With a specified non-inferiority margin of 10%, using a two-sided 95% CI and 90% power, the study requires 375 infants per group (total 750 infants).

ETHICS AND DISSEMINATION

Ethical approval has been granted by the relevant human research ethics committees at The Royal Women's Hospital (13/12), The Royal Children's Hospital (33144A), The Mercy Hospital for Women (R13/34), and the South-Eastern Norway Regional Health Authority (2013/1657). The trial is currently recruiting at 9 centres in Australia and Norway. The trial results will be published in peer-reviewed international journals, and presented at national and international conferences.

TRIAL REGISTRATION NUMBER

Australian New Zealand Clinical Trials Registry ID: ACTRN12613000303741.

Heated humidified high-flow nasal cannula therapy in children

Heated humidified high-flow nasal cannula therapy (HHHFNC) was originally described as a mode of respiratory support in premature neonates and is now increasingly used in the management of acute respiratory failure in older infants and children. Heating and humidification of gas mixtures allow comfortable delivery of flow rates that match or exceed the patient's inspiratory flow rate. Emerging evidence from observational studies suggests that the use of HHHFNC therapy may be associated with reduced work of breathing, improved ventilation efficiency and a decreased need for intubation in children with respiratory insufficiency. There are several proposed mechanisms of action, and the potential for provision of unpredictable positive distending pressure has caused concern. Randomised controlled trial evidence comparing clinical outcomes with those achieved using other forms of respiratory support is, however, awaited. We review the proposed mechanisms of actions, indications, advantages and complications of HHHFNC therapy in children and describe our approach to its use in the paediatric ward environment.

A randomized pilot study comparing heated humidified high-flow nasal cannulae with NIPPV for RDS

OBJECTIVE

To compare the requirement for endotracheal ventilation in preterm infants treated with heated, humidified high-flow nasal cannula (HHHFNC) with those treated with nasal intermittent positive pressure ventilation (NIPPV) for the primary treatment of respiratory distress syndrome (RDS).

STUDY DESIGN

Randomized, controlled, prospective, single-center pilot study. Infants (gestational age [GA] <35 weeks, birth weight [BW] >1,000 g) with RDS were randomly assigned to receive HHHFNC (38 infants) delivered by Vapotherm® device (Precision Flow™ or 2000 i, Vapotherm Inc., Stevensville, MD), at flows between 1.0 and 5.0 L/min, or NIPPV (38 infants) delivered by the SLE 2000 or 5000. Surfactant was administered as rescue therapy. Analysis was done by intention-to-treat.

RESULTS

Infant's characteristics ([mean ± SD] GA 31.8 ± 2.3 vs. 32.0 ± 2.3 weeks) and cardio-respiratory status at study entry (FiO2 0.25 ± 0.05 vs. 0.26 ± 0.07; SpO2 90 ± 6% vs. 87 ± 12; PCO2 54.4 ± 10.4 vs. 52.6 ± 8.0 mmHg) were comparable for the HHHFNC and NIPPV groups. There was no significant difference in the need for endotracheal ventilation (28.9% vs. 34.2%) between HHHFNC and NIPPV groups. One infant failed HHHFNC and succeeded on NIPPV. The rate of neonatal morbidities (pneumothorax, bronchopulmonary dysplasia, intra-ventricular hemorrhage, necrotizing enterocolitis, patent ductus arteriosus, and nasal trauma) was comparable in both groups. Duration of nasal support was longer with HHHFNC compared with NIPPV (5.4 ± 4.0 vs. 2.6 ± 1.9 days, P = 0.006) but the duration of endotracheal ventilation, time to full feeds, and length of stay were comparable.

CONCLUSIONS

Our pilot study suggests that HHHFNC maybe as effective as NIPPV in preventing endotracheal ventilation in the primary treatment of RDS in premature infants (<35 weeks GA and BW >1,000 g).

High flow nasal cannula for continuous positive airway pressure weaning in preterm neonates: A single-centre experience

AIM

High flow nasal cannula therapy (HFNC) is an emerging method of non-invasive respiratory support therapy for premature infants. Recent evidence around its safety and efficacy for post-extubation respiratory support is encouraging. However, its effect on long-term respiratory outcomes is not known. The aim of this study is to determine the effect of HFNC on respiratory outcomes (chronic lung disease (CLD), need for home oxygen) when used to wean babies from continuous positive airway pressure (CPAP).

METHODS

This retrospective study compared respiratory outcomes in infants born <32 weeks gestation needing any respiratory support at birth in two epochs - epoch I (2004-2007) verus epoch II (2008-2011). HFNC was available to be used as a CPAP weaning modality in epoch II.

