Prospective randomized multicenter comparison of high-frequency oscillatory ventilation and conventional ventilation in preterm infants of less than 30 weeks with respiratory distress syndrome

The critical role of technologies in neonatal care

Neonatal care has made significant advances in the last few decades. As a result, mortality and morbidity in high-risk infants, such as extremely preterm infants or those infants with birth-related brain injury, has reduced significantly. Many of these advances have been facilitated or delivered through development of medical technologies allowing clinical teams to be better supported with the care they deliver or provide new therapies and diagnostics to improve management. The delivery of neonatal intensive care requires the provision of medical technologies that are easy to use, reliable, accurate and ideally developed for the unique needs of the newborn population. Many technologies have been developed and commercialised following adult trials without ever being studied in neonatal patients despite the unique characteristics of this population. Increasingly, funders and industry are recognising this major challenge which has resulted in initiatives to develop new ideas from concept through to clinical care. This review explores some of the key medical technologies used in neonatal care and the evidence to support their adoption to improve outcomes. A number of devices have yet to realise their full potential and will require further development to optimise and find their ideal target population and clinical benefit. Examples of emerging technologies, which may soon become more widely used, are also discussed. As neonatal care relies more on medical technologies, we need to be aware of the impact on care pathways, especially from a human factors approach, the associated costs and subsequent benefits to patients alongside the supporting evidence.

Effect of individualized positive end-expiratory pressure based on electrical impedance tomography guidance on pulmonary ventilation distribution in patients who receive abdominal thermal perfusion chemotherapy

Background

Electrical impedance tomography (EIT) has been shown to be useful in guiding individual positive end-expiratory pressure titration for patients with mechanical ventilation. However, the appropriate positive end-expiratory pressure (PEEP) level and whether the individualized PEEP needs to be adjusted during long-term surgery (>6 h) were unknown. Meanwhile, the effect of individualized PEEP on the distribution of pulmonary ventilation in patients who receive abdominal thermoperfusion chemotherapy is unknown. The primary aim of this study was to observe the effect of EIT-guided PEEP on the distribution of pulmonary ventilation in patients undergoing cytoreductive surgery (CRS) combined with hot intraperitoneal chemotherapy (HIPEC). The secondary aim was to analyze their effect on postoperative pulmonary complications.

Methods

A total of 48 patients were recruited and randomly divided into two groups, with 24 patients in each group. For the control group (group A), PEEP was set at 5 cm H2O, while in the EIT group (group B), individual PEEP was titrated and adjusted every 2 h with EIT guidance. Ventilation distribution, respiratory/circulation parameters, and PPC incidence were compared between the two groups.

Results

The average individualized PEEP was 10.3 ± 1.5 cm H2O, 10.2 ± 1.6 cm H2O, 10.1 ± 1.8 cm H2O, and 9.7 ± 2.1 cm H2O at 5 min, 2 h, 4 h, and 6 h after tracheal intubation during CRS + HIPEC. Individualized PEEP was correlated with ventilation distribution in the regions of interest (ROI) 1 and ROI 3 at 4 h mechanical ventilation and ROI 1 at 6 h mechanical ventilation. The ventilation distribution under individualized PEEP was back-shifted for 6 h but moved to the control group's ventral side under PEEP 5 cm H2O. The respiratory and circulatory function indicators were both acceptable either under individualized PEEP or PEEP 5 cm H2O. The incidence of total PPCs was significantly lower under individualized PEEP (66.7%) than PEEP 5 cm H2O (37.5%) for patients with CRS + HIPEC.

Conclusion

The appropriate individualized PEEP was stable at approximately 10 cm H2O during 6 h for patients with CRS + HIPEC, along with better ventilation distribution and a lower total PPC incidence than the fixed PEEP of 5 cm H2O.Clinical trial registration: identifier ChiCTR1900023897.

Congenital Cataracts in Preterm Infants: A Review

A congenital cataract is one of the most treatable causes of visual impairment during infancy. Preterm infants who are born alive before 37 weeks of pregnancy need special care, including proper age documentation, preoperative assessment, and monitoring postoperatively for at least 24 hours. Management of cataracts in preterm infants is critical as regards the timing of cataract surgery and the challenges associated with cataract surgery and posterior segment management for retinopathy of prematurity (ROP). This narrative review aims to provide comprehensive insight and up-to-date clinical research findings regarding the pathophysiology and management of congenital cataracts in preterm infants.

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.

Lung protection strategy with high-frequency oscillatory ventilation improves respiratory outcomes at two years in preterm respiratory distress syndrome: a before and after, quality improvement study

INTRODUCTION

Bronchopulmonary dysplasia (BPD) remains one of the major challenges of extreme prematurity. High-frequency oscillatory ventilation (HFOV) with volume guarantee (HFOV-VG) can be used as an early-rescue ventilation to protect developing lungs. However, the studies exploring the impact of this ventilatory strategy on neonatal respiratory morbidity are very limited. This study aimed at documenting the improvement in respiratory outcomes in mechanically ventilated preterm newborns, after the implementation of a new mechanical ventilation respiratory bundle.

METHODS

A prospective, quality improvement study was conducted between January 2012 and December 2018 in a third level NICU in Madrid, Spain. Infants born <32 weeks of gestation with severe respiratory distress syndrome (RDS) and requiring invasive mechanical ventilation were included. The intervention consisted of a new ventilation respiratory care bundle, with HFOV as early rescue therapy using low high-frequency tidal volumes (Vthf) and higher frequencies (15-20 Hz). Criteria for HFOV start were impaired oxygenation or ventilation on conventional ventilation, or peak inspiratory pressures >15 cmH₂O. Two cohorts of mechanically ventilated patients were compared, cohort 1 (2012-2013, baseline period) and cohort 2 (2016-2018, after implementation of the new bundle). Clinical outcomes at 36 weeks and 2 years of postmenstrual age were compared between the groups.

RESULTS

A total of 216 patients were included, the median gestational age was 26 weeks (IQR 25-28) and median birth weight was 895 g (IQR 720-1160). There were no significant differences in survival between the groups, but patients with the protective ventilation strategy (cohort 2) had higher survival without BPD 2-3 (OR 2.93, 95%CI 1.41-6.05). At 2 years of postmenstrual age, patients in cohort 2 also had a higher survival free of baseline respiratory treatment and hospital respiratory admissions than the control group (adjusted OR 2.33, 95%CI 1.10-4.93, p=.03). The results did not suggest significant differences in neurologic development.

CONCLUSIONS

In extreme premature related severe respiratory failure, the use of a lung protective HFOV-VG strategy was proven to be a useful quality improvement intervention in our unit, leading to better pulmonary outcomes at 36 weeks and additional improved respiratory prognosis at two years of age.

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.

