Neurally adjusted ventilatory assist compared to other forms of triggered ventilation for neonatal respiratory support

Study protocol for a randomised cross-over trial of Neurally adjusted ventilatory Assist for Neonates with Congenital diaphragmatic hernias: the NAN-C study

BACKGROUND

Neurally adjusted ventilatory assist (NAVA) is a mode of mechanical ventilation that delivers oxygen pressures in proportion to electrical signals of the diaphragm. The proportional assistance can be adjusted by the clinician to reduce the patient's work of breathing. Several case series of infants with congenital diaphragmatic hernias (CDH) have shown that NAVA may reduce oxygenation index and mean airway pressures. To date, no clinical trial has compared NAVA to standard methods of mechanical ventilation for babies with CDH.

METHODS

The aim of this dual-centre randomised cross-over trial is to compare post-operative NAVA with assist control ventilation (ACV) for infants with CDH. If eligible, infants will be enrolled for a ventilatory support tolerance trial (VSTT) to assess their suitability for randomisation. If clinically stable during the VSTT, infants will be randomised to receive either NAVA or ACV first in a 1:1 ratio for a 4-h period. The oxygenation index, respiratory severity score and cumulative sedative medication use will be measured.

DISCUSSION

Retrospective studies comparing NAVA to ACV in neonates with congenital diaphragmatic hernia have shown the ventilatory mode may improve respiratory parameters and benefit neonates. To our knowledge, this is the first prospective cross-over trial comparing NAVA to ACV.

TRIAL REGISTRATION

NAN-C was prospectively registered on ClinicalTrials.gov NCT05839340  Registered on May 2023.

Neonatal respiratory support strategies-short and long-term respiratory outcomes

Mechanical ventilation (MV), although life-saving, is associated with chronic respiratory morbidity in both preterm and term born infants. New ventilation modes have been developed with the aim of minimising lung injury. These include invasive and non-invasive respiratory support strategies, techniques for less invasive surfactant administration (LISA) and closed-loop automated oxygen control (CLAC) systems. Increasingly, newborn infants with signs of respiratory distress are stabilised on continuous positive airway pressure (CPAP) and receive LISA. Early CPAP when compared to mechanical ventilation reduced the incidence of BPD and respiratory morbidity at 18 to 22 months corrected age. Nasal intermittent positive pressure ventilation reduced treatment failure rates compared to CPAP, but not bronchopulmonary dysplasia (BPD). LISA compared with intubation and surfactant delivery reduced BPD, but there is no evidence from randomised trials regarding long-term respiratory and neurodevelopmental outcomes. Synchronisation of positive pressure inflations with the infant's respiratory efforts used with volume targeting should be applied for infants requiring intubation as this strategy reduces BPD. A large RCT with long term follow up data demonstrated that prophylactic high frequency oscillatory ventilation (HFOV) improved respiratory and functional outcomes at school age, but those effects were not maintained after puberty. CLAC systems appear promising, but their effect on long term clinical outcomes has not yet been explored in randomised trials. Further studies are required to determine the role of newer ventilation modes such as neurally adjusted ventilator assist (NAVA). All such respiratory support strategies should be tested in randomised controlled trials powered to assess long-term outcomes.

The prevention and management strategies for neonatal chronic lung disease

INTRODUCTION

Survival from even very premature birth is improving, but long-term respiratory morbidity following neonatal chronic lung disease (bronchopulmonary dysplasia (BPD)) has not reduced. Affected infants may require supplementary oxygen at home, because they have more hospital admissions particularly due to viral infections and frequent, troublesome respiratory symptoms requiring treatment. Furthermore, adolescents and adults who had BPD have poorer lung function and exercise capacity.

AREAS COVERED

Antenatal and postnatal preventative strategies and management of infants with BPD. A literature review was undertaken using PubMed and Web of Science.

