Neurally adjusted ventilator assist (NAVA) reduces asynchrony during non-invasive ventilation for severe bronchiolitis

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.

Noninvasive Neurally Adjusted Ventilatory Assist in Infants With Bronchiolitis: Respiratory Outcomes in a Single-Center, Retrospective Cohort, 2016-2018

OBJECTIVES

To describe our experience of using noninvasive neurally adjusted ventilatory assist (NIV-NAVA) in infants with bronchiolitis, its association with the evolution of respiratory effort, and PICU outcomes.

DESIGN

Retrospective analysis of a prospectively curated, high-frequency electronic database.

SETTING

A PICU in a university-affiliated maternal-child health center in Canada.

PATIENTS

Patients younger than 2 years old who were admitted with a diagnosis of acute bronchiolitis and treated with NIV-NAVA from October 2016 to June 2018.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Patient characteristics, as well as respiratory and physiologic parameters, including electrical diaphragmatic activity (Edi), were extracted from the electronic database. Respiratory effort was estimated using the modified Wood Clinical Asthma Score (mWCAS) and the inspiratory Edi. A comparison in the respiratory effort data was made between the 2 hours before and 2 hours after starting NIV-NAVA. In the two seasons, 64 of 205 bronchiolitis patients were supported with NIV-NAVA. These 64 patients had a median (interquartile range [IQR]) age of 52 days (32-92 d), and there were 36 of 64 males. Treatment with NIV-NAVA was used after failure of first-tier noninvasive respiratory support; 25 of 64 patients (39%) had at least one medical comorbidity. NIV-NAVA initiation was associated with a moderate decrease in mWCAS from 3.0 (IQR, 2.5-3.5) to 2.5 (IQR, 2.0-3.0; p < 0.001). NIV-NAVA initiation was also associated with a statistically significant decrease in Edi ( p < 0.01). However, this decrease was only clinically relevant in infants with a 2-hour baseline Edi greater than 20 μV; here, the before and after Edi was 44 μV (IQR, 33-54 μV) compared with 27 μV (IQR, 21-36 μV), respectively ( p < 0.001). Overall, six of 64 patients (9%) required endotracheal intubation.

CONCLUSIONS

In this single-center retrospective cohort, in infants with bronchiolitis who were considered to have failed first-tier noninvasive respiratory support, the use of NIV-NAVA was associated with a rapid decrease in respiratory effort and a 9% intubation rate.

Respiratory effort during noninvasive positive pressure ventilation and continuous positive airway pressure in severe acute viral bronchiolitis

OBJECTIVES

To assess if noninvasive positive pressure ventilation (NIPPV) is associated with a greater reduction in respiratory effort as compared to continuous positive airway pressure (CPAP) during severe acute bronchiolitis, with both supports set either clinically or physiologically.

METHODS

Twenty infants (median [IQR] age 1.2 [0.9; 3.2] months) treated <24 h with noninvasive respiratory support (CPAP Clin, set at 7 cmH₂ O, or NIPPV Clin) for bronchiolitis were included in a prospective single-center crossover study. Esogastric pressures were measured first with the baseline support, then with the other support. For each support, recordings were performed with the clinical setting and a physiological setting (CPAP Phys and NIPPV Phys), aiming at normalising respiratory effort. Patients were then treated with the optimal support. The primary outcome was the greatest reduction in esophageal pressure-time product (PTP_ES /min). Other outcomes included improvement of the other components of the respiratory effort.

RESULTS

NIPPV Clin and Phys were associated with a lower PTP_ES /min (164 [105; 202] and 106 [78; 161] cmH₂ O s/min, respectively) than CPAP Clin (178 [145; 236] cmH₂ O s/min; p = 0.01 and 2 × 10^-4 , respectively). NIPPV Clin and Phys were also associated with a significant reduction of all other markers of respiratory effort as compared to CPAP Clin. PTP_ES /min with NIPPV (Clin or Phys) was not different from PTP_ES /min with CPAP Phys. There was no significant difference between physiological and clinical settings.

