Neurally triggered breaths reduce trigger delay and improve ventilator response times in ventilated infants with bronchiolitis

Total face mask with neurally adjusted ventilatory assist as a rescue therapy in infants with severe bronchiolitis

Severe bronchiolitis patients are often supported with non-invasive ventilation (NIV). In case of NIV failure, we recently started to use non-invasive neurally adjusted ventilatory assist ventilation (NIV-NAVA) with a total face mask interface (TFM) and report now our experience with this modality of respiratory support. Retrospective study was made from October 2022 to May 2023 at the Geneva University Hospital Paediatric Intensive Care Unit. Inclusion criteria were children, aged from 0 to 6 months, with severe bronchiolitis with initial NIV failure and switch to NIV-NAVA-TFM. From 49 children with respiratory syncytial virus (RSV)-induced bronchiolitis requiring any form of respiratory support, 10 (median age 61 days (IQR 44-73) failing CPAP or NIV underwent rescue treatment with NIV-NAVA using a TFM. Patients were switched to TFM-NIV-NAVA 8 h (IQR 3-22) after admission for 24.5 h (IQR 13-60). After initiation of TFM-NIV-NAVA, oxygenation improved significantly as early as 1 h after initiation, whereas transcutaneous CO2 values remained stable. None of the patients needed to be intubated and there was no episode of TFM discontinuation due to interface discomfort or other unwanted side effects. Sedation was used in all patients with high proportion of intravenous dexmedetomidine. Median ventilatory assistance duration was 2.5 days (IQR 2-4) and median PICU stay was 4.5 (IQR 3-6).   Conclusion: In infants with severe RSV-induced bronchiolitis, respiratory support with TFM-NIV-NAVA seems to be feasible as a rescue therapy and might be considered in selected patients. What is Known: • Bronchiolitic patients with NIV support failure may require invasive mechanical ventilation. • Interface related complications, especially facial sores, can be a cause of NIV failure. What is New: • Total face mask with non-invasive neurally adjusted ventilatory assist (TFM-NIV-NAVA) seems feasible as a rescue therapy in deteriorating patients with CPAP or NIV failure. • TFM-NIV-NAVA can improve oxygenation rapidly in patients with aggravating hypoxemia and seems to be well tolerated.

Comparison of neurally adjusted ventilatory assist and synchronized intermittent mandatory ventilation in preterm infants after patent ductus arteriosus ligation: a retrospective study

OBJECTIVE

This study aimed to compare the efficacy of neurally adjusted ventilatory assist (NAVA) to synchronized intermittent mandatory ventilation (SIMV) in preterm infants requiring mechanical ventilation after patent ductus arteriosus (PDA) ligation.

METHODS

A retrospective analysis was conducted on intubated preterm infants who underwent PDA ligation at our hospital from July 2021 to January 2023. Infants were divided into NAVA or SIMV groups based on the ventilation mode after surgery.

RESULTS

Fifty preterm infants were included. During treatment, peak inspiratory pressure (PIP) and mean airway pressure (MAP) were lower with NAVA compared to SIMV (PIP: 19.1 ± 2.9 vs. 22.4 ± 3.6 cmH2O, P < 0.001; MAP: 9.1 ± 1.8 vs. 10.9 ± 2.7 cmH2O, P = 0.002). PaO2 and PaO2/FiO2 were higher with NAVA (PaO2: 94.0 ± 11.7 vs. 84.8 ± 15.8 mmHg, P = 0.031; PaO2/FiO2: 267 [220-322] vs. 232 [186-290] mmHg, P = 0.025). Less sedation was required with NAVA (midazolam: 1.5 ± 0.5 vs. 1.1 ± 0.3 μg/kg/min, P < 0.001).

CONCLUSION

Compared to SIMV, early use of NAVA post PDA ligation in preterm infants was associated with decreased PIP and MAP. Early NAVA was also associated with reduced sedation needs and improved oxygenation. However, further studies are warranted to quantify the benefits of NAVA ventilation.

Trends in the Incidence of Bronchopulmonary Dysplasia after the Introduction of Neurally Adjusted Ventilatory Assist (NAVA)

OBJECTIVE

This study investigates the difference in the rates of bronchopulmonary dysplasia in very low birth weight infants before and after the introduction of neurally adjusted ventilatory assist (NAVA).

STUDY DESIGN

A retrospective cohort study comparing rates of Bronchopulmonary dysplasia (BPD) before and after implementation of NAVA. Eligibility criteria included all very low birth weight VLBW neonates needing ventilation. For analysis, each cohort was divided into three subgroups based on gestational age. Changes in the rate of BPD, length of stay, tracheostomy rates, invasive ventilator days, and home oxygen therapy were compared.

RESULTS

There were no differences in the incidence of BPD in neonates at 23-25 6/7 weeks' and 29-32 weeks' gestation between the two cohorts. A higher incidence of BPD was seen in the 26-28 5/7 weeks' gestation NAVA subgroup compared to controls (86% vs. 68%, p = 0.05). No significant difference was found for ventilator days, but infants in the 26-28 6/7 subgroup in the NAVA cohort had a longer length of stay (98 ± 34 days vs. 82 ± 24 days, p = 0.02), a higher percentage discharged on home oxygen therapy (45% vs. 18%, respectively, p = 0.006), and higher tracheostomy rates (3/36 vs. 0/60, p = 0.02), compared to the control group.

CONCLUSIONS

The NAVA mode was not associated with a reduction in BPD when compared to other modes of ventilation. Unexpected increases were seen in BPD rates, home oxygen therapy rates, tracheostomy rates, and the length of stay in the NAVA subgroup born at 26-28 6/7 weeks' gestation.

Synchronized Invasive Mechanical Ventilation

Respiratory care of premature neonates has witnessed substantial advances in the last two decades and has played a crucial role in decreasing early mortality in this population. This review outlines advances in techniques of synchronization and modes of synchronized invasive mechanical ventilation in neonates. The use of synchronized ventilation in the neonatal population was delayed as compared to adults, mainly because of technical reasons. Coordinating the infant's respiratory effort and the onset of mechanical ventilation in the neonatal population has requested high sensitivity instruments.

