Neurally adjusted ventilatory assist in extremely low-birthweight infants

Non-invasive ventilatory support in neonates: An evidence-based update

Non-invasive ventilatory support (NIV) is considered the gold standard in the care of preterm infants with respiratory distress syndrome (RDS). NIV from birth is superior to mechanical ventilation (MV) for the prevention of death or bronchopulmonary dysplasia (BPD), with a number needed to treat between 25 and 35. Various methods of NIV are available, some of them extensively researched and with well proven efficacy, whilst others are needing further research. Nasal continuous positive airway pressure (nCPAP) has replaced routine invasive mechanical ventilation (MV) for the initial stabilization and the treatment of RDS. Choosing the most suitable form of NIV and the most appropriate patient interface depends on several factors, including gestational age, underlying lung pathophysiology and the local facilities. In this review, we present the currently available evidence on NIV as primary ventilatory support to preventing intubation and for secondary ventilatory support, following extubation. We review nCPAP, nasal high-flow cannula, nasal intermittent positive airway pressure ventilation, bi-level positive airway pressure, nasal high-frequency oscillatory ventilation and nasal neurally adjusted ventilatory assist modes. We also discuss most suitable NIV devices and patient interfaces during resuscitation of the newborn in the delivery room.

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.

Effect of electrical activity of the diaphragm waveform patterns on SpO2 for extremely preterm infants ventilated with neurally adjusted ventilatory assist

OBJECTIVE

This study aimed to evaluate the association between electrical activity of the diaphragm (Edi) waveform patterns and peripheral oxygen saturation (SpO₂ ) in extremely preterm infants who are ventilated with neurally adjusted ventilatory assist (NAVA).

STUDY DESIGN

We conducted a retrospective cohort study at a level III neonatal intensive care unit. Extremely preterm infants born at our hospital between November 2019 and November 2020 and ventilated with NAVA were included. We collected Edi waveform data and classified them into four Edi waveform patterns, including the phasic pattern, central apnea pattern, irregular low-voltage pattern, and tonic burst pattern. We analyzed the Edi waveform pattern for the first 15 h of collectable data in each patient. To investigate the association between Edi waveform patterns and SpO₂ , we analyzed the dataset every 5 min as one data unit. We compared the proportion of each waveform pattern between the desaturation (Desat [+]) and non-desaturation (Desat [-]) groups.

RESULTS

We analyzed collected data for 105 h (1260 data units). The proportion of the phasic pattern in the Desat (+) group was significantly lower than that in the Desat (-) group (p < .001). However, the proportions of the central apnea, irregular low-voltage, and tonic burst patterns in the Desat (+) group were significantly higher than those in the Desat (-) group (all p < .05).

CONCLUSION

Our results indicate that proportions of Edi waveform patterns have an effect on desaturation of SpO₂ in extremely preterm infants who are ventilated with NAVA.

Effects of skin-to-skin care on electrical activity of the diaphragm in preterm infants during neurally adjusted ventilatory assist

BACKGROUND

Skin-to-skin care (SSC) reduces neonatal mortality and morbidity and is widely implemented in the neonatal intensive care unit. However, changes in respiratory effort during SSC in ventilated preterm infants remain unclear.

AIMS

To evaluate the effect of SSC on electrical activity of the diaphragm (Edi) and vital signs in premature infants who are intubated and under neurally adjusted ventilatory assist ventilation.

STUDY DESIGN

We performed an observational cross-over study. Data were measured in three periods: before (pre-SSC period), during (SSC period), and after (post-SSC period) SSC. Stable 30-min data in each period were extracted.

SUBJECTS

Thirty-four SSC procedures were performed in 14 preterm infants with a median gestational age of 25.3 weeks (interquartile range, 24, 26.4) and a birth weight of 659 g (566, 694). The median postnatal age was 41 days (31, 53) at the study with a median postmenstrual age of 31.3 weeks (30.4, 32.5).

OUTCOME MEASURES

Median values of Edi peak, Edi minimum, respiratory rate, SpO₂, and heart rate were measured in each condition. The Kruskal-Wallis test with Bonferroni multiple comparisons was used to compare each parameter in each period.

RESULTS

Median Edi peak and Edi minimum values were significantly lower during SSC compared with pre- and post-SSC, without any change in respiratory rate, SpO₂, or heart rate.

CONCLUSIONS

Respiratory efforts as evaluated by Edi are significantly reduced during SSC in ventilated preterm infants.

Application of Neurally Adjusted Ventilatory Assist in Premature Neonates Less Than 1,500 Grams With Established or Evolving Bronchopulmonary Dysplasia

Background: Very low birth weight premature (VLBW) infants with bronchopulmonary dysplasia (BPD) often need prolonged respiratory support, which is associated with worse outcomes. The application of neurally adjusted ventilatory assist ventilation (NAVA) in infants with BPD has rarely been reported. This study investigated whether NAVA is safe and can reduce the duration respiratory support in VLBW premature infants with established or evolving BPD. Methods: This retrospective matched-cohort study included patients admitted to our NICU between April 2017 to April 2019 who were born at <32 weeks' gestation with birthweight of <1,500 g. The study groups (NAVA group) were infants who received NAVA ventilation as a sequel mode of ventilation after at least 2 weeks of traditional respiratory support after birth. The control group were preterm infants who required traditional respiratory support beyond first 2 weeks of life and were closely matched to the NAVA patients by gestational age and birthweight. The primary outcome was to compare the total duration of respiratory support between the NAVA group and the control group. The secondary outcomes were comparisons of duration of invasive and non-invasive support, oxygen therapy, length of stay, severity of BPD, weight gain and sedation need between the groups. Results: There were no significant differences between NAVA group and control group in the primary and most of the secondary outcomes (all P > 0.05). However, NAVA was well tolerated and there was a decrease in the need of sedation (p = 0.012) after switching to NAVA. Conclusion: NAVA, when used as a sequel mode of ventilation, in premature neonates <1,500 g with evolving or established BPD showed a similar effect compared to conventional ventilation in respiratory outcomes. NAVA can be safely used in this patient population and potentially can decrease the need of sedation.

