Randomised trial of volume controlled versus time cycled, pressure limited ventilation in preterm infants with respiratory distress syndrome

A Retrospective Cohort Study of the Impact of Implementing Volume-Targeted Compared to Pressure-Limited Ventilation in a Single-Center, Level III Neonatal Intensive Care Unit in Oman

Background The use of volume-targeted ventilation (VTV) in neonatology has been introduced in the last decade. This study was performed to determine the impact of clinical implementation of volume-targeted conventional mechanical ventilation using the volume guarantee mode in mechanical ventilation of all neonates needing mechanical ventilation compared to pressure-limited ventilation (PLV) modes. The mortality rate, duration of mechanical ventilation, and bronchopulmonary dysplasia were the primary outcomes of the study. Methodology This retrospective cohort study was conducted at a level III-VI neonatal intensive care unit (NICU) within a tertiary academic hospital in Oman. All intubated neonates admitted to the NICU within two time periods, i.e., the PLV cohort: January 2011 to December 2013 (three years), and the VTV cohort: January 2017 to December 2019 (three years), were eligible for inclusion in the study. Neonates were excluded if they had multiple congenital anomalies, tracheostomy, and those with a Do Not Resuscitate status. A predetermined data set was collected retrospectively from electronic records. The PLV and VTV cohorts were compared, and SPSS version 25 (IBM Corp., Armonk, NY, USA) was used for data analysis. Results A total of 290 neonates were included (PLV: n = 138, and VTV: n = 152). The two cohorts were statistically similar in their baseline characteristics, including gestational age, birth weight, Apgar scores, indications for mechanical ventilation, age at intubation, need for surfactant therapy, and age at extubation. The VTV cohort had a significantly lower mortality rate (n (%) = 10 (6.6%) vs. 21 (15.3%), p = 0.02). An insignificant trend of lower duration of ventilation was observed in the VTV cohort (34.5 vs. 50.5 hours, p = 0.24). There was no significant difference in bronchopulmonary dysplasia (16 (21.3%) vs. 12 (17.8%), p = 0.18). VTV was associated with a significant reduction in pulmonary hemorrhage (1 (0.7%) vs. 8 (5.7%), p = 0.04), episodes of hypocapnia (2 vs. 3/patient, p = 0.04), and episodes of hypercapnia (0 vs 1/patient, p = 0.04). Conclusions The implementation of VTV in clinical practice in our level III-VI NICU was associated with significant advantages, including reduction in mortality, pulmonary hemorrhage, and episodes of hypercapnia and hypocapnia. A large prospective, randomized, and multicenter trial is recommended to confirm these findings.

Interventions to Reduce Severe Brain Injury Risk in Preterm Neonates: A Systematic Review and Meta-analysis

Importance

Interventions to reduce severe brain injury risk are the prime focus in neonatal clinical trials.

Objective

To evaluate multiple perinatal interventions across clinical settings for reducing the risk of severe intraventricular hemorrhage (sIVH) and cystic periventricular leukomalacia (cPVL) in preterm neonates.

Data Sources

MEDLINE, Embase, CENTRAL (Cochrane Central Register of Controlled Trials), and CINAHL (Cumulative Index to Nursing and Allied Health Literature) databases were searched from inception until September 8, 2022, using prespecified search terms and no language restrictions.

Study Selection

Randomized clinical trials (RCTs) that evaluated perinatal interventions, chosen a priori, and reported 1 or more outcomes (sIVH, cPVL, and severe brain injury) were included.

Data Extraction and Synthesis

Two co-authors independently extracted the data, assessed the quality of the trials, and evaluated the certainty of the evidence using the Cochrane GRADE (Grading of Recommendations, Assessment, Development, and Evaluation) approach. Fixed-effects pairwise meta-analysis was used for data synthesis.

Main Outcomes and Measures

The 3 prespecified outcomes were sIVH, cPVL, and severe brain injury.

Results

A total of 221 RCTs that assessed 44 perinatal interventions (6 antenatal, 6 delivery room, and 32 neonatal) were included. Meta-analysis showed with moderate certainty that antenatal corticosteroids were associated with small reduction in sIVH risk (risk ratio [RR], 0.54 [95% CI, 0.35-0.82]; absolute risk difference [ARD], -1% [95% CI, -2% to 0%]; number needed to treat [NNT], 80 [95% CI, 48-232]), whereas indomethacin prophylaxis was associated with moderate reduction in sIVH risk (RR, 0.64 [95% CI, 0.52-0.79]; ARD, -5% [95% CI, -8% to -3%]; NNT, 20 [95% CI, 13-39]). Similarly, the meta-analysis showed with low certainty that volume-targeted ventilation was associated with large reduction in risk of sIVH (RR, 0.51 [95% CI, 0.36-0.72]; ARD, -9% [95% CI, -13% to -5%]; NNT, 11 [95% CI, 7-23]). Additionally, early erythropoiesis-stimulating agents (RR, 0.68 [95% CI, 0.57-0.83]; ARD, -3% [95% CI, -4% to -1%]; NNT, 34 [95% CI, 22-67]) and prophylactic ethamsylate (RR, 0.68 [95% CI, 0.48-0.97]; ARD, -4% [95% CI, -7% to 0%]; NNT, 26 [95% CI, 13-372]) were associated with moderate reduction in sIVH risk (low certainty). The meta-analysis also showed with low certainty that compared with delayed cord clamping, umbilical cord milking was associated with a moderate increase in sIVH risk (RR, 1.82 [95% CI, 1.03-3.21]; ARD, 3% [95% CI, 0%-6%]; NNT, -30 [95% CI, -368 to -16]).

Conclusions and Relevance

Results of this study suggest that a few interventions, including antenatal corticosteroids and indomethacin prophylaxis, were associated with reduction in sIVH risk (moderate certainty), and volume-targeted ventilation, early erythropoiesis-stimulating agents, and prophylactic ethamsylate were associated with reduction in sIVH risk (low certainty) in preterm neonates. However, clinicians should carefully consider all of the critical factors that may affect applicability in these interventions, including certainty of the evidence, before applying them to clinical practice.

Ventilator Management in Extremely Preterm Infants

Advances in ventilation strategies for infants in the NICU have led to increased survival of extremely preterm infants. More than 75% of infants born at less than or equal to 27 weeks' gestation require initial mechanical ventilation for survival due to developmental immaturity of their lungs and respiratory drive. Various ventilators using different technologies and involving multiple management strategies are available for use in this population. Centers across the world have successfully used conventional, high-frequency oscillatory and high-frequency jet ventilation to manage respiratory failure in extremely preterm infants. This review explores the existing evidence for each mode of ventilation and the importance of individualizing ventilator management strategies when caring for extremely preterm infants.

Persistent pulmonary hypertension of the newborn: Historical perspectives

For many decades, persistent pulmonary hypertension of the newborn (PPHN) remained a baffling disorder, often confused with cyanotic congenital heart disease, with a very high mortality. Originally described as a condition characterized by clear lung fields and profound hypoxemia, modern diagnostic techniques and novel therapeutics have improved the outcomes of affected newborns. This paper will review the historical aspects of PPHN and enable the reader to see how far we have come but also how far we have to go in conquering this unique disorder.

