Crossover trial comparing pressure support with synchronized intermittent mandatory ventilation

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.

Optimal Conventional Mechanical Ventilation in Full-Term Newborns: A Systematic Review

BACKGROUND

Most studies examining the best mechanical ventilation strategies in newborn infants have been performed in premature infants with respiratory distress syndrome.

PURPOSE

To identify and synthesize the evidence regarding optimal mechanical ventilation strategies in full-term newborns.

METHODS

Systematic review carried out according to the methods described in the PRISMA statement.

SEARCH STRATEGY

Searches in MEDLINE, EMBASE, CINAHL, and the Cochrane Library in March 2017, with an updated search and hand searches of reference lists of relevant articles in August 2017.

STUDY SELECTION

Studies were included if they were published between 1996 and 2017, involved newborns with gestational age of 37 to 42 weeks, were randomized controlled trials, intervention or crossover studies, and addressed outcomes affecting oxygenation and/or ventilation, and/or short-term outcomes including duration of mechanical ventilation. Because of the large heterogeneity between the studies, it was not possible to synthesize the results in meta-analyses. The results are presented according to thematic analysis.

RESULTS

No individual study reported research exclusively in newborns 37 to 42 weeks of gestation. Eight studies fulfilled the inclusion criteria, but the population in all these studies included both premature and term newborns. Evidence about mechanical ventilation tailored exclusively to full-term newborns is scarce.

IMPLICATION FOR PRACTICE

Synchronized intermittent mandatory ventilation with a 6 mL/kg tidal volume and a positive end-expiratory pressure of 8 cm H2O may be advantageous in full-term newborns.

IMPLICATION FOR RESEARCH

There is an urgent need for high-quality studies, preferably randomized controlled trials, in full-term newborns requiring mechanical ventilation to optimize oxygenation, ventilation, and short-term outcomes, potentially stratified according to the underlying pathology.

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.

Synchronized mechanical ventilation for respiratory support in newborn infants

BACKGROUND

During synchronised mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient-triggered ventilation.

OBJECTIVES

To compare the efficacy of:(i) synchronised mechanical ventilation, delivered as high-frequency positive pressure ventilation (HFPPV) or patient-triggered ventilation (assist control ventilation (ACV) and synchronous intermittent mandatory ventilation (SIMV)), with conventional ventilation or high-frequency oscillation (HFO);(ii) different types of triggered ventilation (ACV, SIMV, pressure-regulated volume control ventilation (PRVCV), SIMV with pressure support (PS) and pressure support ventilation (PSV)).

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 5), MEDLINE via PubMed (1966 to June 5 2016), EMBASE (1980 to June 5 2016), and CINAHL (1982 to June 5 2016). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials comparing synchronised ventilation delivered as HFPPV to CMV, or ACV/SIMV to CMV or HFO in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS, PRVCV and PSV) in neonates.

DATA COLLECTION AND ANALYSIS

Data were collected regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks' postmenstrual age (PMA) and duration of weaning/ventilation.Eight comparisons were made: (i) HFPPV versus CMV; (ii) ACV/SIMV versus CMV; (iii) SIMV or SIMV + PS versus HFO; iv) ACV versus SIMV; (v) SIMV plus PS versus SIMV; vi) SIMV versus PRVCV; vii) SIMV vs PSV; viii) ACV versus PSV. Data analysis was conducted using relative risk for categorical outcomes, mean difference for outcomes measured on a continuous scale.

MAIN RESULTS

Twenty-two studies are included in this review. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk (RR) for pneumothorax was 0.69, 95% confidence interval (CI) 0.51 to 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (mean difference (MD) -38.3 hours, 95% CI -53.90 to -22.69). SIMV or SIMV + PS was associated with a greater risk of moderate/severe BPD compared to HFO (RR 1.33, 95% CI 1.07 to 1.65) and a longer duration of mechanical ventilation compared to HFO (MD 1.89 days, 95% CI 1.04 to 2.74).ACV compared to SIMV was associated with a trend to a shorter duration of weaning (MD -42.38 hours, 95% CI -94.35 to 9.60). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV versus CMV and a non-significant trend towards a higher mortality rate using triggered ventilation versus CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes.