Pathogenesis and prevention of intraventricular hemorrhage

Despite improvements in the mortality rates of preterm infants, rates of germinal matrix intraventricular hemorrhage (IVH) have remained static with an overall incidence of 25% in infants less than 32 weeks. The importance of the lesion relates primarily to the underlying injury to the developing brain and the associated long-term neurodevelopmental consequences. This clinical-orientated review focuses on the pathogenesis of IVH and discusses the evidence behind proposed prevention strategies.

Longitudinal changes in lung function in very prematurely born young people receiving high-frequency oscillation or conventional ventilation from birth

OBJECTIVE

To examine changes in lung function over time in extremely prematurely born adolescents.

WORKING HYPOTHESIS

Changes in lung function during adolescence would vary by ventilation mode immediately after birth.

STUDY DESIGN

Longitudinal follow-up study.

PATIENT SUBJECT SELECTION

Participants from the United Kingdom Oscillation Study who were randomized at birth to high-frequency oscillation (HFO) or conventional ventilation (CV) were assessed at 11-14 years (n = 319) and at 16-19 years (n = 159).

METHODOLOGY

Forced expiratory flow (FEF), forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and lung volumes including functional residual capacity (FRC) were reported as z-scores. The diffusion capacity of the lungs for carbon monoxide (DLCO) was measured. Lung function trajectories were compared by mode of ventilation using mixed models. Changes in z-scores were scaled to 5-year average follow-up.

RESULTS

There were significant changes in the mean FEF75, FEF50, FEF25, FEV1, FVC, and DLCO z-scores within the CV and HFO cohorts, but no significant differences in the changes between the two groups. The mean FRC z-score increased in both groups, with an average change of greater than one z-score. The mean FEV1/FVC z-score increased significantly in the CV group, but not in the HFO group (difference in slopes: p = 0.02). Across the population, deterioration in lung function was associated with male sex, white ethnicity, lower gestational age at birth, postnatal corticosteroids, oxygen dependency at 36 weeks postmenstrual age, and lower birth weight, but not ventilation mode.

CONCLUSIONS

There was little evidence that the mode of ventilation affected changes in lung function over time.

Mechanical Ventilation in Pediatric and Neonatal Patients

Pediatric acute respiratory distress syndrome (PARDS) remains a significant cause of morbidity and mortality, with mortality rates as high as 50% in children with severe PARDS. Despite this, pediatric lung injury and mechanical ventilation has been poorly studied, with the majority of investigations being observational or retrospective and with only a few randomized controlled trials to guide intensivists. The most recent and universally accepted guidelines for pediatric lung injury are based on consensus opinion rather than objective data. Therefore, most neonatal and pediatric mechanical ventilation practices have been arbitrarily adapted from adult protocols, neglecting the differences in lung pathophysiology, response to injury, and co-morbidities among the three groups. Low tidal volume ventilation has been generally accepted for pediatric patients, even in the absence of supporting evidence. No target tidal volume range has consistently been associated with outcomes, and compliance with delivering specific tidal volume ranges has been poor. Similarly, optimal PEEP has not been well-studied, with a general acceptance of higher levels of F_iO₂ and less aggressive PEEP titration as compared with adults. Other modes of ventilation including airway pressure release ventilation and high frequency ventilation have not been studied in a systematic fashion and there is too little evidence to recommend supporting or refraining from their use. There have been no consistent outcomes among studies in determining optimal modes or methods of setting them. In this review, the studies performed to date on mechanical ventilation strategies in neonatal and pediatric populations will be analyzed. There may not be a single optimal mechanical ventilation approach, where the best method may simply be one that allows for a personalized approach with settings adapted to the individual patient and disease pathophysiology. The challenges and barriers to conducting well-powered and robust multi-institutional studies will also be addressed, as well as reconsidering outcome measures and study design.

High-frequency ventilation in preterm infants and neonates

High-frequency ventilation (HFV) has been used as a respiratory support mode for neonates for over 30 years. HFV is characterized by delivering tidal volumes close to or less than the anatomical dead space. Both animal and clinical studies have shown that HFV can effectively restore lung function, and potentially limit ventilator-induced lung injury, which is considered an important risk factor for developing bronchopulmonary dysplasia (BPD). Knowledge of how HFV works, how it influences cardiorespiratory physiology, and how to apply it in daily clinical practice has proven to be essential for its optimal and safe use. We will present important aspects of gas exchange, lung-protective concepts, clinical use, and possible adverse effects of HFV. We also discuss the study results on the use of HFV in respiratory distress syndrome in preterm infants and respiratory failure in term neonates. IMPACT: Knowledge of how HFV works, how it influences cardiorespiratory physiology, and how to apply it in daily clinical practice has proven to be essential for its optimal and safe use. Therefore, we present important aspects of gas exchange, lung-protective concepts, clinical use, and possible adverse effects of HFV. The use of HFV in daily clinical practice in lung recruitment, determination of the optimal continuous distending pressure and frequency, and typical side effects of HFV are discussed. We also present study results on the use of HFV in respiratory distress syndrome in preterm infants and respiratory failure in term neonates.

Surfactant replacement therapy: from biological basis to current clinical practice

This review summarizes the current knowledge on the physiological action of endogenous and exogenous pulmonary surfactant, the role of different types of animal-derived and synthetic surfactants for RDS therapy, different modes of administration, potential risks and strategies of ventilation, and highlights the most promising aims for future development. Scientists have clarified the physicochemical properties and functions of the different components of surfactant, and part of this successful research is derived from the characterization of genetic diseases affecting surfactant composition or function. Knowledge from functional tests of surfactant action, its immunochemistry, kinetics and homeostasis are important also for improving therapy with animal-derived surfactant preparations and for the development of modified surfactants. In the past decade newly designed artificial surfactants and additives have gained much attention and have proven different advantages, but their particular role still has to be defined. For clinical practice, alternative administration techniques as well as postsurfactant ventilation modes, taking into account alterations in lung mechanics after surfactant placement, may be important in optimizing the potential of this most important drug in neonatology.

Ventilation strategies in transition from neonatal respiratory distress to chronic lung disease

Despite the advance in neonatal care over the past few decades, preventing preterm infants with respiratory distress syndrome progress to bronchopulmonary dysplasia remained challenging. In this review, we will discuss the respiratory support strategies in preterm infants with RDS evolving into BPD based on the changes in pulmonary mechanics and pathophysiology as well as currently available evidence.