Volume-Targeted Ventilation

Volume-targeted ventilation (VTV) has been increasingly used in neonatology. In systematic reviews, VTV has been shown to reduce the risk of neonatal morbidities and improve long-term outcomes. It is adaptive ventilation using complex computer algorithms to deliver ventilator inflations with expired tidal volumes close to a target set by clinicians. Significant endotracheal tube leak and patient-ventilator interactions may complicate VTV and make ventilator parameters and waveforms difficult to interpret. In this article, we review the rationale for using VTV and the evidence supporting its use and provide practical advice for clinicians ventilating newborn infants.

The Intertemporal Role of Respiratory Support in Improving Neonatal Outcomes: A Narrative Review

Defining improvements in healthcare can be challenging due to the need to assess multiple outcomes and measures. In neonates, although progress in respiratory support has been a key factor in improving survival, the same degree of improvement has not been documented in certain outcomes, such as bronchopulmonary dysplasia. By exploring the evolution of neonatal respiratory care over the last 60 years, this review highlights not only the scientific advances that occurred with the application of invasive mechanical ventilation but also the weakness of the existing knowledge. The contributing role of non-invasive ventilation and less-invasive surfactant administration methods as well as of certain pharmacological therapies is also discussed. Moreover, we analyze the cost-benefit of neonatal care-respiratory support and present future challenges and perspectives.

Bayesian network meta-analysis of the efficacy of 22 ventilation strategies in premature infants with respiratory distress syndrome

Introduction: Respiratory Distress Syndrome (RDS) is a common lung disease in the neonatal period. The infants are mostly premature, with a high mortality rate and many complications. Currently, respiratory support therapy is still one of the primary treatment measures for RDS in preterm infants. There are 22 modes of ventilation currently in use.Areas covered: We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, EMBASE, MEDLINE, CINAHL, and Web of Science by using a combination of Medical Subject Headings (MeSH) and text words. The search time limit is set from the establishment of the above-mentioned databases to August 2020.Expert opinion: In total, 37 randomized controlled trials were included for the network meta-analysis, which consisted of 5,101 patients who received one of 22 ventilation modes. The results of the network meta-analysis showed that the Volume-Control (by adjusting tidal volume) ventilation mode is the most successful in reducing the mortality of preterm infants with RDS, followed by Synchronized Intermittent Mechanical Ventilation and Volume Guaranteed Ventilation. This network meta-analysis highlights the variability in techniques within treatment of acute respiratory distress syndrome in premature infants and compares different ventilation strategies. This study is registered with PROSPERO, number CRD42020213050.Conclusion: This network meta-analysis highlights the variability in techniques within treatment of acute respiratory distress syndrome in premature infants and compares different ventilation strategies. Future studies need to be rigorous in design and delivery and include comprehensive descriptions of all aspects of methodology to further enable appraisal and interpretation of results. This study is registered with PROSPERO, number CRD42020213050.

Inspiratory Pressure Rise Time, Ventilator Hardware, and Software Influence Regional Ventilation in a Simulated Bronchopulmonary Dysplasia Lung Model

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a heterogeneous disease that poses a challenge when ventilating premature infants. The purpose of this study was to determine how inspiratory pressure rise time (IRT), different ventilators, and their software updates affect the balance of ventilation among 2 heterogeneous lung units.

METHODS

A passive dual-chamber lung model was constructed using the IngMar ASL5000 to approximate moderate BPD. One chamber had a short time constant, and the other had a long time constant. Three ventilators were used to provide pressure control intermittent mandatory ventilation: the Servo-i, an Avea ventilator with the volume guarantee software update, and an Avea ventilator without the volume guarantee software update. Using the same settings for pressure control intermittent mandatory ventilation, the IRT was adjusted between minimum and maximum settings. Data from 100 consecutive breaths/IRT were obtained. Inspiration time to 90% of plateau pressure was used as a surrogate for IRT; this was defined as the time needed to achieve a pressure of 18 cm H₂O at the simulated trachea and was measured in 5 random breaths using ImageJ for each ventilator at each IRT. Outcome variables were tidal volume, peak inspiratory flow, mean inspiratory pressure, and volume balance (%) defined as the difference in chamber tidal volumes divided by total tidal volume. Linear regression was used to assess the impact of the IRT and ventilators on the different variables.

RESULTS

In this model, increasing IRT decreased peak inspiratory flow, mean inspiratory pressure, chamber-specific tidal volume, and volume balance. Furthermore, different ventilator hardware and software influenced the waveforms in pressure control intermittent mandatory ventilation, which independently affected the measured variables.

CONCLUSIONS

In a lung model of BPD with 2 very heterogeneous lung units, prolonging IRT without any volume balancing measures improved volume balance between the chambers at the expense of total tidal volume. Furthermore, the different ventilators acted as independent factors from the measured inspiration time to 90% of plateau pressure.

Development and Validation of a Dynamic Nomogram to Predict the Risk of Neonatal White Matter Damage

Purpose

White matter damage (WMD) was defined as the appearance of rough and uneven echo enhancement in the white matter around the ventricle. The aim of this study was to develop and validate a risk prediction model for neonatal WMD.

Materials and Methods

We collected data for 1,733 infants hospitalized at the Department of Neonatology at The First Affiliated Hospital of Zhengzhou University from 2017 to 2020. Infants were randomly assigned to training (n = 1,216) or validation (n = 517) cohorts at a ratio of 7:3. Multivariate logistic regression and least absolute shrinkage and selection operator (LASSO) regression analyses were used to establish a risk prediction model and web-based risk calculator based on the training cohort data. The predictive accuracy of the model was verified in the validation cohort.

Results

We identified four variables as independent risk factors for brain WMD in neonates by multivariate logistic regression and LASSO analysis, including gestational age, fetal distress, prelabor rupture of membranes, and use of corticosteroids. These were used to establish a risk prediction nomogram and web-based calculator (https://caowenjun.shinyapps.io/dynnomapp/). The C-index of the training and validation sets was 0.898 (95% confidence interval: 0.8745-0.9215) and 0.887 (95% confidence interval: 0.8478-0.9262), respectively. Decision tree analysis showed that the model was highly effective in the threshold range of 1-61%. The sensitivity and specificity of the model were 82.5 and 81.7%, respectively, and the cutoff value was 0.099.

Conclusion

This is the first study describing the use of a nomogram and web-based calculator to predict the risk of WMD in neonates. The web-based calculator increases the applicability of the predictive model and is a convenient tool for doctors at primary hospitals and outpatient clinics, family doctors, and even parents to identify high-risk births early on and implementing appropriate interventions while avoiding excessive treatment of low-risk patients.

Current views of complications associated with neonatal ventilation

Infants born prematurely require external respiratory support device like ventilation for the purpose of life saving. However, these ventilation machines have complications that sometimes unfortunately result in morbidity. New ventilation techniques have been developed to prevent morbidity, but have yet to be fully evaluated. The present review article would discuss current aspects of this life saving gear especially for pediatric patients in clinical setting. Besides basic ventilation apparatus, advancements in the filed like proportional assist ventilation, volume targeted ventilation would be discussed.

Volume-targeted versus pressure-limited ventilation in neonates

BACKGROUND

Damage caused by lung overdistension (volutrauma) has been implicated in the development of bronchopulmonary dysplasia (BPD). Modern neonatal ventilation modes can target a set tidal volume as an alternative to traditional pressure-limited ventilation (PLV) using a fixed inflation pressure. Volume-targeted ventilation (VTV) aims to produce a more stable tidal volume in order to reduce lung damage and stabilise the partial pressure of carbon dioxide (pCO2).

