Pharyngeal pressure with high-flow nasal cannulae in premature infants

High Flow Nasal Cannula for Weaning Nasal Continuous Positive Airway Pressure in Preterm Infants: A Systematic Review and Meta-Analysis

INTRODUCTION

The aim of this study was to systematically review the benefits and harms of using a high-flow nasal cannula (HFNC) for weaning continuous positive airway pressure (CPAP) support in preterm infants.

METHODS

Cochrane Central, EMBASE, Medline, and Web of Science were searched from inception to July 15, 2023. Randomised clinical trials (RCTs) comparing weaning CPAP using HFNC versus weaning CPAP alone and evaluating predefined outcomes were included. Two authors independently performed data extraction and methodological quality assessment. Meta-analysis was conducted using a random-effects model, and the certainty of evidence was assessed using Cochrane GRADE.

RESULTS

Among 843 identified records, seven RCTs involving 781 preterm infants were eligible for analysis. The meta-analysis found no statistically significant difference in duration of respiratory support when using HFNC for weaning compared to weaning CPAP alone (mean difference (95% confidence interval) 3.52 (-0.02, 7.05); 5 RCTs; participants = 488; I2 = 29%). The evidence certainty was downgraded to low due to study limitations and imprecision. There were no significant differences in secondary outcomes, except for a lower occurrence of nasal trauma with HFNC for weaning CPAP compared to weaning CPAP alone (relative risk (95% confidence interval) 0.61 (0.38, 0.99); 4 RCTs; participants = 335; I2 = 0%). The evidence certainty for the secondary outcomes was low to very low.

CONCLUSION

Low certainty of evidence suggests using HFNC for weaning CPAP in preterm infants may not impact the duration of respiratory support. Caution is advised when considering HFNC for weaning CPAP, especially in extremely preterm infants, until additional supportive evidence on its safety becomes available.

Microbial signatures in amniotic fluid at preterm birth and association with bronchopulmonary dysplasia

BACKGROUND

Microbiome dysbiosis can have long-lasting effects on our health and induce the development of various diseases. Bronchopulmonary dysplasia (BPD) is a multifactorial disease with pre- and postnatal origins including intra-amniotic infection as main risk factor. Recently, postnatal pathologic lung microbiota colonization was associated with BPD. The objectives of this prospective observational cohort study were to describe differences in bacterial signatures in the amniotic fluid (AF) of intact pregnancies without clinical signs or risk of preterm delivery and AF samples obtained during preterm deliveries and their variations between different BPD disease severity stages.

METHODS

AF samples were collected under sterile conditions during fetal intervention from intact pregnancies (n = 17) or immediately before preterm delivery < 32 weeks (n = 126). Metabarcoding based approaches were used for the molecular assessment of bacterial 16S rRNA genes to describe bacterial community structure.

RESULTS

The absolute amount of 16S rRNA genes was significantly increased in AF of preterm deliveries and detailed profiling revealed a reduced alpha diversity and a significant change in beta diversity with a reduced relative abundance of 16S rRNA genes indicative for Lactobacillus and Acetobacter while Fusobacterium, Pseudomonas, Ureaplasma and Staphylococcus 16S rRNA gene prevailed. Although classification of BPD by disease severity revealed equivalent absolute 16S rRNA gene abundance and alpha and beta diversity in no, mild and moderate/severe BPD groups, for some 16S rRNA genes differences were observed in AF samples. Bacterial signatures of infants with moderate/severe BPD showed predominance of 16S rRNA genes belonging to the Escherichia-Shigella cluster while Ureaplasma and Enterococcus species were enriched in AF samples of infants with mild BPD.

CONCLUSIONS

Our study identified distinct and diverse intrauterine 16S rRNA gene patterns in preterm infants immediately before birth, differing from the 16S rRNA gene signature of intact pregnancies. The distinct 16S rRNA gene signatures at birth derive from bacteria with varying pathogenicity to the immature lung and are suited to identify preterm infants at risk. Our results emphasize the prenatal impact to the origins of BPD.

Optimising success of neonatal extubation: Respiratory support

In this review, we examine lung physiology before, during and after neonatal extubation and propose a three-phase model for the extubation procedure. We perform meta-analyses to compare different modes of non-invasive respiratory support after neonatal extubation and based on the findings, the following clinical recommendations are made.

State of the art on neonatal noninvasive respiratory support: How physiological and technological principles explain the clinical outcomes

Noninvasive respiratory support has gained significant popularity in neonatal units because of its potential to reduce lung injury associated with invasive mechanical ventilation. To minimize lung injury, clinicians aim to apply for noninvasive respiratory support as early as possible. However, the physiological background and the technology behind such support modes are not always clear, and many open questions remain regarding the indications of use and clinical outcomes. This narrative review discusses the currently available evidence for various noninvasive respiratory support modes applied in Neonatal Medicine in terms of physiological effects and indications. Reviewed modes include nasal continuous positive airway pressure, nasal high-flow therapy, noninvasive high-frequency oscillatory ventilation, nasal intermittent positive pressure ventilation (NIPPV), synchronized NIPPV and noninvasive neurally adjusted ventilatory assist. To enhance clinicians' awareness of each support mode's strengths and limitations, we summarize technical features related to the functioning mechanisms of devices and the physical properties of the interfaces commonly used for providing noninvasive respiratory support to neonates. We finally address areas of current controversy and suggest possible areas of research for implementing noninvasive respiratory support in neonatal intensive care units.

Changes in the patterns of respiratory support and incidence of bronchopulmonary dysplasia; a single center experience

BACKGROUND

With the advances in neonatal intensive care, the survival rate of extremely preterm infants is increasing. However, bronchopulmonary dysplasia (BPD) remains a major cause of morbidity among infants in this group. This study examined the changes in respiratory support modalities, specifically heated humidified high-flow nasal cannula (HHHFNC), and their association with BPD incidence among preterm infants born at < 29 weeks of gestation.

METHOD

This population-based retrospective cohort study included infants born at < 29 weeks of gestation between 2016 and 2020. Data regarding the use and duration of respiratory support modalities were obtained, including mechanical ventilation, continuous positive airway pressure, HHHFNC, and low-flow oxygen therapy. Additionally, the incidence of BPD was determined in the included infants. Trend analysis for each respiratory support modality and BPD incidence rate was performed to define the temporal changes associated with changes in BPD rates. In addition, a logistic regression model was developed to identify the association between BPD and severity grade using HHHFNC.

RESULTS

Three Hundred and sixteen infants were included in this study. The use and duration of HHHFNC therapy increased during the study period. Throughout the study period, the overall incidence of BPD was 49%, with no significant trends. The BPD rate was significantly higher in the infants who received HHHFNC than in those who did not (52% vs. 39%, P = 0.03). Analysis of BPD severity grades showed that both grade 1 BPD (34% vs. 21%, P = 0.03) and grade 2 BPD (12% vs. 1%, P < 0.01) were significantly more common among infants who received HHHFNC than among those who did not. In contrast, the incidence of grade 3 BPD was lower in infants who received HHFNC (6% vs. 17%, P < 0.01). The duration in days of HHHFNC was found to significantly predict BPD incidence (OR 1.04 [95%CI: 1.01-1.06], P < 0.01) after adjusting for confounding variables.

CONCLUSION

The use of HHHFNC in extremely preterm infants born at < 29 weeks of gestation is increasing. There was a significant association between the duration of HHHFNC therapy and the development of BPD in extremely preterm infants born at < 29 weeks of gestation.

Nasal high flow therapy for primary respiratory support in preterm infants

BACKGROUND

Nasal high flow (nHF) therapy provides heated, humidified air and oxygen via two small nasal prongs, at gas flows of more than 1 litre/minute (L/min), typically 2 L/min to 8 L/min. nHF is commonly used for non-invasive respiratory support in preterm neonates. It may be used in this population for primary respiratory support (avoiding, or prior to the use of mechanical ventilation via an endotracheal tube) for prophylaxis or treatment of respiratory distress syndrome (RDS). This is an update of a review first published in 2011 and updated in 2016.

OBJECTIVES

To evaluate the benefits and harms of nHF for primary respiratory support in preterm infants compared to other forms of non-invasive respiratory support.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date March 2022.

SELECTION CRITERIA

We included randomised or quasi-randomised trials comparing nHF with other forms of non-invasive respiratory support for preterm infants born less than 37 weeks' gestation with respiratory distress soon after birth.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane Neonatal methods. Our primary outcomes were 1. death (before hospital discharge) or bronchopulmonary dysplasia (BPD), 2. death (before hospital discharge), 3. BPD, 4. treatment failure within 72 hours of trial entry and 5. mechanical ventilation via an endotracheal tube within 72 hours of trial entry. Our secondary outcomes were 6. respiratory support, 7. complications and 8. neurosensory outcomes. We used GRADE to assess the certainty of evidence.

