Neurally adjusted ventilator assist in very low birth weight infants: Current status

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.

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.

Rates of Bronchopulmonary Dysplasia Following Implementation of a Novel Prevention Bundle

IMPORTANCE

Bronchopulmonary dysplasia (BPD) rates in the United States remain high and have changed little in the last decade.

OBJECTIVE

To develop a consistent BPD prevention bundle in a systematic approach to decrease BPD.

DESIGN, SETTING, AND PARTICIPANTS

This quality improvement study included 484 infants with birth weights from 501 to 1500 g admitted to a level 3 neonatal intensive care unit in the Kaiser Permanente Southern California system from 2009 through 2019. The study period was divided into 3 periods: 1, baseline (2009); 2, initial changes based on ongoing cycles of Plan-Do-Study-Act (2010-2014); and 3, full implementation of successive Plan-Do-Study-Act results (2015-2019).

INTERVENTIONS

A BPD prevention system of care bundle evolved with a shared mental model that BPD is avoidable.

MAIN OUTCOMES AND MEASURES

The primary outcome was BPD in infants with less than 33 weeks' gestational age (hereafter referred to as BPD <33). Other measures included adjusted BPD <33, BPD severity grade, and adjusted median postmenstrual age (PMA) at hospital discharge. Balancing measures were adjusted mortality and adjusted mortality or specified morbidities.

RESULTS

The study population included 484 infants with a mean (SD) birth weight of 1070 (277) g; a mean (SD) gestational age of 28.6 (2.9) weeks; 252 female infants (52.1%); and 61 Black infants (12.6%). During the 3 study periods, BPD <33 decreased from 9 of 29 patients (31.0%) to 3 of 184 patients (1.6%) (P < .001 for trend); special cause variation was observed. The standardized morbidity ratio for the adjusted BPD <33 decreased from 1.2 (95% CI, 0.7-1.9) in 2009 to 0.4 (95% CI, 0.2-0.8) in 2019. The rates of combined grades 1, 2, and 3 BPD decreased from 7 of 29 patients (24.1%) to 17 of 183 patients (9.3%) (P < .008 for trend). Grade 2 BPD rates decreased from 3 of 29 patients (10.3%) to 5 of 183 patients (2.7%) (P = .02 for trend). Adjusted median PMA at home discharge decreased by 2 weeks, from 38.2 (95% CI, 37.3-39.1) weeks in 2009 to 36.8 (95% CI, 36.6-37.1) weeks during the last 3 years (2017-2019) of the full implementation period. Adjusted mortality was unchanged, whereas adjusted mortality or specified morbidities decreased significantly.

CONCLUSIONS AND RELEVANCE

A sustained low rate of BPD was observed in infants after the implementation of a detailed BPD system of care.

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.

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.

SÍNDROME POSTERIOR DO TRONCO CEREBRAL E O USO DE VENTILAÇÃO ASSISTIDA AJUSTADA NEURALMENTE (NAVA) EM LACTENTE

Objective:

To report a rare case of dorsal brainstem syndrome in an infant after hypoxic-ischemic episode due to severe sepsis and the use of neurally adjusted ventilatory assist (NAVA) to aid in diagnosis and in the removal of mechanical ventilation.

Case description:

A 2-month-old male infant, previously healthy, presented with severe sepsis that evolved to dorsal brainstem syndrome, which usually occurs after hypoxic-ischemic injury in neonates and infants, and is related to very specific magnetic resonance images. Due to neurological lesions, thei nfant remained in mechanical ventilation. A NAVA module was installed to keep track of phrenic nerve conduction to the diaphragm, having successfully showed neural conduction and helped removing mechanical ventilation.

Comments:

Dorsal brainstem syndrome is a rare condition that should be considered after hypoxic-ischemic episode in infants.

Neuromuscular disorders and chronic ventilation

Morbidity and mortality have decreased in patients with neuromuscular disease due to implementation of therapies to augment cough and improve ventilation. Infants with progressive neuromuscular disease will eventually develop respiratory complications as a result of muscle weakness and their inability to compensate during periods of increased respiratory loads. The finding of nocturnal hypercapnia is often the trigger for initiating non-invasive ventilation and studies have shown that its use not only may improve sleep-disordered breathing, but also that it may have an effect on daytime function, symptoms related to hypercapnia, and partial pressure of CO₂. It is important to understand the respiratory physiology of this population and to understand the benefits and limitations of assisted ventilation.