OBJECTIVES

To determine whether VTV compared with PLV leads to reduced rates of death and death or BPD in newborn infants and to determine whether use of VTV affected outcomes including air leak, cranial ultrasound findings and neurodevelopment.

SEARCH METHODS

We used the standard search strategy of Cochrane Neonatal to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 12), MEDLINE via PubMed (1966 to 13 January 2017), Embase (1980 to 13 January 2017) and CINAHL (1982 to 13 January 2017). We also searched clinical trials databases, conference proceedings and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials. We contacted the principal investigators of studies to obtain supplementary information.

SELECTION CRITERIA

Randomised and quasi-randomised trials comparing VTV versus PLV in infants of less than 44 weeks' postmenstrual age and reporting clinically relevant outcomes.

DATA COLLECTION AND ANALYSIS

We assessed risk of bias for each trial using Cochrane methodology. We evaluated quality of evidence for each outcome using GRADE criteria. We tabulated mortality, rates of BPD, short-term clinical outcomes and long-term developmental outcomes.

STATISTICS

for categorical outcomes, we calculated typical estimates for risk ratios (RR), risk differences (RD) and number needed to treat for an additional beneficial outcome (NNTB). For continuous variables, we calculated typical estimates for mean differences (MD). We used 95% confidence intervals (CI) and assumed a fixed-effect model for meta-analysis.

MAIN RESULTS

Twenty randomised trials met our inclusion criteria; 16 parallel trials (977 infants) and four cross-over trials (88 infants). No studies were blinded and the quality of evidence for outcomes assessed varied from moderate to low.We found no difference in the primary outcome, death before hospital discharge, between VTV modes versus PLV modes (typical RR 0.75, 95% CI 0.53 to 1.07; low quality evidence). However, there was moderate quality evidence that the use of VTV modes resulted in a reduction in the primary outcome, death or BPD at 36 weeks' gestation (typical RR 0.73, 95% CI 0.59 to 0.89; typical NNTB 8, 95% CI 5 to 20) and the following secondary outcomes: rates of pneumothorax (typical RR 0.52, 95% CI 0.31 to 0.87; typical NNTB 20, 95% CI 11 to 100), mean days of mechanical ventilation (MD -1.35 days, 95% CI -1.83 to -0.86), rates of hypocarbia (typical RR 0.49, 95% CI 0.33 to 0.72; typical NNTB 3, 95% CI 2 to 5), rates of grade 3 or 4 intraventricular haemorrhage (typical RR 0.53, 95% CI 0.37 to 0.77; typical NNTB 11, 95% CI 7 to 25) and the combined outcome of periventricular leukomalacia with or without grade 3 or 4 intraventricular haemorrhage (typical RR 0.47, 95% CI 0.27 to 0.80; typical NNTB 11, 95% CI 7 to 33). VTV modes were not associated with any increased adverse outcomes.

AUTHORS' CONCLUSIONS

Infants ventilated using VTV modes had reduced rates of death or BPD, pneumothoraces, hypocarbia, severe cranial ultrasound pathologies and duration of ventilation compared with infants ventilated using PLV modes. Further studies are needed to identify whether VTV modes improve neurodevelopmental outcomes and to compare and refine VTV strategies.

Lung Injury and Bronchopulmonary Dysplasia in Newborn Infants

Bronchopulmonary dysplasia is the most common morbidity among surviving premature infants. Injury to the developing lung is the result of the interaction between a susceptible host and a number of contributing factors such as mechanical ventilation and infection. The resulting persistent impairment of pulmonary function and need for ongoing therapy are the underlying characteristics of bronchopulmonary dysplasia. Important insights into the pathogenesis of bronchopulmonary dysplasia have led to numerous therapies and preventive approaches. Although significant progress has been made, in order to further affect the incidence and severity of the disease, we need to further study (a) the genetically determined predisposing factors, (b) the relative contribution of the various pathogenetic pathways, and, most important, (c) how to best translate the knowledge gained from these studies into effective clinical approaches.

Modalities of Mechanical Ventilation: Volume-Targeted Versus Pressure-Limited

BACKGROUND

Respiratory distress syndrome remains the most common admission diagnosis in the neonatal intensive care unit. Healthcare providers have a clear appreciation for the potential harm to pulmonary structures that have been associated with mechanical ventilation (MV) in the preterm infant. Although life sustaining, the goal is to optimally ventilate while limiting trauma to the neonatal lung in order to preserve long-term cardiopulmonary and neurodevelopmental outcomes.

PURPOSE

To describe, compare, and contrast 2 primary methods of neonatal MV, pressure-limited ventilation (PLV) and volume-targeted ventilation (VTV), highlighting key considerations during therapy.

METHODS

A comprehensive search of the literature was completed using the following databases: CINAHL, Cochrane, Google Scholar, and PubMed. Research articles that were published in English over the last 10 years were reviewed for key information to describe and support the topic. Expert content review was conducted prior to publication by respiratory care providers, neonatal nurse practitioners, staff nurses, and neonatologist.

FINDINGS

Technology is rapidly evolving, with the newest mechanical ventilators providing the clinician with real-time data not previously available. Advanced microprocessors and feedback mechanisms can better support various ventilatory strategies including PLV and VTV. Renewed interest in volume ventilation has led many clinicians to ask about current evidence to support ventilatory modalities with regard to timing, settings, and short- and long-term effects.

IMPLICATIONS FOR PRACTICE

The clinician understands that neonatal pulmonary status is frequently changing based on gestational age, current age, and physiologic influences. Evidence supporting recommendations for the described MV modalities of PLV and VTV is provided for both preterm and term neonates.

IMPLICATIONS FOR RESEARCH

Comparison between MV strategies, specifically PLV and VTV, including short- and long-term neurodevelopmental outcomes, is needed. Recommendations regarding physiologic tidal volume for the extremely preterm infant are lacking.

Real-time pulmonary graphics

Real-time pulmonary graphics now enable clinicians to view lung mechanics and patient-ventilator interactions on a breath-to-breath basis. Displays of pressure, volume, and flow waveforms, pressure-volume and flow-volume loops, and trend screens enable clinicians to customize ventilator settings based on the underlying pathophysiology and responses of the individual patient. This article reviews the basic concepts of pulmonary graphics and demonstrates how they contribute to our understanding of respiratory physiology and the management of neonatal respiratory failure.

Advances in respiratory support for high risk newborn infants

BACKGROUND

A significant proportion of premature infants present with respiratory failure early in life and require supplemental oxygen and some form of mechanical respiratory support.

FINDINGS

Many technical advances in the devices for neonatal respiratory support have occurred in recent years and new management strategies have been developed and evaluated in this population. This article describes some of these novel methods and discusses their application and possible advantages and limitations.

CONCLUSION

Newer methods of respiratory support have led to marked improvement in outcome of premature infants with respiratory failure. Some of these strategies are very promising but further investigation to evaluate their short term efficacy and impact on long term respiratory and other relevant outcomes is needed before wider use.

Mechanical ventilation modes for respiratory distress syndrome in infants: a systematic review and network meta-analysis

Introduction

The effects of different mechanical ventilation (MV) modes on mortality outcome in infants with respiratory distress syndrome (RDS) are not well known.

Methods

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) in the Cochrane Library, EMBASE, MEDLINE, CINAHL, and Web of Science for studies published through April 2014 that assessed mortality in infants with RDS given different MV modes. We assessed studies for eligibility, extracted data, and subsequently pooled the data. A Bayesian fixed-effects model was used to combine direct comparisons with indirect evidence. We also performed sensitivity analyses and rankings of the competing treatment modes.