EXPERT OPINION

There are effective preventative strategies which include caffeine, postnatal corticosteroids, vitamin A, and volume guarantee ventilation. Side-effects, however, have appropriately caused clinicians to reduce use of systemically administered corticosteroids to infants only at risk of severe BPD. Promising preventative strategies which need further research are surfactant with budesonide, less invasive surfactant administration (LISA), neurally adjusted ventilatory assist (NAVA) and stem cells. The management of infants with established BPD is under-researched and should include identifying the optimum form of respiratory support on the neonatal unit and at home and which infants will most benefit in the long term from pulmonary vasodilators, diuretics, and bronchodilators.

Early origins of respiratory disease

Chronic respiratory morbidity is unfortunately common in childhood, particularly in those born very prematurely or with congenital anomalies affecting pulmonary development and those with sickle cell disease. Our research group, therefore, has focused on the early origins of chronic respiratory disease. This has included assessing antenatal diagnostic techniques and potentially therapeutic interventions in infants with congenital diaphragmatic hernia. Undertaking physiological studies, we have increased the understanding of the premature baby's response to resuscitation and evaluated interventions in the delivery suite. Mechanical ventilation modes have been optimised and randomised controlled trials (RCTs) with short- and long-term outcomes undertaken. Our studies highlighted respiratory syncytial virus lower respiratory tract infections (LRTIs) and other respiratory viral LRTIs had an adverse impact on respiratory outcomes of prematurely born infants, who we demonstrated have a functional and genetic predisposition to respiratory viral LRTIs. We have described the long-term respiratory outcomes for children with sickle cell disease and importantly identified influencing factors. In conclusion, it is essential to undertake long term follow up of infants at high risk of chronic respiratory morbidity if effective preventative strategies are to be developed.

The use of neurally-adjusted ventilatory assist (NAVA) for infants with congenital diaphragmatic hernia (CDH)

OBJECTIVES

Newborns with congenital diaphragmatic hernia (CDH) can have complex respiratory problems which are worsened by ventilatory induced lung injury. Neurally adjusted ventilator assist (NAVA) is a potentially promising ventilation mode for this population, as it can result in improved patient-ventilator interactions and provision of adequate gas exchange at lower airway pressures.

CONTENT

A literature review was undertaken to provide an overview of NAVA and examine its role in the management of infants with CDH.

SUMMARY

NAVA in neonates has been used in CDH infants who were stable on ventilatory support or being weaned from mechanical ventilation and was associated with a reduction in the level of respiratory support.

OUTLOOK

There is, however, limited evidence regarding the efficacy of NAVA in infants with CDH, with only short-term benefits being investigated. A prospective, multicentre study with long term follow-up is required to appropriately assess NAVA in this population.

Improved nutritional outcomes with neurally adjusted ventilatory assist (NAVA) in premature infants: a single tertiary neonatal unit's experience