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.

A narrative review of advanced ventilator modes in the pediatric intensive care unit

Respiratory failure is a common reason for pediatric intensive care unit admission. The vast majority of children requiring mechanical ventilation can be supported with conventional mechanical ventilation (CMV) but certain cases with refractory hypoxemia or hypercapnia may require more advanced modes of ventilation. This paper discusses what we have learned about the use of advanced ventilator modes [e.g., high-frequency oscillatory ventilation (HFOV), high-frequency percussive ventilation (HFPV), high-frequency jet ventilation (HFJV) airway pressure release ventilation (APRV), and neurally adjusted ventilatory assist (NAVA)] from clinical, animal, and bench studies. The evidence supporting advanced ventilator modes is weak and consists of largely of single center case series, although a few RCTs have been performed. Animal and bench models illustrate the complexities of different modes and the challenges of applying these clinically. Some modes are proprietary to certain ventilators, are expensive, or may only be available at well-resourced centers. Future efforts should include large, multicenter observational, interventional, or adaptive design trials of different rescue modes (e.g., PROSpect trial), evaluate their use during ECMO, and should incorporate assessments through volumetric capnography, electric impedance tomography, and transpulmonary pressure measurements, along with precise reporting of ventilator parameters and physiologic variables.

Neurally Adjusted Ventilator Assist in Infants With Acute Respiratory Failure: A Literature Scoping Review

OBJECTIVES

To map the evidence for neurally adjusted ventilatory assist strategies, outcome measures, and sedation practices in infants less than 12 months with acute respiratory failure using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews guidance.

DATA SOURCES

CINAHL, MEDLINE, COCHRANE, JBI, EMBASE, PsycINFO, Google scholar, BNI, AMED. Trial registers included the following: ClinicalTrials.gov, European Union clinical trials register, International Standardized Randomized Controlled Trial Number register. Also included were Ethos, Grey literature, Google, dissertation abstracts, EMBASE conference proceedings.

STUDY SELECTION

Abstracts were screened followed by review of full text. Articles incorporating a heterogeneous population of both infants and older children were assessed, and where possible, data for infants were extracted. Fifteen articles were included. Ten articles were primary research: randomized controlled trial (n = 3), cohort studies (n = 4), retrospective data analysis (n = 2), case series (n = 1). Other articles are expert opinion (n = 2), neurally adjusted ventilatory assist updates (n = 1), and a literature review (n = 2). Three studies included exclusively infants. We also included 12 studies reporting jointly on infants and children.

DATA EXTRACTION

A standardized data extraction tool was used.

DATA SYNTHESIS

Key findings were that evidence related to neurally adjusted ventilatory assist ventilation strategies in infants and related to specific primary conditions is limited. The setting of neurally adjusted ventilatory assist level is not consistent, and how to optimize this mode of ventilation was not documented. Outcome measures varied considerably, most studies focused on improvements in respiratory and physiological variables. Sedation use is variable with regard to medication type and dose. There is an indication that less sedation is required in patients receiving neurally adjusted ventilatory assist, but no conclusive evidence to support this.

CONCLUSIONS

This review highlights a lack of standardized strategies for neurally adjusted ventilatory assist ventilation and sedation practices among infants with acute respiratory failure. Studies were limited by small sample sizes and a lack of focus on specific patient groups. Robust studies are needed to provide evidence-based clinical recommendations for the use of neurally adjusted ventilatory assist in infants with acute respiratory failure.

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.

Efficacy and safety of exogenous surfactant therapy in patients under 12 months of age invasively ventilated for severe bronchiolitis (SURFABRON): protocol for a multicentre, randomised, double-blind, controlled, non-profit trial

INTRODUCTION

Some evidence indicates that exogenous surfactant therapy may be effective in infants with acute viral bronchiolitis, even though more confirmatory data are needed. To date, no large multicentre trials have evaluated the effectiveness and safety of exogenous surfactant in severe cases of bronchiolitis requiring invasive mechanical ventilation (IMV).

METHODS AND ANALYSIS

This is a multicentre randomised, placebo-controlled, double-blind study, performed in 19 Italian paediatric intensive care units (PICUs). Eligible participants are infants under the age of 12 months hospitalised in a PICU, suffering from severe acute hypoxaemic bronchiolitis, requiring IMV. We adopted a more restrictive definition of bronchiolitis, including only infants below 12 months of age, to maintain the population as much homogeneous as possible. The primary outcome is to evaluate whether exogenous surfactant therapy (Curosurf, Chiesi Pharmaceuticals, Italy) is effective compared with placebo (air) in reducing the duration of IMV in the first 14 days of hospitalisation, in infants suffering from acute hypoxaemic viral bronchiolitis. Secondary outcomes are duration of non-invasive mechanical ventilation in the post-extubation phase, number of cases requiring new intubation after previous extubation within 14 days from randomisation, PICU and hospital length of stay (LOS), duration of oxygen dependency, effects on oxygenation and ventilatory parameters during invasive mechanical respiratory support, need for repeating treatment within 24 hours of first treatment, use of other interventions (eg, high-frequency oscillatory ventilation, nitric oxide, extracorporeal membrane oxygenation), mortality within the first 14 days of PICU stay and before hospital discharge, side effects and serious adverse events.

ETHICS AND DISSEMINATION

The trial design and protocol have received approval by the Italian National Agency for Drugs (AIFA) and by the Regional Ethical Committee of Verona University Hospital (1494CESC). Findings will be disseminated through publication in peer-reviewed journals, conference/meeting presentations and media.

TRIAL REGISTRATION NUMBER

Clinicaltrials.gov, issue date 22 May 2019. NCT03959384.