Results

In total, 20 randomized controlled trials were included for the network meta-analysis, which consisted of 2,832 patients who received one of 16 ventilation modes. Compared with synchronized intermittent mandatory ventilation (SIMV) + pressure support ventilation (PSV), time-cycled pressure-limited ventilation (TCPL) (hazard ratio (HR) 0.290; 95% confidence interval (CI) 0.071 to 0.972), high-frequency oscillatory ventilation (HFOV) (HR 0.294; 95% CI 0.080 to 0.852), SIMV + volume-guarantee (VG) (HR 0.122; 95% CI 0.014 to 0.858), and volume-controlled (V-C) (HR 0.139; 95% CI 0.024 to 0.677) ventilation modes are associated with lower mortality. The combined results of available ventilation modes were not significantly different in regard to the incidences of patent ductus arteriosus and intraventricular hemorrhage.

Conclusion

Compared with the SIMV + PSV ventilation mode, the TCPL, HFOV, SIMV + VG, and V-C ventilation modes are associated with lower mortality.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0843-7) contains supplementary material, which is available to authorized users.

Volume-targeted ventilation is more suitable than pressure-limited ventilation for preterm infants: a systematic review and meta-analysis

OBJECTIVE

To assess the effect of volume-targeted ventilation (VTV) compared with pressure-limited ventilation (PLV) in preterm infants.

METHOD

We searched the Cochrane Library (Issue 3, 2013), PubMed (1966 to 5 March 2013), China National Knowledge Infrastructure (CNKI) and periodical databases (1979 to 5 March 2013). We selected randomised controlled trials (RCTs) and quasi-RCTs of VTV versus PLV as active interventions in preterm infants. We performed meta-analyses using the Cochrane statistical package RevMan 5.0.

RESULTS

Eighteen trials met our inclusion criteria. There was no evidence that VTV modes reduced the incidence of death (relative risk (RR) 0.73, 95% CI 0.51 to 1.05). The use of VTV modes resulted in a reduction in the incidence of bronchopulmonary dysplasia (BPD) (RR 0.61, 95% CI 0.46 to 0.82) and duration of mechanical ventilation (mean difference (MD) -2.0 days, 95% CI -3.14 to -0.86). VTV modes also resulted in reductions in intraventricular haemorrhage (IVH) (RR 0.65, 95% CI 0.42 to 0.99), grade 3/4 IVH (RR 0.55, 95% CI 0.39 to 0.79), periventricular leukomalacia (PVL) (RR 0.33, 95% CI 0.15 to 0.72), pneumothorax (RR 0.52, 95% CI 0.29 to 0.93), failure of primary mode of ventilation (RR 0.64, 95% CI 0.43 to 0.94), hypocarbia (RR 0.56, 95% CI 0.33 to 0.96), mean airway pressure (MD -0.54 cmH2O, 95% CI -1.05 to -0.02) and days of supplemental oxygen administration (MD -1.68 days, 95% CI -2.47 to -0.88).

CONCLUSIONS

Preterm infants ventilated using VTV modes had reduced duration of mechanical ventilation, incidence of BPD, failure of primary mode of ventilation, hypocarbia, grade 3/4 IVH, pneumothorax and PVL compared with preterm infants ventilated using PLV modes. There was no evidence that infants ventilated with VTV modes had reduced death compared to infants ventilated using PLV modes.

Effects of synchronized intermittent mandatory ventilation versus pressure support plus volume guarantee ventilation in the weaning phase of preterm infants*

OBJECTIVE

To compare the effects and short-term outcomes of pressure support ventilation with volume guarantee versus synchronized intermittent mandatory ventilation in the weaning phase of very low-birth weight infants with respiratory distress syndrome.

DESIGN

Randomized controlled prospective study.

SETTING

Tertiary care neonatal unit.

PATIENTS

A total of 60 premature infants who were less than 33 weeks' gestation and/or less than 1,500 g birth weight and received mechanical ventilation because of respiratory distress syndrome were studied.

INTERVENTIONS

All infants were ventilated from the time of admission with synchronized intermittent positive pressure ventilation mode after surfactant treatment for respiratory distress syndrome and then switched to pressure support ventilation with volume guarantee or synchronized intermittent mandatory ventilation mode in the weaning phase. The ventilatory variables and neonatal outcomes were recorded in each group.

MEASUREMENTS AND MAIN RESULTS

The mean peak inflation pressure was higher in synchronized intermittent mandatory ventilation group (p < 0.001) and the mean airway pressure was higher in pressure support ventilation with volume guarantee group (p = 0.03), whereas mean tidal volume and respiratory rates were similar in both groups. The prevalence of postextubation atelectasis was higher in synchronized intermittent mandatory ventilation group, but the difference was not statistically significant (p = 0.08). No differences were found in the prevalence of reintubation, patent ductus arteriosus, intraventricular hemorrhage, retinopathy of prematurity, bronchopulmonary dysplasia, and pneumothorax between the groups.

CONCLUSIONS

Pressure support ventilation with volume guarantee mode may be a safe and feasible mode during the weaning phase of very low-birth weight infants on mechanical ventilation support for respiratory distress syndrome with respect to reducing the frequency of postextubation atelectasis and using less peak inflation pressure.

Early neonatal outcomes of volume guaranteed ventilation in preterm infants with respiratory distress syndrome

BACKGROUND

Volume guaranteed (VG) synchronized intermittent mandatory ventilation (SIMV) is a novel mode of SIMV that provides automatic adjustment of the peak inspiratory pressure for ensuring a minimum set tidal volume and there are limited data about the effects of VG ventilation on short term neonatal outcomes in preterm infants with respiratory distress syndrome (RDS).

OBJECTIVE

The main objective of this study was to evaluate the effect of VG ventilation on duration of ventilation and total supplemental oxygen. We also aimed to compare the early neonatal outcomes of VG ventilation versus conventional SIMV on short-term outcomes in preterm babies with RDS who were given surfactant.

METHODS

In this randomized controlled study, preterm infants who were admitted with RDS and given surfactant were divided into 2 groups: group 1 included infants ventilated on conventional SIMV (n = 30) and group 2 included infants ventilated on VG ventilation (n = 42). Neonatal morbidities such as air leak, bronchopulmonary dysplasia (BPD), intraventricular hemorrhage (IVH), retinopathy of prematurity (ROP), necrotizing enterocolitis (NEC) and duration of mechanical ventilation and total oxygen supplementation were all recorded.

RESULTS

There were no significant differences between two groups in terms of demographic features. Infants ventilated with VG mode had significantly shorter duration of ventilation and need of total supplemental oxygen. The incidences of oxygen related short term complications including BPD, ROP, and IVH were also significantly lower in these infants compared with those ventilated with conventional SIMV. No significant differences were found between two groups with respect to NEC and air leak.

CONCLUSION

In conclusion, VG ventilation in combination with surfactant treatment significantly reduced both duration of mechanical ventilation and early neonatal oxygen related morbidities including BPD, ROP and IVH in preterm infants with RDS. This data favors the use of VG ventilation in respiratory support of premature infants.

