Comparing changing neurally adjusted ventilatory assist (NAVA) levels in intubated and recently extubated neonates

The Diaphragmatic Initiated Ventilatory Assist (DIVA) trial: study protocol for a randomized controlled trial comparing rates of extubation failure in extremely premature infants undergoing extubation to non-invasive neurally adjusted ventilatory assist versus non-synchronized nasal intermittent positive pressure ventilation

BACKGROUND

Invasive mechanical ventilation contributes to bronchopulmonary dysplasia (BPD), the most common complication of prematurity and the leading respiratory cause of childhood morbidity. Non-invasive ventilation (NIV) may limit invasive ventilation exposure and can be either synchronized or non-synchronized (NS). Pooled data suggest synchronized forms may be superior. Non-invasive neurally adjusted ventilatory assist (NIV-NAVA) delivers NIV synchronized to the neural signal for breathing, which is detected with a specialized catheter. The DIVA (Diaphragmatic Initiated Ventilatory Assist) trial aims to determine in infants born 240/7-276/7 weeks' gestation undergoing extubation whether NIV-NAVA compared to non-synchronized nasal intermittent positive pressure ventilation (NS-NIPPV) reduces the incidence of extubation failure within 5 days of extubation.

METHODS

This is a prospective, unblinded, pragmatic, multicenter phase III randomized clinical trial. Inclusion criteria are preterm infants 24-276/7 weeks gestational age who were intubated within the first 7 days of life for at least 12 h and are undergoing extubation in the first 28 postnatal days. All sites will enter an initial run-in phase, where all infants are allocated to NIV-NAVA, and an independent technical committee assesses site performance. Subsequently, all enrolled infants are randomized to NIV-NAVA or NS-NIPPV at extubation. The primary outcome is extubation failure within 5 days of extubation, defined as any of the following: (1) rise in FiO2 at least 20% from pre-extubation for > 2 h, (2) pH ≤ 7.20 or pCO2 ≥ 70 mmHg; (3) > 1 apnea requiring positive pressure ventilation (PPV) or ≥ 6 apneas requiring stimulation within 6 h; (4) emergent intubation for cardiovascular instability or surgery. Our sample size of 478 provides 90% power to detect a 15% absolute reduction in the primary outcome. Enrolled infants will be followed for safety and secondary outcomes through 36 weeks' postmenstrual age, discharge, death, or transfer.

DISCUSSION

The DIVA trial is the first large multicenter trial designed to assess the impact of NIV-NAVA on relevant clinical outcomes for preterm infants. The DIVA trial design incorporates input from clinical NAVA experts and includes innovative features, such as a run-in phase, to ensure consistent technical performance across sites.

TRIAL REGISTRATION

www.

CLINICALTRIALS

gov , trial identifier NCT05446272 , registered July 6, 2022.

Novel forms of ventilation in neonates: Neurally adjusted ventilatory assist and proportional assist ventilation

Patient-triggered modes of ventilation are currently the standard of practice in the care of term and preterm infants. Maintaining spontaneous breathing during mechanical ventilation promotes earlier weaning and possibly reduces ventilator-induced diaphragmatic dysfunction. A further development of assisted ventilation provides support in proportion to the respiratory effort and enables the patient to have full control of their ventilatory cycle. In this paper we will review the literature on two of these modes of ventilation: neurally adjusted ventilatory assist (NAVA) and proportional assist ventilation (PAV), propose future studies and suggest clinical applications of these modes.

Case Report: Neurally adjusted ventilatory assist as an effective rescue treatment for pulmonary interstitial emphysema in extremely low birth weight infants

Pulmonary interstitial emphysema (PIE) is a complication observed in extremely low birth weight (ELBW) infants on mechanical ventilation. Despite various proposed therapeutic interventions, the success rates have shown inconsistency. Neurally adjusted ventilatory assist (NAVA) stands out as a novel respiratory support mode, offering lower pressure and tidal volume in comparison to conventional ventilation methods. In this case report, we present five ELBW infants with refractory PIE who were transitioned to NAVA ventilation. Following the switch to NAVA, all cases of PIE gradually resolved. In contrast to traditional modes, NAVA provided respiratory support with significantly lower fraction of inspired oxygen, reduced peak inspiratory pressure, diminished mean airway pressure, and decreased tidal volume within 7 days of NAVA utilization (p = 0.042, 0.043, 0.043, and 0.042, respectively). Consequently, we propose that NAVA could serve as a valuable rescue treatment for ELBW infants with PIE.