Respiratory support for infants with bronchiolitis, a narrative review of the literature

Bronchiolitis is a common viral disease that significantly affects infants less than 12 months of age. The purpose of this review is to present a review of the current knowledge of the uses of respiratory support in the management of infants with bronchiolitis presenting to hospital. We electronically searched MEDLINE, Cochrane, CINAHL and EMBASE (inception to 25th March 2018), to manually search for clinical trials that address the management strategies for respiratory support of infants with bronchiolitis. We identified 120 papers who met the inclusion criteria, of which 33 papers were relevant for this review with only nine randomized controlled trials. This review demonstrated that non-invasive respiratory support reduced the need for escalation of therapy, particularly the proportion of intubations required for infants with bronchiolitis. Additionally, clear economic benefits have been demonstrated when non-invasive ventilation has been used. The potential early use of non-invasive respiratory supports such as nasal high flow therapy and non-invasive ventilation may have an impact on health care costs and reduction in ICU admissions and intubation rates. High-grade evidence demonstrates safety and quality of high flow therapy in general ward settings.

Utilization of Neurally Adjusted Ventilatory Assist (NAVA) Mode in Infants and Children Undergoing Congenital Heart Surgery: A Retrospective Review

We assessed the feasibility and the impact of NAVA compared to conventional modes of mechanical ventilation in ventilatory and gas exchange parameters in post-operative children with congenital heart disease. Infants and children (age < 18 years) that underwent congenital heart surgery were enrolled. Patients were ventilated with conventional synchronized intermittent mechanical ventilation (SIMV) and subsequently transitioned to NAVA during their cardiovascular intensive care unit (CVICU) stay. The ventilatory and gas exchange parameters for the 24 h pre- and post-transition to NAVA were compared. Additional parameters assessed included pain scores and sedation requirements. Eighty-one patients met inclusion criteria with a median age of 21 days (interquartile range 13 days-2 months). The majority of patients enrolled (75.3%) had complex congenital heart disease with high surgical severity scores. The transition to NAVA was tolerated by all patients without complications. The mean peak inspiratory pressure (PIP) was 1.8 cm H₂O lower (p < 0.001) and mean airway pressure (P_aw) was 0.5 cm H₂O lower (p = 0.009) on NAVA compared to conventional modes of mechanical ventilation. There was no significant difference in patients' respiratory rate, tidal volume, arterial pH, pCO₂, and lactate levels between the two modes of ventilation. There was a decreased sedation requirement during the time of NAVA ventilation. Comfort scores did not differ significantly with ventilator mode change. We concluded that NAVA is safe and well-tolerated mode of mechanical ventilation for our cohort of patients after congenital heart surgery. Compared to conventional ventilation there was a statistically significant decrease in PIP and P_aw on NAVA.

Neurally Adjusted Ventilatory Assist Is Associated with Greater Initial Extubation Success in Postoperative Congenital Heart Disease Patients when Compared to Conventional Mechanical Ventilation

Extubation failure is associated with considerable morbidity and mortality in postoperative patients with congenital heart disease (CHD). The study purpose was to investigate initial extubation success utilizing neurally adjusted ventilatory assist (NAVA) compared with pressure-regulated volume controlled, synchronized intermittent mandatory ventilation with pressure support (SIMV-PRVC + PS) for ventilatory weaning in patients who required prolonged mechanical ventilation (MV). Also, total days on MV, inotropes, sedation, analgesia, and pediatric intensive care unit (PICU) length of stay (LOS) between both groups were compared. This was a non-randomized pilot study utilizing historical controls (SIMV-PRVC + PS; n  = 40) compared with a prospective study population (NAVA; n  = 35) in a Level I PICU and was implemented to help future trial designs. All patients ( n  = 75) required prolonged MV ≥96 hours due to their complex postoperative course. Ventilator weaning initiation and management was standardized between both groups. Ninety-seven percent of the NAVA group was successfully extubated on the initial attempt, while 80% were in the SIMV-PRVC + PS group ( p  = 0.0317). Patients placed on NAVA were eight times more likely to have successful initial extubation (odds ratio [OR]: 8.50, 95% confidence interval [CI]: 1.01, 71.82). The NAVA group demonstrated a shorter median duration on MV (9.0 vs. 11.0 days, p  = 0.032), PICU LOS (9.0 vs. 13.5 days, p  < 0.0001), and shorter median duration of days on dopamine (8.0 vs. 11.0 days, p  = 0.0022), milrinone (9.0 vs. 12.0 days, p  = 0.0002), midazolam (8.0 vs. 12.0 days, p  < 0.0001), and fentanyl (9.0 vs. 12.5 days, p  < 0.0001) compared with the SIMV-PRVC + PS group. NAVA compared with SIMV-PRVC + PS was associated with a greater initial extubation success rate. NAVA should be considered as a mechanical ventilator weaning strategy in postoperative congenital heart disease (CHD) patients and warrants further investigation.

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

BACKGROUND

Effective synchronisation of infant respiratory effort with mechanical ventilation may allow adequate gas exchange to occur at lower peak airway pressures, potentially reducing barotrauma and volutrauma and development of air leaks and bronchopulmonary dysplasia. During neurally adjusted ventilatory assist ventilation (NAVA), respiratory support is initiated upon detection of an electrical signal from the diaphragm muscle, and pressure is provided in proportion to and synchronous with electrical activity of the diaphragm (EADi). Compared to other modes of triggered ventilation, this may provide advantages in improving synchrony.

OBJECTIVES

Primary• To determine whether NAVA, when used as a primary or rescue mode of ventilation, results in reduced rates of bronchopulmonary dysplasia (BPD) or death among term and preterm newborn infants compared to other forms of triggered ventilation• To assess the safety of NAVA by determining whether it leads to greater risk of intraventricular haemorrhage (IVH), periventricular leukomalacia, or air leaks when compared to other forms of triggered ventilation Secondary• To determine whether benefits of NAVA differ by gestational age (term or preterm)• To determine whether outcomes of cross-over trials performed during the first two weeks of life include peak pressure requirements, episodes of hypocarbia or hypercarbia, oxygenation index, and the work of breathing SEARCH METHODS: We performed searches of the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cohrane Library; MEDLINE via Ovid SP (January 1966 to March 2017); Embase via Ovid SP (January 1980 to March 2017); the Cumulative Index to Nursing and Allied Health Literature (CINAHL) via EBSCO host (1982 to March 2017); and the Web of Science (1985 to 2017). We searched abstracts from annual meetings of the Pediatric Academic Societies (PAS) (2000 to 2016); meetings of the European Society of Pediatric Research (published in Pediatric Research); and meetings of the Perinatal Society of Australia and New Zealand (PSANZ) (2005 to 2016). We also searched clinical trials databases to March 2017.