AUTHORS' CONCLUSIONS

Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronised ventilation. Triggered ventilation in the form of SIMV ± PS resulted in a greater risk of BPD and duration of ventilation compared to HFO. Optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential that newer forms of triggered ventilation are tested in randomised trials that are adequately powered to assess long-term outcomes before they are incorporated into routine clinical practice.

Synchronized mechanical ventilation for respiratory support in newborn infants

BACKGROUND

During synchronised mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient-triggered ventilation.

OBJECTIVES

To compare the efficacy of:(i) synchronised mechanical ventilation, delivered as high-frequency positive pressure ventilation (HFPPV) or patient-triggered ventilation (assist control ventilation (ACV) and synchronous intermittent mandatory ventilation (SIMV)), with conventional ventilation or high-frequency oscillation (HFO);(ii) different types of triggered ventilation (ACV, SIMV, pressure-regulated volume control ventilation (PRVCV), SIMV with pressure support (PS) and pressure support ventilation (PSV)).

SEARCH METHODS

We used the standard search strategy of the Cochrane Neonatal Review group to search the Cochrane Central Register of Controlled Trials (CENTRAL 2016, Issue 5), MEDLINE via PubMed (1966 to June 5 2016), EMBASE (1980 to June 5 2016), and CINAHL (1982 to June 5 2016). We also searched clinical trials databases, conference proceedings, and the reference lists of retrieved articles for randomised controlled trials and quasi-randomised trials.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials comparing synchronised ventilation delivered as HFPPV to CMV, or ACV/SIMV to CMV or HFO in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS, PRVCV and PSV) in neonates.

DATA COLLECTION AND ANALYSIS

Data were collected regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks' postmenstrual age (PMA) and duration of weaning/ventilation.Eight comparisons were made: (i) HFPPV versus CMV; (ii) ACV/SIMV versus CMV; (iii) SIMV or SIMV + PS versus HFO; iv) ACV versus SIMV; (v) SIMV plus PS versus SIMV; vi) SIMV versus PRVCV; vii) SIMV vs PSV; viii) ACV versus PSV. Data analysis was conducted using relative risk for categorical outcomes, mean difference for outcomes measured on a continuous scale.

MAIN RESULTS

Twenty-two studies are included in this review. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk (RR) for pneumothorax was 0.69, 95% confidence interval (CI) 0.51 to 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (mean difference (MD) -38.3 hours, 95% CI -53.90 to -22.69). SIMV or SIMV + PS was associated with a greater risk of moderate/severe BPD compared to HFO (RR 1.33, 95% CI 1.07 to 1.65) and a longer duration of mechanical ventilation compared to HFO (MD 1.89 days, 95% CI 1.04 to 2.74).ACV compared to SIMV was associated with a trend to a shorter duration of weaning (MD -42.38 hours, 95% CI -94.35 to 9.60). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV versus CMV and a non-significant trend towards a higher mortality rate using triggered ventilation versus CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes.

AUTHORS' CONCLUSIONS

Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronised ventilation. Triggered ventilation in the form of SIMV ± PS resulted in a greater risk of BPD and duration of ventilation compared to HFO. Optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential that newer forms of triggered ventilation are tested in randomised trials that are adequately powered to assess long-term outcomes before they are incorporated into routine clinical practice.

Comparison of Two Levels of Pressure Support Ventilation on Success of Extubation in Preterm Neonates: A Randomized Clinical Trial

Background:

Pressure Support Ventilation (PSV) is one of the modes of mechanical ventilation that can be used alone as a weaning strategy in neonates. However, studies on the appropriate pressure level for this mode in neonates are limited.

Objectives:

Because the use of adequate pressure support in this mode, keeping the appropriate neonate’s tidal volume, and preventing the respiratory complications, this study was aimed to compare extubation failure in the two levels of pressure support ventilation of 10 and 14 cmH2O when removing the neonates from the ventilator.

Materials & Methods:

In this randomized clinical trial 50 premature infants of 27-37 weeks with respiratory distress syndrome (RDS) were under mechanical ventilation for at least 48 hours, were randomly assigned to two groups. One group was extubated in PSV mode with pressure of 14 cmH₂O and the other with 10 cmH₂O. Extubation failure rate and complications such as pneumothorax, death and respiratory parameters were compared in the two groups.