RESULTS

A total of 1286 infants (epoch I: 597 vs. epoch II: 689), mean (standard deviation) gestation, 28.1 (2.2) versus 28.5 (2.3) weeks were enrolled, with 222 (32%) receiving HFNC in epoch II. Overall median duration of respiratory support increased by 150 h in epoch II (P = 0.03), primarily as HFNC hours. A reduction in duration of invasive ventilation and CPAP along with 6% (P = 0.01) reduction in CLD rates was observed in epoch II. No change in home oxygen therapy rates was noted. In logistic regression, HFNC had no significant effect on rates of CLD or home oxygen.

CONCLUSIONS

Introduction of HFNC for weaning nasal CPAP seems to have a minimal effect on CLD rates. The effect of HFNC on long-term outcomes needs to be further evaluated.

Acute Neonatal Respiratory Failure

Acute respiratory failure requiring assisted ventilation is one of the most common reasons for admission to the neonatal intensive care unit. Respiratory failure is the inability to maintain either normal delivery of oxygen to the tissues or normal removal of carbon dioxide from the tissues. It occurs when there is an imbalance between the respiratory workload and ventilatory strength and endurance. Definitions are somewhat arbitrary but suggested laboratory criteria for respiratory failure include two or more of the following: PaCO₂ > 60 mmHg, PaO₂ < 50 mmHg or O₂ saturation <80 % with an FiO₂ of 1.0 and pH < 7.25 (Wen et al. 2004).

High-flow nasal cannula: recommendations for daily practice in pediatrics

High-flow nasal cannula (HFNC) is a relatively new device for respiratory support. In pediatrics, HFNC use continues to increase as the system is easily set up and is well tolerated by patients. The use of nasal cannula adapted to the infant’s nares size to deliver heated and humidified gas at high flow rates has been associated with improvements in washout of nasopharyngeal dead space, lung mucociliary clearance, and oxygen delivery compared with other oxygen delivery systems. HFNC may also create positive pharyngeal pressure to reduce the work of breathing, which positions the device midway between classical oxygen delivery systems, like the high-concentration face mask and continuous positive airway pressure (CPAP) generators. Currently, most of the studies in the pediatric literature suggest the benefits of HFNC therapy only for moderately severe acute viral bronchiolitis. But, the experience with this device in neonatology and adult intensive care may broaden the pediatric indications to include weaning from invasive ventilation and acute asthma. As for any form of respiratory support, HFNC initiation in patients requires close monitoring, whether it be for pre- or inter-hospital transport or in the emergency department or the pediatric intensive care unit.

Review finds insufficient evidence to support the routine use of heated, humidified high-flow nasal cannula use in neonates

A literature review was carried out following concerns about the use of heated, humidified, high-flow nasal cannulae (HHFNC) in premature infants. Randomised trials following extubation showed that HHFNC was associated with similar or greater reintubation rates than nasal continuous positive airway pressure, but significantly better nasal trauma scores. Infections with Ralstonia bacteria were an issue.

CONCLUSION

There is insufficient evidence to support the routine use of HHFNC for premature infants and further research is required.

Respiratory mechanics during NCPAP and HHHFNC at equal distending pressures

OBJECTIVE

To compare the effect of heated, humidified, high-flow nasal cannula (HHHFNC) and nasal continuous positive airways pressure (NCPAP) on lung function and mechanics in preterm infants with respiratory distress syndrome (RDS) at the same level of retropharyngeal pressure (Prp).

DESIGN

Randomised crossover trial.

SETTING

Neonatal intensive care unit, Ospedale Maggiore Policlinico, Milan, Italy.

PATIENTS

20 preterm infants (gestational age: 31±1 wks) with mild-moderate RDS requiring non-invasive respiratory support within 96 h after birth.

INTERVENTIONS

Infants were exposed to a randomised sequence of NCPAP and HHHFNC at different settings (2, 4 and 6 cmH₂O for NCPAP and 2, 4, 6 L/min for HHHFNC) to enable comparison at the same level of Prp.

MAIN OUTCOME MEASURES

Tidal volume by respiratory inductance plethysmography, pleural pressure estimated by oesophageal pressure, and gas exchange were evaluated at each setting and used to compute breathing pattern parameters, lung mechanics and work of breathing (WOB).

RESULTS

A poor linear regression between flow and Prp was found during HHHFNC (Prp=0.3+0.7*flow; r²=0.37). Only in 15 out of 20 infants it was possible to compare HHHFNC and NCPAP at a Prp of 2 and 4 cmH₂O. No statistically significant differences were found in breathing pattern, gas exchange, lung mechanics and total WOB. Resistive WOB in the upper airways was slightly but significantly higher during HHHFNC (0.65 (0.49;1.09) vs 1.57 (0.85;2.09) cmH₂O median (IQR)).