Volume-limited and volume-targeted ventilation

This article shows that volume-targeted ventilation is physiologically more logical than pressure-limited ventilation, and is associated with a reduced risk of pneumothorax, hypocarbia, duration of ventilation, death or bronchopulmonary dysplasia, and severe intraventricular hemorrhage. Therefore, it should now be adopted as the main mode for mechanical ventilation of preterm neonates.

Impact of volume guarantee on synchronized ventilation in preterm infants: a randomized controlled trial

PURPOSE

The aim of this randomized controlled trial was to assess whether the addition of volume guarantee (VG) to triggered ventilation decreases the duration of ventilation in very low birth weight (VLBW) infants with respiratory distress syndrome (RDS).

METHODS

Infants were randomized into two groups to initially receive either assist/control (A/C) or A/C plus VG ventilation and then weaned with synchronized intermittent mandatory ventilation (SIMV) or SIMV plus VG.

RESULTS

Forty-five infants were included in the study. The demographic and clinical characteristics, values of tidal volume (VT), peak inspiratory pressure (PIP), fraction of inspired oxygen, carbon dioxide tension, and pH were similar for all participating infants initially. During the follow-up, the VT levels were more stable, and the PIP levels were significantly decreasing in the VG group. Although the duration of ventilation was shorter in the VG group, this trend was not statistically significant. The incidences of death and bronchopulmonary dysplasia (BPD) were not significantly different, but the combined outcome of death or BPD was lower in the VG group. Although the VG group experienced less frequent BPD, periventricular leukomalacia, and intraventricular hemorrhage, these differences were not statistically different.

CONCLUSION

The VG option, when combined with A/C (in the acute phase of RDS) and SIMV (in the weaning), reduced VT variability, and may have shortened the duration of ventilation in VLBW infants. Overall mortality and BPD rates did not change, but their combined outcome was significantly improved in infants treated with VG modes as compared to those treated with synchronized pressure-limited modes alone.

The effects of closed tracheal suctioning plus volume guarantee on cerebral hemodynamics

OBJECTIVE

To compare the effects of open tracheal suctioning (OS) plus intermittent mandatory ventilation (IMV) vs. closed tracheal suctioning (CS) plus volume guarantee ventilation (VG) on changes in mean cerebral blood-flow velocity (CBFv) of ventilated very low birth weight (VLBW) infants.

STUDY DESIGN

A total of 75 normotensive, ventilated VLBW infants (with normal cranial ultrasounds) had monitoring of mean CBFv, PCO2 and mean arterial blood pressure (MABP) before, during and after 220 tracheal suctioning sessions during the first week of life. Multiple linear regression analysis was used to determine the factor(s) influencing the magnitude of relative changes from baseline in mean CBFv after suctioning.

RESULT

In all, 49 VLBW infants receiving IMV had monitoring during 124 OS sessions between July 2002 and May 2005; 26 VLBW infants receiving VG had monitoring during 96 CS sessions between January 2006 and July 2007. The average magnitude of relative changes in mean CBFv was significantly less with CS+VG, and was associated with the magnitude of relative changes in PCO2 and suctioning-ventilator group.

CONCLUSION

The average magnitude of relative changes in mean CBFv was reduced in VLBW infants with CS+VG vs. OS+IMV.

Bronchopulmonary Dysplasia: Development and Progression in the Neonatal Intensive Care Unit

Advances in neonatology have led to increased survival at younger gestational ages. These advances have included the ability to provide and titrate oxygen, improved modalities of assisted ventilation, improved nutritional and environmental support, and surfactant therapy. As a result of increasing survival of these immature infants, bronchopulmonary dysplasia (BPD) has become a consistent outcome despite improvements in technology. Varying definitions of BPD have emerged in an effort to best identify infants at risk for long-term adverse outcome and those who might benefit most from preventive therapies. Underlying abnormal pulmonary development of extremely preterm infants in the face of exposure to oxygen, assisted ventilation and inflammation make this a complex, multifactorial disease. Recent focus has been directed at preventing and treating inflammation. Efforts to minimize the inflammatory process include avoiding hyperoxia, minimizing injury from assisted ventilation, and preventing and treating postnatal infections. Additional therapies to modulate inflammation, such as steroid therapy or inhaled nitric oxide, need further investigation of both short- and long-term outcomes before routine use can be recommended.

Volume-targeted versus pressure-limited ventilation for preterm infants: a systematic review and meta-analysis

BACKGROUND

The causes of bronchopulmonary dysplasia (BPD) are multifactorial. Overdistension of the lung (volutrauma) is considered an important contribution. As an alternative to traditional pressure-limited ventilation (PLV), modern neonatal ventilators offer modes which can target a set tidal volume.

OBJECTIVES

To determine whether volume-targeted neonatal ventilation, compared with PLV, reduces death or BPD.

METHODS

We performed a systematic review and meta-analysis using the methodology of the Neonatal Review Group of the Cochrane Collaboration. A comprehensive literature search was undertaken, and data for prespecified outcomes were combined where appropriate using the fixed effects model.

RESULTS

Nine trials were eligible. Volume-targeted ventilation resulted in a reduction in: the combined outcome of death or BPD [typical relative risk, RR, 0.73 (95% confidence interval, 0.57-0.93), numbers needed to treat, NNT, 8 (95% CI 5-33)], the incidence of pneumothorax [typical RR 0.46 (95% CI 0.25-0.84), NNT 17 (95% CI 10-100)], days of ventilation [weighted mean difference 0.8 days (log-transformed data, p = 0.05)], hypocarbia (pCO(2) <35 mm Hg/4.7 kPa); [typical RR 0.56 (95% CI 0.33-0.96), NNT 4 (95% CI 2-25)], and the combined outcome of periventricular leukomalacia or grade 3-4 intraventricular hemorrhage [typical RR 0.48 (95% CI 0.28-0.84), NNT 11 (95% CI 7-50)].

CONCLUSIONS

Compared with PLV, infants ventilated using volume-targeted ventilation had reduced death/BPD, duration of ventilation, pneumothoraces, hypocarbia and periventricular leukomalacia/severe intraventricular hemorrhage. Further studies are needed to assess neurodevelopmental outcomes.

Volume-targeted versus pressure-limited ventilation in the neonate

BACKGROUND

Damage caused by lung overdistension (volutrauma) has been implicated in the development bronchopulmonary dysplasia (BPD). Modern neonatal ventilation modes can target a set tidal volume as an alternative to traditional pressure-limited ventilation using a fixed inflation pressure. Volume targeting aims to produce a more stable tidal volume in order to reduce lung damage and stabilise pCO(2)

OBJECTIVES

To determine whether volume-targeted ventilation (VTV) compared with pressure-limited ventilation (PLV) leads to reduced rates of death and BPD in newborn infants. Secondary objectives were to determine whether use of VTV affected outcomes including air leak, cranial ultrasound findings and neurodevelopment.

SEARCH STRATEGY

The search strategy comprised searches of the Cochrane Central Register of Controlled Trials, MEDLINE PubMed 1966 to January 2010, and hand searches of reference lists of relevant articles and conference proceedings.

SELECTION CRITERIA

All randomised and quasi-randomised trials comparing the use of volume-targeted versus pressure-limited ventilation in infants of less than 28 days corrected age.

DATA COLLECTION AND ANALYSIS

Two review authors assessed the methodological quality of eligible trials and extracted data independently. When appropriate, meta-analysis was conducted to provide a pooled estimate of effect. For categorical data the relative risk (RR) and risk difference (RD) were calculated with 95% confidence intervals. Number needed to treat was calculated when RD was statistically significant. Continuous data were analysed using weighted mean difference.