CONCLUSION

NIPPV is associated with a significant reduction in respiratory effort as compared to CPAP set at +7 cmH₂ O in infants with severe acute bronchiolitis. CPAP Phys performs as well as NIPPV Clin.

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.

Implementation of noninvasive neurally adjusted ventilatory assist in pediatric acute respiratory failure: a controlled before-after quality improvement study

Backgrounds

Pediatric noninvasive neurally adjusted ventilatory assist (NIV-NAVA) has been shown to improve patient-ventilator interaction but no data on clinical outcomes are available. Aim of this study was to compare NIV-NAVA with noninvasive pressure support (NIV-PS) in children with acute hypoxemic respiratory failure (AHRF), in a single-center before-after study. A cohort of thirty-four NIV-PS patients (before group) admitted to our PICU within the 2 years prior NAVA introduction was compared with a cohort of thirty children treated with NIV-NAVA during implementation phase (after group). The primary end-point was intubation rate between groups. Days on mechanical ventilation, number of invasive devices, nosocomial infections, PICU/hospital length of stay (LOS), and physiological parameters at 2 and 24 h after admission were considered.

Results

Intubation rate was lower in the NIV-NAVA group as compared to the NIV-PS group (p = 0.006). Patients treated with NIV-NAVA required fewer invasive devices (p = 0.032) and had lower incidence of ventilator-acquired pneumonia (p = 0.004) and shorter PICU (p = 0.032) and hospital LOS (p = 0.013). At 2 h, NIV-NAVA compared with NIV-PS resulted in higher paO₂:FIO₂ (p = 0.017), lower paCO₂ (p = 0.002), RR (p = 0.026), and HR (p = 0.009).

Conclusions

Early NIV-NAVA vs NIV-PS was associated to lower intubation rate and shorter PICU and hospital LOS. Further studies are needed in order to confirm these preliminary data.

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.

Use of bilevel positive pressure ventilation in patients with bronchiolitis

RATIONAL

This study aims at describing the use of bilevel positive airway pressure (BiPAP) in infants with severe bronchiolitis.

WORKING HYPOTHESIS

The use of BiPAP in infants with bronchiolitis may be associated with a worst outcome.

STUDY DESIGN

A single-center retrospective study performed from October 2013 to April 2016.

METHODOLOGY

All infants from 1 day to 6 months of age admitted in the pediatric intensive care unit (PICU) were included if they had a clinical diagnosis of bronchiolitis and if they required any type of noninvasive ventilation (NIV), including high flow nasal cannula, continuous positive airway pressure and BiPAP at admission in PICU. There was no local written protocol regarding the ventilator management during the study.

RESULTS

Overall, 252 infants (median age 45 (26-72) days) were included in the study and 110 infants (44%) were supported by BiPAP at admission. More infants were born preterm in the group of patients supported by BiPAP at admission. No complication related to NIV occurred. Patients in the BiPAP group had a longer duration of noninvasive support as well as a longer PICU length of stay. However, hospital length of stay did not differ according to the type of respiratory support at admission.

CONCLUSION

The use of BiPAP was not associated with endotracheal intubation, however it was associated with increased PICU length of stay and increased duration of NIV.

Outcomes of ventilatory asynchrony in patients with inspiratory effort

Objective

To identify the relationship of patient-ventilator asynchrony with the level of sedation and hemogasometric and clinical results.

Methods

This was a prospective study of 122 patients admitted to the intensive care unit who underwent > 24 hours of invasive mechanical ventilation with inspiratory effort. In the first 7 days of ventilation, patient-ventilator asynchrony was evaluated daily for 30 minutes. Severe patient-ventilator asynchrony was defined as an asynchrony index > 10%.