SELECTION CRITERIA

We included randomised and quasi-randomised clinical trials including cross-over trials comparing NAVA with other modes of triggered ventilation (assist control ventilation (ACV),synchronous intermittent mandatory ventilation plus pressure support (SIMV ± PS), pressure support ventilation (PSV), or proportional assist ventilation (PAV)) used in neonates.

DATA COLLECTION AND ANALYSIS

Primary outcomes of interest from randomised controlled trials were all-cause mortality, bronchopulmonary dysplasia (BPD; defined as oxygen requirement at 28 days), and a combined outcome of all-cause mortality or BPD. Secondary outcomes were duration of mechanical ventilation, incidence of air leak, incidence of IVH or periventricular leukomalacia, and survival with an oxygen requirement at 36 weeks' postmenstrual age.Outcomes of interest from cross-over trials were maximum fraction of inspired oxygen, mean peak inspiratory pressure, episodes of hypocarbia, and episodes of hypercarbia measured across the time period of each arm of the cross-over. We planned to assess work of breathing; oxygenation index, and thoraco-abdominal asynchrony at the end of the time period of each arm of the cross-over study.

MAIN RESULTS

We included one randomised controlled study comparing NAVA versus patient-triggered time-cycled pressure-limited ventilation. This study found no significant difference in duration of mechanical ventilation, nor in rates of BPD, pneumothorax, or IVH.

AUTHORS' CONCLUSIONS

Risks and benefits of NAVA compared to other forms of ventilation for neonates are uncertain. Well-designed trials are required to evaluate this new form of triggered ventilation.

Recent Advances in Pediatric Ventilatory Assistance

In this review on respiratory assistance, we aim to discuss the following recent advances: the optimization and customization of mechanical ventilation, the use of high-frequency oscillatory ventilation, and the role of noninvasive ventilation. The prevention of ventilator-induced lung injury and diaphragmatic dysfunction is now a key aspect in the management of mechanical ventilation, since these complications may lead to higher mortality and prolonged length of stay in intensive care units. Different physiological measurements, such as esophageal pressure, electrical activity of the diaphragm, and volumetric capnography, may be useful objective tools to help guide ventilator assistance. Companies that design medical devices including ventilators and respiratory monitoring platforms play a key role in knowledge application. The creation of a ventilation consortium that includes companies, clinicians, researchers, and stakeholders could be a solution to promote much-needed device development and knowledge implementation.

Neurally Adjusted Ventilatory Assist for Noninvasive Support in Neonates

Noninvasive ventilation (NIV) is frequently used in the NICU to avoid intubation or as postextubation support for spontaneously breathing infants experiencing respiratory distress. Neurally adjusted ventilatory assist (NAVA) is used as a mode of noninvasive support in which both the timing and degree of ventilatory assist are controlled by the patient. NIV-NAVA has been successfully used clinically in neonates as a mode of ventilation to prevent intubation, allow early extubation, and as a novel way to deliver nasal continuous positive airway pressure.

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.

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.

Non-invasive ventilation with neurally adjusted ventilatory assist in newborns

Neurally adjusted ventilatory assist (NAVA) is a mode of ventilation in which both the timing and degree of ventilatory assist are controlled by the patient. Since NAVA uses the diaphragm electrical activity (Edi) as the controller signal, it is possible to deliver synchronized non-invasive NAVA (NIV-NAVA) regardless of leaks and to monitor continuously patient respiratory pattern and drive. Advantages of NIV-NAVA over conventional modes include improved patient-ventilator interaction, reliable respiratory monitoring and self-regulation of respiratory support. In theory, these characteristics make NIV-NAVA an ideal mode to provide effective, appropriate non-invasive support to newborns with respiratory insufficiency. NIV-NAVA has been successfully used clinically in neonates as a mode of ventilation to prevent intubation, to allow early extubation, and as a novel way to deliver nasal continuous positive airway pressure. The use of NAVA in neonates is described with an emphasis on studies and clinical experience with NIV-NAVA.

Health economic modeling of the potential cost saving effects of Neurally Adjusted Ventilator Assist

OBJECTIVES

Asynchrony between patient and ventilator breaths is associated with increased duration of mechanical ventilation (MV). Neurally Adjusted Ventilatory Assist (NAVA) controls MV through an esophageal reading of diaphragm electrical activity via a nasogastric tube mounted with electrode rings. NAVA has been shown to decrease asynchrony in comparison to pressure support ventilation (PSV). The objective of this study was to conduct a health economic evaluation of NAVA compared with PSV.

METHODS

We developed a model based on an indirect link between improved synchrony with NAVA versus PSV and fewer days spent on MV in synchronous patients. Unit costs for MV were obtained from the Swedish intensive care unit register, and used in the model along with NAVA-specific costs. The importance of each parameter (proportion of asynchronous patients, costs, and average MV duration) for the overall results was evaluated through sensitivity analyses.

RESULTS

Base case results showed that 21% of patients ventilated with NAVA were asynchronous versus 52% of patients receiving PSV. This equals an absolute difference of 31% and an average of 1.7 days less on MV and a total cost saving of US$7886 (including NAVA catheter costs). A breakeven analysis suggested that NAVA was cost effective compared with PSV given an absolute difference in the proportion of asynchronous patients greater than 2.5% (49.5% versus 52% asynchronous patients with NAVA and PSV, respectively). The base case results were stable to changes in parameters, such as difference in asynchrony, duration of ventilation and daily intensive care unit costs.