MAIN RESULTS

We included 13 studies (2540 infants) in this updated review. There are nine studies awaiting classification and 13 ongoing studies. The included studies differed in the comparator treatment (continuous positive airway pressure (CPAP) or nasal intermittent positive pressure ventilation (NIPPV)), the devices for delivering nHF and the gas flows used. Some studies allowed the use of 'rescue' CPAP in the event of nHF treatment failure, prior to any mechanical ventilation, and some allowed surfactant administration via the INSURE (INtubation, SURfactant, Extubation) technique without this being deemed treatment failure. The studies included very few extremely preterm infants less than 28 weeks' gestation. Several studies had unclear or high risk of bias in one or more domains. Nasal high flow compared with continuous positive airway pressure for primary respiratory support in preterm infants Eleven studies compared nHF with CPAP for primary respiratory support in preterm infants. When compared with CPAP, nHF may result in little to no difference in the combined outcome of death or BPD (risk ratio (RR) 1.09, 95% confidence interval (CI) 0.74 to 1.60; risk difference (RD) 0, 95% CI -0.02 to 0.02; 7 studies, 1830 infants; low-certainty evidence). Compared with CPAP, nHF may result in little to no difference in the risk of death (RR 0.78, 95% CI 0.44 to 1.39; 9 studies, 2009 infants; low-certainty evidence), or BPD (RR 1.14, 95% CI 0.74 to 1.76; 8 studies, 1917 infants; low-certainty evidence). nHF likely results in an increase in treatment failure within 72 hours of trial entry (RR 1.70, 95% CI 1.41 to 2.06; RD 0.09, 95% CI 0.06 to 0.12; number needed to treat for an additional harmful outcome (NNTH) 11, 95% CI 8 to 17; 9 studies, 2042 infants; moderate-certainty evidence). However, nHF likely does not increase the rate of mechanical ventilation (RR 1.04, 95% CI 0.82 to 1.31; 9 studies, 2042 infants; moderate-certainty evidence). nHF likely results in a reduction in pneumothorax (RR 0.66, 95% CI 0.40 to 1.08; 10 studies, 2094 infants; moderate-certainty evidence) and nasal trauma (RR 0.49, 95% CI 0.36 to 0.68; RD -0.06, 95% CI -0.09 to -0.04; 7 studies, 1595 infants; moderate-certainty evidence). Nasal high flow compared with nasal intermittent positive pressure ventilation for primary respiratory support in preterm infants Four studies compared nHF with NIPPV for primary respiratory support in preterm infants. When compared with NIPPV, nHF may result in little to no difference in the combined outcome of death or BPD, but the evidence is very uncertain (RR 0.64, 95% CI 0.30 to 1.37; RD -0.05, 95% CI -0.14 to 0.04; 2 studies, 182 infants; very low-certainty evidence). nHF may result in little to no difference in the risk of death (RR 0.78, 95% CI 0.36 to 1.69; RD -0.02, 95% CI -0.10 to 0.05; 3 studies, 254 infants; low-certainty evidence). nHF likely results in little to no difference in the incidence of treatment failure within 72 hours of trial entry compared with NIPPV (RR 1.27, 95% CI 0.90 to 1.79; 4 studies, 343 infants; moderate-certainty evidence), or mechanical ventilation within 72 hours of trial entry (RR 0.91, 95% CI 0.62 to 1.33; 4 studies, 343 infants; moderate-certainty evidence). nHF likely results in a reduction in nasal trauma, compared with NIPPV (RR 0.21, 95% CI 0.09 to 0.47; RD -0.17, 95% CI -0.24 to -0.10; 3 studies, 272 infants; moderate-certainty evidence). nHF likely results in little to no difference in the rate of pneumothorax (RR 0.78, 95% CI 0.40 to 1.53; 4 studies, 344 infants; moderate-certainty evidence). Nasal high flow compared with ambient oxygen We found no studies examining this comparison. Nasal high flow compared with low flow nasal cannulae We found no studies examining this comparison.

AUTHORS' CONCLUSIONS

The use of nHF for primary respiratory support in preterm infants of 28 weeks' gestation or greater may result in little to no difference in death or BPD, compared with CPAP or NIPPV. nHF likely results in an increase in treatment failure within 72 hours of trial entry compared with CPAP; however, it likely does not increase the rate of mechanical ventilation. Compared with CPAP, nHF use likely results in less nasal trauma and likely a reduction in pneumothorax. As few extremely preterm infants less than 28 weeks' gestation were enrolled in the included trials, evidence is lacking for the use of nHF for primary respiratory support in this population.

Weaning and extubation from neonatal mechanical ventilation: an evidenced-based review

Mechanical ventilation is a lifesaving treatment used to treat critical neonatal patients. It facilitates gas exchange, oxygenation, and CO2 removal. Despite advances in non-invasive ventilatory support methods in neonates, invasive ventilation (i.e., ventilation via an endotracheal tube) is still a standard treatment in NICUs. This ventilation approach may cause injury despite its advantages, especially in preterm neonates. Therefore, it is recommended that neonatologists consider weaning neonates from invasive mechanical ventilation as soon as possible. This review examines the steps required for the neonate's appropriate weaning and safe extubation from mechanical ventilation.

Diaphragm electrical activity during weaning of nasal high-flow therapy in preterm infants

OBJECTIVE

To determine whether electrical activity of the diaphragm (Edi) changes with weaning nasal high-flow (HF) therapy in preterm infants according to a standardised protocol.

DESIGN

Prospective observational cohort study.

SETTING

Neonatal intensive care unit.

PATIENTS

Preterm infants born at <32 weeks gestation, receiving nasal HF as part of routine clinical care.

INTERVENTIONS

Infants recruited to the study had their HF weaned according to set clinical criteria. Edi was measured using a modified gastric feeding tube serially from baseline (pre-wean) to 24-hours post-wean.

MAIN OUTCOME MEASURES

Change in Edi from baseline was measured at four time points up to 24 hours after weaning. Minimum Edi during expiration, maximum Edi during inspiration and amplitude of the Edi signal (Edi_delta) were measured. Clinical parameters (heart rate, respiratory rate and fraction of inspired oxygen) were also recorded.

RESULTS

Forty preterm infants were recruited at a mean corrected gestational age of 31.6 (±2.7) weeks. Data from 156 weaning steps were analysed, 91% of which were successful. Edi did not change significantly from baseline during flow reduction steps, but a significant increase in diaphragm activity was observed when discontinuing HF (median increase in Edi_delta immediately post-discontinuation 1.7 µV (95% CI: 0.6 to 3.0)) and at 24 hours 1.9 µV (95% CI: 0.7 to 3.8)). No significant difference in diaphragm activity was observed between successful and unsuccessful weaning steps.

CONCLUSIONS

A protocolised approach to weaning has a high probability of success. Edi does not change with reducing HF rate, but significantly increases with discontinuation of HF from 2 L/min.

Noninvasive Ventilation in Preterm Infants: Factors Influencing Weaning Decisions and the Role of the Silverman-Andersen Score

The factors influencing weaning of preterm infants from noninvasive ventilation (NIV) are poorly defined and the weaning decisions are often driven by subjective judgement rather than objective measures. To standardize quantification of respiratory effort, the Silverman-Andersen Score (SAS) was included in our nursing routine. We investigated the factors that steer the weaning process and whether the inclusion of the SAS would lead to more stringent weaning. Following SAS implementation, we prospectively evaluated 33 neonates born ≤ 32 + 0 weeks gestational age. Age-, weight- and sex-matched infants born before routine SAS evaluation served as historic control. In 173 of 575 patient days, NIV was not weaned despite little respiratory distress (SAS ≤ 2), mainly due to bradycardias (60% of days without weaning), occurring alone (40%) or in combination with other factors such as apnea/desaturations. In addition, “soft factors” that are harder to grasp impact on weaning decisions, whereas the SAS overall played a minor role. Consequently, ventilation times did not differ between the groups. In conclusion, NIV weaning is influenced by various factors that override the absence of respiratory distress limiting the predictive value of the SAS. An awareness of the factors that influence weaning decisions is important as prolonged use of NIV has been associated with adverse outcome. Guidelines are necessary to standardize NIV weaning practice.

Randomized Trial to Compare Nasoduodenal Tube and Nasogastric Tube Feeding in Infants with Bronchiolitis on High-Flow Nasal Cannula

Objectives In this article, we aimed to determine if there is a difference in length of respiratory support between nasoduodenal (NDT) and nasogastric tube (NGT) feedings in patients with bronchiolitis on high-flow nasal cannula (HFNC).