Lung-protective ventilatory strategies in intubated preterm neonates with RDS

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

Effect of the I/E ratio on CO2 removal during high-frequency oscillatory ventilation with volume guarantee in a neonatal animal model of RDS

The objective of this study was to analyze the effect of I/E ratio on carbon dioxide (CO2) elimination during high-frequency oscillatory ventilation (HFOV) combined with volume guarantee (VG). Five 2-day-old piglets were studied before and after a bronchoalveolar lavage (BAL). The effect of an I/E ratio of 1:1 and 1:2 with (VG-ON) and without VG (VG-OFF) on PaCO2, as well as delta and mean airway pressures at the airway opening (∆Phf-ao, mPaw-ao) and at the tracheal level (∆Phf-t, mPaw-t) were evaluated at frequencies of 5, 8, 11, and 14 Hz. With the VG-ON, PaCO2 was significant lower with the I/E ratio of 1:2 at 5 Hz compared with the 1:1. mPaw-t was higher than mPaw-ao, with 1:1 I/E ratio, and on VG-ON, this difference was statistically significant.

CONCLUSION

"In this animal study and with this ventilator, the I/E ratio of 1:1 compared to 1:2 in HFOV and VG-ON did not produce a higher CO2 lavage as when HFOV was used without the VG modality. Even more, a lower PaCO2 was found when using the lower frequency and 1:2 ratio compared to 1:1. So in contrast to non-VG HFOV mode, using a fixed tidal volume, no significant changes on CO2 elimination are observed during HFOV when the I/E ratios of 1:1 and 1:2 are compared at different frequencies."

WHAT IS KNOWN

•The tidal volume on HFOV is determinant in CO 2 removal, and this is generated by delta pressure and the length of the inspiratory time. What is New: •HFOV combined with VG, an I/E ratio of 1:2 is more effective to remove CO 2 , and this is not related to the tidal volume.

Mechanical Ventilation and Bronchopulmonary Dysplasia

Mechanical ventilation is an important potentially modifiable risk factor for the development of bronchopulmonary dysplasia. Effective use of noninvasive respiratory support reduces the risk of lung injury. Lung volume recruitment and avoidance of excessive tidal volume are key elements of lung-protective ventilation strategies. Avoidance of oxidative stress, less invasive methods of surfactant administration, and high-frequency ventilation are also important factors in lung injury prevention.

Elective high frequency oscillatory ventilation versus conventional ventilation for acute pulmonary dysfunction in preterm infants

BACKGROUND

Respiratory failure due to lung immaturity is a major cause of mortality in preterm infants. Although the use of intermittent positive pressure ventilation (IPPV) in neonates with respiratory failure saves lives, its use is associated with lung injury and chronic lung disease. A newer form of ventilation called high frequency oscillatory ventilation has been shown in experimental studies to result in less lung injury.

OBJECTIVES

The objective of this review was to determine the effect of the elective use of high frequency oscillatory ventilation (HFOV) as compared to conventional ventilation (CV) on the incidence of chronic lung disease (CLD), mortality and other complications associated with prematurity and assisted ventilation in preterm infants who were mechanically ventilated for respiratory distress syndrome (RDS).

SEARCH METHODS

Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts, conference and symposia proceedings; and from expert informants and handsearching of journals by The Cochrane Collaboration, mainly in the English language. The search was updated in January 2009 and again in November 2014.

SELECTION CRITERIA

Randomised controlled trials comparing HFOV and CV in preterm or low birth weight infants with pulmonary dysfunction, mainly due to RDS, who required assisted ventilation. Randomisation and commencement of treatment needed to be as soon as possible after the start of CV and usually in the first 12 hours of life.

DATA COLLECTION AND ANALYSIS

The methodological quality of each trial was independently reviewed by the review authors. The standard effect measures were relative risk (RR) and risk difference (RD). From 1/RD the number needed to benefit (NNTB) to produce one outcome was calculated. For all measures of effect, 95% confidence intervals (CIs) were used. For interpretation of subgroup analyses, a P value for subgroup differences as well as the I(2) statistic for between-subgroup heterogeneity were calculated. Meta-analysis was performed using both a fixed-effect and a random-effects model. Where heterogeneity was over 50%, the random-effects model RR was also reported.

MAIN RESULTS

Nineteen eligible studies involving 4096 infants were included. Meta-analysis comparing HFOV with CV revealed no evidence of effect on mortality at 28 to 30 days of age or at approximately term equivalent age. These results were consistent across studies and in subgroup analyses. The risk of CLD in survivors at term equivalent gestational age was significantly reduced with the use of HFOV but this effect was inconsistent across studies, even after the meta-analysis was restricted to studies that applied a high lung volume strategy with HFOV. Subgroup analysis by HFOV strategy showed a similar effect in trials with a more strict lung volume recruitment strategy, targeting a very low fraction of inspired oxygen (FiO2), and trials with a less strict lung volume recruitment strategy and with a somewhat higher or unspecified target FiO2. Subgroup analyses by age at randomisation, routine surfactant use or not, type of high frequency ventilator (oscillator versus flow interrupter), inspiratory to expiratory (I:E) ratio of high frequency ventilator (1:1 versus 1:2) and CV strategy (lung protective or not) could not sufficiently explain the heterogeneity. Pulmonary air leaks, defined as gross air leaks or pulmonary interstitial emphysema, occurred more frequently in the HFOV group, whereas the risk of severe retinopathy of prematurity was significantly reduced.Although in some studies an increased risk of severe grade intracranial haemorrhage and periventricular leukomalacia was found, the overall meta-analysis revealed no significant differences in effect between HFOV and CV. The short-term neurological morbidity with HFOV was only found in the subgroup of two trials not using a high volume strategy with HFOV. Most trials did not find a significant difference in long-term neurodevelopmental outcome, although one recent trial showed a significant reduction in the risk of cerebral palsy and poor mental development.

AUTHORS' CONCLUSIONS

There is evidence that the use of elective HFOV compared with CV results in a small reduction in the risk of CLD, but the evidence is weakened by the inconsistency of this effect across trials. Probably many factors, both related to the intervention itself as well as to the individual patient, interact in complex ways. In addition, the benefit could be counteracted by an increased risk of acute air leak. Adverse effects on short-term neurological outcomes have been observed in some studies but these effects are not significant overall. Most trials reporting long-term outcome have not identified any difference.

Prognosis of very preterm infants with severe respiratory distress syndrome receiving mechanical ventilation

OBJECTIVE

To evaluate the prognosis of very preterm infants with severe respiratory distress syndrome (RDS) receiving mechanical ventilation.

METHODS

A total of 288 preterm infants mechanically ventilated for severe RDS and completed follow-up till 18 months of corrected age comprised these study subjects. The associations of prenatal and postnatal factors, mode and duration of conventional mechanical ventilation (CMV), medication and treatment, and complications with cerebral palsy or mental developmental index (MDI) < 70 at 18 months of age were analyzed.