Results:

Twenty five neonates in each group were assessed. Weaning time, extubation failure rate, and mean airway pressure was lesser in PSV of 10 cmH20 group than Level of 14 cmH2O and those differences were statistically significant (P<0.05). Difference between work of breathing, ventilation time, pneumothorax and mortality rate between two groups were not statistically significant (P>0.05).

Conclusion:

The results of our study show that extubation of the neonates using 10 CmH₂O in PSV mode increases the success rate of extubation. Although when Volume- assured PSV can be used, it is more logical to use it for guaranteeing tidal volume, but using the appropriate level of pressure support when the PSV mode is used alone is inevitable and further studies are necessary to demonstrate the level of pressure in this mode.

Acute Neonatal Respiratory Failure

Acute respiratory failure requiring assisted ventilation is one of the most common reasons for admission to the neonatal intensive care unit. Respiratory failure is the inability to maintain either normal delivery of oxygen to the tissues or normal removal of carbon dioxide from the tissues. It occurs when there is an imbalance between the respiratory workload and ventilatory strength and endurance. Definitions are somewhat arbitrary but suggested laboratory criteria for respiratory failure include two or more of the following: PaCO₂ > 60 mmHg, PaO₂ < 50 mmHg or O₂ saturation <80 % with an FiO₂ of 1.0 and pH < 7.25 (Wen et al. 2004).

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.

Neonatal ventilatory techniques - which are best for infants born at term?

Few studies have examined ventilatory modes exclusively in infants born at term. Synchronous intermittent mandatory ventilation (SIMV) compared to intermittent mandatory ventilation (IMV) is associated with a shorter duration of ventilation. The limited data on pressure support, volume targeted ventilation and neurally adjusted ventilatory assist demonstrate only short term benefits in term born infants. Favourable results of high-frequency oscillatory ventilation (HFOV) in infants with severe respiratory failure were not confirmed in the two randomised trials. Nitric oxide (NO) in term born infants, except in those with congenital diaphragmatic hernia (CDH), reduces the combined outcome of death and requirement for extracorporeal membrane oxygenation (ECMO). In infants with severe refractory hypoxaemic respiratory failure, ECMO, except in infants with CDH, reduced mortality and the combined outcome of death and severe disability at long-term follow-up. Randomised studies with long term outcomes are required to determine the optimum modes of ventilation in term born infants.

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.

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.

Synchronized mechanical ventilation for respiratory support in newborn infants

BACKGROUND

During synchronized mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. If synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing baro/volutrauma, air leak and bronchopulmonary dysplasia. Synchronous ventilation can potentially be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient triggered ventilation.

OBJECTIVES

To compare the efficacy of: (i) synchronized mechanical ventilation, delivered as high frequency positive pressure ventilation (HFPPV) or patient triggered ventilation - assist control ventilation (ACV) or synchronous intermittent mandatory ventilation (SIMV)) with conventional ventilation (CMV) (ii) different types of triggered ventilation (ACV, SIMV, pressure regulated volume control ventilation (PRVCV) and SIMV plus pressure support (PS) SEARCH STRATEGY: Searches from 1985-2007 of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2, 2007),Oxford Database of Perinatal Trials, MEDLINE, previous reviews, abstracts and symposia proceedings; hand searches of journals in the English language and contact with expert informants.

SELECTION CRITERIA

Randomised or quasi-randomised clinical trials comparing synchronized ventilation delivered as high frequency positive pressure ventilation (HFPPV) or triggered ventilation (ACV/SIMV) to conventional mechanical ventilation (CMV) in neonates. Randomised trials comparing different triggered ventilation modes (ACV, SIMV, SIMV plus PS and PRVCV) in neonates.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including mortality, air leaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intraventricular haemorrhage (grades 3 and 4), bronchopulmonary dysplasia (BPD) (oxygen dependency beyond 28 days), moderate/severe BPD (oxygen/respiratory support dependency beyond 36 weeks postmenstrual age (PMA) and duration of weaning/ventilation. Four comparisons were made: (i) HFPPV vs. CMV; (ii) ACV/SIMV vs. CMV; (iii) ACV vs. SIMV or PRVCV vs. SIMV (iv) SIMV plus PS vs. SIMV. Data analysis was conducted using relative risk for categorical outcomes, weighted mean difference for outcomes measured on a continuous scale.