CONCLUSIONS

Despite differing mechanisms for generating positive airway pressure, when compared at the same Prp, NCPAP and HHHFNC provide similar effects on all the outcomes explored.

Physiologic effect of high-flow nasal cannula in infants with bronchiolitis

OBJECTIVE

To assess the effect of delivering high-flow nasal cannula flow on end-expiratory lung volume, continuous distending pressure, and regional ventilation distribution in infants less than 12 months old with bronchiolitis.

DESIGN

Prospective observational clinical study.

SETTING

Nineteen bed medical and surgical PICU.

PATIENTS

Thirteen infants with bronchiolitis on high-flow nasal therapy.

INTERVENTIONS

The study infants were measured on a flow rate applied at 2 and 8 L/min through the high-flow nasal cannula system.

MEASUREMENTS AND RESULTS

Ventilation distribution was measured with regional electrical impedance amplitudes and end-expiratory lung volume using electrical impedance tomography. Changes in continuous distending pressure were measured from the esophagus via the nasogastric tube. Physiological variables were also recorded. High-flow nasal cannula delivered at 8 L/min resulted in significant increases in global and anterior end-expiratory lung volume (p < 0.01) and improvements in the physiological variables of respiratory rate, SpO2, and FIO2 when compared with flows of 2 L/min.

CONCLUSION

In infants with bronchiolitis, high-flow nasal cannula oxygen/air delivered at 8 L/min resulted in increases in end-expiratory lung volume and improved respiratory rate, FIO2, and SpO2.

The evidence for high flow nasal cannula devices in infants

High flow nasal cannula (HFNC) devices deliver an adjustable mixture of heated and humidified oxygen and air at a variable flow rate. Over recent years HFNC devices have become a frequently used method of non-invasive respiratory support in infants and preterm neonates that is generally popular amongst clinicians and nursing staff due to ease of use and being well tolerated by patients. Despite this rapid adoption relatively little is known about the exact mechanisms of action of HFNC however and only recently have data from randomised controlled trials started to become available. We describe the features of a modern HFNC device and discuss current knowledge about the mechanisms of action and results of clinical studies in preterm neonates and infants with bronchiolitis. We also highlight future areas of research that are likely to increase our understanding, inform best clinical practice and strengthen the evidence base for the use of HFNC.

High-flow nasal cannula therapy for respiratory support in children

BACKGROUND

Respiratory support is a central component of the management of critically ill children. It can be delivered invasively via an endotracheal tube or non-invasively via face mask, nasal mask, nasal cannula or oxygen hood/tent. Invasive ventilation can be damaging to the lungs, and the tendency to use non-invasive forms is growing. However, non-invasive delivery is often poorly tolerated by children. High-flow nasal cannula (HFNC) oxygen delivery is a relatively new therapy that shows the potential to reduce the need for intubation and be better tolerated by children than other non-invasive forms of support. HFNC therapy differs from other non-invasive forms of treatment in that it delivers heated, humidified and blended air/oxygen via nasal cannula at rates > 2 L/kg/min. This allows the user to deliver high concentrations of oxygen and to potentially deliver continuous distending pressure; this treatment often is better tolerated by the child.

OBJECTIVES

To determine whether HFNC therapy is more effective than other forms of non-invasive therapy in paediatric patients who require respiratory support.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 4); MEDLINE via PubMed (January 1966 to April 2013); EMBASE (January 1980 to April 2013); CINAHL (1982 to April 2013); and LILACS (1982 to April 2013). Abstracts from conference proceedings, theses and dissertations and bibliographical references to relevant studies were also searched. We applied no restriction on language.

SELECTION CRITERIA

We planned to included randomized controlled trials (RCTs) and quas-randomized trials comparing HFNC therapy with other forms of non-invasive respiratory support for children. Non-invasive support encompassed cot, hood or tent oxygen; low-flow nasal cannulae (flow rates ≤ 2 L/min); and continuous positive airway pressure (CPAP) or bilevel positive airway pressure (BiPAP) delivered via facial or nasal mask/cannula. Treatment failure was defined by the need for additional respiratory support. We excluded children with a diagnosis of bronchiolitis.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed all studies for selection and data extraction. We used standard methodological procedures expected by The Cochrane Collaboration.