RESULTS

The incidences of CP among study subjects were 17, 5, and 2% in infants less than 28, 28-30, and 30-32 weeks, respectively. The incidences of MDI < 70 were 49, 24, and 13% in infants less than 28 weeks, 28-30 weeks, and 30-32 weeks, respectively. Antenatal corticosteroids, preeclampsia, fetal distress, early and late bacteremia, and decreased weight gain were associated with CP and an MDI < 70. In the CP and MDI < 70 groups, the number of infants on CMV was significantly higher than on high-frequency oscillatory ventilation (HFOV). Longer duration of mechanical ventilation and blood transfusions were associated with an increased risk of having an MDI < 70 or CP. The complications in study subjects associated with an MDI < 70 or CP were BPD, NEC, and IVH grade III-IV.

CONCLUSION

The prognosis of very preterm infants with severe RDS may be influenced by several prenatal and postnatal factors. HFOV although decreased the duration of mechanical ventilation, whether it will decrease the incidence of neurodevelopmental disability, needs to be explored further.

Late outcomes of a randomized trial of high-frequency oscillation in neonates

BACKGROUND

Results from an observational study involving neonates suggested that high-frequency oscillatory ventilation (HFOV), as compared with conventional ventilation, was associated with superior small-airway function at follow-up. Data from randomized trials are needed to confirm this finding.

METHODS

We studied 319 adolescents who had been born before 29 weeks of gestation and had been enrolled in a multicenter, randomized trial that compared HFOV with conventional ventilation immediately after birth. The trial involved 797 neonates, of whom 592 survived to hospital discharge. We compared follow-up data from adolescents who had been randomly assigned to HFOV with follow-up data from those who had been randomly assigned to conventional ventilation, with respect to lung function and respiratory health, health-related quality of life, and functional status, as assessed with the use of questionnaires completed when the participants were 11 to 14 years of age. The primary outcome was forced expiratory flow at 75% of the expired vital capacity (FEF75).

RESULTS

The HFOV group had superior results on a test of small-airway function (z score for FEF75, -0.97 with HFOV vs. -1.19 with conventional therapy; adjusted difference, 0.23 [95% confidence interval, 0.02 to 0.45]). There were significant differences in favor of HFOV in several other measures of respiratory function, including forced expiratory volume in 1 second, forced vital capacity, peak expiratory flow, diffusing capacity, and impulse-oscillometric findings. As compared with the conventional-therapy group, the HFOV group had significantly higher ratings from teachers in three of eight school subjects assessed, but there were no other significant differences in functional outcomes.

CONCLUSIONS

In a randomized trial involving children who had been born extremely prematurely, those who had undergone HFOV, as compared with those who had received conventional ventilation, had superior lung function at 11 to 14 years of age, with no evidence of poorer functional outcomes. (Funded by the National Institute for Health Research Health Technology Assessment Programme and others.).

Incidence of hypo- and hyper-capnia in a cross-sectional European cohort of ventilated newborn infants

OBJECTIVE

To determine the incidence of hypo- and hyper-capnia in a European cohort of ventilated newborn infants.

DESIGN AND SETTING

Two-point cross-sectional prospective study in 173 European neonatal intensive care units.

PATIENTS AND METHODS

Patient characteristics, ventilator settings and measurements, and blood gas analyses were collected for endotracheally ventilated newborn infants on two separate dates.

RESULTS

A total of 1569 blood gas analyses were performed in 508 included patients with a mean±SD Pco2 of 48±12 mm Hg or 6.4±1.6 kPa (range 17-104 mm Hg or 2.3-13.9 kPa). Hypocapnia (Pco2<30 mm Hg or 4 kPa) and hypercapnia (Pco2>52 mm Hg or 7 kPa) was present in, respectively, 69 (4%) and 492 (31%) of the blood gases. Hypocapnia was most common in the first 3 days of life (7.3%) and hypercapnia after the first week of life (42.6%). Pco2 was significantly higher in preterm infants (49 mm Hg or 6.5 kPa) than term infants (43 mm Hg or 5.7 kPa) and significantly lower during pressure-limited ventilation (47 mm Hg or 6.3±1.6 kPa) compared with volume-targeted ventilation (51 mm Hg or 6.8±1.7 kPa) and high-frequency ventilation (50 mm Hg or 6.7±1.7 kPa).

CONCLUSIONS

This study shows that hypocapnia is a relatively uncommon finding during neonatal ventilation. The higher incidence of hypercapnia may suggest that permissive hypercapnia has found its way into daily clinical practice.

Comparison of High Frequency Positive Pressure Mechanical Ventilation (HFPPV) With Conventional Method in the Treatment of Neonatal Respiratory Failure

Background

Respiratory failure is a major problem in neonatal medicine in all over the world and has different causes. Using mechanical ventilation is one of its major treatments.

Objectives

Different strategies have been expressed in this context, including high frequency mechanical ventilation.

Patients and Methods

This study is a prospective randomized clinical trial conducted on all newborns with respiratory failure hospitalized in the NICU of Tehran vali-asr Hospital during 2009.These patients were divided in to two groups through block Randomization method; conventional mechanical ventilation group and high frequency ventilation group.

Results

Intraventricular hemorrhage (IVH) and air leak (e.g. pneumothorax) were less in HFPPV group than conventional group (P = 0.012 and P = 0.038). The mean time needed for mechanical ventilation was lower in HFPPV group, but this difference was not statistically significant (P = 0.922). Needing to O2 in 28 days of age was almost equal in both groups (P = 0. 99). Mortality, and refractory hypoxia and PVL were lower in HFPPV group, but the difference was not statistically significant (P = 0.301, P = 0. 508, P = 0. 113).

Conclusions

Treatment of neonatal respiratory failure with high rate mechanical ventilation may reduce some complications.

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.

Elective high-frequency oscillatory versus conventional ventilation in preterm infants: a systematic review and meta-analysis of individual patients' data

BACKGROUND

Population and study design heterogeneity has confounded previous meta-analyses, leading to uncertainty about effectiveness and safety of elective high-frequency oscillatory ventilation (HFOV) in preterm infants. We assessed effectiveness of elective HFOV versus conventional ventilation in this group.

METHODS

We did a systematic review and meta-analysis of individual patients' data from 3229 participants in ten randomised controlled trials, with the primary outcomes of death or bronchopulmonary dysplasia at 36 weeks' postmenstrual age, death or severe adverse neurological event, or any of these outcomes.

FINDINGS

For infants ventilated with HFOV, the relative risk of death or bronchopulmonary dysplasia at 36 weeks' postmenstrual age was 0.95 (95% CI 0.88-1.03), of death or severe adverse neurological event 1.00 (0.88-1.13), or any of these outcomes 0.98 (0.91-1.05). No subgroup of infants (eg, gestational age, birthweight for gestation, initial lung disease severity, or exposure to antenatal corticosteroids) benefited more or less from HFOV. Ventilator type or ventilation strategy did not change the overall treatment effect.