Results

A total of 339,652 respiratory cycles were evaluated in 504 observations. The mean asynchrony index was 37.8% (standard deviation 14.1 - 61.5%). The prevalence of severe patient-ventilator asynchrony was 46.6%. The most frequent patient-ventilator asynchronies were ineffective trigger (13.3%), autotrigger (15.3%), insufficient flow (13.5%), and delayed cycling (13.7%). Severe patient-ventilator asynchrony was related to the level of sedation (ineffective trigger: p = 0.020; insufficient flow: p = 0.016; premature cycling: p = 0.023) and the use of midazolam (p = 0.020). Severe patient-ventilator asynchrony was also associated with hemogasometric changes. The persistence of severe patient-ventilator asynchrony was an independent risk factor for failure of the spontaneous breathing test, ventilation time, ventilator-associated pneumonia, organ dysfunction, mortality in the intensive care unit, and length of stay in the intensive care unit.

Conclusion

Patient-ventilator asynchrony is a frequent disorder in critically ill patients with inspiratory effort. The patient’s interaction with the ventilator should be optimized to improve hemogasometric parameters and clinical results. Further studies are required to confirm these results.

Emerging approaches in pediatric mechanical ventilation

INTRODUCTION

The use of mechanical ventilation is an invaluable tool in caring for critically ill patients. Enhancing our capabilities in mechanical ventilation has been instrumental in the ability to support clinical conditions and diseases which were once associated with high mortality. Areas covered: Within this manuscript, we will look to discuss emerging approaches to improving the care of pediatric patients who require mechanical ventilation. After an extensive literature search, we will provide a brief review of the history and pathophysiology of acute respiratory distress syndrome, an assessment of several ventilator settings, a discussion on assisted ventilation, review of therapy used to rescue in severe respiratory failure, methods of monitoring the effects of mechanical ventilation, and nutrition. Expert opinion: As we have advanced in our care, we are seeing children survive illnesses that would have once claimed their lives. Given this knowledge, we must continue to advance the research in pediatric critical care to understand the means in which we can tailor the therapy to the patient in efforts to efficiently liberate them from mechanical ventilation once their illness has resolved.

Monitoring of Respiratory Muscle Function in Critically Ill Children

OBJECTIVES

This review discusses the different techniques used at the bedside to assess respiratory muscle function in critically ill children and their clinical applications.

DATA SOURCES

A scoping review of the medical literature on respiratory muscle function assessment in critically ill children was conducted using the PubMed search engine.

STUDY SELECTION

We included all scientific, peer-reviewed studies about respiratory muscle function assessment in critically ill children, as well as some key adult studies.

DATA EXTRACTION

Data extracted included findings or comments about techniques used to assess respiratory muscle function.

DATA SYNTHESIS

Various promising physiologic techniques are available to assess respiratory muscle function at the bedside of critically ill children throughout the disease process. During the acute phase, this assessment allows a better understanding of the pathophysiological mechanisms of the disease and an optimization of the ventilatory support to increase its effectiveness and limit its potential complications. During the weaning process, these physiologic techniques may help predict extubation success and therefore optimize ventilator weaning.

CONCLUSIONS

Physiologic techniques are useful to precisely assess respiratory muscle function and to individualize and optimize the management of mechanical ventilation in children. Among all the available techniques, the measurements of esophageal pressure and electrical activity of the diaphragm appear particularly helpful in the era of individualized ventilatory management.

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.

Neurally adjusted ventilatory assist versus pressure support ventilation in patient-ventilator interaction and clinical outcomes: a meta-analysis of clinical trials

Background

The objective of this study was to conduct a meta-analysis comparing neurally adjusted ventilatory assist (NAVA) with pressure support ventilation (PSV) in adult ventilated patients with patient-ventilator interaction and clinical outcomes.

Methods

The PubMed, the Web of Science, Scopus, and Medline were searched for appropriate clinical trials (CTs) comparing NAVA with PSV for the adult ventilated patients. RevMan 5.3 was performed for comparing NAVA with PSV in asynchrony index (AI), ineffective efforts, auto-triggering, double asynchrony, premature asynchrony, breathing pattern (Peak airway pressure (Paw_peek), mean airway pressure (Paw_mean), tidal volume (V_T, mL/kg), minute volume (MV), respiratory muscle unloading (peak electricity of diaphragm (EAdi_peak), P 0.1, V_T/EAdi), clinical outcomes (ICU mortality, duration of ventilation days, ICU stay time, hospital stay time).