MAIN RESULTS

Our search yielded 922 records. A total of 109 relevant records were retrieved with reference to our search criteria. After duplicates and irrelevant studies were removed, 69 studies were further scrutinized. Of these, 11 studies involved children. No study matched our inclusion criteria.

AUTHORS' CONCLUSIONS

Based on the results of this review, no evidence is available to allow determination of the safety or effectiveness of HFNC as a form of respiratory support in children.

High-flow nasal cannulae in very preterm infants after extubation

BACKGROUND

The use of high-flow nasal cannulae is an increasingly popular alternative to nasal continuous positive airway pressure (CPAP) for noninvasive respiratory support of very preterm infants (gestational age, <32 weeks) after extubation. However, data on the efficacy or safety of such cannulae in this population are lacking.

METHODS

In this multicenter, randomized, noninferiority trial, we assigned 303 very preterm infants to receive treatment with either high-flow nasal cannulae (5 to 6 liters per minute) or nasal CPAP (7 cm of water) after extubation. The primary outcome was treatment failure within 7 days. Noninferiority was determined by calculating the absolute difference in the risk of the primary outcome; the margin of noninferiority was 20 percentage points. Infants in whom treatment with high-flow nasal cannulae failed could be treated with nasal CPAP; infants in whom nasal CPAP failed were reintubated.

RESULTS

The use of high-flow nasal cannulae was noninferior to the use of nasal CPAP, with treatment failure occurring in 52 of 152 infants (34.2%) in the nasal-cannulae group and in 39 of 151 infants (25.8%) in the CPAP group (risk difference, 8.4 percentage points; 95% confidence interval, -1.9 to 18.7). Almost half the infants in whom treatment with high-flow nasal cannulae failed were successfully treated with CPAP without reintubation. The incidence of nasal trauma was significantly lower in the nasal-cannulae group than in the CPAP group (P=0.01), but there were no significant differences in rates of serious adverse events or other complications.

CONCLUSIONS

Although the result for the primary outcome was close to the margin of noninferiority, the efficacy of high-flow nasal cannulae was similar to that of CPAP as respiratory support for very preterm infants after extubation. (Funded by the National Health and Medical Research Council; Australian New Zealand Clinical Trials Network number, ACTRN12610000166077.).

Comparison of the pharyngeal pressure provided by two heated, humidified high-flow nasal cannulae devices in premature infants

AIMS

This study aims to determine if there is a difference in the pharyngeal pressure, measured as a surrogate for continuous positive distending airway pressure, delivered to premature infants between two commonly used heated, humidified high-flow nasal cannulae (HHHFNC) devices: Fisher & Paykel Healthcare HHHFNC and Vapotherm 2000i.

METHODS

Pharyngeal pressure measurements were taken from stable premature infants receiving HHHFNC for respiratory support. Flow rates of 2-8 L/min were studied.

RESULTS

Nine infants had pharyngeal pressure measurements recorded with both HHHFNC devices at flow rates of 2-8 L/min. There was no difference in pharyngeal pressures recorded between devices at flow rates of 2-6 L/min; measured pressure was linearly associated with flow (R(2) = 0.9). At flow rates of 7 L/min, Vapotherm delivered a mean (standard deviation) pharyngeal pressure of 4.7 (2.2) cmH2 O compared with 4.23 (2.2) cmH2 O by the Fisher & Paykel device (P = 0.04). At a flow of 8 L/min, the mean pharyngeal pressure via Vapotherm was 4.9 (2.2) cmH2 O compared with 4.1 (2.3) cmH2 O with the Fisher & Paykel device (P = 0.05).

CONCLUSIONS

Both HHHFNC delivered similar pharyngeal pressures at flow rates of 2-6 L/min. The pressure limiter valve of the Fisher & Paykel device attenuated the pharyngeal pressures at flows of 7 and 8 L/min. Vapotherm trended towards higher delivered pharyngeal pressure at flow rates 7 and 8 L/min, but the clinical significance of the difference remains unclear.

A randomized controlled trial to compare heated humidified high-flow nasal cannulae with nasal continuous positive airway pressure postextubation in premature infants

OBJECTIVE

To determine whether postextubation respiratory support via heated, humidified, high-flow nasal cannulae (HHHFNC) results in a greater proportion of infants younger than 32 weeks' gestation being successfully extubated after a period of endotracheal positive pressure ventilation compared with conventional nasal continuous positive airway pressure (NCPAP).

STUDY DESIGN

We randomly assigned preterm ventilated infants to Vapotherm HHHFNC or NCPAP after extubation. The primary outcome, extubation failure, was defined by prespecified failure criteria in the 7 days after extubation.