MAIN RESULTS

Fourteen studies were eligible for inclusion. The meta-analysis demonstrates that HFPPV compared to CMV was associated with a reduction in the risk of air leak (typical relative risk for pneumothorax was 0.69, 95% CI 0.51, 0.93). ACV/SIMV compared to CMV was associated with a shorter duration of ventilation (weighted mean difference -34.8 hours, 95% CI -62.1, -7.4). ACV compared to SIMV was associated with a trend to a shorter duration of weaning (weighted mean difference -42.4 hours, 95% CI -94.4, 9.6). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of BPD. There was a non-significant trend towards a lower mortality rate using HFPPV vs. CMV and a non-significant trend towards a higher mortality rate using triggered ventilation vs. CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes. Since the last review, two new patient triggered modes have been included: pressure regulated volume control ventilation (PRVCV) and SIMV plus pressure support. Each of these methods of ventilation has only been tested in single randomised trials with no significant advantages in important outcomes.

AUTHORS' CONCLUSIONS

Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in air leak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronized ventilation. Further trials are needed to determine whether synchronized ventilation is associated with other benefits, but optimisation of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials. It is essential newer forms of triggered ventilation are tested in adequately powered randomised trials with long-term outcomes before they are incorporated into routine clinical practice.

Volume guarantee ventilation

Recognition that volume, not pressure, is the key factor in ventilator-induced lung injury and the association of hypocarbia with neonatal brain injury demonstrate the importance of better control delivered tidal volume. New microprocessor-based ventilator modalities combine advantages of pressure-limited ventilation with the ability to deliver a more consistent tidal volume. This article discusses automatic weaning of peak inspiratory pressure in response to changing lung compliance and respiratory effort. More consistent tidal volume, fewer excessively large breaths, lower peak pressure, less hypocapnia, shorter duration of mechanical ventilation, and lower levels of inflammatory cytokines have been documented in short-term clinical trials. It remains to be seen if these short-term benefits ultimately lead to a reduced incidence of chronic lung disease.

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.

Impact of volume guarantee ventilation on arterial carbon dioxide tension in newborn infants: a randomised controlled trial

OBJECTIVE

To compare the effects of the two modes of ventilation, synchronous intermittent positive pressure ventilation (SIPPV) and SIPPV with Volume Guarantee (VG), on arterial carbon dioxide tension (PaCO(2)) immediately after neonatal unit admission.

STUDY DESIGN

Randomised study of ventilation mode for premature inborn infants admitted to two tertiary neonatal units. After admission, infants were randomised to receive either SIPPV or VG using a Dräger Babylog 8000 plus ventilator. In the SIPPV group, peak airway pressure was set clinically. In the VG group, desired tidal volume was set at 4 ml/kg, with the ventilator adjusting peak inspiratory pressure to deliver this volume. The study was completed once the first arterial PaCO(2) was available, with the desirable range defined as 5-7 kPa.

RESULTS

PaCO(2) was significantly higher in the VG group (VG: 5.7 kPa, SIPPV: 4.9 kPa; p=0.03). The VG group had fewer out-of-range PaCO(2) values (VG: 42%, SIPPV: 57%) and fewer instances of hypocarbia <5 kPa (VG: 32%, SIPPV: 57%) but neither difference achieved statistical significance. Regression analysis showed PaCO(2) was negatively correlated with gestation (r=-0.41, p=0.01) and also with the mode of ventilation (r=0.32, p<0.05). In the VG group, all infants 23-25 weeks' gestation had out-of-range PaCO(2) values. VG significantly reduced the incidence of out-of-range PaCO(2) and hypocarbia in infants over 25 weeks' gestation (VG: 27%, SIPPV: 61%; p<0.05).

CONCLUSION

Using this strategy, VG appears feasible in the initial stabilisation of infants over 25 weeks' gestation, with a halving of the incidence of hypocarbia. In the small number of babies studied below this gestation, VG was not found to be effective.