Results

Our meta-analysis included 12 studies involving a total of 331 adult ventilated patients, AI was significantly lower in NAVA group [mean difference (MD) -12.82, 95% confidence interval (CI): -21.20 to -4.44, I²=88%], and using subgroup analysis, grouped by mechanical ventilation, the results showed that NAVA also had lower AI than PSV (Mechanical ventilation, MD -9.52, 95% CI: -17.85 to -1.20, I²=87%), (Non-invasive ventilation (NIV), MD -24.55, 95% CI: -35.40 to -13.70, I²=0%). NAVA was significantly lower than the PSV in auto-triggering (MD -0.28, 95% CI: -0.51 to -0.05, I²=10%), and premature triggering (MD -2.49, 95% CI: -3.77 to -1.21, I²=29%). There were no significant differences in double triggering, ineffective efforts, breathing pattern (Paw_mean, Paw_peak, V_T, MV), and respiratory muscle unloading (EAdi_peak, P 0.1, V_T/EAdi). For clinical outcomes, NAVA was significantly lower than the PSV (MD -2.82, 95% CI: -5.55 to -0.08, I²=0%) in the duration of ventilation, but two groups did not show significant differences in ICU mortality, ICU stay time, and hospital stay time.

Conclusions

NAVA is more beneficial in patient-ventilator interaction than PSV, and could decrease the duration of ventilation.

Feasibility of Non-invasive Neurally Adjusted Ventilator Assist After Congenital Diaphragmatic Hernia Repair

BACKGROUND

The use of neurally adjusted ventilator assist (NAVA) in congenital diaphragmatic hernia (CDH) patients has been historically deemed unwise, since the trigger for breaths is the electromyographic activity of the diaphragmatic muscle. We report on our NAVA experience in CDH patients.

METHODS

We performed an IRB-approved retrospective review of newborns from 1/1/2012-1/1/2017 at a Level I Children's Surgery Center undergoing CDH repair. Data obtained included demographics, defect type and repair, respiratory support, and outcomes.

RESULTS

Seven infants with CDH were placed on noninvasive-NAVA (NIV-NAVA) after extubation. All seven patients underwent open transabdominal repair, with five requiring patch repair. All survived to discharge, and one year after birth. When we compared this group to a contemporary cohort of patients who also underwent CDH repair, we found no significant differences in birth weight, postmenstrual age, or gender. However, there was a significantly higher need for inhaled nitric oxide (p = 0.002), high frequency oscillatory ventilation (p = 0.016), and extracorporeal membranous oxygenation support (p = 0.045) in the NIV-NAVA cohort.

CONCLUSION

This is the first report of NIV-NAVA being successfully utilized as an adjunct to wean infants from conventional ventilation after CDH repair, even in those who require patch repair or with more significant disease severity.

LEVELS OF EVIDENCE

III- Retrospective Comparative Study.

Neurally adjusted ventilatory assist in extremely low-birthweight infants

BACKGROUND

Neurally adjusted ventilatory assist (NAVA) is expected to improve respiratory outcomes in preterm infants, but it has not yet been evaluated. We investigated whether NAVA could improve respiratory outcomes and reduce sedation use in extremely low-birthweight infants (ELBWI).

METHODS

A retrospective cohort study was conducted based on patient charts at the Nagano Children's Hospital neonatal intensive care unit, Japan. Infants who were born at <27 weeks' gestation were included. We assessed the prevalence of bronchopulmonary dysplasia (BPD), home oxygen therapy (HOT), duration of intubation, and sedation use.

RESULTS

The NAVA group consisted of 14 ELBWI who were born at <27 weeks' gestation between September 2013 and September 2015. A total of 21 ELBWI born between September 2011 and September 2013, before NAVA implementation, served as the control group. There were no significant differences in the perinatal background characteristics between the two groups. For respiratory outcomes, no significant between-group differences were found in the prevalence of BPD and HOT or the duration of intubation. The total duration of sedation use was not significantly different between the two groups, but in the NAVA group, midazolam was discontinued in all cases after the infants were switched to NAVA.