INTERPRETATION

HFOV seems equally effective to conventional ventilation in preterm infants. Our results do not support selection of preterm infants for HFOV on the basis of gestational age, birthweight for gestation, initial lung disease severity, or exposure to antenatal corticosteroids.

FUNDING

Nestlé Belgium, Belgian Red Cross, and Dräger International.

Sequential meta-analysis: an efficient decision-making tool

BACKGROUND

A cumulative meta-analysis of successive randomized controlled trials (RCTs) can be used to decide whether enough evidence has been obtained comparing a control and an intervention treatment or whether a new RCT should be initiated. In general, no adjustment is made for repeatedly testing the null hypothesis of treatment equivalence on cumulative data. Neither can the power of the statistical test be quantified. Recently, trial sequential analysis (TSA) was suggested to '. . . establish when firm evidence is reached in cumulative meta-analysis'. TSA is based on alpha-spending functions and necessitates a prior estimate of the total information size. Various information sizes were suggested.

PURPOSE

The aim of this study is to compare TSA with sequential meta-analysis (SMA) following Whitehead's boundaries approach.

METHODS

We compare TSA and SMA by re-analysis of a number of published examples.

RESULTS

Re-analysis of the examples shows that for an SMA: (1) no prior estimate for total information size is necessary and thus one set of boundaries suffices; (2) stopping a cumulative meta-analysis for futility is an option; (3) the power can be quantified; (4) point and interval estimates are adjusted for the multiple testing; and (5) gains in efficiency can be achieved, both for efficacy and for futility and thus ethical and economical benefits can be obtained.

LIMITATIONS

Estimates for between-trial variability are unstable for a small number of trials. The behavior of a newly proposed estimate should be subject of further investigation.

CONCLUSION

SMA is a useful tool to investigate the cumulative evidence from successive RCTs.

High-frequency oscillatory ventilation is not associated with increased risk of neuropathology compared with positive pressure ventilation: a preterm primate model

High-frequency oscillatory ventilation (HFOV) may improve pulmonary outcome in very preterm infants, but the effects on the brain are largely unknown. We hypothesized that early prolonged HFOV compared with low volume positive pressure ventilation (LV-PPV) would not increase the risk of delayed brain growth or injury in a primate model of neonatal chronic lung disease. Baboons were delivered at 127 +/- 1 d gestation (dg; term approximately 185 dg), ventilated for 22-29 d with either LV-PPV (n = 6) or HFOV (n = 5). Gestational controls were delivered at 153 dg (n = 4). Brains were assessed using quantitative histology. Body, brain, and cerebellar weights were lower in both groups of prematurely delivered animals compared with controls; the brain to body weight ratio was higher in HFOV compared with LV-PPV, and the surface folding index was lower in the LV-PPV compared with controls. In both ventilated groups compared with controls, there was an increase in astrocytes and microglia and a decrease in oligodendrocytes (p < 0.05) in the forebrain and a decrease in cerebellar granule cell proliferation (p < 0.01); there was no difference between ventilated groups. LV-PPV and HFOV ventilation in prematurely delivered animals is associated with decreased brain growth and an increase in subtle neuropathologies; HFOV may minimize adverse effects on brain growth.

High-frequency oscillatory ventilation for acute respiratory distress syndrome

OBJECTIVE

To evaluate the effectiveness of HFOV in pediatric patients with acute respiratory distress syndrome.

METHODS

In this retrospective study, we reviewed all 20 pediatric patients, who were consecutively ventilated with HFOV in the pediatric intensive care unit of a tertiary medical center, from January 2006 to February 2007.

RESULTS

A total of 20 patients were enrolled. The median age of the subjects was 70 (3-168) months; 10 were male. All patients received conventional ventilation before HFOV. After initiation of HFOV, there was an immediate and sustained increase in PaO(2)/FiO(2) ratio. The PaO(2)/FiO(2) ratio was elevated and OI was decreased significantly after 10-20 minutes and maintained for at least 48 hours (p= 0.03, both). Thirteen of the 20 patients were successfully weaned. No significant change in the mean arterial pressure and heart rate was noted after HFOV. Overall survival rate was 65%. Of 20 patients, 11 patients suffered from extrapulmonary ARDS (ARDSexp) and 9 from pulmonary ARDS (ARDSp). When HFOV was initiated, there was significant increase in PaO(2)/FiO(2) and decrease in OI in ARDSexp compared to ARDSp (p= 0.03, both). Also mortality rate was significantly lower in patients with ARDSexp (9% vs.66%), (p= 0.01).

CONCLUSION

In our study, HFOV was effective in oxygenation and seems to be safe for pediatric ARDS patients. HFOV affected ARDSp and ARDSexp paediatric patients differently. However prospective, randomized controlled trials are needed to identify its benefits over conventional modes of mechanical ventilation.

Elective high frequency oscillatory ventilation versus conventional ventilation for acute pulmonary dysfunction in preterm infants

BACKGROUND

Respiratory failure due to lung immaturity is a major cause of mortality in preterm infants. Although the use of intermittent positive pressure ventilation (IPPV) in neonates with respiratory failure saves lives, its use is associated with lung injury and chronic lung disease (CLD). A newer form of ventilation called high frequency oscillatory ventilation (HFOV) has been shown to result in less lung injury in experimental studies.

OBJECTIVES

The objective of this review is to determine the effect of the elective use of high frequency oscillatory ventilation (HFOV) as compared to conventional ventilation (CV) on the incidence of chronic lung disease, mortality and other complications associated with prematurity and assisted ventilation in preterm infants who are mechanically ventilated for respiratory distress syndrome (RDS).

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts, conferences and symposia proceedings, expert informants, journal hand searching by the Cochrane Collaboration, mainly in the English language. The search was updated in January 2009.

SELECTION CRITERIA

Randomised controlled trials comparing HFOV and CV in preterm or low birth weight infants with pulmonary dysfunction, mainly due to RDS, who required assisted ventilation. Randomisation and commencement of treatment needed to be as soon as possible after the start of CV and usually in the first 12 hours of life.

DATA COLLECTION AND ANALYSIS

The methodological quality of each trial was independently reviewed by the various authors. The standard effect measures are relative risk (RR) and risk difference (RD). From 1/RD the number needed to treat (NNT) to produce one outcome were calculated. For all measures of effect, 95% confidence intervals were used. In subgroup analyses the 99% CIs are also given for summary RRs in the text. Meta-analysis was performed using a fixed effects model. Where heterogeneity was over 50%, the random effects RR is also given.