During neurally adjusted ventilatory assist (NAVA)/non-invasive (NIV) NAVA, a modified nasogastric feeding tube with electrodes, monitors the electrical activity of the diaphragm (Edi). The Edi waveform determines the delivered pressure from the ventilator. Infant breathing is in synchrony with the ventilator and therefore is more comfortable with less work of breathing. Our aim was to determine if infants on NAVA had improved nutritional outcomes compared to infants managed on conventional respiratory support. A retrospective study was undertaken. Infants on NAVA were matched with two conventionally ventilated controls by gestational age, birth weight, sex, antenatal steroid exposure, and whether inborn or transferred ex utero. NAVA/NIV-NAVA was delivered by the SERVO-n® Maquet Getinge group ventilator. Conventional ventilation included pressure and volume control ventilation, and non-invasive ventilation included nasal intermittent positive pressure ventilation, triggered biphasic positive airway pressure, continuous positive airway pressure and heated humidified high flow oxygen. The measured outcome was discharge weight z scores. Eighteen "NAVA" infants with median gestational age (GA) of 25.3 (23.6-27.1) weeks and birth weight (BW) of 765 (580-1060) grams were compared with 36 controls with GA 25.2 (23.4-28) weeks (p = 0.727) and BW 743 (560-1050) grams (p = 0.727). There was no significant difference in the rates of postnatal steroids (61% versus 36% p = 0.093), necrotising enterocolitis (22% versus 11% p = 0.279) in the NAVA/NIV NAVA compared to the control group. There were slightly more infants who were breastfed at discharge in the NAVA/NIV NAVA group compared to controls: breast feeds (77.8% versus 58.3%), formula feeds (11.1% versus 30.6%), and mixed feeds (11.1% versus 11.1%), but this difference was not significant (p = 0.275). There was no significant difference in the birth z scores 0.235 (-1.56 to 1.71) versus -0.05 (-1.51 to -1.02) (p = 0.248) between the groups. However, the discharge z score was significantly in favour of the NAVA/NIV-NAVA group: -1.22 (-2.66 to -0.12) versus -2.17 (-3.79 to -0.24) in the control group (p = 0.033).Conclusion: The combination of NAVA/NIV-NAVA compared to conventional invasive and non-invasive modes may contribute to improved nutritional outcomes in premature infants.

The Intertemporal Role of Respiratory Support in Improving Neonatal Outcomes: A Narrative Review

Defining improvements in healthcare can be challenging due to the need to assess multiple outcomes and measures. In neonates, although progress in respiratory support has been a key factor in improving survival, the same degree of improvement has not been documented in certain outcomes, such as bronchopulmonary dysplasia. By exploring the evolution of neonatal respiratory care over the last 60 years, this review highlights not only the scientific advances that occurred with the application of invasive mechanical ventilation but also the weakness of the existing knowledge. The contributing role of non-invasive ventilation and less-invasive surfactant administration methods as well as of certain pharmacological therapies is also discussed. Moreover, we analyze the cost-benefit of neonatal care-respiratory support and present future challenges and perspectives.

Neurally-Adjusted Ventilatory Assist (NAVA) versus Pneumatically Synchronized Ventilation Modes in Children Admitted to PICU

Traditionally, invasively ventilated children in the paediatric intensive care unit (PICU) are weaned using pneumatically-triggered ventilation modes with a fixed level of assist. The best weaning mode is currently not known. Neurally adjusted ventilatory assist (NAVA), a newer weaning mode, uses the electrical activity of the diaphragm (Edi) to synchronise ventilator support proportionally to the patient’s respiratory drive. We aimed to perform a systematic literature review to assess the effect of NAVA on clinical outcomes in invasively ventilated children with non-neonatal lung disease. Three studies (n = 285) were included for analysis. One randomised controlled trial (RCT) of all comers showed a significant reduction in PICU length of stay and sedative use. A cohort study of acute respiratory distress syndrome (ARDS) patients (n = 30) showed a significantly shorter duration of ventilation and improved sedation with the use of NAVA. A cohort study of children recovering from cardiac surgery (n = 75) showed significantly higher extubation success, shorter duration of ventilation and PICU length of stay, and a reduction in sedative use. Our systematic review presents weak evidence that NAVA may shorten the duration of ventilation and PICU length of stay, and reduce the requirement of sedatives. However, further RCTs are required to more fully assess the effect of NAVA on clinical outcomes and treatment costs in ventilated children.

Evidence for the Management of Bronchopulmonary Dysplasia in Very Preterm Infants