Methods A single-center nonblinded parallel randomized control trial at a tertiary care hospital was designed. Pediatric patients ≤ 12 months old with bronchiolitis, on HFNC, requiring nutrition via a feeding tube were eligible. Patients were randomized to NGT or NDT and stratified into low- and high-risk groups. Length of respiratory support was the primary outcome. Secondary outcomes included length of stay, number of emesis events, maximum level of respiratory support, number of X-rays to confirm tube placement, number of attempts to place the tube by staff, adverse events during placement, instances of pediatric intensive care unit admission, and emergency room visits and hospital readmissions within 7 and 30 days after discharge.

Results Forty patients were randomized, 20 in each arm. There were no significant differences in baseline characteristics. We found no significant difference in length of respiratory support between the two groups (NGT 0.84 incidence rate ratio [0.58, 1.2], p = 0.34). None of the secondary outcomes showed significant differences. Each arm reported one adverse event: nasal trauma in the NGT group and pneumothorax in the NDT group.

Conclusion For infants with bronchiolitis on HFNC that need enteric tube feedings, we find no difference in duration of respiratory support or other clinically relevant outcomes for those with NGT or NDT. These results should be interpreted in the context of a limited sample size and an indirect primary outcome of length of respiratory support that may be influenced by other factors besides aspiration events.

Preclinical Assessment of Nebulized Surfactant Delivered through Neonatal High Flow Nasal Cannula Respiratory Support

High-flow nasal cannula (HFNC) is a non-invasive respiratory support (NRS) modality to treat premature infants with respiratory distress syndrome (RDS). The delivery of nebulized surfactant during NRS would represent a truly non-invasive method of surfactant administration and could reduce NRS failure rates. However, the delivery efficiency of nebulized surfactant during HFNC has not been evaluated in vitro or in animal models of respiratory distress. We, therefore, performed first a benchmark study to compare the surfactant lung dose delivered by commercially available neonatal nasal cannulas (NCs) and HFNC circuits commonly used in neonatal intensive care units. Then, the pulmonary effect of nebulized surfactant delivered via HFNC was investigated in spontaneously breathing rabbits with induced respiratory distress. The benchmark study revealed the surfactant lung dose to be relatively low for both types of NCs tested (Westmed NCs 0.5 ± 0.45%; Fisher & Paykel NCs 1.8 ± 1.9% of a nominal dose of 200 mg/kg of Poractant alfa). The modest lung doses achieved in the benchmark study are compatible with the lack of the effect of nebulized surfactant in vivo (400 mg/kg), where arterial oxygenation and lung mechanics did not improve and were significantly worse than the intratracheal instillation of surfactant. The results from the present study indicate a relatively low lung surfactant dose and negligible effect on pulmonary function in terms of arterial oxygenation and lung mechanics. This negligible effect can, for the greater part, be explained by the high impaction of aerosol particles in the ventilation circuit and upper airways due to the high air flows used during HFNC.

Use of high flow nasal cannula in Spanish neonatal units

INTRODUCTION

The use of high-flow cannula therapy (HFNC) in neonatal units has increased in recent years, but there are no consensus guidelines on its indications and application strategies. Our aim was to know the rate of use of HFNC, their indications and the management variability among Spanish neonatal units.

MATERIAL AND METHODS

Twenty-five-question survey for medical and nursing staff. Level II and III units were contacted by phone and sent in Google forms between September 2016 and December 2018.

RESULTS

Ninety-seven responses (63.9% medical, 36.1% nursing), from 69 neonatal units representing 15 autonomous communities (87% level of care III; 13% level II). All units except one have HFNC with a humidified and heated system. Their most frequent indications are: non-invasive ventilation weaning (79.4%), bronchiolitis (69.1%), respiratory distress of the term newborn (58.8%), after extubation (50.5%). Minimum flow (1-5 L/min) and maximum flow (5-15 L/min) are variable between units. 22.7% have experienced some adverse effect from its use (9 air leak, 12 nasal trauma). Less than half have an employment protocol, but all the answers agree on the usefulness of national recommendations.

CONCLUSIONS

HFNC therapy is widely used in Spanish units, but there is great variability in its indications and strategies of use. National recommendations would be applicable in most units and would allow unifying its use.

Treatment of Pediatric Patients With High-Flow Nasal Cannula and Considerations for Oral Feeding: A Review of the Literature

PURPOSE

High-Flow Nasal Cannula (HFNC) has become an increasingly common means of noninvasive respiratory support in pediatrics and is being used in infants and children with respiratory distress both inside and outside of the intensive care units. Despite the widespread use of HFNC, there remains a paucity of data on optimal flow rates and its impact on morbidity, mortality, and desired outcomes. Given the scarcity of information in these critical areas, it is not surprising that guidelines for initiation of oral feeding do not exist. This review article will review HFNC mechanisms of action, its use in specific populations and settings, and finally what is known about initiation of feeding during this therapy.

CONCLUSIONS

The practice of withholding oral feeding solely, because of HFNC, is not supported in the literature at the time of this writing, but in the absence of safety data from clinical trials, clinicians should proceed with caution and consider patient-specific factors while making decisions about oral feeding. Well-controlled prospective clinical trials are needed for development of best practice clinical guidelines and attainment of optimal outcomes.

High-flow nasal cannula in children with asthma exacerbation: A review of current evidence

Asthma is the commonest obstructive airway disease and the leading cause of morbidity in children. In the pediatric population, acute exacerbations of asthma are a frequent cause of presentations and hospital admissions. An acute asthma exacerbation is potentially life-threatening; it is predominantly treated using conventional oxygen therapy with bronchodilators and systemic corticosteroids. The treatment of those who do not respond to conventional therapy is escalated to noninvasive positive pressure ventilation (NIPPV) before invasive ventilation. Although NIPPV has demonstrated benefits and safety, it still has limitations such as treatment intolerance caused mainly by discomfort and complications. High-flow oxygen therapy administered through a nasal cannula (HFNC) provides respiratory support with adequate airway humidity and has demonstrated safety and benefits in clinical practice. In the present review, we discuss HFNC and variations in HFNC use, focusing on its feasibility and current evidence of using it on children with asthma exacerbations.

Nasal Continuous Positive Airway Pressure and High-Flow Nasal Cannula Today

This study reviews the mechanisms of action and physiologic effects of nasal continuous positive airway pressure (nCPAP) and high-flow nasal cannula (HFNC) in preterm infants with respiratory distress syndrome, discusses the main characteristics of available devices and patients' interfaces, reports on risk of failure and possible adverse effects, and summarizes clinical evidence regarding effectiveness for preventing mechanical ventilation as primary respiratory support or after extubation in the neonatal intensive care unit. nCPAP is preferred to HFNC as primary mode of noninvasive respiratory support in preterm infants with respiratory distress syndrome, whereas HFNC is an effective alternative to nCPAP after extubation.

Pharyngeal pressure due to high-flow nasal cannula devices in preterm infants

BACKGROUND

In infants, a high-flow nasal cannula (HFNC) generates continuous positive pressure on the upper airway. This study aimed to evaluate the association between pharyngeal pressure and flow rate, and the association between pharyngeal pressure and bodyweight for two types of HFNC devices commonly used in preterm infants: the Optiflow Junior, hereafter "FP" (Fisher & Paykel, Auckland, New Zealand), and the Precision Flow, hereafter "VT" (Vapotherm, Exeter, NH, USA).

METHODS

Pharyngeal pressure measurements were performed in 12 preterm infants who received HFNC support. Flow rates of 1 to 4 L/kg/min were studied.

RESULTS

The median weight at the time of measurement was 1,290 g (range, 953-1,932 g). The FP was used in eight infants and the VT in four. In both of the groups, the flow rate and pharyngeal pressure appeared to be positively correlated except for the premature cannula in the FP group. At a flow rate of ≥2 L/kg/min, there was a positive correlation between the bodyweight and pharyngeal pressure in infants with premature and neonatal cannulas in the FP group. Conversely, at the same flow rate, there was a negative correlation between the bodyweight and pharyngeal pressure in infants with a SOLO cannula in the VT group.

CONCLUSIONS

In preterm infants, the flow rate and pharyngeal pressure were positively correlated in many HFNC cannulas. However, the pharyngeal pressure and bodyweight appeared to be positively and negatively correlated in the FP and VT groups, respectively. Future studies with larger sample sizes should further investigate this issue.

Cerebral oxygenation is stable in preterm infants transitioning to heated humidified high-flow nasal cannula therapy

AIM

To assess cerebral oxygenation in premature infants who are transitioning from nasal continuous positive airway pressure (nCPAP) to heated humidified high-flow nasal cannula therapy (HFNC).

METHODS

A prospective observational study done in a single-centre neonatal intensive care unit (NICU). Regional cerebral oxygen saturations (RcSO₂ ) were measured using frequency-domain near-infrared spectroscopy (FD-NIRS) in very low birthweight (VLBW) premature infants born at <32 weeks transitioning from nCPAP to HFNC.