Lung-protective ventilatory strategies in intubated preterm neonates with RDS

This article provides a narrative review of lung-protective ventilatory strategies (LPVS) in intubated preterm infants with RDS. A description of strategies is followed by results on short-and long-term respiratory and neurodevelopmental outcomes. Strategies will include patient-triggered or synchronized ventilation, volume targeted ventilation, the technique of intubation, surfactant administration and rapid extubation to NCPAP (INSURE), the open lung concept, strategies of high-frequency ventilation, and permissive hypercapnia. Based on this review single recommendations on optimal LPVS cannot be made. Combinations of several strategies, individually applied, most probably minimize or avoid potential serious respiratory and cerebral complications like bronchopulmonary dysplasia and cerebral palsy.

Neurally Adjusted Ventilatory Assist in Preterm Infants With Established or Evolving Bronchopulmonary Dysplasia on High-Intensity Mechanical Ventilatory Support: A Single-Center Experience

OBJECTIVES

The aim of the present study was to report possible improvements in ventilator variables associated with a transition from synchronized intermittent mandatory ventilation to neurally adjusted ventilatory assist in preterm infants with bronchopulmonary dysplasia who required a high level of mechanical ventilatory support in a single center.

DESIGN

Retrospective study.

SETTING

Neonatal ICU.

PATIENTS

Twenty-nine preterm infants with a median gestational age of 25.4 weeks (range, 23.4-30.3 wk) and a median birth weight of 680 g (range, 370-1,230 g) and who were supported with a mechanical ventilator for more than 4 weeks and had a respiratory severity score greater than four during conventional mechanical ventilation prior to conversion to neurally adjusted ventilatory assist.

INTERVENTIONS

Comparison of ventilatory variables, work of breathing, and blood gas values during conventional ventilation and at various time intervals after the change to neurally adjusted ventilatory assist.

MEASUREMENTS AND MAIN RESULTS

The values of various ventilatory variables and other measurements were obtained 1 hour before neurally adjusted ventilatory assist and 1, 4, 12, and 24 hours after conversion to neurally adjusted ventilatory assist. During neurally adjusted ventilatory assist, the peak inspiratory pressure (20.12 ± 2.93 vs 14.15 ± 3.55 cm H2O; p < 0.05), mean airway pressure (11.15 ± 1.29 vs 9.57 ± 1.27 cm H2O; p < 0.05), and work of breathing (0.86 ± 0.22 vs 0.46 ± 0.12 J/L; p < 0.05) were significantly decreased, and the blood gas values were significantly improved. Significantly lower FIO2 and improved oxygen saturation were observed during neurally adjusted ventilatory assist compared with conventional ventilation support. The RSS values decreased and sustained during neurally adjusted ventilatory assist (4.85 ± 1.63 vs 3.21 ± 1.01; p < 0.001).

CONCLUSIONS

The transition from synchronized intermittent mandatory ventilation to neurally adjusted ventilatory assist ventilation was associated with improvements in ventilator variables, oxygen saturation, and blood gas values in infants with bronchopulmonary dysplasia in a single center. This study suggests the possible clinical utility of neurally adjusted ventilatory assist as a weaning modality for bronchopulmonary dysplasia patients in the neonatal ICU.

Physiology of non-invasive respiratory support

Non-invasive ventilation (NIV) is used in neonates to treat extrathoracic and intrathoracic airway obstruction, parenchymal lung disease and disorders of control of breathing. Avoidance of airway intubation is associated with a reduction in the incidence of chronic lung disease among preterm infants with respiratory distress syndrome. Use of nasal continuous positive airway pressure (nCPAP) may help establish and maintain functional residual capacity (FRC), decrease respiratory work, and improve gas exchange. Other modes of non-invasive ventilation, which include heated humidified high-flow nasal cannula therapy (HHHFNC), nasal intermittent mandatory ventilation (NIMV), non-invasive pressure support ventilation (NI-PSV), and bi-level CPAP (SiPAP™), have also been shown to provide additional benefit in improving breathing patterns, reducing work of breathing, and increasing gas exchange when compared with nCPAP. Newer modes, such as neurally adjusted ventilatory assist (NAVA), hold the promise of improving patient-ventilator synchrony and so might ultimately improve outcomes for preterm infants with respiratory distress.