CONCLUSION

This study showed economically favorable results for NAVA versus PSV. Our results show that only a minor decrease in the proportion of asynchronous patients with NAVA is needed for investments to pay off and generate savings. Future studies need to confirm this result by directly relating improved synchrony to the number of days on MV.

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

BACKGROUND

To determine the prevalence of main inspiratory asynchrony events during non-invasive intermittent positive-pressure ventilation (NIV) for severe bronchiolitis. Ventilator response time and asynchrony were compared in neurally adjusted ventilator assist (NAVA) and in pressure assist/control (PAC) modes.

METHODS

This prospective physiological study was performed in a university hospital's paediatric intensive care unit and included 11 children (aged 35.2 ± 23 days) with respiratory syncytial virus bronchiolitis with failure of nCPAP. Patients received NIV for 2 hr in PAC mode followed by 2 hr in NAVA mode. Electrical activity of the diaphragm and pressure curves were recorded for 10 min. Trigger delay, main asynchronies (auto-triggering, double triggering, or non-triggered breaths) were analyzed, and the asynchrony index was calculated for each period.

RESULTS

The asynchrony index was lower during NAVA than during PAC (3 ± 3% vs. 38 ± 21%, P < 0.0001), and the trigger delay was shorter (43.9 ± 7.2 vs. 116.0 ± 38.9 ms, P < 0.0001). Ineffective efforts were significantly less frequent in NAVA mode (0.54 ± 1.5 vs. 21.8 ± 16.5 events/min, P = 0.01). Patient respiratory rates were similar, but the ventilator rate was higher in NAVA than in PAC mode (59.5 ± 17.9 vs. 49.8 ± 8.5/min, P = 0.03). The TcPCO2 baselines values (64 ± 12 mmHg vs. 62 ± 9 mmHg during NAVA, P = 0.30) were the same and their evolution over the 2 hr study period (-6 ± 10 mmHg vs. -12 ± 17 mmHg during NAVA, P = 0.36) did not differ.

CONCLUSION

Patient-ventilator inspiratory asynchronies and trigger delay were dramatically lower in NAVA mode than in PAC mode during NIV in infants with severe bronchiolitis.

Neurally adjusted ventilatory assist (NAVA) allows patient-ventilator synchrony during pediatric noninvasive ventilation: a crossover physiological study

Introduction

The need for intubation after a noninvasive ventilation (NIV) failure is frequent in the pediatric intensive care unit (PICU). One reason is patient-ventilator asynchrony during NIV. Neurally adjusted ventilatory assist (NAVA) is a mode of ventilation controlled by the patient’s neural respiratory drive. The aim of this study was to assess the feasibility and tolerance of NIV-NAVA in children and to evaluate its impact on synchrony and respiratory effort.

Methods

This prospective, physiologic, crossover study included 13 patients requiring NIV in the PICU of Sainte-Justine’s Hospital from October 2011 to May 2013. Patients were successively ventilated in conventional NIV as prescribed by the physician in charge (30 minutes), in NIV-NAVA (60 minutes), and again in conventional NIV (30 minutes). Electrical activity of the diaphragm (EAdi) and airway pressure were simultaneously recorded to assess patient-ventilator synchrony.

Results

NIV-NAVA was feasible and well tolerated in all patients. One patient asked to stop the study because of anxiety related to the leak-free facial mask. Inspiratory trigger dys-synchrony and cycling-off dys-synchrony were significantly shorter in NIV-NAVA versus initial and final conventional NIV periods (both P <0.05). Wasted efforts were also decreased in NIV-NAVA (all values expressed as median and interquartile values) (0 (0 to 0) versus 12% (4 to 20) and 6% (2 to 22), respectively; P <0.01). As a whole, total time spent in asynchrony was reduced to 8% (6 to 10) in NIV-NAVA, versus 27% (19 to 56) and 32% (21 to 38) in conventional NIV before and after NIV-NAVA, respectively (P =0.05).

Conclusion

NIV-NAVA is feasible and well tolerated in PICU patients and allows improved patient-ventilator synchronization. Larger controlled studies are warranted to evaluate the clinical impact of these findings.

Trial registration

ClinicalTrials.gov NCT02163382. Registered 9 June 2014.

Evolution of inspiratory diaphragm activity in children over the course of the PICU stay

PURPOSE

Diaphragm function should be monitored in critically ill patients, as full ventilatory support rapidly induces diaphragm atrophy. Monitoring the electrical activity of the diaphragm (EAdi) may help assess the level of diaphragm activity, but such monitoring results are difficult to interpret because reference values are lacking. The aim of this study was to describe EAdi values in critically ill children during a stay in the pediatric intensive care unit (PICU), from the acute to recovery phases, and to assess the impact of ventilatory support on EAdi.

METHODS

This was a prospective longitudinal observational study of children requiring mechanical ventilation for ≥24 h. EAdi was recorded using a validated method in the acute phase, before extubation, after extubation, and before PICU discharge.

RESULTS

Fifty-five critically ill children were enrolled in the study. Median maximum inspiratory EAdi (EAdimax) during mechanical ventilation was 3.6 [interquartile range (IQR) 1.2-7.6] μV in the acute phase and 4.8 (IQR 2.0-10.7) μV in the pre-extubation phase. Periods of diaphragm inactivity (with no detectable inspiratory EAdi) were frequent during conventional ventilation, even with a low level of support. EAdimax in spontaneous ventilation was 15.4 (IQR 7.4-20.7) μV shortly after extubation and 12.6 (IQR 8.1-21.3) μV before PICU discharge. The difference in EAdimax between mechanical ventilation and post-extubation periods was significant (p < 0.001). Patients intubated mainly because of a lung pathology exhibited higher EAdi (p < 0.01), with a similar temporal increase.

CONCLUSIONS

This is the first systematic description of EAdi evolution in children during their stay in the PICU. In our patient cohort, diaphragm activity was frequently low in conventional ventilation, suggesting that overassistance or oversedation is common in clinical practice. EAdi monitoring appears to be a helpful tool to detect such situations.