Neurally adjusted ventilatory assist in infants: A review article

Neurally adjusted ventilatory assist (NAVA) and non-invasive (NIV)-NAVA are innovative modes of synchronized and proportional respiratory support. They can synchronize with the patients' breathing and promote patient comfort. Both techniques are increasingly being used these years, however experience with their use in newborns and premature infants in Taiwan is relatively few. Because increasing evidence supports the use of NAVA and NIV-NAVA in newborns and premature infants requiring respiratory assist to achieve better synchrony, the aim of this article is to discuss whether NAVA can provide better synchronization and comfort for ventilated newborns and premature babies. In a review of recent literature, we found that NAVA and NIV-NAVA appear to be superior to conventional invasive and non-invasive ventilation. Nevertheless, some of the benefits are controversial. For example, treatment failure in premature infants is common due to insufficient triggering of electrical activity of the diaphragm (EAdi) and frequent apnea, highlighting the differences between premature infants and adults in settings and titration. Further, we suggest how to adjust the settings of NAVA and NIV-NAVA in premature infants to reduce clinical adverse events and extubation failure. In addition to assist in the use of NAVA, EAdi can also serve as a continuous and real-time monitor of vital signs, assisting physicians in the administration of sedatives, evaluation of successful extubation, and as a reference for the patient's respiratory condition during special procedures.

Non-invasive neurally adjusted ventilatory assist in preterm infants with RDS: effect of changing NAVA levels

We aimed to examine the effect of changing levels of support (NAVA level) during non-invasive neurally adjusted ventilatory assist (NIV-NAVA) in preterm infants with respiratory distress syndrome (RDS) on electrical diaphragm activity. This is a prospective, single-centre, interventional, exploratory study in a convenience sample. Clinically stable preterm infants supported with NIV-NAVA for RDS were eligible. Patients were recruited in the first 24 h after the start of NIV-NAVA. Following a predefined titration protocol, NAVA levels were progressively increased starting from a level of 0.5 cmH₂O/µV and with increments of 0.5 cmH₂O/µV every 3 min, up to a maximum level of 4.0 cmH₂O/µV. We measured the evolution of peak inspiratory pressure and the electrical signal of the diaphragm (Edi) during NAVA level titration. Twelve infants with a mean (SD) gestational age at birth of 30.6 (3.5) weeks and birth weight of 1454 (667) g were enrolled. For all patients a breakpoint could be identified during the titration study. The breakpoint was on average (SD) at a level of 2.33 (0.58) cmH₂O/µV. With increasing NAVA levels, the respiratory rate decreased significantly. No severe complications occurred.Conclusions: Preterm neonates with RDS supported with NIV-NAVA display a biphasic response to changing NAVA levels with an identifiable breakpoint. This breakpoint was at a higher NAVA level than commonly used in this clinical situation. Immature neural feedback mechanisms warrant careful monitoring of preterm infants when supported with NIV-NAVA.Trial registration: clinicaltrials.gov NCT03780842. Date of registration December 12, 2018. What is Known: • Non-invasive neurally adjusted ventilatory assist (NIV-NAVA) is a safe, feasible and effective way to support respiration in preterm infants. • Intact neural feedback mechanisms are needed to protect the lung from overdistension in neurally adjusted ventilatory assist. What is New: • Preterm infants with acute RDS have a similar pattern of respiratory unloading as previously described. • Neural feedback mechanisms seem to be immature with the risk of insufficient support and lung injury due to overdistension of the lung.

Patient-Ventilator Synchrony in Extremely Premature Neonates during Non-Invasive Neurally Adjusted Ventilatory Assist or Synchronized Intermittent Positive Airway Pressure: A Randomized Crossover Pilot Trial

INTRODUCTION

Synchronization of non-invasive ventilation is challenging in extremely premature infants. We compared patient-ventilator synchrony between non-invasive neurally adjusted ventilatory assist (NIV-NAVA) using transdiaphragmatic (Edi) catheter and synchronized intermittent positive airway pressure (SiPAP) using an abdominal trigger.

METHODS

This study was a monocentric, randomized, crossover trial in premature infants born before 28 weeks of gestation, aged 3 days or more, and below 32 weeks postmenstrual age. NIV-NAVA and SiPAP were applied in a random order for 2 h with analysis of data from the second hour. The primary outcome was the asynchrony index.