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.

Performance of neonatal ventilators in volume targeted ventilation mode

AIM

To test the hypothesis that in volume targeted ventilation modes, ventilator performance would vary according to ventilator type.

METHODS

Four neonatal ventilators: Draeger Babylog 8000 (Draeger Medical, Germany), SLE 5000 infant ventilator (SLE systems, UK), Stephanie paediatric ventilator (F. Stephan Biomedical, German) and V.I.P. Bird gold (Viasys Healthcare, USA) were assessed using a lung model. Delivered peak pressure, inflation time, mean airway pressure (MAP) and volume were measured.

RESULTS

At the same preset ventilator settings, the Stephanie and V.I.P. Bird ventilators delivered significantly lower peak pressures and tended to deliver lower MAPs than the other two ventilators. At a volume targeted ventilation level of 5 mL, the SLE and the V.I.P. Bird delivered significantly shorter inflation times. The above differences related to differences in the airway pressure waveforms delivered by the four ventilators. The V.I.P. Bird had a less variable volume delivery, but this was always significantly lower than the preset volume guarantee level but higher than the volume displayed by the ventilator.

CONCLUSION

In volume targeted ventilation modes, performance differs between neonatal ventilator types; these results may have implications for clinical practise.

A crossover analysis of mandatory minute ventilation compared to synchronized intermittent mandatory ventilation in neonates

BACKGROUND

Mandatory minute ventilation (MMV) is a novel ventilator mode that combines synchronized intermittent mandatory ventilation (SIMV) breaths with pressure-supported spontaneous breaths to maintain a desired minute volume. The SIMV rate is automatically adjusted to maintain minute ventilation.

OBJECTIVE

To evaluate MMV in a cohort of infants without parenchymal lung disease alternately ventilated by MMV and SIMV.

DESIGN/METHODS

Neonates >33 weeks' gestational age and electively intubated for medical or surgical procedures were enrolled. Exclusionary criteria included: nonintact respiratory drive or active pulmonary disease. Infants were randomized to receive 2 hours of either SIMV or MMV and then crossed over to the other mode for 2 hours. Ventilator parameters and end-tidal CO(2) (etCO(2)) were measured via inline, mainstream monitoring and recorded every minute.

RESULTS

In total, 20 infants were evaluated. No statistically significant differences were found for overall means between etCO(2), minute volumes, peak inspiratory pressure (PIP), or positive end expiratory pressure (PEEP). However, there was a significant difference in the type of ventilator breaths given and in the mean airway pressure. Additionally, there was a statistically significant negative trend in MMV over time compared to SIMV, although this was subtle and could have been due to extreme cases.

CONCLUSIONS

Neonates with an intact respiratory drive can be successfully managed with MMV without an increase in etCO(2). While this mode generates similar PIP and PEEP, the decrease in mechanical breaths and the mean airway pressure generated with MMV may reduce the risk of some of the long-term complications associated with mechanical ventilation.

Volume-targeted versus pressure-limited ventilation in the neonate

BACKGROUND

Inflammation caused by lung overdistension (volutrauma) is thought to be important in the pathogenesis of bronchopulmonary dysplasia (BPD). Preterm infants with variable lung compliance are particularly at risk. Volume-targeted neonatal ventilators have been developed as alternatives to traditional pressure-limited ventilators. They deliver consistent, appropriate tidal volumes with the aim of reducing lung damage. It is suggested that these would provide an effective, safer means of ventilating the newborn infant.

OBJECTIVES

To determine whether volume-targeted ventilation compared with pressure-limited ventilation leads to reduced rates of death and BPD in newborn infants. Secondary objectives were to determine whether use of volume modes affected clinical outcomes such as incidence of airleak, growth, duration of ventilation or cranial ultrasound findings.

SEARCH STRATEGY

The search strategy comprised searches of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2004), MEDLINE PubMed 1966 to November 2004, 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 neonates in the first 28 days of life.

DATA COLLECTION AND ANALYSIS

Two 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 (WMD).