RESULTS

A total of 132 ventilated infants younger than 32 weeks' gestation were randomized to receive either HHHFNC (n = 67) or NCPAP (n = 65). Extubation failure occurred in 15 (22%) of the HHHFNC group compared with 22 (34%) of the NCPAP group. There was no difference in the number of infants reintubated in the first week. Treatment with HHHFNC reduced the nasal trauma score 3.1 (SD 7.2) versus NCPAP 11.8 (SD 10.7), P < .001.

CONCLUSIONS

HHHFNC and NCPAP produced similar rates of extubation failure.

Effect of HFNC flow rate, cannula size, and nares diameter on generated airway pressures: an in vitro study

Increased use of non-invasive forms of respiratory support such as CPAP and HFNC in premature infants has generated a need for further investigation of the pulmonary effects of such therapies. In a series of in vitro tests, we measured delivered proximal airway pressures from a HFNC system while varying both the cannula flow and the ratio of nasal prong to simulated nares diameters. Neonatal and infant sized nasal prongs (3.0 and 3.7 mm O.D.) were inserted into seven sizes of simulated nares (range: 3-7 mm I.D. from anatomical measurements in 1-3 kg infants) for nasal prong-to-nares ratios ranging from 0.43 to 1.06. The nares were connected to an active test lung set at: TV 10 ml, 60 breaths/min, Ti 0.35 sec, compliance 1.6 ml/cm H₂O and airway resistance 70 cm H₂O/(L/sec), simulating a 1-3 kg infant with moderately affected lungs. A Fisher & Paykel Healthcare HFNC system with integrated pressure relief valve was set to flow rates of 1-6 L/min while cannula and airway pressures and cannula and mouth leak flows were measured during simulated mouth open, partially closed and fully closed conditions. Airway pressure progressively increased with both increasing HFNC flow rate and nasal prong-to-nares ratio. At 6 L/min HFNC flow with mouth open, airway pressures remained <1.7 cm H₂O for all ratios; and <10 cm H₂O with mouth closed for ratios <0.9. For ratios >0.9 and 50% mouth leak, airway pressures rapidly increased to 18 cm H₂O at 2 L/min HFNC flow followed by a pressure relief valve limited increase to 24 cm H₂O at 6 L/min. Safe and effective use of HFNC requires careful selection of an appropriate nasal prong-to-nares ratio even with an integrated pressure relief valve.

High-flow nasal cannula: transient fashion or new method of non-invasive ventilatory assistance?

Respiratory failure in the premature infants remains a difficult challenge. An alternative to the use of nasal continuous positive airway pressure (NCPAP) as a non-invasive modality to support respiratory distress in premature infants has been the recent introduction of high flow nasal cannula (HFNC) devices in many neonatal units. There has been increased use of HFNC presumably because of anecdotal reports and experience that it is easy to use, and well tolerated by the infants, while experiencing decreased nasal septumerosion. The paucity of evidence regarding its efficacy and safety, would support a caution approach to the use of HFNC. Particular concern has focused on the imprecise regulation and generation of pressure that may occur at higher flows especially in the smallest of infants.

Noise levels of neonatal high-flow nasal cannula devices--an in-vitro study

BACKGROUND

Excessive ambient noise levels have been identified as a potential risk factor for adverse outcome in very preterm infants. Noise level measurements for continuous positive airway pressure (CPAP) devices demonstrated that these constantly exceed current recommendations. The use of high-flow nasal cannula (HFNC) as an alternative non-invasive ventilation modality has become more popular in recent years in neonatal care.

OBJECTIVE

To study noise levels of two HFNC devices commonly used in newborns. As a comparison, noise levels of a continuous flow CPAP device were also studied.

METHODS

In-vitro study. The noise levels of two contemporary HFNC devices (Fisher & Paykel NHF™ and Vapotherm Precision Flow®) and one CPAP device (Dräger Babylog® 8000 plus) were measured in the oral cavity of a newborn manikin in an incubator in a quiet environment. HFNC flows of 4-8 l/min and CPAP pressures of 4-8 cm H2O were applied. The CPAP flow was set at 8 l/min as per unit practice.

RESULTS

Vapotherm HFNC generated the highest noise levels, measuring 81.2-91.4 dB(A) with increasing flow. Fisher & Paykel HFNC noise levels were between 78.8 and 81.2 dB(A). The CPAP device generated the lowest noise levels between 73.9 and 77.4 dB(A).

CONCLUSIONS

Both HFNC devices generated higher noise levels than the CPAP device. All noise levels were far above current recommendations of the American Academy of Pediatrics. In light of the long duration of non-invasive respiratory support of very preterm infants, less noisy devices are required to prevent the potentially adverse effects of continuing excessive noise exposure in the neonatal intensive care unit.