Validation of the accuracy of a transport ventilator utilizing a pediatric animal model

OBJECTIVE

The objective of this study was to evaluate 2 transport ventilators utilizing both a test lung and a pediatric animal model.

METHODS

Two transport ventilators were utilized for evaluations. A test lung or intubated, sedated pigs (n = 9) with healthy and injured lungs were ventilated using control and support modes. A test lung was used to evaluate alarm responsiveness, FIO2 accuracy, oxygen consumption, and duration of battery power. Pigs were utilized to evaluate the exhalation valve, ventilator response, volume accuracy, and noninvasive functionality. Respiratory mechanics were determined using a forced oscillation technique, and airway flow and pressure waveforms were acquired utilizing a pneumotachograph.

RESULTS

For both ventilators, FIO2 accuracy was within 10% error. On an E cylinder of oxygen, the EMV+ operated for 3 hours 48 minutes and the LTV 1200 for 1 hour 4 minutes. On battery power, the LTV 1200 ventilated for 6 hours 51 minutes and the EMV+ for 12 hours 8 minutes. Ventilator response time was less (36%), and delta pressure was greater (38%) for the EMV+ utilizing noninvasive ventilation. The percent error for displayed volume was less than 10% for the EMV+.

CONCLUSIONS

In this study, we demonstrate that there are differences between the 2 ventilators in regard to oxygen consumption, duration of battery power, and volume accuracy. Clinicians should be aware of these differences to optimize the choice and use of both ventilators depending on clinical need/setting.

Application of neurally adjusted ventilatory assist in neonates

Neurally adjusted ventilatory assist (NAVA) uses the electrical activity of the diaphragm (Edi) as a neural trigger to synchronize mechanical ventilatory breaths with the patient's neural respiratory drive. Using this signal enables the ventilator to proportionally support the patient's instantaneous drive on a breath-by-breath basis. Synchrony can be achieved even in the presence of significant air leaks, which make this an attractive choice for invasive and non-invasive ventilation of the neonate. This paper describes the Edi signal, neuroventilatory coupling, and patient-ventilator synchrony including the functional concept of NAVA. Safety features, NAVA terminology, and clinical application of NAVA to unload respiratory musculature are presented. The use of the Edi signal as a respiratory vital sign for conventional ventilation is discussed. The results of animal and adult studies are briefly summarized and detailed descriptions of all NAVA-related research in pediatric and neonatal patients are provided. Further studies are needed to determine whether NAVA will have significant impact on the overall outcomes of neonates.

Optimizing patient-ventilator synchrony during invasive ventilator assist in children and infants remains a difficult task*

OBJECTIVES

To document and compare the prevalence of asynchrony events during invasive-assisted mechanical ventilation in pressure support mode and in neurally adjusted ventilatory assist in children.

DESIGN

Prospective, randomized, and crossover study.

SETTING

Pediatric and Neonatal Intensive Care Unit, University Hospital of Geneva, Switzerland.

PATIENTS

Intubated and mechanically ventilated children, between 4 weeks and 5 years old.

INTERVENTIONS

Two consecutive ventilation periods (pressure support and neurally adjusted ventilatory assist) were applied in random order. During pressure support, three levels of expiratory trigger setting were compared: expiratory trigger setting as set by the clinician in charge (PSinit), followed by a 10% (in absolute values) increase and decrease of the clinician's expiratory trigger setting. The pressure support session with the least number of asynchrony events was defined as PSbest. Therefore, three periods were compared: PSinit, PSbest, and neurally adjusted ventilatory assist. Asynchrony events, trigger delay, and inspiratory time in excess were quantified for each of them.

MEASUREMENTS AND MAIN RESULTS

Data from 19 children were analyzed. Main asynchrony events during PSinit were autotriggering (3.6 events/min [0.7-8.2]), ineffective efforts (1.2/min [0.6-5]), and premature cycling (3.5/min [1.3-4.9]). Their number was significantly reduced with PSbest: autotriggering 1.6/min (0.2-4.9), ineffective efforts 0.7/min (0-2.6), and premature cycling 2/min (0.1-3.1), p < 0.005 for each comparison. The median asynchrony index (total number of asynchronies/triggered and not triggered breaths ×100) was significantly different between PSinit and PSbest: 37.3% [19-47%] and 29% [24-43%], respectively, p < 0.005). With neurally adjusted ventilatory assist, all types of asynchrony events except double-triggering and inspiratory time in excess were significantly reduced resulting in an asynchrony index of 3.8% (2.4-15%) (p < 0.005 compared to PSbest).

CONCLUSIONS

Asynchrony events are frequent during pressure support in children despite adjusting the cycling off criteria. Neurally adjusted ventilatory assist allowed for an almost ten-fold reduction in asynchrony events. Further studies should determine the clinical impact of these findings.

Ventilation distribution measured with EIT at varying levels of pressure support and Neurally Adjusted Ventilatory Assist in patients with ALI

PURPOSE

The purpose of this study was to compare the effect of varying levels of assist during pressure support (PSV) and Neurally Adjusted Ventilatory Assist (NAVA) on the aeration of the dependent and non-dependent lung regions by means of Electrical Impedance Tomography (EIT).

METHODS

We studied ten mechanically ventilated patients with Acute Lung Injury (ALI). Positive-End Expiratory Pressure (PEEP) and PSV levels were both 10 cm H₂O during the initial PSV step. Thereafter, we changed the inspiratory pressure to 15 and 5 cm H₂O during PSV. The electrical activity of the diaphragm (EAdi) during pressure support ten was used to define the initial NAVA gain (100 %). Thereafter, we changed NAVA gain to 150 and 50 %, respectively. After each step the assist level was switched back to PSV 10 cm H₂O or NAVA 100 % to get a new baseline. The EIT registration was performed continuously.

