Ventilation practices in the neonatal intensive care unit: a cross-sectional study

Global and Regional Heterogeneity of Lung Aeration in Neonates with Different Respiratory Disorders: A Physiologic Observational Study

BACKGROUND

Aeration heterogeneity affects lung stress and influences outcomes in adults with acute respiratory distress syndrome (ARDS). The authors hypothesize that aeration heterogeneity may differ between neonatal respiratory disorders and is associated with oxygenation, so its evaluation may be relevant in managing respiratory support.

METHODS

This was an observational prospective study. Neonates with respiratory distress syndrome, transient tachypnea of the neonate, evolving bronchopulmonary dysplasia, and neonatal ARDS were enrolled. Quantitative lung ultrasound and transcutaneous blood gas measurements were simultaneously performed. Global aeration heterogeneity (with its intra- and interpatient components) and regional aeration heterogeneity were primary outcomes; oxygenation metrics were the secondary outcomes.

RESULTS

A total of 230 (50 respiratory distress syndrome, transient tachypnea of the neonate or evolving bronchopulmonary dysplasia, and 80 neonatal ARDS) patients were studied. Intrapatient aeration heterogeneity was higher in transient tachypnea of the neonate (mean ± SD, 61 ± 33%) and evolving bronchopulmonary dysplasia (mean ± SD, 57 ± 20%; P < 0.001), with distinctive aeration distributions. Interpatient aeration heterogeneity was high for all disorders (Gini-Simpson index, between 0.6 and 0.72) except respiratory distress syndrome (Gini-Simpson index, 0.5), whose heterogeneity was significantly lower than all others (P < 0.001). Neonatal ARDS and evolving bronchopulmonary dysplasia had the most diffuse injury and worst gas exchange metrics. Regional aeration heterogeneity was mostly localized in the upper anterior and posterior zones. Aeration heterogeneity and total lung aeration had an exponential relationship (P < 0.001; adj-R2 = 0.62). Aeration heterogeneity is associated with greater total lung aeration (i.e., higher heterogeneity means a relatively higher proportion of normally aerated lung zones, thus greater aeration; P < 0.001; adj-R2 = 0.83) and better oxygenation metrics upon multivariable analyses.

CONCLUSIONS

Global aeration heterogeneity and regional aeration heterogeneity differ among neonatal respiratory disorders. Transient tachypnea of the neonate and evolving bronchopulmonary dysplasia have the highest intrapatient aeration heterogeneity. Transient tachypnea of the neonate, evolving bronchopulmonary dysplasia, and neonatal ARDS have the highest interpatient aeration heterogeneity, but the latter two have the most diffuse injury and worst gas exchange. Higher aeration heterogeneity is associated with better total lung aeration and oxygenation.

EDITOR’S PERSPECTIVE

Neonatal respiratory care practice among level III and IV NICUs in New England

OBJECTIVES

To assess respiratory care guidelines and explore variations in management of very low birth weight (VLBW) infants within a collaborative care framework. Additionally, to gather clinical leaders' perspectives on guidelines and preferences for ventilation modalities.

STUDY DESIGN

Leaders from each NICU participated in a practice survey regarding the prevalence of unit clinical guidelines, and management, at many stages of care.

RESULTS

Units have an average of 4.3 (±2.1) guidelines, of 9 topics queried. Guideline prevalence was not associated with practice or outcomes. An FiO2 requirement of 0.3-0.4 and a CPAP of 6-7 cmH2O, are the most common thresholds for surfactant administration, which is most often done after intubation, and followed by weaning from ventilatory support. Volume targeted ventilation is commonly used. Extubation criteria vary widely.

CONCLUSIONS

Results identify trends and areas of variation and suggest that the presence of guidelines alone is not predictive of outcome.