Nasopharyngeal airway pressures in bronchiolitis patients treated with high-flow nasal cannula oxygen therapy

BACKGROUND

Heated, humidified, high-flow nasal cannula oxygen therapy (HHHFNC) has been used to improve ventilation in preterm infants. There are no data on airway pressures generated and efficacy in bronchiolitis.

OBJECTIVE

The objective of this study was to determine nasopharyngeal (NP) pressures generated with HHHFNC therapy in bronchiolitis.

METHODS

We conducted a prospective, observational study to measure NP pressures at varying flow rates of HHHFNC therapy in moderate to severe bronchiolitis. Vital signs, bronchiolitis severity scores, and oxygen saturation were also noted.

RESULTS

Twenty-five patients were enrolled (mean, 78.1 [SD, 30.9] days; weight, 5.3 [SD, 1.1] kg). Nasopharyngeal pressures increased linearly with flow rates up to 6 L/min. Beyond 6 L/min, pressure increase was linear but less accelerated. On average, NP pressure increased by 0.45 cm H2O for each 1-L/min increase in flow rate. There were significant differences between pressures in open- and closed-mouth states for flow rates up to 6 L/min. At 6 L/min, the pressure in open-mouth state was 2.47 cm H2O and that in closed-mouth state was 2.74 cm H2O (P < 0.001). Linear regression analysis revealed that only flow (not weight or gender) had an effect on generated pressure. Bronchiolitis severity scores improved significantly with HHHFNC therapy (pre: 14.5 [SD, 1.4], post: 10.4 [SD, 1.2]; P < 0.001).

CONCLUSIONS

Increasing flow rates of HHHFNC therapy are associated with linear increases in NP pressures in bronchiolitis patients. Larger studies are needed to assess the clinical efficacy of HHHFNC therapy in bronchiolitis.

Weaning infants from mechanical ventilation

Protracted mechanical ventilation is associated with increased morbidity and mortality in preterm infants and thus the earliest possible weaning from mechanical ventilation is desirable. Weaning protocols may be helpful in achieving more rapid reduction in support. There is no clear consensus regarding the level of support at which an infant is ready for extubation. An improved ability to predict when a preterm infant has a high likelihood of successful extubation is highly desirable. In this article, available evidence is reviewed and reasonable evidence-based recommendations for expeditious weaning and extubation are provided.

Which continuous positive airway pressure system is best for the preterm infant with respiratory distress syndrome?

Various commercial and home-made continuous positive airway pressure (CPAP) systems are described in this article. CPAP may be delivered via a range of device-patient interfaces; nasal CPAP is most common, and short binasal prongs impose the least extrinsic load impedance on the infant. The source of pressure generation is categorized as either constant pressure or constant flow. The efficacy of different systems may vary according to whether lung volume recruitment, airway patency, minimization of work of breathing, or central nervous system stimulation are the primary goal of the clinical decision to use CPAP therapy.

Humidified high flow nasal cannulae: current practice in Australasian nurseries, a survey

AIM

Humidified High Flow Nasal Cannula (HHFNC) has been increasingly adopted as a new means of respiratory support throughout the world. However, evidence to support its safety and efficacy is limited. The aim of the present survey was to determine current practices regarding the usage of HHFNC by neonatologists in Australia and New Zealand.

METHODS

Surveys were sent to all 167 neonatologists identified by the list of centres in the Australia and New Zealand Neonatal Network.

RESULTS

A total of 157 surveys were sent to valid email addresses: 111 (71%) responded of which 105 (67%) had completed the questionnaire. HHFNC is used in 17 (63%) of neonatal intensive care units in Australia and New Zealand. It is most commonly used to reduce nasal trauma (91%) and provide continuous positive airways pressure (62%). The main perceived benefits of HHFNC were the easier application and care of the infant (86%), and improved tolerance by the baby (84%). Rain out leading to fluid instillation into the upper airway (59%) was the most common problem.

CONCLUSION

This survey has provided a snapshot of the practice of HHFNC usage in Australia and New Zealand in 2010 and has revealed that HHFNC use is widespread and that clinical practices are diverse. The majority of neonatologists acknowledge that there is limited evidence to support its efficacy and safety, and would be happy to participate in clinical trials to address how best to deliver HHFNC.