NAVA-synchronized compared to nonsynchronized noninvasive ventilation for apnea, bradycardia, and desaturation events in VLBW infants

Neurally adjusted ventilatory assistance (NAVA) can overcome technical difficulties with synchronizing noninvasive ventilation breaths with the patient, a modality often used in very low birthweight infants (VLBW) with apnea of prematurity (AOP). This study is a retrospective single-center investigation into whether NAVA-synchronized noninvasive (niNAVA) ventilation is better than nonsynchronized (nasal intermittent positive pressure ventilation [nIPPV]) for symptomatic apnea in VLBW infants. Nursing records of apnea, bradycardia, and/or desaturations were abstracted from the electronic medical records of 108 VLBW infants admitted to the neonatal intensive care unit (NICU) from 2015 to 2017 who received either of the two modalities, 61 epochs of niNAVA totaling 488 days and 103 epochs of nIPPV totaling 886.5 days. niNAVA was associated with a significant reduction in the number of isolated bradycardic events/day (0.48 ± 0.14 vs 1.35 ± 0.27; P = .019) and overall bradycardias/day (2.42 ± 0.47 vs 4.02 ± 0.53; P = .042) and there were more epochs with no events with niNAVA compared with nIPPV (23.0% vs 6.8%; P = .004). These results justify a prospective trial of NAVA-synchronized noninvasive ventilation for VLBW infants with caffeine-resistant AOP.

Processing transcutaneous electromyography measurements of respiratory muscles, a review of analysis techniques

Transcutaneous electromyography (tc-EMG) has been used to measure the electrical activity of respiratory muscles during inspiration in various studies. Processing the raw tc-EMG signal of these inspiratory muscles has shown to be difficult as baseline noise, cardiac interference, cross-talk and motion artefacts can influence the signal quality. In this review we will discuss the most important sources of signal noise in tc-EMG of respiratory muscles and the various techniques described to suppress or reduce this signal noise. Furthermore, we will elaborate on the options available to develop or improve an algorithm that can be used to guide the approach for analysis of tc-EMG signals of inspiratory muscles in future research.

Approaches to Noninvasive Respiratory Support in Preterm Infants: From CPAP to NAVA

Endotracheal intubation and invasive mechanical ventilation have been mainstays in respiratory care of neonates with respiratory distress syndrome. Together with antenatal steroids and surfactant, this approach has accounted for significant reductions in neonatal mortality. However, with the increased survival of very low birthweight infants, the incidence of bronchopulmonary dysplasia (BPD), the primary respiratory morbidity of prematurity, has also increased. Arrest of alveolar growth and development and the abnormal development of the pulmonary vasculature after birth are the primary causes of BPD. However, invasive ventilation-associated lung inflammation and airway injury have long been believed to be important contributors. In fact, discontinuing invasive ventilation in favor of noninvasive respiratory support has been considered the single best approach that neonatologists can implement to reduce BPD. In this review, we present and discuss the mechanisms, efficacy, and long-term outcomes of the four main approaches to noninvasive respiratory support of the preterm infant currently in use: nasal continuous positive airway pressure, high-flow nasal cannula, nasal intermittent mandatory ventilation, and neurally adjusted ventilatory assist. We show that noninvasive ventilation can decrease rates of intubation and the need for invasive ventilation in preterm infants with respiratory distress syndrome. However, none of these noninvasive approaches decrease rates of BPD. Accordingly, noninvasive respiratory support should be considered for clinical goals other than the reduction of BPD.

Non-invasive neurally adjusted ventilatory assist versus nasal intermittent positive-pressure ventilation in preterm infants born before 30 weeks' gestation

BACKGROUND

Non-invasive neurally adjusted ventilatory assist (NIV-NAVA), a mode of non-invasive ventilation (NIV) controlled by diaphragmatic electrical activity, may be superior to other NIV as a respiratory support after extubation in preterm infants, but no report has compared NIV-NAVA with other NIV methods. We evaluated the effectiveness and adverse effects of NIV-NAVA after extubation in preterm infants <30 weeks of gestation.

METHODS

This retrospective study involved patients who were born before 30 weeks of gestation. We mainly used NIV-NAVA or nasal intermittent positive-pressure ventilation (NIPPV) for preterm infants as the NIV after extubation and compared these two groups. The primary outcome was treatment failure. The secondary outcomes were extubation failure and adverse events. Treatment failure was defined as a change of NIV (NIPPV was switched to NIV-NAVA, or NIV-NAVA was switched to NIPPV) or reintubation ≤7 days after extubation.

RESULTS

Fifteen patients were in the NIV-NAVA group, and 19 were in the NIPPV group. The gestational age of the NIV-NAVA group was younger than that of the NIPPV group (25.7 ± 2.4 weeks vs 27.3 ± 1.8 weeks). Treatment failure occurred in six cases (40%) in the NIV-NAVA group and in nine cases (47.4%) in the NIPPV group, and no significant difference was demonstrated. No significant difference in adverse events was noted.

CONCLUSIONS

NIV-NAVA has advantages compared with NIPPV as the NIV for premature infants after extubation. NIV-NAVA can also be used safely without a significant difference in the rate of complications compared with NIPPV.