RESULTS

Median gestational age was 27 weeks and median birthweight was 924 g. Recordings were performed at a median gestational age of 30 weeks and a median postnatal age of 10 days. Median weight at study entry was 1111 g. Cerebral oxygenation was not significantly different in infants transitioning from nCPAP to HFNC (66% vs 66%).

CONCLUSION

No difference in cerebral oxygenation in premature infants transitioning from nCPAP to HFNC was observed. This finding is reassuring and further supports the use of HFNC in preterm infants.

Effect of the measurement of the work of breathing on the respiratory outcome of preterms

RATIONALE

There are no validated criteria for the choice of the optimal type of noninvasive respiratory support (NRS) and most appropriate settings in preterms.

METHODS

The work of breathing (WOB) during oxygen (O2) alone, nasal continuous positive pressure (nCPAP) and high flow nasal cannula (HFNC) was compared in preterm babies (23-30 weeks' gestation, "physiological group") needing any type of noninvasive respiratory support ("baseline" NRS) at 4 weeks of life. Babies were thereafter treated with the NRS associated with the greatest reduction in WOB ("optimal NRS"). The respiratory outcome at 36 weeks" gestation of these babies was compared to a "control" group treated with NRS based on standard noninvasive parameters. Preterm babies were prospectively enrolled in 3 centers and randomized into the "physiological" or "control" group.

RESULTS

Thirty babies were randomized. WOB with "baseline" NRS was higher than the "optimal" NRS and the consequent NRS chosen by physicians (p = 0.001). WOB was lower during HFNC than during O2 (p = 0.032) but WOB was comparable between nCPAP and HFNC, and between nCPAP and O2. Notably, WOB was near to normal during spontaneous breathing with O2. Respiratory outcome at 36 week' gestation was comparable between the 2 groups.

CONCLUSION

The optimization of NRS by means of the measurement of WOB in preterms requiring any type of NRS at 4 weeks of life was able to decrease the WOB but had no effect on the clinical outcome at 36 weeks' gestation.

Disruptions in the development of feeding for infants with congenital heart disease

Congenital heart disease (CHD) is the most common birth defect for infants born in the United States, with approximately 36,000 affected infants born annually. While mortality rates for children with CHD have significantly declined, there is a growing population of individuals with CHD living into adulthood prompting the need to optimise long-term development and quality of life. For infants with CHD, pre- and post-surgery, there is an increased risk of developmental challenges and feeding difficulties. Feeding challenges carry profound implications for the quality of life for individuals with CHD and their families as they impact short- and long-term neurodevelopment related to growth and nutrition, sensory regulation, and social-emotional bonding with parents and other caregivers. Oral feeding challenges in children with CHD are often the result of medical complications, delayed transition to oral feeding, reduced stamina, oral feeding refusal, developmental delay, and consequences of the overwhelming intensive care unit (ICU) environment. This article aims to characterise the disruptions in feeding development for infants with CHD and describe neurodevelopmental factors that may contribute to short- and long-term oral feeding difficulties.

[Use of high flow nasal cannula in Spanish neonatal units]

INTRODUCTION

The use of high-flow cannula therapy (HFNC) in neonatal units has increased in recent years, but there are no consensus guidelines on its indications and application strategies. Our aim was to know the rate of use of HFNC, their indications and the management variability among Spanish neonatal units.

MATERIAL AND METHODS

Twenty-five-question survey for medical and nursing staff. Level II and III units were contacted by phone and sent in Google forms between September 2016 and December 2018.

RESULTS

Ninety-seven responses (63.9% medical, 36.1% nursing), from 69 neonatal units representing 15 autonomous communities (87% level of care III; 13% level II). All units except one have HFNC with a humidified and heated system. Their most frequent indications are: non-invasive ventilation weaning (79.4%), bronchiolitis (69.1%), respiratory distress of the term newborn (58.8%), after extubation (50.5%). Minimum flow (1-5 L/min) and maximum flow (5-15 L/min) are variable between units. 22.7% have experienced some adverse effect from its use (9 air leak, 12 nasal trauma). Less than half have an employment protocol, but all the answers agree on the usefulness of national recommendations.

CONCLUSIONS

HFNC therapy is widely used in Spanish units, but there is great variability in its indications and strategies of use. National recommendations would be applicable in most units and would allow unifying its use.

Gas flow in preterm infants treated with bubble CPAP: an observational study

OBJECTIVE

To measure the nasal gas flow in infants treated with bubble continuous positive airway pressure (CPAP) and compare it with commonly used flows during nasal high flow (nHF) treatment.

DESIGN

This is a prospective, single-centre study. Bubble CPAP pressure was measured at the nasal prongs. Set gas flow was reduced until bubbling in the water chamber just ceased. Set gas flow without bubbling then approximated flow entering the infant's nose ('delivered flow').

SETTING

Neonatal intensive care at The Royal Women's Hospital, Melbourne, Australia.

PATIENTS

Clinically stable preterm infants receiving bubble CPAP therapy.

MAIN OUTCOME MEASURE

Delivered flow (L/min) when bubbling stopped at a range of clinically set CPAP pressures (cm H₂O).

RESULTS

Forty-four infants were studied, with a mean (SD) gestational age at birth of 28.4 (2.2) weeks and birth weight of 1154 (419) g. At the time of the study, infants had a median (IQR) age of 4.5 (2-12) days and a mean (SD) weight of 1205 (407) g. Delivered flow ranged from 0.5 to 9.0 L/min, and increased with higher set CPAP pressures (median 3.5 L/min at CPAP 5 cm H₂O vs 6.3 L/min at CPAP 8 cm H₂O) and heavier weights (median 3.5 L/min in infants <1000 g vs 6.5 L/min for infants >1500 g).

CONCLUSIONS

Nasal gas flows during bubble CPAP in preterm infants are similar to flows used during nHF and increase with higher set bubble CPAP pressures and in larger infants. Trial registration number ACTRN12619000197134.

Oral feeding for infants and children receiving nasal continuous positive airway pressure and high flow nasal cannula: a systematic review

BACKGROUND

The aim of this systematic review was to determine whether introduction of oral feeding for infants and children receiving nasal continuous positive airway pressure (nCPAP) or high flow nasal cannula (HFNC) respiratory support facilitates achievement of full oral feeding without adverse effects, compared to no oral feeding (NPO; nil per oral) on CPAP or HFNC.

METHODS

A protocol was lodged with the PROSPERO International Prospective Register of Systematic Reviews. We searched Medline, Embase, CINAHL, CENTRAL and AustHealth from database inception to 10th June 2020. Study population included children (preterm to < 18 years) on nCPAP or HFNC who were orally feeding. Primary outcomes included full or partial oral feeding and oropharyngeal aspiration. Secondary outcomes examined adverse events including clinical signs of aspiration, aspiration pneumonia and deterioration in respiratory status.

RESULTS

The search retrieved 1684 studies following duplicate removal. Title and abstract screening identified 70 studies for full text screening and of these, 16 were included in the review for data extraction. Methods of non-invasive ventilation (NIV) included nCPAP (n = 6), nCPAP and HFNC (n = 5) and HFNC (n = 5). A metanalysis was not possible as respiratory modes and cohorts were not comparable. Eleven studies reported on adverse events. Oral feeding safety was predominantly based on retrospective data from chart entries and clinical signs, with only one study using an instrumental swallow evaluation (VFSS) to determine aspiration status.

CONCLUSIONS

Findings are insufficient to conclude whether commencing oral feeding whilst on nCPAP or HFNC facilitates transition to full oral feeding without adverse effects, including oropharyngeal aspiration. Further research is required to determine the safety and efficacy of oral feeding on CPAP and HFNC for infants and children.

TRIAL REGISTRATION

PROSPERO registration number:  CRD42016039325 .

Correlation of Early Nutritional Supply and Development of Bronchopulmonary Dysplasia in Preterm Infants <1,000 g

Background: Bronchopulmonary dysplasia (BPD) has multifactorial origins and is characterized by distorted physiological lung development. The impact of nutrition on the incidence of BPD is less studied so far. Methods: A retrospective single center analysis was performed on n = 207 preterm infants <1,000 g and <32 weeks of gestation without severe gastrointestinal complications to assess the impact of variations in nutritional supply during the first 2 weeks of life on the pulmonary outcome. Infants were grouped into no/mild and moderate/severe BPD to separate minor and major limitations in lung function. Results: After risk adjustment for gestational age, birth weight, sex, multiples, and antenatal steroids, a reduced total caloric intake and carbohydrate supply as the dominant energy source during the first 2 weeks of life prevailed statistically significant in infants developing moderate/severe BPD (p < 0.05). Enteral nutritional supply was increased at a slower rate with prolonged need for parenteral nutrition in the moderate/severe BPD group while breast milk provision and objective criteria of feeding intolerance were equally distributed in both groups. Conclusion: Early high caloric intake is correlated with a better pulmonary outcome in preterm infants <1,000 g. Our results are in line with the known strong impact of nutrient supply on somatic growth and psychomotor development. Our data encourage paying special attention to further decipher the ideal nutritional requirements for unrestricted lung development and promoting progressive enteral nutrition in the absence of objective criteria of feeding intolerance.