MAIN RESULTS

Four randomised trials were identified that addressed the outcomes of this review, recruiting a total of 178 preterm infants. All were recruited during the first 72 hours of life. Caregivers and those evaluating the outcomes of trials were not masked. All trials report high rates of follow-up, although one trial with uneven patient distribution may have had some post-randomisation attrition. No significant difference was found for death by hospital discharge, and no trials reported the combined outcome of death or BPD. When secondary outcomes were examined, pooled analysis of the trials showed that volume-targeted ventilation resulted in significant reductions in duration of ventilation [WMD -2.93 days (-4.28, -1.57)] and rates of pneumothorax [typical RR 0.23 (0.07, 0.76), RD -0.11 (-0.20, -0.03), NNT 9]. There was also a significant difference in rates of severe (Grade 3 or 4) intraventricular haemorrhage favouring the volume-targeted group [typical RR 0.32 (0.11, 0.90), RD -0.16 (-0.29, -0.03), NNT 6]. There was a reduction in the incidence of BPD (supplemental oxygen at 36 weeks) amongst surviving infants, of borderline statistical significance [typical RR 0.34 (0.11, 1.05), RD -0.14 (-0.27, 0.00), NNT=7]. No significant differences were found for failure of mode of ventilation, use of neuromuscular paralysis, patent ductus arteriosus, airleak of any sort or pulmonary interstitial emphysema alone, cranial ultrasound abnormalities or periventricular leucomalacia. None of the trials addressed growth, death after discharge from hospital or neurodevelopmental outcome.

AUTHORS' CONCLUSIONS

Although rates of death and BPD were not significantly different between the two ventilator strategies, statistically significant effects favouring volume targeting were shown for some clinically important outcomes. However, the numbers of trials and infants randomised are small and further studies are required to confirm the role of volume targeting in neonatal ventilation.

Pressure support ventilation combined with volume guarantee versus synchronized intermittent mandatory ventilation: a pilot crossover trial in premature infants in their weaning phase

OBJECTIVE

To compare pressure support ventilation combined with volume guarantee (PSV-VG) to synchronized intermittent mandatory ventilation (SIMV) regarding safety, course of blood gases, and infant-ventilator interaction in premature infants.

DESIGN

Prospective, two-treatment, crossover pilot study.

SETTING

Tertiary care neonatal unit.

PATIENTS

Twenty-five ventilated premature infants: median (range) gestational age 26.1 wks (23.1-35.7), birth weight 765 g (450-3170), age at study 5 days (2-27), in their weaning phase.

INTERVENTIONS

Infants were studied for three 30-min periods, starting from SIMV, followed by PSV-VG, and back again to SIMV. After concluding the last period, all infants were switched back to PSV-VG. On the next day, infants were studied in the opposite direction. During each period, vital parameters, ventilation parameters, degree of physical activity, duration of rhythmic breathing, and the number of vital signs monitor alarms were recorded.

MEASUREMENTS AND MAIN RESULTS

Nineteen infants (84%) could be successfully ventilated with PSV-VG till the next day. PSV-VG achieved a similar oxygenation level as SIMV but with significantly lower ventilation pressures. Comparable ventilation was achieved, but infants with strong respiratory drive were more liable to hyperventilation episodes during PSV-VG. Although infants breathed more rhythmically during PSV-VG, suggesting better infant-ventilator synchrony, the infants' behavioral state and the fluctuations in blood gases did not differ.

CONCLUSIONS

The potentials of PSV-VG to improve infant-ventilator synchrony and to decrease pressure needed to ventilate premature lungs are promising, even though the changes were small. However, its benefits during acute illness and on the final outcome remain to be proven.

Is there an advantage of using pressure support ventilation with volume guarantee in the initial management of premature infants with respiratory distress syndrome? A pilot study

OBJECTIVE

To evaluate the feasibility of using the pressure support ventilation with volume guarantee (PSV-VG) as an initial ventilatory mode in preterm infants with respiratory distress syndrome (RDS) after surfactant treatment to achieve accelerated weaning of peak inspiratory pressure (PIP) and mean airway pressure (MAP).