Background: Very preterm birth often results in the development of bronchopulmonary dysplasia (BPD) with an inverse correlation of gestational age and birthweight. This very preterm population is especially exposed to interventions, which affect the development of BPD. Objective: The goal of our review is to summarize the evidence on these daily procedures and provide evidence-based recommendations for the management of BPD. Methods: We conducted a systematic literature research using MEDLINE/PubMed on antenatal corticosteroids, surfactant-replacement therapy, caffeine, ventilation strategies, postnatal corticosteroids, inhaled nitric oxide, inhaled bronchodilators, macrolides, patent ductus arteriosus, fluid management, vitamin A, treatment of pulmonary hypertension and stem cell therapy. Results: Evidence provided by meta-analyses, systematic reviews, randomized controlled trials (RCTs) and large observational studies are summarized as a narrative review. Discussion: There is strong evidence for the use of antenatal corticosteroids, surfactant-replacement therapy, especially in combination with noninvasive ventilation strategies, caffeine and lung-protective ventilation strategies. A more differentiated approach has to be applied to corticosteroid treatment, the management of patent ductus arteriosus (PDA), fluid-intake and vitamin A supplementation, as well as the treatment of BPD-associated pulmonary hypertension. There is no evidence for the routine use of inhaled bronchodilators and prophylactic inhaled nitric oxide. Stem cell therapy is promising, but should be used in RCTs only.

"Current concepts in assisted mechanical ventilation in the neonate" - Part 2: Understanding various modes of mechanical ventilation and recommendations for individualized disease-based approach in neonates

Mechanical ventilation is a lifesaving intervention in critically ill preterm and term neonates. However, it has the potential to cause significant damage to the lungs resulting in long-term complications. Understanding the pathophysiological process and having a good grasp of the basic concepts of conventional and high-frequency ventilation is essential for any medical or allied healthcare practitioner involved in the neonates' respiratory management. This review aims to describe the various types and modes of ventilation usually available in neonatal units. It also describes recommendations of an individualized disease-based approach to mechanical ventilation strategies implemented in the authors' institutions.

Can visual inspection of the electrical activity of the diaphragm improve the detection of patient-ventilator asynchronies by pediatric critical care physicians?

BACKGROUND

Patient-ventilator asynchronies are challenging during pediatric mechanical ventilation. We hypothesized that monitoring the electrical activity of the diaphragm (EAdi) together with the "standard" airway opening pressure (Pao) and flow-time waveforms during pressure support ventilation would improve the ability of a cohort of critical care physicians to detect asynchronies in ventilated children.

METHODS

We recorded the flow, Pao and EAdi waveforms in ten consecutive patients. The recordings were split in periods of 15 s, each reproducing a ventilator screenshot. From this pool, a team of four experts selected the most representative screenshots including at least one of the three most common asynchronies (missed efforts, auto-triggering and double triggering) and split them into two versions, respectively showing or not the EAdi waveforms. The screenshots were shown in random order in a questionnaire to sixty experienced pediatric intensivists that were asked to identify any episode of patient-ventilator asynchrony.

RESULTS

Among the ten patients included in the study, only eight had EAdi tracings without artifacts and were analyzed. When the Eadi waveform was shown, the auto-triggering detection improved from 13% to 67% (P<0.0001) and the missed efforts detection improved from 43% to 95% (P<0.0001). The detection of double triggering, instead, did not improve (85% with the EAdi vs. 78% without the EAdi waveform; P=0.52).

CONCLUSIONS

This single center study suggests that the EAdi waveform may improve the ability of pediatric intensivists to detect missed efforts and auto-triggering asynchronies. Further studies are required to determine the clinical implications of these findings.

Diaphragm-triggered non-invasive respiratory support in preterm infants

BACKGROUND

Diaphragm-triggered non-invasive respiratory support, commonly referred to as NIV-NAVA (non-invasive neurally adjusted ventilatory assist), uses the electrical activity of the crural diaphragm to trigger the start and end of a breath. It provides variable inspiratory pressure that is proportional to an infant's changing inspiratory effort. NIV-NAVA has the potential to provide effective, non-invasive, synchronised, multilevel support and may reduce the need for invasive ventilation; however, its effects on short- and long-term outcomes, especially in the preterm infant, are unclear.