Predicting Nasal High-Flow Treatment Success in Newborn Infants with Respiratory Distress Cared for in Nontertiary Hospitals

OBJECTIVE

To evaluate demographic and clinical variables as predictors of nasal high-flow treatment success in newborn infants with respiratory distress cared for in Australian nontertiary special care nurseries.

STUDY DESIGN

A secondary analysis of the HUNTER trial, a multicenter, randomized controlled trial evaluating nasal high-flow as primary respiratory support for newborn infants with respiratory distress who were born ≥31 weeks of gestation and with birth weight ≥1200 g, and cared for in Australian nontertiary special care nurseries. Treatment success within 72 hours after randomization to nasal high-flow was determined using objective criteria. Univariable screening and multivariable analysis was used to determine predictors of nasal high-flow treatment success.

RESULTS

Infants (n = 363) randomized to nasal high-flow in HUNTER were included in the analysis; the mean gestational age was 36.9 ± 2.7 weeks and birth weight 2928 ± 782 g. Of these infants, 290 (80%) experienced nasal high-flow treatment success. On multivariable analysis, nasal high-flow treatment success was predicted by higher gestational age and lower fraction of inspired oxygen immediately before randomization, but not strongly. The final model was found to have an area under the curve of 0.65, which after adjustment for optimism was found to be 0.63 (95% CI, 0.57-0.70).

CONCLUSIONS

Gestational age and supplemental oxygen requirement may be used to guide decisions regarding the most appropriate initial respiratory support for newborn infants in nontertiary special care nurseries. Further prospective research is required to better identify which infants are most likely to be successfully treated with nasal high-flow.

TRIAL REGISTRATION

ACTRN12614001203640.

The Relationship between Oxidative Stress, Intermittent Hypoxemia, and Hospital Duration in Moderate Preterm Infants

INTRODUCTION

Lipid peroxidation products are present following oxidation of polyunsaturated fatty acids in the eye, brain, and various cell membranes. Elevated levels of lipid peroxidation products and increased intermittent hypoxemia (IH) events have been associated with adverse outcomes in extremely preterm infants. The moderate preterm newborn has a still-developing oxidant defense system and immature respiratory control, but little is known about lipid peroxidation levels and IH in this larger and more common preterm population.

OBJECTIVE

To determine the association between oxidative stress and IH in moderate preterm infants.

METHOD

Oxygen saturation was continuously monitored in 51 moderate preterm infants (i.e., 31 + 0/7 to 33 + 6/7 weeks' gestation). Urine samples were collected at the end of the first and second weeks of life. Samples were analyzed for total lipid peroxidation products (neurofurans, isofurans, neuroprostanes, isoprostanes, and di-homo-isofurans).

RESULT

At week 1, there was a correlation between increased IH frequency and neurofurans (p < 0.04) and di-homo-isofurans (p < 0.003). At week 2, there was no correlation between IH and lipid peroxidation markers. Ele-vations in neurofurans, isofurans, neuroprostanes, and di-homo-isofurans in the first and/or second week of life were associated with a longer stay in hospital.

CONCLUSION

Elevations in lipid peroxidation biomarkers in moderate preterm infants during their first weeks of life are associated with a higher frequency of IH and prolonged hospitalization.

Measurement of airway pressure during high-flow nasal therapy in apnoeic oxygenation: a randomised controlled crossover trial. Anaesthesia 2020;76:27-35. [PMID: 32776518 DOI: 10.1111/anae.15224]

It is recognised that high-flow nasal therapy can prevent desaturation during airway management. Studies in spontaneously breathing patients show an almost linear relationship between flow rate and positive airway pressure in the nasopharynx. Positive airway pressure has been suggested as one of the possible mechanisms explaining how high-flow nasal therapy works. However, data on pressures generated by high-flow nasal therapy in apnoeic adults under general anaesthesia are absent. This randomised controlled crossover trial investigated airway pressures generated by different flow rates during high-flow nasal therapy in anaesthetised and paralysed apnoeic patients, comparing pressures with closed and open mouths. Following induction of anaesthesia and neuromuscular blockade, a continuous jaw thrust was used to enable airway patency. Airway pressure was measured in the right main bronchus, the middle of the trachea and the pharynx, using a fibreoptically-placed catheter connected to a pressure transducer. Each measurement was randomised with respect to closed or open mouth and different flow rates. Twenty patients undergoing elective surgery were included (mean (SD) age 38 (18) years, BMI 25.0 (3.3) kg.m^-2 , nine women, ASA physical status 1 (35%), 2 (55%), 3 (10%). While closed mouths and increasing flow rates demonstrated non-linear increases in pressure, the pressure increase was negligible with an open mouth. Airway pressures remained below 10 cmH₂ O even with closed mouths and flow rates up to 80 l.min^-1 ; they were not influenced by catheter position. This study shows an increase in airway pressures with closed mouths that depends on flow rate. The generated pressure is negligible with an open mouth. These data question positive airway pressure as an important mechanism for maintenance of oxygenation during apnoea.

Early Neonatal Oxygen Exposure Predicts Pulmonary Morbidity and Functional Deficits at 1 Year

OBJECTIVE

To evaluate the predictive value of cumulative oxygen exposure thresholds over the first 2 postnatal weeks, linking them to bronchopulmonary dysplasia (BPD) and 1-year pulmonary morbidity and lung function in extremely low gestational age newborns.

STUDY DESIGN

Infants (N = 704) enrolled in the Prematurity and Respiratory Outcomes Program, a multicenter prospective cohort study, that survived to discharge were followed through their neonatal intensive care unit hospitalization to 1-year corrected age. Cumulative oxygen exposure (Oxygen_AUC14) thresholds were derived from univariate models of BPD, stratifying infants into high-, intermediate-, and low-oxygen exposure groups. These groups were then used in multivariate logistic regressions to prospectively predict post-prematurity respiratory disease (PRD), respiratory morbidity score (RMS) in the entire cohort, and pulmonary function z scores (N = 108 subset of infants) at 1-year corrected age.

RESULTS

Over the first 14 postnatal days, infants exposed to high oxygen averaged ≥33.1% oxygen, infants exposed to intermediate oxygen averaged 29.1%-33.1%, and infants exposed to low oxygen were below both cutoffs. In multivariate models, infants exposed to high oxygen showed increased PRD and RMS, whereas infants exposed to intermediate oxygen demonstrated increased moderate/severe RMS. Infants in the high/intermediate groups had decreased forced expiratory volume at 0.5 seconds/forced vital capacity ratio.

CONCLUSIONS

Oxygen_AUC14 establishes 3 thresholds of oxygen exposure that risk stratify infants early in their neonatal course, thereby predicting short-term (BPD) and 1-year (PRD, RMS) respiratory morbidity. Infants with greater Oxygen_AUC14 have altered pulmonary function tests at 1 year of age, indicating early evidence of obstructive lung disease and flow limitation, which may predispose extremely low gestational age newborns to increased long-term pulmonary morbidity.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01435187.

Bacterial Colonization within the First Six Weeks of Life and Pulmonary Outcome in Preterm Infants <1000 g

Bronchopulmonary dysplasia (BPD) is a multifactorial disease mainly provoked by pre- and postnatal infections, mechanical ventilation, and oxygen toxicity. In severely affected premature infants requiring mechanical ventilation, association of bacterial colonization of the lung and BPD was recently disclosed. To analyze the impact of bacterial colonization of the upper airway and gastrointestinal tract on moderate/severe BPD, we retrospectively analyzed nasopharyngeal and anal swabs taken weekly during the first 6 weeks of life at a single center in n = 102 preterm infants <1000 g. Colonization mostly occurred between weeks 2 and 6 and displayed a high diversity requiring categorization. Analyses of deviance considering all relevant confounders revealed statistical significance solely for upper airway colonization with bacteria with pathogenic potential and moderate/severe BPD (p = 0.0043) while no link could be established to the Gram response or the gastrointestinal tract. Our data highlight that specific colonization of the upper airway poses a risk to the immature lung. These data are not surprising taking into account the tremendous impact of microbial axes on health and disease across ages. We suggest that studies on upper airway colonization using predefined categories represent a feasible approach to investigate the impact on the pulmonary outcome in ventilated and non-ventilated preterm infants.