CONCLUSIONS

NAVA was safe in preterm infants and had a similar effect to conventional mechanical ventilation with regard to respiratory outcomes and sedation use in the chronic phase; thus, NAVA could be used in the early phase, at least before BPD worsens to improve respiratory outcomes in ELBWI.

Non-invasive ventilation practices in children across Europe

OBJECTIVES

To describe the diversity in practice in non-invasive ventilation (NIV) in European pediatric intensive care units (PICUs).

WORKING HYPOTHESIS

No information about the use of NIV in Pediatrics across Europe is currently available, and there might be a wide variability regarding the approach.

STUDY DESIGN

Cross-sectional electronic survey.

METHODOLOGY

The survey was distributed to the ESPNIC mailing list and to researchers in different European centers.

RESULTS

One hundred one units from 23 countries participated. All respondent units used NIV. Almost all PICUs considered NIV as initial respiratory support (99.1%), after extubation (95.5% prophylactically, 99.1% therapeutically), and 77.5% as part of palliative care. Overall NIV use outside the PICUs was 15.5% on the ward, 20% in the emergency department, and 36.4% during transport. Regarding respiratory failure cause, NIV was delivered in pneumonia (97.3%), bronchiolitis (94.6%), bronchospasm (75.2%), acute pulmonary edema (84.1%), upper airway obstruction (76.1%), and in acute respiratory distress syndrome (91% if mild, 53.1% if moderate, and 5.3% if severe). NIV use in asthma was less frequent in Northern European units in comparison to Central and Southern European PICUs (P = 0.007). Only 47.7% of the participants had a written protocol about NIV use. Bilevel NIV was applied mostly through an oronasal mask (44.4%), and continuous positive airway pressure through nasal cannulae (39.8%). If bilevel NIV was required, 62.3% reported choosing pressure support (vs assisted pressure-controlled ventilation) in infants; and 74.5% in older children.

CONCLUSIONS

The present study shows that NIV is a widespread technique in European PICUs. Practice across Europe is variable.

Early Noninvasive Neurally Adjusted Ventilatory Assist Versus Noninvasive Flow-Triggered Pressure Support Ventilation in Pediatric Acute Respiratory Failure: A Physiologic Randomized Controlled Trial

OBJECTIVE

Neurally adjusted ventilatory assist has been shown to improve patient-ventilator interaction in children with acute respiratory failure. Objective of this study was to compare the effect of noninvasive neurally adjusted ventilatory assist versus noninvasive flow-triggered pressure support on patient-ventilator interaction in children with acute respiratory failure, when delivered as a first-line respiratory support.

DESIGN

Prospective randomized crossover physiologic study.

SETTING

Pediatric six-bed third-level PICU.

PATIENTS

Eighteen children with acute respiratory failure needing noninvasive ventilation were enrolled at PICU admission.

INTERVENTIONS

Enrolled children were allocated to receive two 60-minutes noninvasive flow-triggered pressure support and noninvasive neurally adjusted ventilatory assist trials in a crossover randomized sequence.

MEASUREMENTS AND MAIN RESULTS

Primary endpoint was the asynchrony index. Parameters describing patient-ventilator interaction and gas exchange were also considered as secondary endpoints. Noninvasive neurally adjusted ventilatory assist compared to noninvasive flow-triggered pressure support: 1) reduced asynchrony index (p = 0.001) and the number of asynchronies per minute for each type of asynchrony; 2) it increased the neuroventilatory efficiency index (p = 0.001), suggesting better neuroventilatory coupling; 3) reduced inspiratory and expiratory delay times (p = 0.001) as well as lower peak and mean airway pressure (p = 0.006 and p = 0.038, respectively); 4) lowered oxygenation index (p = 0.043). No adverse event was reported.

CONCLUSIONS

In children with mild early acute respiratory failure, noninvasive neurally adjusted ventilatory assist was feasible and safe. Noninvasive neurally adjusted ventilatory assist compared to noninvasive flow-triggered pressure support improved patient-ventilator interaction.