High-flow nasal cannulae for respiratory support of preterm infants: a review of the evidence

BACKGROUND

High-flow nasal cannulae (HFNC) are gaining in popularity as a form of non-invasive respiratory support for preterm infants in neonatal intensive care units around the world. They are proposed as an alternative to nasal continuous positive airway pressure (NCPAP) in a variety of clinical situations, including post-extubation support, primary therapy from birth and 'weaning' from NCPAP.

OBJECTIVES

To present and discuss the available evidence for the use of HFNC in the preterm population.

METHODS

An internet-based literature search for relevant, original research articles (both randomised studies and not) on the use of HFNC in preterm infants was undertaken.

RESULTS

A total of 19 studies were included in the review. Distending pressure generated by HFNC in preterm infants increases with increasing flow rate and decreasing infant size and varies according to the amount of leak around the prongs. HFNC may be as effective as NCPAP at improving respiratory parameters such as tidal volume and work of breathing in preterm infants, but probably only at flow rates >2 litres/min. The efficacy and safety of HFNC in preterm infants remain to be determined.

CONCLUSIONS

There is growing evidence of the feasibility of HFNC as an alternative to other forms of non-invasive ventilation in preterm infants. However, there remains uncertainty about the efficacy and safety of HFNC in this population. Until the results of larger randomised trials are known, widespread use of HFNC to treat preterm infants cannot be recommended.

High-flow nasal cannulae and nasal continuous positive airway pressure use in non-tertiary special care nurseries in Australia and New Zealand

AIM

Non-tertiary centres (NTCs) in Australia and New Zealand are increasingly providing non-invasive respiratory support, including high-flow nasal cannulae (HFNC) and nasal continuous positive airway pressure (nCPAP), to newborn infants. We aimed to determine the proportion of NTCs in these countries treating newborn infants with HFNC and nCPAP, and how these therapies are used.

METHODS

We surveyed public and private NTCs in Australia and public NTCs in New Zealand. The survey, directed at senior medical and nursing staff, consisted of questions regarding unit demographics, HFNC and nCPAP use.

RESULTS

One hundred seventeen responses were received regarding HFNC use, from 88% (80/91) of public hospitals and 64% (37/58) of private hospitals surveyed. Ten (8.5%) responders (nine public and one private) used HFNC; all used the Fisher & Paykel system. HFNC was used for respiratory distress syndrome from birth (9/10 units), as a weaning mode from nCPAP (5/10 units) and as treatment for apnoea (3/10 units). Flow rates used ranged from 1 to 8 L/min, with typical minimum flow of 1 L/min and maximum of 4-6 L/min. The main perceived advantage of HFNC was 'ease of use'. In the units treating newborn infants with nCPAP, it was used either in an ongoing fashion (43 units), short term or episodically (four units), or only for stabilisation prior to transfer (11 units). Excluding those units using nCPAP only for stabilisation and non-responders, 47/108 (44%) units were using nCPAP.

CONCLUSIONS

HFNC is being used in NTCs in Australia and New Zealand, and the use of nCPAP has increased over time.

High flow nasal cannula for respiratory support in preterm infants

BACKGROUND

High flow nasal cannulae (HFNC) are small, thin, tapered cannulae used to deliver oxygen or blended oxygen and air at flow rates of > 1 L/min. HFNC can be used to provide high concentrations of oxygen and may deliver positive end-expiratory pressure.

OBJECTIVES

To compare the safety and efficacy of HFNC with other forms of non-invasive respiratory support in preterm infants.

SEARCH STRATEGY

The strategy included searches of the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2010), MEDLINE, CINAHL, EMBASE and abstracts from conference proceedings.

SELECTION CRITERIA

Randomised or quasi-randomised trials comparing HFNC with other non-invasive forms of respiratory support in preterm infants immediately after birth or following extubation.

DATA COLLECTION AND ANALYSIS

Data were extracted and analysed by the authors. Relative risk, risk difference and number needed to treat were calculated.

MAIN RESULTS

Four studies were identified for inclusion in the review. The studies differed in the interventions compared (nasal continuous positive airway pressure (CPAP), humidified HFNC, non-humidified HFNC), the flow rates provided and the indications for respiratory support. Meta-analysis and subgroup analysis were not possible. When used as primary respiratory support after birth, one trial found similar rates of treatment failure in infants treated with HFNC and nasal CPAP. Following extubation, one trial found that infants treated with HFNC had a significantly higher rate of reintubation than those treated with nasal CPAP. Another trial found similar rates of reintubation for humidified and non-humidified HFNC, and the fourth trial found no difference between two different models of equipment used to deliver humidified HFNC.