Nasal high-flow oxygen in pediatric anesthesia and airway management

Nasal High-Flow (NHF) is weight-dependent in children, aimed to match peak inspiratory flow and thereby deliver an accurate FiO₂ with a splinting pressure of 4-6 cm H₂ O. During apnea in children, NHF oxygen can double the expected time to desaturation below 90% in well children but there is no ventilatory exchange; therefore, children do not "THRIVE". Total intravenous anesthesia competency to maintain spontaneous breathing is an important adjunct for successful NHF oxygenation technique during anesthesia. Jaw thrust to maintain a patent upper airway is paramount until surgical instrumentation occurs. There is no evidence to support safe use of NHF oxygen with LASER use due to increased risk of airway fire.

Nasal high flow in preterm infants: A dose-finding study

OBJECTIVE

To investigate the relationship between applied flows of nasal high flow (NHF) and physiological outcomes and work of breathing (WOB), to identify an optimal delivery flow which results in reduced WOB in preterm infants.

DESIGN

A prospective observational clinical study with randomly applied NHF rates.

PATIENTS AND SETTING

Preterm infants within 72 hours of commencement of NHF respiratory support.

INTERVENTIONS

Infants were initially placed on 8 L/min of NHF and flows of 2, 4, and 6 L/min were then applied in random order.

MEASUREMENTS AND RESULTS

WOB was measured using transcutaneous electromyography and respiratory inductance plethysmography. Physiological variables were also recorded. Measurements taken 10 minutes after each flow change were compared with 8 L/min. Sixteen infants with a median gestational age of 28 (range 24-31) weeks and postnatal age of 14 (2-55) days were included in the study. The median flow rate before the study was 6 (4-8) L/min and a fraction of inspired oxygen (FiO₂ ) was 0.21 (0.21-0.26). Changes in flow resulted in changes in activity in the front diaphragm (P = .027) and intercostals (P = .034). The electrical activity of the front diaphragm at 8 L/min was significantly lower than that at 2 L/min (P = .016). Respiratory rate was lowest at 6 L/min (P = .002) and SpO₂ /FiO₂ was highest at 8 L/min (P < .04).

CONCLUSION

In preterm infants, changes in WOB resulting from randomly applied levels of NHF can be demonstrated by measuring the electrical activity of the diaphragm and intercostal muscles with transcutaneous electromyography. In combination with physiological measurements, the similarities in electrical activity between 4, 6, and 8 L/min suggest that these three flows may be equally as effective.

Mechanisms of nasal high flow therapy in newborns

In newborns, it is unclear how nasal high flow (NHF) generates positive airway pressure. In addition, the reported benefits of NHF such as reduction in work of breathing may be independent of airway pressure. The authors hypothesized that during NHF the area of leak and the flow determine airway pressure and that NHF can reduce the required minute ventilation to maintain gas exchange. In response to NHF, pressure was measured in the upper airways of 9 newborns and ventilation was measured in another group of 17 newborns. In a bench model, airway pressures were measured during NHF with different prong sizes, nare sizes, and flows. The airway pressures during 8 L/min NHF were greater when a larger cannula versus a smaller cannula was used (P < 0.05). NHF reduced minute ventilation in 16 of 17 neonates, with a mean decrease of 24% from a baseline of 0.66 L/min (SD 0.21) (P < 0.001), and was unrelated to changes in airway pressure; arterial oxygen saturation by pulse oximetry (SpO2) and tissue CO₂ were unchanged. In the bench model, the airway pressure remained <2 cmH₂O when <50% of the “nare” was occluded by the prongs. As the leak area decreased, because of a smaller nare or a larger cannula, the airway pressure increased exponentially and was dependent on flow. In newborns NHF using room air substantially reduced minute ventilation without affecting gas exchange irrespective of a decrease or an increase of respiratory rate. NHF generates low positive airway pressure that exponentially increases with flow and occlusion of the nares.

NEW & NOTEWORTHY In healthy newborns, nasal high flow (NHF) with room air reduced minute ventilation by one-fourth without affecting gas exchange but, in contrast to adults, produced variable response in respiratory rate during sleep. During NHF, pressure in the upper airways did not exceed 2 cmH₂O at 8 L/min (3.4 L·min⁻¹·kg⁻¹) and was unaffected by opening of the mouth. NHF can generate higher pressure with larger prongs that decrease the leak around the cannula or by increasing the flow rate.

Weaning strategies for the withdrawal of non-invasive respiratory support applying continuous positive airway pressure in preterm infants: a systematic review and meta-analysis

BACKGROUND

The optimal method to wean preterm infants from non-invasive respiratory support (NIVRS) with nasal continuous positive airway pressure (CPAP) or high-flow nasal cannula is still unclear, and methods used vary considerably between neonatal units.

OBJECTIVE

Perform a systematic review and meta-analysis to determine the most effective strategy for weaning preterm infants born before 37 weeks' gestation from NIVRS.

METHOD

EMBASE, MEDLINE, CINAHL, Google and Cochrane Central Register of Controlled Trials were searched for randomised controlled trials comparing different weaning strategies of NIVRS in infants born before 37 weeks' gestation.

RESULTS

Fifteen trials (1.547 infants) were included. With gradual pressure wean, the relative risk of successful weaning at the first attempt was 1.30 (95% CI 0.93 to 1.83), as compared with sudden discontinuation. Infants were weaned at a later postmenstrual age (PMA) (median difference (MD) 0.93 weeks (95% CI 0.19 to 1.67)). A stepdown strategy to nasal cannula resulted in an almost 3-week reduction in the PMA at successful weaning (MD -2.70 (95% CI -3.87 to -1.52)) but was associated with a significantly longer duration of oxygen supplementation (MD 7.80 days (95% CI 5.31 to 10.28)). A strategy using interval training had no clinical benefits. None of the strategies had any effect on the risk of chronic lung disease or the duration of hospital stay.

CONCLUSION

A strategy of gradual weaning of airway pressure might increase the chances of successful weaning. Stepdown strategy from CPAP to nasal cannula is a useful alternative resulting in an earlier weaning, but the focus should remain on continued weaning in order to avoid prolonged oxygen supplementation. Interval training should probably not be used.

Physiological effects of high-flow nasal cannula therapy in preterm infants

OBJECTIVE

High-flow nasal cannula (HFNC) therapy is increasingly used in preterm infants despite a paucity of physiological studies. We aimed to investigate the effects of HFNC on respiratory physiology.

STUDY DESIGN

A prospective randomised crossover study was performed enrolling clinically stable preterm infants receiving either HFNC or nasal continuous positive airway pressure (nCPAP). Infants in three current weight groups were studied: <1000 g, 1000-1500 g and >1500 g. Infants were randomised to either first receive HFNC flows 8-2 L/min and then nCPAP 6 cm H₂O or nCPAP first and then HFNC flows 8-2 L/min. Nasopharyngeal end-expiratory airway pressure (pEEP), tidal volume, dead space washout by nasopharyngeal end-expiratory CO₂ (pEECO₂), oxygen saturation and vital signs were measured.

RESULTS

A total of 44 preterm infants, birth weights 500-1900 g, were studied. Increasing flows from 2 to 8 L/min significantly increased pEEP (mean 2.3-6.1 cm H₂O) and reduced pEECO₂ (mean 2.3%-0.9%). Tidal volume and transcutaneous CO₂ were unchanged. Significant differences were seen between pEEP generated in open and closed mouth states across all HFNC flows (difference 0.6-2.3 cm H₂O). Infants weighing <1000 g received higher pEEP at the same HFNC flow than infants weighing >1000 g. Variability of pEEP generated at HFNC flows of 6-8 L/min was greater than nCPAP (2.4-13.5 vs 3.5-9.9 cm H₂O).

CONCLUSIONS

HFNC therapy produces clinically significant pEEP with large variability at higher flow rates. Highest pressures were observed in infants weighing <1000 g. Flow, weight and mouth position are all important determinants of pressures generated. Reductions in pEECO₂ support HFNC's role in dead space washout.

Hypopharyngeal oxygen concentration and pressures delivered by low flow nasal cannula in preterm infants: Relationship with flow, gas mixture, and infant's weight

BACKGROUND

Low flow nasal cannula (LFNC) are frequently used in preterm infants. However, the delivered inspired oxygen concentration and airway pressures are not well established.

OBJECTIVE

To determine the fraction of inspired oxygen (FiO₂ ) and hypopharyngeal pressures generated by LFNC at different gas flows, gas mixture concentrations and infant's weight.

DESIGN/METHODS

Serial samples of hypopharyngeal gas were obtained in 33 very low birth weight infants who were receiving oxygen with LFNC. Measurements were obtained with different gas flows and oxygen concentrations. FiO₂ was measured using an electrochemical cell analyzer and hypopharyngeal pressures with a pressure transducer.