MAIN RESULTS

Seventeen eligible studies of 3,652 infants were included. Meta-analysis comparing HFOV with CV revealed no evidence of effect on mortality at 28 - 30 days of age or at approximately term equivalent age. These results were consistent across studies and in subgroup analyses. The effect of HFOV on CLD in survivors at term equivalent gestational age was inconsistent across studies and the reduction was of borderline significance overall. The effect was similar in trials with a high lung volume strategy for HFOV targeting at very low FiO(2) and trials with a high lung volume strategy with somewhat higher or unspecified target FiO(2). Subgroups of trials showed a significant reduction in CLD with HFOV when no surfactant was used, when piston oscillators were used for HFOV, when lung protective strategies for CV were not used, when randomisation occurred at two to six hours of age, and when inspiratory:expiratory ratio of 1:2 was used for HFOV. In the meta-analysis of all trials, pulmonary air leaks occurred more frequently in the HFOV group.In some studies, short-term neurological morbidity with HFOV was found, but this effect was not statistically significant overall. The subgroup of two trials not using a high volume strategy with HFOV found increased rates of Grade 3 or 4 intraventricular haemorrhage and of periventricular leukomalacia. An adverse effect of HFOV on long-term neurodevelopment was found in one large trial but not in the five other trials that reported this outcome. The rate of retinopathy of prematurity is reduced overall in the HFOV group.

AUTHORS' CONCLUSIONS

There is no clear evidence that elective HFOV offers important advantages over CV when used as the initial ventilation strategy to treat preterm infants with acute pulmonary dysfunction. There may be a small reduction in the rate of CLD with HFOV use, but the evidence is weakened by the inconsistency of this effect across trials and the overall borderline significance. Future trials on elective HFOV should target those infants who are at most risk of CLD (extremely preterm infants), compare different strategies for generating HFOV and CV, and report important long-term neurodevelopmental outcomes.

Neonatal ventilators: how do they differ?

Remarkable technological advances over the past two decades have brought dramatic changes to the neonatal intensive care unit. Microprocessor-based mechanical ventilation has replaced time-cycled, pressure-limited, intermittent mandatory ventilation with almost limitless options for the management of respiratory failure in the prematurely born infant. Unfortunately, much of the infusion of technology occurred before the establishment of a convincing evidence base. This review focuses on the basic principles of mechanical ventilation, nomenclature and the characteristics of both conventional and high-frequency devices.

Feasibility of weaning and direct extubation from open lung high-frequency ventilation in preterm infants

OBJECTIVE

High-frequency ventilation (HFV) is increasingly used in preterm infants, but data on weaning and extubation are limited. We aimed to establish if weaning the continuous distending pressure (CDP) below 8 cm H2O and the Fio2 below 0.30 is feasible in preterm infants on open lung HFV and if these settings result in successful extubation.

DESIGN

Retrospective cohort study.

SETTING

Neonatal intensive care unit in a university hospital.

PATIENTS

Preterm infants ventilated and directly extubated from HFV between January 2003 and August 2005.

MEASUREMENTS AND MAIN RESULTS

Data on patient characteristics, ventilator settings, gas exchange, respiratory support after extubation and the number of patients failing extubation (i.e., reintubation within 48 hr) were retrospectively collected. Two hundred fourteen infants, accounting for 242 ventilation periods, were included in the study. The CDP, but not the Fio2, decreased significantly in the 24-hr period before extubation, resulting in a mean CDP of 6.8 +/- 1.6 cm H2O and a mean Fio2 of 0.25 at the time of extubation. At these settings, 193 (90%) infants were successfully extubated. Multivariate logistic regression analysis showed that birth weight was the only independent variable positively associated with successful extubation.

CONCLUSION

This study shows that weaning the CDP below 8 cm H2O with an Fio2 below 0.30 is feasible during open lung HFV and extubation at these settings can be successful in preterm infants. In our series, a 90% success rate was observed. The value of this approach should be prospectively compared with conventional weaning and extubation strategies.

Ventilation strategies and adjunctive therapy in severe lung disease

Respiratory failure caused by severe lung disease is a common reason for admission to the pediatric and neonatal intensive care units. Efforts to decrease morbidity and mortality have fueled investigations into innovative methods of ventilation, kinder gentler ventilation techniques, pharmacotherapeutic adjuncts, and extracorporeal life support modalities. This article discusses the rationale for and experience with some of these techniques.

Lung protective ventilatory strategies in very low birth weight infants

Respiratory distress syndrome (RDS) is the most common respiratory diagnosis in preterm infants. Surfactant therapy and mechanical ventilation using conventional or high-frequency ventilation have been the standard of care in the management of RDS. Bronchopulmonary dysplasia (BPD) continues to remain as a major morbidity in very low birth weight infants despite these treatments. There is no significant difference in pulmonary outcome when an optimal lung volume strategy is used with conventional or high-frequency ventilation. Lung injury is directly related to the duration of invasive ventilation via the endotracheal tube. Studies using noninvasive ventilation, such as nasal continuous positive airway pressure and noninvasive positive pressure ventilation, have shown to decrease postextubation failures as well as a trend toward reduced risk of BPD. Lung protective ventilatory strategy may involve noninvasive ventilation as a primary therapy or following surfactant administration in very preterm infants with RDS. Initial steps in the management of preterm infants may also include sustained inflation to establish functional residual capacity, followed by noninvasive ventilation to minimize lung injury and subsequent development of BPD.

Ventilatory strategies for the extremely premature infant

Bronchopulmonary dysplasia (BPD), which has long-term adverse outcomes, is common following extremely premature birth. BPD has a multifactorial etiology, including a high level or prolonged use of mechanical ventilation. Numerous research studies, therefore, have attempted to identify ventilatory techniques which reduce the likelihood of baro/volutrauma and hence BPD; these have been critically examined in this review, particularly with regard to their relevance to the extremely prematurely born infant. This has highlighted that few randomized studies of ventilatory strategies have concentrated exclusively on those high-risk infants. Overall, in prematurely born infants, advantages have been suggested by the results of studies examining pressure support, proportional assist and volume-targeted ventilation. In addition, High-Frequency Oscillatory Ventilation (HFOV) may reduce the deterioration seen in lung function of prematurely born infants over the first year after birth. In conclusion, more randomized studies are required which concentrate exclusively on the extremely prematurely born population who are at highest risk of BPD. It is essential in such studies that long-term follow-up assessment is inbuilt so that the benefits/adverse effects can be appropriately identified.

Utilization of the lower inflection point of the pressure-volume curve results in protective conventional ventilation comparable to high frequency oscillatory ventilation in an animal model of acute respiratory distress syndrome

INTRODUCTION

Studies comparing high frequency oscillatory and conventional ventilation in acute respiratory distress syndrome have used low values of positive end-expiratory pressure and identified a need for better recruitment and pulmonary stability with high frequency.