OBJECTIVES

To assess the effectiveness and safety of diaphragm-triggered non-invasive respiratory support in preterm infants (< 37 weeks' gestation) when compared to other non-invasive modes of respiratory support (nasal intermittent positive pressure ventilation (NIPPV); nasal continuous positive airway pressure (nCPAP); high-flow nasal cannulae (HFNC)), and to assess preterm infants with birth weight less than 1000 grams or less than 28 weeks' corrected gestation at the time of intervention as a sub-group.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2019, Issue 5), MEDLINE via PubMed (1946 to 10 May 2019), Embase (1947 to 10 May 2019), and CINAHL (1982 to 10 May 2019). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials (RCTs) and quasi-randomised trials.

SELECTION CRITERIA

Randomised and quasi-randomised controlled trials that compared diaphragm-triggered non-invasive versus other non-invasive respiratory support in preterm infants.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials, assessed trial quality and extracted data from included studies. We performed fixed-effect analyses and expressed treatment effects as mean difference (MD), risk ratio (RR), and risk difference (RD) with 95% confidence intervals (CIs). We used the generic inverse variance method to analyse specific outcomes for cross-over trials. We used the GRADE approach to assess the certainty of evidence.

MAIN RESULTS

There were two small randomised controlled trials including a total of 23 infants eligible for inclusion in the review. Only one trial involving 16 infants included in the analysis reported on either of the primary outcomes of the review. This found no difference in failure of modality between NIV-NAVA and NIPPV (RR 0.33, 95% CI 0.02 to 7.14; RD -0.13, 95% CI -0.41 to 0.16; 1 study, 16 infants; heterogeneity not applicable). Both trials reported on secondary outcomes of the review, specific for cross-over trials (total 22 infants; 1 excluded due to failure of initial modality). One study involving seven infants reported a significant reduction in maximum FiO₂ with NIV-NAVA compared to NIPPV (MD -4.29, 95% CI -5.47 to -3.11; heterogeneity not applicable). There was no difference in maximum electric activity of the diaphragm (Edi) signal between modalities (MD -1.75, 95% CI -3.75 to 0.26; I² = 0%) and a significant increase in respiratory rate with NIV-NAVA compared to NIPPV (MD 7.22, 95% CI 0.21 to 14.22; I² = 72%) on a meta-analysis of two studies involving a total of 22 infants. The included studies did not report on other outcomes of interest.

AUTHORS' CONCLUSIONS

Due to limited data and very low certainty evidence, we were unable to determine if diaphragm-triggered non-invasive respiratory support is effective or safe in preventing respiratory failure in preterm infants. Large, adequately powered randomised controlled trials are needed to determine if diaphragm-triggered non-invasive respiratory support in preterm infants is effective or safe.

Precision Medicine in Neonates: Future Perspectives for the Lung

Bronchopulmonary dysplasia (BPD) is the most common complication of pre-term birth with long lasting sequelae. Since its first description more than 50 years ago, many large randomized controlled trials have been conducted, aiming to improve evidence-based knowledge on the optimal strategies to prevent and treat BPD. However, most of these intervention studies have been performed on a population level without regard for the variation in clinical and biological diversity (e.g., gestational age, ethnicity, gender, or disease progression) between patients that is driven by the complex interaction of genetic pre-disposition and environmental exposures. Nevertheless, clinicians provide daily care such as lung protective interventions on an individual basis every day despite the fact that research supporting individualized or precision medicine for monitoring or treating pre-term lungs is immature. This narrative review summarizes four potential developments in pulmonary research that might facilitate the process of individualizing lung protective interventions to prevent development of BPD. Electrical impedance tomography and electromyography of the diaphragm are bedside monitoring tools to assess regional changes in lung volume and ventilation and spontaneous breathing effort, respectively. These non-invasive tools allow a more individualized optimization of invasive and non-invasive respiratory support. Investigation of the genomic variation in caffeine metabolism in pre-term infants can be used to optimize and individualize caffeine dosing regimens. Finally, volatile organic compound analysis in exhaled breath might accurately predict BPD at an early stage of the disease, enabling clinicians to initiate preventive strategies for BPD on an individual basis. Before these suggested diagnostic or monitoring tools can be implemented in daily practice and improve individualized patient care, future research should address and overcome their technical difficulties, perform extensive external validation and show their additional value in preventing BPD.