RESULTS

33 infants with a mean BW of 910 ± 284 g and 27 ± 1.7 weeks gestational age were studied at 36 ± 22 days after birth. FiO₂ increased proportionally to gas flow, but with large variability: median (range) FiO ₂ were 0.33 (0.23-0.54), 0.44 (0.29-0.67), 0.57 (0.33-0.81), and 0.69 (0.51-0.92) at 0.1, 0.3, 0.5, and 1 L/minute, respectively. Significantly higher mean FiO ₂ were observed despite low flows in infants ≤ 1000 g compared to those > 1000 g (0.5 ± 0.1 vs 0.4 ± 0.07 at 0.3 L/minute; 0.66 ± 0.09 vs 0.5 ± 0.08 with 0.5 L/minute, respectively, P < .05). Hypopharyngeal pressures increased proportionally to gas flow with high variability: mean ± standard deviation pressures were 1.5 ± 0.8; 2.8 ± 1.2; 4.6 ± 1.3; 6.1 ± 1.6 cm H ₂ O at 0.5, 1, 2, and 3 L/minute of gas flow. Peak pressures > 15 cm H ₂ O were frequently observed with gas flows ≥ 2 L/min.

CONCLUSIONS

Large variability in FiO₂ and hypopharyngeal pressures were observed with oxygen administration through LFNC. Very high FiO ₂ were observed despite low flows in infants < 1000 g. Excessive peak pressures can be generated with flows ≥ 2 L/minute especially among infants < 1000 g.

Is Nasal High Flow Inferior to Continuous Positive Airway Pressure for Neonates?

Nasal high-flow therapy (nHF) is increasingly used for neonates, with perceived benefits including reduced rates of nasal trauma and parent and nursing staff preference. Current evidence suggests that although nHF is a reasonable alternative for postextubation support of preterm infants, continuous positive airway pressure is a superior modality for primary support of respiratory distress syndrome. Minimal evidence exists for use of nHF in extremely preterm infants less than 28 weeks' gestation. Depending on clinician preference, units may still choose nHF in some settings, although careful choice of appropriate patients, and availability of rescue continuous positive airway pressure, is essential.

Effect of randomization of nasal high flow rate in preterm infants

OBJECTIVE

To assess the effect of nasal high flow (NHF) cannula on end-expiratory level (EEL), continuous distending pressure (CDP) and regional ventilation distribution in preterm infants.

DESIGN

A prospective observational clinical study with randomly applied NHF rates.

PATIENTS AND SETTING

Preterm infants requiring continuous positive airway pressure (CPAP) respiratory support in a Neonatal Intensive Care Unit.

INTERVENTIONS

Infants were measured on randomly applied flow rates at 2, 4, and 6 L/min of NHF and compared with bubble CPAP.

MEASUREMENTS AND RESULTS

Regional ventilation distribution and EEL were measured using electrical impedance tomography (EIT) and respiratory inductance plethysmography (RIP) in 24 preterm infants (31.19 ± 1.17 weeks corrected age). Changes in CDP were measured from the esophagus via the nasogastric tube. Physiological variables were also recorded. There were no differences in ventilation distribution, EEL or CDP between CPAP and NHF (P > .05). However, the physiological variables of FiO₂ (P = .01) and SpO₂ /FiO₂ (P < .01) were improved on CPAP compared with NHF.

CONCLUSION

NHF applied in random order with flow rates between 2 to 6 L/min was equally as good as CPAP in maintaining EEL and ventilation distribution in stable preterm infants. Overall oxygenation was better on CPAP compared to NHF.

Nasal High-Flow Therapy for Newborn Infants in Special Care Nurseries

BACKGROUND

Nasal high-flow therapy is an alternative to nasal continuous positive airway pressure (CPAP) as a means of respiratory support for newborn infants. The efficacy of high-flow therapy in nontertiary special care nurseries is unknown.

METHODS

We performed a multicenter, randomized, noninferiority trial involving newborn infants (<24 hours of age; gestational age, ≥31 weeks) in special care nurseries in Australia. Newborn infants with respiratory distress and a birth weight of at least 1200 g were assigned to treatment with either high-flow therapy or CPAP. The primary outcome was treatment failure within 72 hours after randomization. Infants in whom high-flow therapy failed could receive CPAP. Noninferiority was determined by calculating the absolute difference in the risk of the primary outcome, with a noninferiority margin of 10 percentage points.

RESULTS

A total of 754 infants (mean gestational age, 36.9 weeks, and mean birth weight, 2909 g) were included in the primary intention-to-treat analysis. Treatment failure occurred in 78 of 381 infants (20.5%) in the high-flow group and in 38 of 373 infants (10.2%) in the CPAP group (risk difference, 10.3 percentage points; 95% confidence interval [CI], 5.2 to 15.4). In a secondary per-protocol analysis, treatment failure occurred in 49 of 339 infants (14.5%) in the high-flow group and in 27 of 338 infants (8.0%) in the CPAP group (risk difference, 6.5 percentage points; 95% CI, 1.7 to 11.2). The incidences of mechanical ventilation, transfer to a tertiary neonatal intensive care unit, and adverse events did not differ significantly between the groups.

CONCLUSIONS

Nasal high-flow therapy was not shown to be noninferior to CPAP and resulted in a significantly higher incidence of treatment failure than CPAP when used in nontertiary special care nurseries as early respiratory support for newborn infants with respiratory distress. (Funded by the Australian National Health and Medical Research Council and Monash University; HUNTER Australian and New Zealand Clinical Trials Registry number, ACTRN12614001203640.).

National surveys of UK and Italian neonatal units highlighted significant differences in the use of non-invasive respiratory support

AIM

This study compared how non-invasive respiratory support (NRS) was provided in neonatal units in Italy and the UK.

METHODS

An NRS questionnaire was sent to tertiary neonatal centres, identified by national societies, from November 2015 to May 2016.

RESULTS

Responses were received from 49/57 (86%) UK units and 103/115 (90%) Italian units. NRS was started in the delivery room by 61% of UK units and 85% of Italian units. In neonatal intensive care units, 33% of UK units used nasal high-flow therapy (HFT) as primary support, compared to 3% in Italy. Nasal continuous positive airway pressure (CPAP) was used in 57% of UK units and 90% of Italian units. The commonest starting flow rate on nasal HFT for term and preterm infants was 6 L/min in the UK, while Italian units mainly used this flow for term infants. In the UK, 67% of units decreased nasal HFT by 1 L/min per day. In Italy, infants on nasal CPAP were weaned by 1 cm H₂ O per day in 39% of units.

CONCLUSION

The way that NRS was managed for very preterm infants differed between the UK and Italy, reflecting a lack of evidence on optimal NRS and the use of local protocols.

Effect of high frequency oscillatory high flow nasal cannula on carbon dioxide clearance in a premature infant lung model: A bench study

OBJECTIVE

This study compared CO₂ clearance in a premature infant lung model connected to a high flow nasal cannula (HFNC) system supplied with oscillatory versus non-oscillatory flow.

DESIGN/METHODS

The lung model was set to compliance 1.0 mL/cmH₂ O, RR 60 breaths/min, and 6 mL tidal volume. A 100% CO₂ was injected at a constant 15 mL/min. To create oscillation, HFNC flow was interrupted at rates of 4-6-8 and 10 Hz. equilibrated end-tidal CO₂ (ETCO₂ ) was recorded with and without oscillation at set flows of 2-8 L/min and repeated for each oscillation frequency.

RESULTS

Overall ETCO₂ decreased significantly (P < 0.001) during both non-oscillatory and oscillatory HFNC as set flow increased from 2 to 8 L/min by 26.3% and 60.8%, respectively. Oscillatory ETCO₂ levels decreased linearly compared to non-oscillatory HFNC with negligible difference at 2 L/min and a 48.4% difference at 8 L/min (P < 0.001). There were no differences in ETCO₂ levels between oscillation frequencies at any flow except at 6 Hz for which ETCO₂ was significantly lower (P < 0.01) than at 4, 8, and 10 Hz for 5-8 L/min HFNC flows. Amplitude of volume oscillations increased with increasing flow from 0.5 mL at 2 L/min to 4.0 mL at 8 L/min (P < 0.001), and decreased with increasing oscillation frequency.

CONCLUSION

Oscillatory HFNC as compared to non-oscillatory was associated with significantly improved CO₂ clearance in this premature infant lung model. This simple modification of the HFNC system may prove to be a useful enhancement to this mode of non-invasive respiratory support for preterm infants at high risk for respiratory failure.