OBJECTIVE

To compare conventional and high frequency ventilation using the lower inflection point of the pressure-volume curve as the determinant of positive end-expiratory pressure to obtain similar levels of recruitment and alveolar stability.

METHODS

After lung lavage of adult rabbits and lower inflection point determination, two groups were randomized: conventional (positive end-expiratory pressure = lower inflection point; tidal volume=6 ml/kg) and high frequency ventilation (mean airway pressures= lower inflection point +4 cmH2O). Blood gas and hemodynamic data were recorded over 4 h. After sacrifice, protein analysis from lung lavage and histologic evaluation were performed.

RESULTS

The oxygenation parameters, protein and histological data were similar, except for the fact that significantly more normal alveoli were observed upon protective ventilation. High frequency ventilation led to lower PaCO2 levels.

DISCUSSION

Determination of the lower inflection point of the pressure-volume curve is important for setting the minimum end expiratory pressure needed to keep the airways opened. This is useful when comparing different strategies to treat severe respiratory insufficiency, optimizing conventional ventilation, improving oxygenation and reducing lung injury.

CONCLUSIONS

Utilization of the lower inflection point of the pressure-volume curve in the ventilation strategies considered in this study resulted in comparable efficacy with regards to oxygenation and hemodynamics, a high PaCO2 level and a lower pH. In addition, a greater number of normal alveoli were found after protective conventional ventilation in an animal model of acute respiratory distress syndrome.

Tracheal suctioning is associated with prolonged disturbances of cerebral hemodynamics in very low birth weight infants

OBJECTIVES

Examining the effects of tracheal suctioning on cerebral hemodynamics of normotensive ventilated very low birth weight (VLBW) infants with normal cranial ultrasounds; determining the factor(s) influencing changes in mean cerebral blood flow velocity (CBFv) after suctioning.

METHODS

Seventy-three VLBW infants had continuous monitoring of mean arterial blood pressure (MABP), PaCO(2), PaO(2) and mean CBFv before, during, and after 202 suctioning sessions during the first week of life. Peak (or nadir) and relative changes of the four variables for 45 min after suctioning were calculated. Multiple linear regression was used to determine the factor(s) influencing changes in mean CBFv after suctioning.

RESULT

Birth weight was 928+/-244 g; gestational age was 27.0+/-2.0 weeks. Mean CBFv increased to 31.0+/-26.4% after suctioning and remained elevated for 25 min. PaCO(2) was highly associated with mean CBFv (P<0.001), whereas MABP and PaO(2) were not.

CONCLUSION

We observed prolonged increases of mean CBFv following suctioning in ventilated VLBW infants that were previously unrecognized. This is concerning since disturbances of CBF may be associated with subsequent brain injury.

Factors effecting adoption of new neonatal and pediatric respiratory technologies

OBJECTIVE

There remains significant variation in the level and rate of adoption of new pediatric respiratory technologies, in spite of two decades of focus on "evidence-based medicine". Nearly 50 years ago Rogers introduced a rubric for understanding issues that effect the adoption of technologies that included four factors plus evidence of advantage. We sought to determine whether Rogers' factors were useful in understanding contrasts between clinical utilization of technology and evidence of advantage.

DESIGN, SETTING, PARTICIPANTS

We conducted a written survey at two international neonatal/pediatric respiratory conferences. We asked about use of four specific indications for high-frequency ventilation (HFV) and nasal continuous positive airway pressure (nCPAP).

RESULTS

These four specific respiratory therapies were aggressively used by most, despite significant differences in the evidence supporting their utility: elective use of HFV (57.4%); HFV to treat ARDS (62.7%); nCPAP for weaning following extubation (83.9%); and nCPAP to avoid intubation (82.1%).

CONCLUSIONS

Evidence of outcomes advantage should be the key factor in assessing potentially beneficial technologies. However, we suggest that understanding the influence of observe-ability, complexity and subjectivity of relative advantage explains much of the contrast between adoption level and outcome evidence. These factors described by Rogers, that encourage adoption of mediocre technologies or that retard adoption of potentially beneficial technologies, should be understood and acknowledged. This perspective can be applied not only to national adoption patterns, but also to adoption of best practices within an individual unit.

What is new in ventilation strategies for the neonate?

A large number of ventilation strategies are now available for the neonate. This review has focused on new information, that is, studies published since 2000 and the implication of their results for current clinical practice. Meta-analysis of randomised trials has demonstrated that assist control and synchronous intermittent mandatory ventilation (SIMV) shortens the duration of ventilation only if started in the recovery rather than the early stage of respiratory disease. A recent randomised trial demonstrated pressure-regulated volume control ventilation may also have no advantages if started early. Weaning by SIMV with pressure support is better (reducing oxygen dependency) than SIMV alone. Meta-analysis of volume-targeted ventilation demonstrated significant reductions in the duration of ventilation and pneumothorax, but the trials were small and of different designs. Volume guarantee may provide more consistent blood gas control. The level of volume targeting appears to be crucial to the success of this technique. Meta-analysis of randomised trials of prophylactic high-frequency oscillation trials has shown a modest reduction in bronchopulmonary dysplasia. Randomised trials have failed to confirm the advantages of nasal continuous positive airway pressure (NCPAP) seen in various non-randomised studies; however, the randomised trials reported to date have been small. Inhaled nitric oxide (NO) does not improve the outcome of prematurely born infants with severe respiratory failure, but early low-dose prolonged iNO appears to have benefits that merit further testing. More randomised trials with long-term outcomes are required to identify the optimal ventilation strategy(ies) for the neonate.

Elective high frequency oscillatory ventilation versus conventional ventilation for acute pulmonary dysfunction in preterm infants

BACKGROUND

Respiratory failure due to lung immaturity is a major cause of mortality in preterm infants. Although the use of intermittent positive pressure ventilation (IPPV) in neonates with respiratory failure saves lives, its use is associated with lung injury and chronic lung disease (CLD). Conventional IPPV is provided at 30-80 breaths per minute, while a newer form of ventilation called high frequency oscillatory ventilation (HFOV) provides 'breaths' at 10 - 15 cycles per second. This has been shown to result in less lung injury in experimental studies.

OBJECTIVES

The objective of this review is to determine the effect of the elective use of high frequency oscillatory ventilation (HFOV) as compared to conventional ventilation (CV) in preterm infants who are mechanically ventilated for respiratory distress syndrome (RDS), on the incidence of chronic lung disease, mortality and other complications associated with prematurity and assisted ventilation.

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, previous reviews including cross references, abstracts, conferences and symposia proceedings, expert informants, journal hand searching by the Cochrane Collaboration, mainly in the English language. The search was updated in April 2007.

SELECTION CRITERIA

Randomised controlled trials comparing HFOV and CV in preterm or low birth weight infants with pulmonary dysfunction, mainly due to RDS, who were given IPPV. Randomisation and commencement of treatment needed to be as soon as possible after the start of IPPV and usually in the first 12 hours of life.