STUDY DESIGN

Initial 24-hour ventilatory parameters were compared in two groups of preterm infants managed by PSV-VG and the synchronized intermittent mandatory ventilation (SIMV) mode in a randomized controlled pilot study after surfactant treatment for RDS. A total of 16 babies were randomized to PSV-VG (1198+/-108 g [mean+/-SEM]; 27.9+/-0.6 weeks) and 18 babies to SIMV (birth weight 1055+/-77 g; gestational age 27.4+/-0.5 weeks). Repeated measures analysis of variance was used to compare serial values of PIP and MAP in the two groups.

RESULTS

The PIP and MAP decreased over time (p<0.001) during the first 24 hours after surfactant administration in both groups but the decrease in MAP was faster in the SIMV group compared to PSV-VG group (p=0.035). The median numbers of blood gases during the first 24 hours were four and two in the SIMV and PSV-VG groups, respectively (p<0.001). The overall outcomes were not significantly different between the two groups.

CONCLUSION

PSV-VG did not offer any ventilatory advantage over SIMV in the initial management of surfactant-treated premature newborns with RDS except for minimizing the number of blood gases.

Synchronized mechanical ventilation for respiratory support in newborn infants

BACKGROUND

During synchronized mechanical ventilation, positive airway pressure and spontaneous inspiration coincide. Thus, if synchronous ventilation is provoked, adequate gas exchange should be achieved at lower peak airway pressures, potentially reducing barotrauma and hence airleak and chronic lung disease. Synchronous ventilation can be achieved by manipulation of rate and inspiratory time during conventional ventilation and employment of patient assisted ventilation.

OBJECTIVES

To compare (i) the efficacy of synchronized mechanical ventilation, delivered as high frequency positive pressure ventilation or triggered ventilation (patient triggered ventilation (PTV) or synchronous intermittent mandatory ventilation (SIMV)) with conventional ventilation(ii) different types of triggered ventilation

SEARCH STRATEGY

Searches from 1985-2004 of the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 3, 2004), Oxford Database of Perinatal Trials, MEDLINE, previous reviews, abstracts and symposia proceedings; hand searches of journals in the English language and contact with expert informants.

SELECTION CRITERIA

Randomized or quasi randomized clinical trials comparing synchronized ventilation delivered as high frequency positive pressure ventilation (HFPPV) or triggered ventilation (PTV/SIMV) to conventional mechanical ventilation (CMV) in neonates. Randomized trials comparing different triggered ventilation modes (PTV and SIMV) in neonates.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes including mortality, airleaks (pneumothorax or pulmonary interstitial emphysema (PIE)), severe intracerebral haemorrhage (grades 3 and 4), chronic lung disease (oxygen dependency beyond 28 days) and duration of weaning/ventilation. Three comparisons were made: (i) HFPPV vs CMV; (ii) PTV/SIMV vs CMV; (iii) PTV vs SIMV. Data analysis was conducted using relative risk for categorical outcomes, weighted mean difference for outcomes measured on a continuous scale.

MAIN RESULTS

Eleven studies were eligible for inclusion. The meta-analysis demonstrate that HFPPV compared to CMV was associated with a reduction in the risk of airleak (typical relative risk for pneumothorax was 0.69, 95% CI 0.51, 0.93). PTV/SIMV compared to CMV was associated with a shorter duration of ventilation (weighted mean difference -34.8 hours, 95% CI -62.1, -7.4). PTV compared to SIMV was associated with a trend to a shorter duration of weaning (weighted mean difference -42.4 hours, 95% CI -94.4, 9.6). Neither HFPPV nor triggered ventilation was associated with a significant reduction in the incidence of chronic lung disease. There was a non-significant trend towards a lower mortality rate using HFPPV versus CMV, but a non-significant trend towards a higher mortality rate using triggered ventilation versus CMV. No disadvantage of HFPPV or triggered ventilation was noted regarding other outcomes.

REVIEWERS' CONCLUSIONS

Compared to conventional ventilation, benefit is demonstrated for both HFPPV and triggered ventilation with regard to a reduction in airleak and a shorter duration of ventilation, respectively. In none of the trials was complex respiratory monitoring undertaken and thus it is not possible to conclude that the mechanism of producing those benefits is by provocation of synchronized ventilation. Further trials are needed to determine whether synchronized ventilation is associated with other benefits, but optimization of trigger and ventilator design with respect to respiratory diagnosis is encouraged before embarking on further trials.