RESULTS

Fourteen patients were included (median [IQR] gestational age at birth 25.6 (25.3-26.4) weeks, median [IQR] birth weight 755 [680-824] g, median [IQR] postnatal age 26.5 [19.8-33.8] days). The median (IQR) asynchrony index was significantly lower in NIV-NAVA versus SiPAP (49.9% [44.1-52.6] vs. 85.8% [74.2-90.9], p < 0.001). Ineffective efforts and auto-triggering were significantly less frequent in NIV-NAVA versus SiPAP (3.0% vs. 32.0% p < 0.001 and 10.0% vs. 26.6%, p = 0.004, respectively). Double triggering was significantly less frequent in SiPAP versus NIV-NAVA (0.0% vs. 9.0%, p < 0.001). No significant difference was observed for premature cycling and late cycling. Peak Edi and swing Edi were significantly lower in NIV-NAVA as compared to SiPAP (7.7 [6.1-9.9] vs. 11.0 [6.7-14.5] μV, p = 0.006; 5.4 [4.2-7.6] vs. 7.6 [4.3-10.8] μV, p = 0.007, respectively). No significant difference was observed between NIV-NAVA and SiPAP for heart rate, respiratory rate, COMFORTneo scores, apnoea, desaturations, or bradycardias.

DISCUSSION/CONCLUSION

NIV-NAVA markedly improves patient-ventilator synchrony as compared to SiPAP in extremely premature infants.

Neurally Adjusted Ventilatory Assist in Newborns

Patient-ventilator asynchrony is very common in newborns. Achieving synchrony is quite challenging because of small tidal volumes, high respiratory rates, and the presence of leaks. Leaks also cause unreliable monitoring of respiratory metrics. In addition, ventilator adjustment must take into account that infants have strong vagal reflexes and demonstrate central apnea and periodic breathing, with a high variability in breathing pattern. Neurally adjusted ventilatory assist (NAVA) is a mode of ventilation whereby the timing and amount of ventilatory assist is controlled by the patient's own neural respiratory drive. As NAVA uses the diaphragm electrical activity (Edi) as the controller signal, it is possible to deliver synchronized assist, both invasively and noninvasively (NIV-NAVA), to follow the variability in breathing pattern, and to monitor patient respiratory drive, independent of leaks. This article provides an updated review of the physiology and the scientific literature pertaining to the use of NAVA in children (neonatal and pediatric age groups). Both the invasive NAVA and NIV-NAVA publications since 2016 are summarized, as well as the use of Edi monitoring. Overall, the use of NAVA and Edi monitoring is feasible and safe. Compared with conventional ventilation, NAVA improves patient-ventilator interaction, provides lower peak inspiratory pressure, and lowers oxygen requirements. Evidence from several studies suggests improved comfort, less sedation requirements, less apnea, and some trends toward reduced length of stay and more successful extubation.

Proportional assist and neurally adjusted ventilation: Clinical knowledge and future trials in newborn infants

Different types of patient triggered ventilator modes have become the mainstay of ventilation in term and preterm newborn infants. Maintaining spontaneous breathing has allowed for earlier weaning and the additive effects of respiratory efforts combined with pre-set mechanical inflations have reduced mean airway pressures, both of which are important components in trying to avoid lung injury and promote normal lung development. New sophisticated modes of assisted ventilation have been developed during the last decades where the control of ventilator support is turned over to the patient. The ventilator detects the respiratory effort and adjusts ventilatory assistance proportionally to each phase of the respiratory cycle, thus enabling the patient to have full control of the start, the duration and the amount of ventilatory assistance. In this paper we will review the literature on the ventilatory modes of proportional assist ventilation and neurally adjusted ventilatory assistance, examine the different ways the signals are analyzed, propose future studies, and suggest ways to apply these modes in the clinical environment.

Feasibility of neurally synchronized and proportional negative pressure ventilation in a small animal model

RATIONALE

Synchronized positive pressure ventilation is possible using diaphragm electrical activity (EAdi) to control the ventilator. It is unknown whether EAdi can be used to control negative pressure ventilation.

AIM

To evaluate the feasibility of using EAdi to control negative pressure ventilation.