Comparison of extubation success using noninvasive positive pressure ventilation (NIPPV) versus noninvasive neurally adjusted ventilatory assist (NI-NAVA)

OBJECTIVE

Compare rates of initial extubation success in preterm infants extubated to NIPPV or NI-NAVA.

STUDY DESIGN

In this pilot study, we randomized 30 mechanically ventilated preterm infants at the time of initial elective extubation to NI-NAVA or NIPPV in a 1:1 assignment. Primary study outcome was initial extubation success.

RESULTS

Rates of continuous extubation for 120 h were 92% in the NI-NAVA group and 69% in the NIPPV group (12/13 vs. 9/13, respectively, p = 0.14). Infants extubated to NI-NAVA remained extubated longer (median 18 vs. 4 days, p = 0.02) and experienced lower peak inspiratory pressures (PIP) than infants managed with NIPPV throughout the first 3 days after extubation. Survival analysis through 14 days post extubation showed a sustained difference in the primary study outcome until 12 days post extubation.

CONCLUSIONS

Our study is the first to suggest that a strategy of extubating preterm infants to NI-NAVA may be more successful.

European Consensus Guidelines on the Management of Respiratory Distress Syndrome - 2019 Update

As management of respiratory distress syndrome (RDS) advances, clinicians must continually revise their current practice. We report the fourth update of "European Guidelines for the Management of RDS" by a European panel of experienced neonatologists and an expert perinatal obstetrician based on available literature up to the end of 2018. Optimising outcome for babies with RDS includes prediction of risk of preterm delivery, need for appropriate maternal transfer to a perinatal centre and timely use of antenatal steroids. Delivery room management has become more evidence-based, and protocols for lung protection including initiation of CPAP and titration of oxygen should be implemented immediately after birth. Surfactant replacement therapy is a crucial part of management of RDS, and newer protocols for its use recommend early administration and avoidance of mechanical ventilation. Methods of maintaining babies on non-invasive respiratory support have been further developed and may cause less distress and reduce chronic lung disease. As technology for delivering mechanical ventilation improves, the risk of causing lung injury should decrease, although minimising time spent on mechanical ventilation using caffeine and, if necessary, postnatal steroids are also important considerations. Protocols for optimising general care of infants with RDS are also essential with good temperature control, careful fluid and nutritional management, maintenance of perfusion and judicious use of antibiotics all being important determinants of best outcome.

Bronchopulmonary dysplasia: what are its links to COPD?

Emerging evidence suggests that adverse early life events can affect long-term health trajectories throughout life. Preterm birth, in particular, is a significant early life event that affects approximately 10% of live births. Worldwide, prematurity is the number one cause of death in children less than 5 years of age and has been shown to disrupt normal lung development with lasting effects into adult life. Along with impaired lung development, interventions used to support gas exchange and other sequelae of prematurity can lead to the development of bronchopulmonary dysplasia (BPD). BPD is a chronic respiratory disease of infancy characterized by alveolar simplification, small airways disease, and pulmonary vascular changes. Although many survivors of BPD improve with age, survivors of BPD often have chronic lung disease characterized by airflow obstruction and intermittent pulmonary exacerbations. Long-term lung function trajectories as measured by FEV1 can be lower in children and adults with a history BPD. In this review, we discuss the epidemiology and manifestations of BPD and its long-term consequences throughout childhood and into adulthood. Available evidence suggests that disrupted lung development, genetic susceptibility and subsequent environment and infectious events that occur in prenatal and postnatal life likely increase the predisposition of children with BPD to develop early onset chronic obstructive pulmonary disease (COPD). The reviews of this paper are available via the supplemental material section.