RESULTS

Tidal impedance variation significantly decreased during descending PSV levels within patients, whereas not during NAVA. The dorsal-to-ventral impedance distribution, expressed according to the center of gravity index, was lower during PSV compared to NAVA. Ventilation contribution of the dependent lung region was equally in balance with the non-dependent lung region during PSV 5 cm H₂O, NAVA 50 and 100 %.

CONCLUSION

Neurally Adjusted Ventilatory Assist ventilation had a beneficial effect on the ventilation of the dependent lung region and showed less over-assistance compared to PSV in patients with ALI.

Interest of monitoring diaphragmatic electrical activity in the pediatric intensive care unit

The monitoring of electrical activity of the diaphragm (EAdi) is a new minimally invasive bedside technology that was developed for the neurally adjusted ventilatory assist (NAVA) mode of ventilation. In addition to its role in NAVA ventilation, this technology provides the clinician with previously unavailable and essential information on diaphragm activity. In this paper, we review the clinical interests of EAdi in the pediatric intensive care setting. Firstly, the monitoring of EAdi allows the clinician to tailor the ventilatory settings on an individual basis, avoiding frequent overassistance leading potentially to diaphragmatic atrophy. Increased inspiratory EAdi levels can also suggest insufficient support, while a strong tonic activity may reflect the patient efforts to increase its lung volume. EAdi monitoring also allows detection of patient-ventilator asynchrony. It can play a role in evaluation of extubation readiness. Finally, EAdi monitoring provides the clinician with better understanding of the ventilatory capacity of patients with acute neuromuscular disease. Further studies are warranted to evaluate the clinical impact of these potential benefits.

Neurally adjusted ventilatory assist: assessing the comfort and feasibility of use in neonates and children

AIM

To evaluate the practical feasibility for nurses working with neurally adjusted ventilatory assist (NAVA) and assess patient comfort and safety when NAVA is initiated.

BACKGROUND

NAVA is a relatively new mode of ventilation. Its application in neonates and children has been widely documented. However, its practical feasibility from a nursing point of view as well as its safety and comfort in these populations compared with conventional modes of ventilation has not been described.

DESIGN

A prospective, observational crossover pilot study.

METHOD

NAVA was compared with the conventional mode of ventilation for 3 h each, and practical feasibility, patient comfort level and safety were assessed.

RESULTS

Twenty-one neonates and children were enrolled into the study. There were no reported adverse events. In most patients, the NAVA catheter was placed too shallow, as measured by the distances from the nose, ear, xiphisternum (NEX) method, according to the manufacturer's instructions. Accurate placement was confirmed by visual inspection of the NAVA positioning window. Patients' comfort did not differ between the conventional mode and NAVA.

CONCLUSIONS

NAVA is feasible, once an accurate signal of the electrical activity of the diaphragm is achieved and seems safe and well tolerated in both neonates and children. Nurses need to gain experience in placing the NAVA catheter and practical recommendations are given.

RELEVANCE TO CLINICAL PRACTICE

NAVA is a promising new mode of ventilation. This article contributes to an increasing body of evidence that NAVA is feasible in neonates and children. There are practical considerations when NAVA is applied in these patient-groups.

Randomized crossover study of neurally adjusted ventilatory assist in preterm infants

OBJECTIVE

To determine whether neurally adjusted ventilatory assist (NAVA), a new method of mechanical ventilation that delivers pressure assistance that is proportional to the electrical activity of the diaphragm (EAdi), could lower the inspiratory pressure and respiratory muscle load in preterm infants supported with ventilators.

STUDY DESIGN

Twenty-six mechanically ventilated preterm infants were randomized to crossover ventilation with NAVA and synchronized intermittent mandatory ventilation (SIMV) with pressure support (PS) for 4 hours each in a randomized order. A 1-hour interval for washout was provided between the 2 modes of ventilation. The ventilator settings were adjusted to maintain similar levels of end-tidal partial pressure of CO(2). The ventilator parameters, vital signs, and gas exchange effects under the 2 ventilatory modes were compared.

RESULTS

Nineteen infants completed the 9-hour crossover comparison protocol. Peak inspiratory pressure (PIP), work of breathing, and peak EAdi with NAVA were lower than those in SIMV with PS. Calculated tidal volume to peak EAdi ratio and PIP to peak EAdi ratio were higher with NAVA. There were no significant differences in mean airway pressure, inspiratory oxygen fraction, and blood gas values. The measurements of vital signs did not differ significantly between the 2 modes.

CONCLUSION

NAVA lowered PIP and reduced respiratory muscle load in preterm infants at equivalent inspiratory oxygen fraction and partial pressure of CO(2) of capillary blood in comparison with SIMV with PS.

Synchronized mechanical ventilation using electrical activity of the diaphragm in neonates

The electrical activity of the diaphragm (Edi) is measured by a specialized nasogastric/orogastric tube positioned in the esophagus at the level of the crural diaphragm. Neurally adjusted ventilatory assist (NAVA) uses the Edi signal as a neural trigger and intrabreath controller to synchronize mechanical ventilatory breaths with the patient's respiratory drive and to proportionally support the patient's respiratory efforts on a breath-by-breath basis. NAVA improves patient-ventilator interaction and synchrony even in the presence of large air leaks, and might therefore be an optimal option for noninvasive ventilation in neonates.

Clinical review: Update on neurally adjusted ventilatory assist--report of a round-table conference

Conventional mechanical ventilators rely on pneumatic pressure and flow sensors and controllers to detect breaths. New modes of mechanical ventilation have been developed to better match the assistance delivered by the ventilator to the patient's needs. Among these modes, neurally adjusted ventilatory assist (NAVA) delivers a pressure that is directly proportional to the integral of the electrical activity of the diaphragm recorded continuously through an esophageal probe. In clinical settings, NAVA has been chiefly compared with pressure-support ventilation, one of the most popular modes used during the weaning phase, which delivers a constant pressure from breath to breath. Comparisons with proportional-assist ventilation, which has numerous similarities, are lacking. Because of the constant level of assistance, pressure-support ventilation reduces the natural variability of the breathing pattern and can be associated with asynchrony and/or overinflation. The ability of NAVA to circumvent these limitations has been addressed in clinical studies and is discussed in this report. Although the underlying concept is fascinating, several important questions regarding the clinical applications of NAVA remain unanswered. Among these questions, determining the optimal NAVA settings according to the patient's ventilatory needs and/or acceptable level of work of breathing is a key issue. In this report, based on an investigator-initiated round table, we review the most recent literature on this topic and discuss the theoretical advantages and disadvantages of NAVA compared with other modes, as well as the risks and limitations of NAVA.