MAIN RESULTS

Twelve randomised trials met our inclusion criteria; nine parallel trials (629 infants) and three crossover trials (64 infants).The use of VTV modes resulted in a reduction in the combined outcome of death or bronchopulmonary dysplasia [typical RR 0.73 (95% CI 0.57 to 0.93), NNT8 (95% CI 5 to 33)]. VTV modes also resulted in reductions in pneumothorax [typical RR 0.46 (95% CI 0.25 to 0.84), NNT 17 (95% CI 10 to 100)], days of ventilation [MD -2.36 (95% CI -3.9 to -0.8)], hypocarbia [typical RR 0.56 (95%CI 0.33 to 0.96), NNT 4 (95% CI 2 to 25)] and the combined outcome of periventricular leukomalacia or grade 3-4 intraventricular haemorrhage [typical RR 0.48 (95% CI 0.28 to 0.84), NNT 11 (95% CI 7 to 50)].

AUTHORS' CONCLUSIONS

Infants ventilated using VTV modes had reduced death and chronic lung disease compared with infants ventilated using PLV modes. Further studies are needed to identify whether VTV modes improve neurodevelopmental outcomes and to compare and refine VTV strategies.

Flow-cycled versus time-cycled synchronized ventilation for neonates

BACKGROUND

Synchronized ventilation of neonates is standard care in industrialized countries. Both flow-cycled and time-cycled modes of synchronized ventilation are in widespread use for assisted ventilation of neonates.

OBJECTIVES

To determine the effect of flow-cycled versus time-cycled synchronized ventilation on the risk of bronchopulmonary dysplasia (BPD) at 36 weeks postmenstrual age (PMA) in neonates requiring assisted ventilation.

SEARCH STRATEGY

We used the standard methods of the Cochrane Neonatal Review Group to search the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library Issue 4, 2009, PubMed (January 1966 to October 2009), EMBASE (January 1974 to October 2009) and CINAHL (January 1982 to October 2009). We checked references and cross-references from identified studies. Abstracts from the proceedings of the Pediatric Academic Societies Meetings (from January 1990 to October 2009) were handsearched. We placed no restrictions on language.

SELECTION CRITERIA

Randomized or quasi-randomized clinical trials comparing flow-cycled with time-cycled synchronized endotracheal ventilation in neonates, reporting on at least one outcome of interest were eligible for inclusion in the review.

DATA COLLECTION AND ANALYSIS

One author (SMS) searched the literature as described above. Selection of studies and data extraction were done separately by two authors (SMS and SKP). Any disagreements were resolved by discussion involving all authors.

MAIN RESULTS

Only two small, short-term, randomized, individual cross-over trials involving a total of 19 preterm neonates met the inclusion criteria of this review. Both trials reported on lung mechanics and short-term respiratory physiology outcomes but not on clinical morbidities or mortality.

AUTHORS' CONCLUSIONS

There is insufficient evidence to determine the safety and efficacy of flow-cycled compared to time-cycled synchronized ventilation in neonates. Large randomized clinical trials using a parallel-group design and reporting on clinically important outcomes are warranted.

State of the art in conventional mechanical ventilation

Despite a shift to noninvasive respiratory support, mechanical ventilation remains an essential tool in the care of critically ill neonates. The availability of a variety of technologically advanced devices with a host of available modes and confusing terminology presents a daunting challenge to the practicing neonatologist. Many of the available modes have not been adequately evaluated in newborn infants and there is paucity of information on the relative merits of those modes that have been studied. This review examines the special challenges of ventilating the extremely low birth weight infants that now constitute an increasing proportion of ventilated infants, attempts to provide a simple functional classification of ventilator modes and addresses the key aspects of synchronized ventilation modes. The rationale for volume-targeted ventilation is presented, the available modes are described and the importance of the open-lung strategy is emphasized. The available literature on volume-targeted modalities is reviewed in detail and general recommendations for their clinical application are provided. Volume guarantee has been studied most extensively and shown to reduce excessively large tidal volumes, decrease incidence of inadvertent hyperventilation, reduce duration of mechanical ventilation and reduce pro-inflammatory cytokines. It remains to be seen whether the demonstrated short-term benefits translate into significant reduction in chronic lung disease. Avoidance of mechanical ventilation by means of early continuous positive airway pressure with or without surfactant administration may still be the most effective way to reduce the risk of lung injury. For babies who do require mechanical ventilation, the combination of volume-targeted ventilation, combined with the open-lung strategy appears to offer the best chance of reducing the risk of bronchopulmonary dysplasia.

New and alternative modes of mechanical ventilation in neonates

Innovative ventilation modes for infants attempt to reduce volume-induced lung damage, to decrease airway pressure and oxygen exposure, and to improve patient comfort. Volume-targeted ventilation results in more consistent tidal volumes, allows automatic weaning of airway pressure, may avoid hypocapnia and may be associated with long-term clinical benefits. Pressure support ventilation allows the patient to control the duration of mechanical breaths. It requires a stable respiratory drive or back-up for apnoea. Pressure support ventilation may be effective for weaning. Proportional assist ventilation was studied in small animal species. In preterm infants with acute and chronic lung disease, ventilator pressure requirements were lower in cross-over short-term comparisons with conventional triggered ventilation. Neurally adjusted ventilatory assist delivers ventilator pressure in proportion and in synchrony with the phasic inspiratory diaphragmatic electrical activity obtained from intra-oesophageal electrodes. Large multicentre clinical trials are required to prove long-term clinical benefits of these new modes.

Newer forms of conventional ventilation for preterm newborns

Although life saving, mechanical ventilation can cause complications such as ventilator-induced lung injury and bronchopulmonary dysplasia in very preterm babies. The ventilator-induced lung injury is multi-factorial. There has been an introduction of a number of newer forms of mechanical ventilation, which are aimed to reduce such complications. These are based on sound physiologic principles and clinicians should familiarize themselves with these advances.

Methods and evidence on volume-targeted ventilation in preterm infants

PURPOSE OF REVIEW

Several modalities of volume-targeted ventilation have been developed for the premature infant or were adopted from those used in older populations. The article describes these modalities, their clinical application in preterm infants and reviews the evidence for the possible beneficial effects in this population.

RECENT FINDINGS

Evidence from physiologic studies indicates increased stability of tidal volume and gas exchange while requiring less ventilatory support. Randomized trials of volume-targeted ventilation indicate faster weaning and shorter duration of mechanical ventilation, but this has not resulted in better respiratory outcome.

SUMMARY

The proposed benefits of volume-targeted ventilation on respiratory outcome have not been fully confirmed by the existing data. Some trends suggest possible benefits, but these need to be further explored. The efficacy of volume-targeted ventilation may be method dependent and may also be influenced by the magnitude of the volume targeted.

Pulmonary complications of mechanical ventilation in neonates

Mechanical ventilation is necessary and life saving in many neonates. Most complications are inherent to this intervention and cannot be confused with iatrogenic errors in judgment or care practices by clinicians. Clinical data suggest that complications such as volutrauma and air leak syndromes can negatively affect long-term pulmonary and non-pulmonary outcomes. Careful attention to many aspects of neonatal care, such as delivery room resuscitation, ventilatory support, and routine care practices, is needed to decrease pulmonary complications of mechanical ventilation. Clinical research is needed to improve mechanical ventilator strategies to reduce pulmonary complications and improve long-term outcomes.