DATA COLLECTION AND ANALYSIS

The methodological quality of each trial was independently reviewed by the various authors. The standard effect measures are relative risk (RR) and risk difference (RD). From 1/RD the number needed to treat (NNT) to produce one outcome were calculated. For all measures of effect, 95% confidence intervals were used. In subgroup analyses the 99% CIs are also given for summary RRs in the text. Meta-analysis was performed using a fixed effects model. Where heterogeneity was over 50%, the random effects RR is also given.

MAIN RESULTS

Fifteen eligible studies of 3,585 infants were included. Meta-analysis comparing HFOV with CV revealed no evidence of effect on mortality at 28 - 30 days of age or at approximately term equivalent age. These results were consistent across studies and in subgroup analyses. The effect of HFOV on CLD in survivors at term equivalent gestational age was inconsistent across studies and the reduction was of borderline significance overall. Subgroups of trials showed a significant reduction in CLD with HFOV when high volume strategy for HFOV was used, when piston oscillators were used for HFOV, when lung protective strategies for CV were not used, when randomisation occurred at two to six hours of age, and when inspiratory:expiratory ratio of 1:2 was used for HFOV. In the meta-analysis of all trials, pulmonary air leaks occurred more frequently in the HFOV group. In some studies, short-term neurological morbidity with HFOV was found, but this effect was not statistically significant overall. The subgroup of two trials not using a high volume strategy with HFOV found increased rates of Grade 3 or 4 intraventricular haemorrhage and of periventricular leukomalacia. An adverse effect of HFOV on long-term neurodevelopment was found in one large trial but not in the five other trials that reported this outcome. The rate of retinopathy of prematurity is reduced overall in the HFOV group.

AUTHORS' CONCLUSIONS

There is no clear evidence that elective HFOV offers important advantages over CV when used as the initial ventilation strategy to treat preterm infants with acute pulmonary dysfunction. There may be a small reduction in the rate of CLD with HFOV use, but the evidence is weakened by the inconsistency of this effect across trials and the overall borderline significance. Future trials on elective HFOV should target those infants who are at most risk of CLD (extremely preterm infants), compare different strategies for generating HFOV and CV, and report important long-term neurodevelopmental outcomes.

High-frequency oscillatory ventilation in infants and children

The goal of mechanical ventilation in patients with acute lung injury is to support gas exchange and mitigate ventilator-associated lung injury. High-frequency oscillatory ventilation relies on the generation of a constant distending pressure, small tidal volumes and rapid respiratory rates with the intent to recruit atelectatic lung, reduce peak inflating pressures and limit volutrauma. The utilization of high-frequency oscillatory ventilation has dramatically increased in neonatal and pediatric intensive care units. As there is an overlap between the intensive care unit and the operating room, anesthesiologists must be familiar with recent advances in the care of infants and children with acute respiratory failure. High-frequency oscillatory ventilation has been used successfully to manage patients with severe respiratory failure who have failed conventional mechanical ventilation. When initiated early, high-frequency oscillatory ventilation has been shown to improve oxygenation and reduce acute and chronic lung injury in neonates, infants and children. Further trials are necessary to better delineate the benefits and risks of this therapy in various patient populations.

Meta-regression analysis of high-frequency ventilation vs conventional ventilation in infant respiratory distress syndrome

OBJECTIVE

There is considerable heterogeneity among randomized trials comparing high-frequency ventilation (HFV) with conventional mechanical ventilation (CMV) in premature neonates with respiratory distress syndrome. We investigated what factors explained differences in outcome among these trials.

DESIGN

Meta-regression analysis of 15 randomized trials.

MEASUREMENTS AND RESULTS

Variables were extracted to explain heterogeneity: year of publication; use of Sensormedics 3100A ventilator for HFV; time on CMV prior to start of study; gestational age; use of surfactant; high lung volume strategy in HFV; and lung protective ventilation strategy in CMV and baseline risk. Chronic lung disease (CLD) and death or CLD were outcome measures. Relative risk ratios were calculated to estimate effect sizes of explanatory variables on reported relative risks. Adjusted estimates of relative risk ratios of high lung volume strategy and lung protective ventilation strategy were 0.42 (95% CI 0.06-2.48) and 2.02 (95% CI 0.18-23.12) for CLD, respectively. The effect of gestational age was less pronounced (RRR=1.17 (95% CI 0.16-8.32) for CLD, respectively). Use of Sensormedics and prior time on CMV had the smallest effects [RRR=0.96 (95% CI 0.47-1.94) and RRR=0.85 (95% CI 0.58-1.24) for CLD, respectively)]. The same results applied to CLD or death as outcome.

CONCLUSIONS

Variation in ventilation strategies that were used in trials comparing HFV with CMV in premature neonates offered the most likely explanation for the observed differences in the outcome of these trials compared with other explanatory factors.

Neuromotor outcome at 2 years of very preterm infants who were treated with high-frequency oscillatory ventilation or conventional ventilation for neonatal respiratory distress syndrome

OBJECTIVE

In a previous multicenter, randomized trial, elective use of high-frequency oscillatory ventilation was compared with the use of conventional ventilation in the management of respiratory distress syndrome in preterm infants <30 weeks. No difference in terms of respiratory outcome was observed, but concerns were raised about an increased rate of severe intraventricular hemorrhage in the high-frequency ventilation group. To evaluate outcome, a follow-up study was conducted until a corrected age of 2 years. We report the results concerning neuromotor outcome.

METHODS

Outcome was able to be evaluated in 192 of the 212 infants who survived until discharge from the neonatal unit: 97 of 105 infants of the high-frequency group and 95 of 104 infants of the conventional ventilation group.

RESULTS

In the infants reviewed, mean birth weight and gestational age were similar in the 2 ventilation groups. As in the overall study population, the following differences were observed between the high-frequency ventilation group and the conventional ventilation group: lower 5-minute Apgar score, fewer surfactant instillations, and a higher incidence of severe intraventricular hemorrhage. At a corrected age of 2 years, 93 of the 97 infants of the high-frequency group and 79 of the 95 infants of the conventional ventilation group did not present any neuromotor disability, whereas 4 infants of the high-frequency group and 16 infants of the conventional ventilation group had cerebral palsy.

CONCLUSIONS

Contrary to our initial concern about the increased rate of severe intraventricular hemorrhage in the high-frequency ventilation group, these data suggest that early use of high-frequency ventilation, compared with conventional ventilation, may be associated with a better neuromotor outcome. Because of the small number of patients studied and the absence of any explanation for this finding, we can conclude only that high-frequency oscillatory ventilation is not associated with a poorer neuromotor outcome.

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.