Absence of inspiratory laryngeal constrictor muscle activity during nasal neurally adjusted ventilatory assist in newborn lambs

In nonsedated newborn lambs, nasal pressure support ventilation (nPSV) can lead to an active glottal closure in early inspiration, which can limit lung ventilation and divert air into the digestive system, with potentially deleterious consequences. During volume control ventilation (nVC), glottal closure is delayed to the end of inspiration, suggesting that it is reflexly linked to the maximum value of inspiratory pressure. Accordingly, the aim of the present study was to test whether inspiratory glottal closure develops at the end of inspiration during nasal neurally adjusted ventilatory assist (nNAVA), an increasingly used ventilatory mode where maximal pressure is also reached at the end of inspiration. Polysomnographic recordings were performed in eight nonsedated, chronically instrumented lambs, which were ventilated with progressively increasing levels of nPSV and nNAVA in random order. States of alertness, diaphragm, and glottal muscle electrical activity, tracheal pressure, Spo(2), tracheal Pet(CO(2)), and respiratory inductive plethysmography were continuously recorded. Although phasic inspiratory glottal constrictor electrical activity appeared during nPSV in 5 of 8 lambs, it was never observed at any nNAVA level in any lamb, even at maximal achievable nNAVA levels. In addition, a decrease in Pco(2) was neither necessary nor sufficient for the development of inspiratory glottal constrictor activity. In conclusion, nNAVA does not induce active inspiratory glottal closure, in contrast to nPSV and nVC. We hypothesize that this absence of inspiratory activity is related to the more physiological airway pressurization during nNAVA, which tightly follows diaphragm electrical activity throughout inspiration.

Asynchrony, neural drive, ventilatory variability and COMFORT: NAVA versus pressure support in pediatric patients. A non-randomized cross-over trial

Purpose

To determine if neurally adjusted ventilatory assist (NAVA) improves asynchrony, ventilatory drive, breath-to-breath variability and COMFORT score when compared to pressure support (PS).

Methods

This is a non-randomized short-term cross-over trial in which 12 pediatric patients with asynchrony (auto-triggering, double triggering or non-triggered breaths) were enrolled. Four sequential 10-min periods of data were recorded after 20 min of ventilatory stabilization (wash-out) at each of the following settings: baseline PS with the ventilator settings determined by the attending physician (1-PS_b); PS after optimization (2-PS_opt); NAVA level set so that maximum inspiratory pressure (P_max) equaled P_max in PS (3-NAVA); same settings as in 2-PS_opt (4-PS_opt).

Results

The median asynchrony index was significantly lower during NAVA (2.0 %) than during 2-PS_opt (8.5 %, p = 0.017) and 4-PS_opt (7.5 %, p = 0.008). In NAVA mode, the NAVA trigger accounted on average for 66 % of triggered breaths. The median trigger delay with respect to neural inspiratory time was significantly lower during NAVA (8.6 %) than during 2-PS_opt (25.2 %, p = 0.003) and 4-PS_opt (28.2 %, p = 0.0005). The median electrical activity of the diaphragm (EAdi) change during trigger delay normalized to maximum inspiratory EAdi difference was significantly lower during NAVA (5.3 %) than during 2-PS_opt (21.7 %, p = 0.0005) and 4-PS_opt (24.6 %, p = 0.001). The coefficient of variation of tidal volume was significantly higher during NAVA (44.2 %) than during 2-PS_opt (19.8 %, p = 0.0002) and 4-PS_opt (23.0 %, p = 0.0005). The median COMFORT score during NAVA (15.0) was lower than that during 2-PS_opt (18.0, p = 0.0125) and 4-PS_opt (17.5, p = 0.039). No significant changes for any variable were observed between 1-PS_b and 2-PS_opt.

Conclusions

Neurally adjusted ventilatory assist as compared to optimized PS results in improved synchrony, reduced ventilatory drive, increased breath-to-breath mechanical variability and improved patient comfort.

Electronic supplementary material

The online version of this article (doi:10.1007/s00134-012-2535-y) contains supplementary material, which is available to authorized users.

Effort-adapted modes of assisted breathing

PURPOSE OF REVIEW

New developments in mechanical ventilation have focused on increasing the patient's control of the ventilator by implementing information on lung mechanics and respiratory drive. Effort-adapted modes of assisted breathing are presented and their potential advantages are discussed.

RECENT FINDINGS

Adaptive support ventilation, proportional assist ventilation with load adjustable gain factors and neurally adjusted ventilatory assist are ventilatory modes that follow the concept of adapting the assist to a defined target, instantaneous changes in respiratory drive or lung mechanics. Improved patient ventilator interaction, sufficient unloading of the respiratory muscles and increased comfort have been recently associated with these ventilator modalities. There are, however, scarce data with regard to outcome improvement, such as length of mechanical ventilation, ICU stay or mortality (commonly accepted targets to demonstrate clinical superiority).

SUMMARY

Within recent years, a major step forward in the evolution of assisted (effort-adapted) modes of mechanical ventilation was accomplished. There is growing evidence that supports the physiological concept of closed-loop effort-adapted assisted modes of mechanical ventilation. However, at present, the translation into a clear outcome benefit remains to be proven. In order to fill the knowledge gap that impedes the broader application, larger randomized controlled trials are urgently needed. However, with clearly proven drawbacks of conventional assisted modes such as pressure support ventilation, it is probably about time to leave these modes introduced decades ago behind.