Volume-targeted ventilation of newborns

Traditional management of neonatal respiratory failure has been accomplished with mechanical ventilation delivered by time-cycled, pressure-limited techniques. Although easy to use, this modality results in the delivery of tidal volumes that vary according to pulmonary compliance. In contrast, volume-targeted ventilation delivers a selected tidal volume at variable peak inspiratory pressure, resulting in consistent tidal volume delivery, even in the face of changing compliance. This article reviews salient features of volume-targeted ventilation and a review of the evidence base.

Matching ventilatory support strategies to respiratory pathophysiology

Neonates can suffer from various diseases that impact differently on lung function according to the specific pulmonary pathophysiology. As a consequence, the optimal respiratory support will vary according to disorder. Most randomized trials have only included prematurely born infants who have respiratory distress syndrome (RDS) or infants who have severe respiratory failure. Meta-analysis of the results has demonstrated that for the prematurely born infant who has RDS, prophylactic high-frequency oscillatory ventilation only results in a modest reduction in bronchopulmonary dysplasia, and patient-triggered ventilation (assist/control or synchronized intermittent mandatory ventilation) reduces the duration of ventilation if started in the recovery phase. Whether the newer triggered modes are more efficacious remains to be appropriately tested. In term infants who have severe respiratory failure, extracorporeal membrane oxygenation increases survival, but inhaled nitric oxide only reduces the need for extracorporeal membrane oxygenation. Research is required to identify the optimum respiratory strategy for infants who have other respiratory disorders, particularly bronchopulmonary dysplasia.

Lung-protective ventilation strategies in neonatology: What do we know—What do we need to know?

OBJECTIVE

Randomized controlled trials (RCTs) investigating various lung-protective ventilation modes or strategies in newborn infants have failed to show clear differences in mortality or bronchopulmonary dysplasia. This review tries to identify possible reasons for this observation, applying modern concepts on ventilator-induced lung injury and lung-protective ventilation.

DATA SOURCE

Published RCTs and systematic reviews on mechanical ventilation in newborn infants were identified by searching PubMed and the Cochrane Library.

DATA SYNTHESIS

A total of 16 RCTs and four systematic reviews comparing high-frequency ventilation with conventional mechanical ventilation (CMV) failed to show consistent differences in mortality and bronchopulmonary dysplasia. Unfortunately, clear information or data on ventilation and oxygenation targets in the search for optimal lung volumes during high-frequency ventilation or CMV is lacking in many RCTs, questioning the validity of the results and the meta-analytic subgroup analysis. Based on improvement in oxygenation, only three RCTs successfully applied the optimal lung volume strategy during high-frequency ventilation. A total of 24 RCTs and three systematic reviews comparing various CMV modes and settings and two RCTs investigating permissive hypercapnia reported no differences in mortality or bronchopulmonary dysplasia. However, the intervention arms in these RCTs did not differ in tidal volume or positive end-expiratory pressures, variables that are considered important determinants in ventilator-induced lung injury. In fact, no RCT in newborn infants has substantiated so far the experimental finding that avoiding large tidal volumes and low positive end-expiratory pressure during CMV is lung protective in newborn infants.

CONCLUSION

RCTs investigating lung-protective ventilation in neonates have mainly focused on comparing high-frequency ventilation with CMV. Most of these RCTs show weaknesses in the design, which may explain the inconsistent effect of high-frequency ventilation on bronchopulmonary dysplasia. RCTs on CMV only focused on comparing various modes and settings, leaving the important question whether reducing tidal volume or increasing positive end-expiratory pressure is also lung protective in newborn infants unanswered.

In support of pressure support

Present generation mechanical ventilators are available with advanced microprocessor-based technology. Greater emphasis is being placed on the patient controlling the ventilator, rather than the physician controlling it. Pressure support ventilation (PSV) is a form of patient-triggered ventilation that supports spontaneous breathing during mechanical ventilation. It is flow-cycled, allowing the patient to determine the inspiratory time and rate. Each spontaneous breath is terminated when inspiratory flow decelerates to a predefined percentage of peak flow. At present, strict comparisons of the usefulness of PSV with other modalities of synchronized ventilation in newborns remain limited. This article reviews the principles and clinical applications of PSV for newborns who have respiratory failure.

A nurse's guide to common mechanical ventilation techniques and modes used in infants. Nursing implications

The need for conventional mechanical ventilation (CMV) is a common one in the neonatal intensive care unit (NICU). The goals of CMV are to facilitate adequate gas exchange, minimize the risk of lung injury/damage, decrease the patient's work of breathing, and optimize the patient's comfort. Although time-cycled, pressure-limited ventilation remains the most common CMV modality, volume-cycled ventilation, assist-control ventilation, pressure-support ventilation, and pressure-control ventilation are sometimes used in the NICU. Pressure-regulated volume control, volume-guaranteed ventilation, volume-assured pressure-support ventilation, and proportional-assist ventilation are emerging hybrid modes of CMV. Although CMV is frequently life saving, it can cause complications if improperly used. Nurses are responsible for the ongoing assessment and care of infants undergoing CMV and are becoming frequently more involved in the weaning process of CMV. This article provides an overview of conventional ventilation, with a focus on common modalities, and ventilation-related nursing interventions.

Volume-targeted ventilation

Recognition that volume, not pressure, is the key factor in ventilator-induced lung injury and the association of hypocarbia and brain injury dictate the need to better control delivered tidal volume. Volume-controlled ventilation, though much improved, still suffers from loss of volume due to endotracheal tube leak and gas compression in the circuit. Recent microprocessor-based modifications of pressure-limited, time-cycled ventilators combine advantages of pressure-limited ventilation with the ability to deliver a more consistent tidal volume. Each of the modes has advantages and disadvantages, with limited data available to judge their effectiveness. The Volume Guarantee mode, studied most thoroughly, provides automatic weaning of peak pressure in response to improving lung compliance and respiratory effort. More consistent tidal volume, fewer excessively large breaths, lower peak pressure, less hypocarbia and lower levels of inflammatory cytokines have been documented. It remains to be seen if these short-term benefits translate into shorter duration of ventilation or reduced incidence of chronic lung disease.

Volume-targeted modes of modern neonatal ventilators: how stable is the delivered tidal volume?

OBJECTIVE

Volume-targeted modes are designed to deliver a constant tidal volume (V(t)) at lowest possible pressure independently of changes in compliance, resistance, and leak of the respiratory system. We examined whether these volume-targeted modes respond rapidly enough to sudden changes in respiratory mechanics (e.g., selective intubation, surfactant administration, endotracheal tube kinking, de-kinking, obstruction), resulting in insufficient or excessive V(t) delivery.

DESIGN AND SETTING

Bench study of six neonatal ventilators in the volume-targeted mode simulating preterm and full-term infant settings on a test lung.

MEASUREMENTS AND RESULTS

Breath-to-breath expiratory V(t) were measured after rapid compliance, resistance, and leak changes. Under our test settings all ventilators showed important volume overshooting following rapid increase in compliance or decrease in resistance. Between one and 16 inflations were required to return to the set V(t). Some ventilators delivered inaccurate V(t) under steady state condition while others showed considerable breath-to-breath V(t) variability.