Nasal high flow therapy for neonates: Current evidence and future directions

Nasal high flow (nHF) therapy is a commonly used method of providing non-invasive respiratory support for neonates. It has several potential mechanisms of action: continuous distending pressure, nasopharyngeal dead space washout, provision of heated and humidified gases and reduction of work of breathing. nHF is used in a number of clinical scenarios for preterm and term infants, including primary respiratory and post-extubation support. In recent years, large trials have generated evidence pertinent to these indications. Novel applications for nHF in neonates warrant further research: during endotracheal intubation, for initial delivery room stabilisation of preterm infants and in conjunction with minimally invasive surfactant therapy.

Neonatal intermittent hypoxemia events are associated with diagnosis of bronchopulmonary dysplasia at 36 weeks postmenstrual age

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a chronic lung disease and major pulmonary complication after premature birth. We have previously shown that increased intermittent hypoxemia (IH) events have been correlated to adverse outcomes and mortality in extremely premature infants. We hypothesize that early IH patterns are associated with the development of BPD.

METHODS

IH frequency, duration, and nadirs were assessed using oxygen saturation (SpO₂) waveforms in a retrospective cohort of 137 extremely premature newborns (<28 weeks gestation). Daily levels of inspired oxygen and mean airway pressure exposures were also recorded.

RESULTS

Diagnosis of BPD at 36 weeks postmenstrual age was associated with increased daily IH, longer IH duration, and a higher IH nadir. Significant differences were detected through day 7 to day 26 of life. Infants who developed BPD had lower mean SpO₂ despite their exposure to increased inspired oxygen and increased mean airway pressure.

CONCLUSIONS

BPD was associated with more frequent, longer, and less severe IH events in addition to increased oxygen and pressure exposure within the first 26 days of life. Early IH patterns may contribute to the development of BPD or aid in identification of neonates at high risk.

Early inspired oxygen and intermittent hypoxemic events in extremely premature infants are associated with asthma medication use at 2 years of age

OBJECTIVE

Extremely premature infants are at risk for childhood wheezing. Early respiratory support and intermittent hypoxemia (IH) events may be associated with adverse breathing outcomes.

STUDY DESIGN

A single-center retrospective cohort study of 137 premature infants <28 weeks gestational age characterized the associations of cumulative oxygen, cumulative mean airway pressure, IH, and oxygen saturation (SpO₂) on the primary outcome of prescription asthma medication use at 2-year follow-up. Relative risk was calculated by generalized estimating equations.

RESULTS

Reported asthma medication use was 46%. At 1-3 days of age, elevated cumulative oxygen exposure, increased daily IH, and lower mean SpO₂ (adjusted for gestational age and sex) and increased cumulative mean airway pressure exposure (unadjusted) were associated with asthma medication use.

CONCLUSION

Increased oxygen and frequent IH events during just the first 3 days of age may help identify extremely premature newborns at risk for symptomatic childhood wheezing requiring prescription asthma medications.

Nasal high-flow therapy decreased electrical activity of the diaphragm in preterm infants during the weaning phase

AIM

We evaluated whether nasal high-flow therapy was better than no respiratory support during the weaning phase in preterm infants.

METHODS

The study was conducted in the neonatal intensive care unit of the Turku University Hospital between September 2014 and August 2015. Preterm infants who were alternating between nasal high-flow therapy and unassisted breathing were enrolled. Electrical activity of the diaphragm (EAdi) was recorded and compared during three-hour time periods for each option.

RESULTS

We studied eight infants at a median gestational age of 31 weeks. The EAdi peak was lower during nasal high-flow therapy when compared to no respiratory support (6.1 μV vs 7.1 μV, p = 0.02), but the EAdi minimum was similar with and without respiratory support. Neural respiratory rate (62 vs 68 per minute, p = 0.02) and the frequency of sighs (27.8 vs 37.9 per hour, p = 0.03) were lower during nasal high-flow therapy than no respiratory support.

CONCLUSION

Nasal high-flow therapy reduced diaphragm activation in our cohort when compared to no respiratory support, as indicated by the lower Edi peak. An increase in the respiratory rate and the sigh frequency without respiratory support also suggests that nasal high-flow therapy provided support during the weaning phase.

Diaphragm electromyography results at different high flow nasal cannula flow rates

Heated, humidified, high-flow nasal cannula (HHHFNC) is increasingly being used, but there is a paucity of evidence as to the optimum flow rates in prematurely born infants. We have determined the impact of three flow rates on the work of breathing (WOB) assessed by transcutaneous diaphragm electromyography (EMG) amplitude in infants with respiratory distress or bronchopulmonary dysplasia (BPD). Flow rates of 4, 6 and 8 L/min were delivered in random order. The mean amplitude of the EMG trace and mean area under the EMG curve (AEMGC) were calculated and the occurrence of bradycardias and desaturations recorded. Eighteen infants were studied with a median gestational age of 27.8 (range 23.9-33.5) weeks and postnatal age of 54 (range 3-122) days. The median flow rate prior to the study was 5 (range 3-8) L/min and the fraction of inspired oxygen (FiO₂) was 0.29 (range 0.21-0.50). There were no significant differences between the mean amplitude of the diaphragm EMG and the AEGMC and the number of bradycardias or desaturations between the three flow rates.Conclusions: In infants with respiratory distress or BPD, there was no advantage of using high (8 L/min) compared with lower flow rates (4 or 6 L/min) during support by HHHFNC. What is known: • Humidified high flow nasal cannulae (HHHFNC) is increasingly being used as a non-invasive form of respiratory support for prematurely born infants. • There is a paucity of evidence regarding the optimum flow rate with 1 to 8 L/min being used. What is new: • We have assessed the work of breathing using the amplitude of the electromyogram of the diaphragm at three HHHFNC flow rates in infants with respiratory distress or BPD. • No significant differences were found in the EMG amplitude results or the numbers of bradycardias or desaturations at 4, 6 and 8 L/min.

Increased use of heated humidified high flow nasal cannula is associated with longer oxygen requirements

AIM

There has been an increased use of heated humidified high flow nasal canula (HFNC) in premature babies (PBs) admitted to our neonatal unit. The aim of this study is to identify clinical characteristics in PBs < 29 weeks gestational age (GA) that distinguish between those who did not or did receive HFNC.

METHODS

This study compared prospectively collected data from 2010 to 2012. Comparisons were undertaken between PBs<29 weeks GA who received continuous positive airway pressure (CPAP: 44/72 (61.1%)) to those who received both CPAP and HFNC (28/72 (38.9%)). Data were analysed using general linear models.

RESULTS

There were no significant differences in baseline characteristics between the groups (GA: 27.6 ± 1.1 vs. 27.5 ± 1.1 (weeks), birth weight: 1066 ± 209 vs. 1057 ± 304 (grams) respectively). When analysing outcome measures with multivariate analysis, we found the corrected GA to cease CPAP and oxygen were significantly longer in the HFNC group (31.2 ± 2.1 vs. 32.7 ± 2.0 weeks, P = 0.01 and 32.8 ± 3.5 vs. 36.5 ± 2.8 weeks, P < 0.0001 respectively).

CONCLUSIONS

Increased use of HFNC has been associated with increased oxygen requirements. These findings highlight the need to review the use of HFNC in small PBs.

Nasal high flow treatment in preterm infants

Nasal High Flow (HF) is a mode of ‘non-invasive’ respiratory support for preterm infants, with several potential modes of action, including generation of distending airway pressure, washout of the nasopharyngeal dead space, reduction of work of breathing, and heating and humidification of inspired gas. HF has several potential advantages over continuous positive airway pressure (CPAP), the most commonly applied form of non-invasive support, such as reduced nasal trauma, ease of use, and infant comfort, which has led to its rapid adoption into neonatal care. In recent years, HF has become a well-established and commonly applied treatment in neonatal care.

Recent trials comparing HF and CPAP as primary support have had differing results. Meta-analyses suggest that primary HF results in an increased risk of treatment failure, but that ‘rescue’ CPAP use in those infants with HF failure results in no greater risk of mechanical ventilation. Even in studies with higher rates of HF failure, the majority of infants were successfully treated with HF, and rates of important neonatal morbidities did not differ between treatment groups. Importantly, these studies have included only infants born at ≥28 weeks’ gestational age (GA). The decision whether to apply primary HF will depend on the value placed on its advantages over CPAP by clinicians, the approach to surfactant treatment, and the severity of respiratory disease in the relevant population of preterm infants.

Post-extubation HF use results in similar rates of treatment failure, mechanical ventilation, and adverse events compared to CPAP. Post-extubation HF appears most suited to infants ≥28 weeks; there are few published data for infants below this gestation, and available evidence suggests that these infants are at high risk of HF failure, although rates of intubation and other morbidities are similar to those seen with CPAP. There is no evidence that using HF to ‘wean’ off CPAP allows for respiratory support to be ceased more quickly, but given its advantages it would appear to be a suitable alternative in infants who require ongoing non-invasive support. Safety data from randomised trials are reassuring, although more evidence in extremely preterm infants (<28 weeks’ GA) is required.