METHODS

Fourteen anesthetized rats were studied (380-590 g) during control, resistive breathing, acute lung injury or CO₂ rebreathing. Positive pressure continuous neurally adjusted ventilatory assist (cNAVA^P+ ) was applied via intubation. Negative pressure cNAVA (cNAVA^P- ) was applied with the animal placed in a sealed box. In part 1, automatic stepwise increments in cNAVA level by 0.2 cmH₂ O/µV every 30 s was applied for cNAVA^P+ , cNAVA^P- , and a 50/50 combination of the two (cNAVA^P± ). In part 2: During 5-min ventilation with cNAVA^P+ or cNAVA^P- we measured circuit, box, and esophageal (Pes) pressure, EAdi, blood pressure, and arterial blood gases.

RESULTS

Part 1: During cNAVA^P+ , pressure in the circuit increased with increasing cNAVA levels, reaching a plateau, and similarly for cNAVA^P- , albeit reversed in sign. This was associated with downregulation of the EAdi. Pes swings became less negative with cNAVA^P+ but, in contrast, Pes swings were more negative during increasing cNAVA^P- levels. Increasing the cNAVA level during cNAVA^P± resulted in an intermediate response. Part 2: no significant differences were observed for box/circuit pressures, EAdi, blood pressure, or arterial blood gases. Pes swings during cNAVA^P- were significantly more negative than during cNAVA^P+ .

CONCLUSION

Negative pressure ventilation synchronized and proportional to the diaphragm activity is feasible in small animals.

Evaluating peak inspiratory pressures and tidal volume in premature neonates on NAVA ventilation

Neurally adjusted ventilatory assist (NAVA) ventilation allows patients to determine their peak inspiratory pressure and tidal volume on a breath-by-breath basis. Apprehension exists about premature neonates' ability to self-regulate breath size. This study describes peak pressure and tidal volume distribution of neonates on NAVA and non-invasive NAVA. This is a retrospective study of stored ventilator data with exploratory analysis. Summary statistics were calculated. Distributional assessment of peak pressure and tidal volume were evaluated, overall and per NAVA level. Over 1 million breaths were evaluated from 56 subjects. Mean peak pressure was 16.4 ± 6.4 in the NAVA group, and 15.8 ± 6.4 in the NIV-NAVA group (t test, p < 0.001). Mean tidal volume was 3.5 ± 2.7 ml/kg.Conclusion:In neonates on NAVA, most pressures and volumes were within or lower than recommended ranges with pressure-limited or volume-guarantee ventilation. What is known: • Limiting peak inspiratory pressures or tidal volumes are the main strategies to minimize ventilator-induced lung injury in neonates. Neurally adjusted ventilatory assist allows neonates to regulate their own peak inspiratory pressures and tidal volumes on a breath-to-breath basis using neural feedback. What is new: • When neonates chose the size of their breaths based on neural feedback, the majority of peak inspiratory pressures and tidal volumes were within or lower than the recommended peak inspiratory pressure or tidal volume ranges with pressure-limited or volume guarantee ventilation.

A Review on Non-invasive Respiratory Support for Management of Respiratory Distress in Extremely Preterm Infants

Majority of extremely preterm infants require positive pressure ventilatory support at the time of delivery or during the transitional period. Most of these infants present with respiratory distress (RD) and continue to require significant respiratory support in the neonatal intensive care unit (NICU). Bronchopulmonary dysplasia (BPD) remains as one of the major morbidities among survivors of the extremely preterm infants. BPD is associated with long-term adverse pulmonary and neurological outcomes. Invasive mechanical ventilation (IMV) and supplemental oxygen are two major risk factors for the development of BPD. Non-invasive ventilation (NIV) has been shown to decrease the need for IMV and reduce the risk of BPD when compared to IMV. This article reviews respiratory management with current NIV support strategies in extremely preterm infants both in delivery room as well as in the NICU and discusses the evidence to support commonly used NIV modes including nasal continuous positive airway pressure (NCPAP), nasal intermittent positive pressure ventilation (NIPPV), bi-level positive pressure (BI-PAP), high flow nasal cannula (HFNC), and newer NIV strategies currently being studied including, nasal high frequency ventilation (NHFV) and non-invasive neutrally adjusted ventilatory assist (NIV-NAVA). Randomized, clinical trials have shown that early NIPPV is superior to NCPAP to decrease the need for intubation and IMV in preterm infants with RD. It is also important to understand that selection of the device used to deliver NIPPV has a significant impact on its success. Ventilator generated NIPPV results in significantly lower rates of extubation failures when compared to Bi-PAP. Future studies should address synchronized NIPPV including NIV-NAVA and early rescue use of NHFV in the respiratory management of extremely preterm infants.