CONCLUSIONS

We observed inaccurate V(t) delivery under specific conditions as well as immediate and sometimes prolonged volume overshooting after a rapid respiratory system compliance increase or resistance decrease in volume-targeted modes of modern neonatal ventilators. Similar discrepancies between the set V(t) and the delivered inflations can be harmful in clinical situations, especially in newborns. Their clinical relevance needs to be clarified with safety studies in the neonatal population and we encourage manufacturers to further improve the ventilators algorithms.

Randomized, controlled trial comparing synchronized intermittent mandatory ventilation and synchronized intermittent mandatory ventilation plus pressure support in preterm infants

BACKGROUND

Prolonged mechanical ventilation is associated with lung injury in preterm infants. In these infants, weaning from synchronized intermittent mandatory ventilation may be delayed by their inability to cope with increased respiratory loads. The addition of pressure support to synchronized intermittent mandatory ventilation can offset these loads and may facilitate weaning.

OBJECTIVE

The purpose of this work was to compare synchronized intermittent mandatory ventilation and synchronized intermittent mandatory ventilation plus pressure support in weaning from mechanical ventilation and the duration of supplemental oxygen dependency in preterm infants with respiratory failure.

METHODS

Preterm infants weighing 500 to 1000 g at birth who required mechanical ventilation during the first postnatal week were randomly assigned to synchronized intermittent mandatory ventilation or synchronized intermittent mandatory ventilation plus pressure support. In both groups, weaning followed a set protocol during the first 28 days. Outcomes were assessed during the first 28 days and until discharge or death.

RESULTS

There were 107 infants enrolled (53 synchronized intermittent mandatory ventilation plus pressure support and 54 synchronized intermittent mandatory ventilation). Demographic and perinatal data, mortality, and morbidity did not differ between groups. During the first 28 days, infants in the synchronized intermittent mandatory ventilation plus pressure support group reached minimal ventilator settings and were extubated earlier than infants in the synchronized intermittent mandatory ventilation group. Total duration of mechanical ventilation, duration of oxygen dependency, and oxygen need at 36 weeks' postmenstrual age alone or combined with death did not differ between groups. However, infants in synchronized intermittent mandatory ventilation plus pressure support within the 700- to 1000-g birth weight strata had a shorter oxygen dependency.

CONCLUSIONS

The results of this study suggest that the addition of pressure support as a supplement to synchronized intermittent mandatory ventilation during the first 28 days may play a role in reducing the duration of mechanical ventilation in extremely low birth-weight infants, and it may lead to a reduced oxygen dependency in the 700- to 1000-g birth weight strata.

Mechanical ventilation of very low birth weight infants: is volume or pressure a better target variable?

OBJECTIVE

To compare the efficacy and safety of volume-controlled (VC) ventilation to time-cycled pressure-limited (TCPL) ventilation in very low birth weight infants with respiratory distress syndrome (RDS).

STUDY DESIGN

Newborns weighing between 600 and 1500 g and with a gestational age of 24 to 31 weeks who had RDS were randomized to receive either VC or TCPL ventilation and treated with a standardized protocol. The 2 modalities were compared by determining the time required to achieve a predetermined success criterion, on the basis of either the alveolar-arterial oxygen gradient <100 mm Hg or the mean airway pressure <8 cm H(2)O. Secondary outcomes included mortality, duration of mechanical ventilation, and complications commonly associated with ventilation.

RESULTS

The mean time to reach the success criterion was 23 hours in the VC group versus 33 hours in the TCPL group (P = .15). This difference was more striking in babies weighing <1000g (21 versus 58 hours; P = .03). Mean duration of ventilation with VC was 255 hours versus 327 hours with TCPL (P = .60). There were 5 deaths in the VC group and 10 deaths in the TCPL group (P = .10). The incidence of other complications was similar.

CONCLUSION

VC ventilation is safe and efficacious in very low birth weight infants and may have advantages when compared with TCPL, especially in smaller infants.

Effects of pressure support ventilation plus volume guarantee vs. high-frequency oscillatory ventilation on lung inflammation in preterm infants

The aim of the present study was to evaluate if high-frequency oscillatory ventilation (HFOV) might reduce lung inflammation in preterm infants with infant respiratory distress syndrome (RDS) in comparison with the early application of another potentially lung-protective ventilation strategy, such as pressure support ventilation plus volume guarantee (PSV + VG). Infants at less than 30 weeks of gestation with RDS were enrolled consecutively in the study if they required mechanical ventilation, and were randomly allocated to receive HFOV or PSV + VG. Bronchial aspirate samples for the measurement of interleukin (IL)-1beta, IL-8, and IL-10 were obtained before surfactant treatment (T1), after 6-18 hr of ventilation (T2), after 24-48 hr of ventilation (T3), and before extubation (T4). Thirteen patients were enrolled in the HFOV group, and 12 in the PSV + VG group. The mean values of IL-1beta, IL-8, and IL-10 at T4 were lower in the HFOV group than in the PSV + VG group. The present study demonstrates that early treatment with HFOV is associated with a reduction of lung inflammation in comparison with PSV + VG in preterm infants with RDS.

Volume-controlled intermittent mandatory ventilation in preterm infants with hypoxemic episodes

OBJECTIVE

To test the hypothesis in ventilated very low birth weight infants with frequent hypoxemic episodes that volume-controlled synchronized intermittent mandatory ventilation (SIMV) vs. pressure-controlled SIMV reduces by at least 20% the time with hypoxemia (defined as SpO(2)<80%).

DESIGN

Randomized cross-over design.

SETTING

University-based tertiary neonatal intensive care unit.

PATIENTS

15 mechanically ventilated very low birth weight infants with frequent hypoxemic episodes.

INTERVENTIONS

The infants were exposed in random order to volume-controlled and pressure-controlled SIMV for 4 h each. The target tidal volume during volume-controlled SIMV was matched to the tidal volume measured during pressure-controlled SIMV. FIO(2) was adjusted using uniform criteria to maintain SpO(2) within the target range (SpO(2) 80-92%).

MEASUREMENTS AND RESULTS

Primary outcome measure was the time with an SpO(2)<80%. Although tidal volume was maintained better during desaturations with volume-controlled SIMV, there was neither a significant difference in time with an SpO(2)<80% (expressed as proportion of total experimental time; median, interquartile range)-volume-control 10.6% (9.2-13.7%) vs. pressure-control 10.8% (8.3-13.3%)-nor in FIO(2) exposure. During volume-controlled SIMV the infants spent less time with an SpO(2) above the target range and had fewer associated bradycardias.

CONCLUSION

Volume-controlled SIMV did not decrease the time with an SpO(2)<80%, although tidal volume was better maintained during these episodes and bradycardias were less frequent than with pressure-controlled SIMV in this population of very low birth weight infants with frequent hypoxemic episodes.

Optimal strategies for newborn ventilation--a synthesis of the evidence

A variety of ventilation modes are available for the newborn. Although, there have been randomised trials assessing certain modes, these have generally only included prematurely born infants with RDS or infants with severe respiratory failure. Meta-analysis of the results of those trials has demonstrated that neither patient triggered nor high frequency oscillatory ventilation is advantageous for the prematurely born infant with RDS, but extracorporeal membrane oxygenation increases survival in infants with severe respiratory failure. Appropriately designed studies are required to determine the role of newer ventilation modes and whether forms of respiratory support avoiding intubation are less injurious to the lungs. Research should also focus on infants with other respiratory disorders, particularly BPD. Prior to further randomised trials being undertaken, it is essential that the optimum method of applying each ventilator mode is identified and it is clearly understood whether differences in ventilator/oscillator performance influence outcome.