AUTHORS' CONCLUSIONS

There is insufficient evidence to establish the safety or effectiveness of HFNC as a form of respiratory support in preterm infants. When used following extubation, HFNC may be associated with a higher rate of reintubation than nasal CPAP. Further adequately powered randomised controlled trials should be undertaken in preterm infants comparing HFNC with nasal CPAP and with other means of respiratory support; or of support following extubation. These trials should measure clinically important outcomes.

High-flow nasal cannula: impact on oxygenation and ventilation in an acute lung injury model

INTRODUCTION

High-flow nasal cannula therapy (HFNC) has been shown to be more effective than continuous positive airway pressure (CPAP) in reducing intubations and ventilator days. HFNC likely provides mechanisms to support respiratory efficiency beyond application of distending pressure. We reason that HFNC washout of nasopharyngeal dead space impacts CO(2) removal along with oxygenation. The aim of this study was to demonstrate the flow dependence of CO(2) reduction and improved oxygenation during HFNC and the dependence on leak around the nasal prongs.

MATERIALS AND METHODS

Neonatal piglets (n=13; 2-6 kg) were injured with IV oleic acid and supported with HFNC at 2 through 8 L/min. High and low leak around the nasal prongs was accomplished by using single and double prong cannulae, respectively. Measurement of hemodynamic, respiratory and blood gas parameters were made at each setting following 10 min for physiologic equilibration. Tracheal pressures were recorded by transmural catheters.

RESULTS

With HFNC, CO(2) trended downward in a flow-dependent manner independent of leak. Oxygenation and tracheal pressures increased in a flow-dependent manner with the greatest effect during double prong. At 8 L/min, tracheal pressures did not exceed 6 ± 1 cmH(2) O.

CONCLUSIONS

HFNC improves gas exchange in a flow-dependent manner; double prong had greater impact on O(2;) single prong had greater impact on CO(2) elimination.

Observational study of humidified high-flow nasal cannula compared with nasal continuous positive airway pressure

OBJECTIVES

To conduct an in vitro evaluation of a humidified high-flow nasal cannula (HFNC) system at different flows, cannula sizes, and air leaks and also an in vivo analysis of mean end-expiratory esophageal pressure (EEEP) from nasal continuous positive airway pressure at 6 cm H(2)O (NCPAP+6) versus HFNC.

STUDY DESIGN

In the in vitro study, we measured HFNC system pressure and flow, with varying degrees of leak and with and without the use of a pressure-limiting valve. In the in vivo study, we measured EEEP in 15 newborns on NCPAP+6 and then on HFNC at 6 L/minute, with flow decreased by 1 L/minute every 30 minutes. Heart rate, respiratory rate, fraction of inspired oxygen, arterial oxygen saturation, respiratory distress syndrome score, and EEEP were recorded for each intervention. Data analysis was done using repeated-measures analysis of variance and linear regression.

RESULTS

In the in vitro study, in the absence of leaks, the pressures were limited by the pressure-limiting valve only at flows > or = 2 L/minute. With leaks of 30% and 50%, delivered pressures were always < 3 cm H(2)O. In the in vivo study, respiratory rate increased from baseline (NCPAP+6) as flow decreased (P < .02). Intrapatient and interpatient coefficients of variation were always high.

CONCLUSIONS

A pressure-limiting valve is necessary in a HFNC system. Although mean EEEP levels were similar in NCPAP+6 and HFNC, tachypnea developed as flow diminished. This system apparently cannot predict EEEP, because of interpatient and intrapatient variation.

Diurnal cortisol levels and cortisol response in youths with obsessive-compulsive disorder

BACKGROUND/AIMS

Recent results indicate a role of the hypothalamic-pituitary-adrenal (HPA) axis in the pathophysiology of obsessive-compulsive disorder (OCD). Although childhood onset is common, the HPA axis has scarcely been studied in young OCD subjects. Therefore, the present study aimed at examining basal and response levels of salivary cortisol in a sample of young OCD subjects.

METHODS

Twenty-three children and adolescents with DSM-IV OCD were compared to a reference group of school children (n = 240-336). The basal cortisol rhythm was measured through saliva samples 3 times/day. The cortisol response to a psychological stressor (exposure therapy in the OCD group and a fire alarm in the reference group) was also examined.

RESULTS

Compared to the reference group, OCD subjects displayed higher early-morning cortisol values (p = 0.005) with no difference between the late-morning and evening values. The cortisol levels in the OCD group diminished in response to the psychological stressor, compared to a positive response in the reference group (p < 0.001). No relation was found between cortisol and clinical parameters.

CONCLUSION

These results support the idea that HPA hyperactivity, commonly found in adult OCD patients, is also present at an earlier stage of development, with specificity for the early-morning peak.