Evolution of mechanical ventilation of the newborn infant

Artificial ventilation of the newborn infant is the foundation of neonatology. Early practitioners included pediatricians, anesthesiologists, cardiologists, respiratory therapists, and engineers. The discovery of surfactant, followed by the death of Patrick Kennedy, jump-started the new area, with investment and research rapidly expanding. The ever more complex design of mechanical ventilators necessitated a more thorough understanding of newborn pulmonary physiology in order to provide support with minimal associated injury. This piece briefly reviews and highlights this history.

Receipt of high-frequency ventilation is associated with acute kidney injury in very preterm neonates

BACKGROUND

High-frequency ventilation (HFV) is frequently used in critically ill preterm neonates. We aimed to determine the incidence of acute kidney injury (AKI) in neonates less than 29 weeks gestation who received HFV in the first week of life and to determine if the rates of AKI differed in those who received other forms of respiratory support.

METHODS

This retrospective cohort study of 24 international, level III/IV neonatal intensive care units (NICUs) included neonates less than 29 weeks gestation from the AWAKEN study database. Exclusion criteria included the following: no intravenous fluids ≥ 48 h, admission ≥ 14 days of life, congenital heart disease requiring surgical repair at < 7 days of life, lethal chromosomal anomaly, death within 48 h, severe congenital kidney abnormalities, inability to determine AKI status, insufficient data on ventilation, and when the diagnosis of early AKI was unable to be made. Subjects were grouped into three groups based on ventilation modes (CPAP/no ventilation, conventional ventilation, and HFV).

RESULTS

The incidence of AKI was highest in the CPAP/no ventilation group, followed by HFV, followed by conventional ventilation (CPAP/no ventilation 48.5% vs. HFV 42.6% vs. conventional ventilation 28.4% (p = 0.009). An increased risk for AKI was found for those on HFV compared to CPAP/no ventilation (HR = 2.65; 95% CI:1.22-5.73).

CONCLUSIONS

HFV is associated with AKI in the first week of life. Neonates on HFV should be screened for AKI. The reasons for this association are not clear. Further studies should evaluate the relationship between ventilator strategies and AKI in premature neonates. A higher resolution version of the Graphical abstract is available as Supplementary information.

Ventilation practices in the neonatal intensive care units in Saudi Arabia, survey of the utilization of volume-targeted ventilation among practicing neonatologists

OBJECTIVE

To assess the current practice in using volume-targeted ventilation among neonatologists working at the Neonatal Intensive Care Units (NICU) of Saudi Arabia.

METHODS

The questionnaire was provided electronically to 153 practicing Neonatologists working in 39 NICUs. The survey's results were received and statistically analyzed.

RESULTS

One hundred nineteen (119) responses were received with, a 78% response rate. Volume Targeted Ventilation (VTV) was used routinely by 67.2%, whereas 21.8% still use only pressure control (PC)/pressure limited (PL) mode. During the acute phase of ventilation support, Assist Control was the most popular synchronized mode, whereas Synchronized Intermittent Mandatory Ventilation (SIMV) with pressure support (PS) or PSV were the two most common modes during the weaning phase, 31.8%, and 31% respectively. The majority of the neonatologists used a tidal volume of 4 ml/kg as the lowest and 6 ml/kg as the highest. The major reasons for not implementing VTV were the limited availability of ventilator devices that have an option of VTV, followed by lack of experience.

CONCLUSION

VTV is the predominant ventilation practice approach among neonatologists working in the KSA. Limited availability and lack of experience in using are the main challenges. Efforts to equip NICUs with the most advanced ventilation technology, enhance practitioners' experience and sufficient training in its use are warranted.

Noninvasive Neurally Adjusted Ventilation versus Nasal Continuous or Intermittent Positive Airway Pressure for Preterm Infants: A Systematic Review and Meta-Analysis

The noninvasive neurally adjusted ventilatory assist (NIV-NAVA) is a newly developed noninvasive ventilation technique with promising clinical and ventilatory outcomes for preterm infants. This systematic review and meta-analysis aimed to investigate whether NIV-NAVA has better clinical and ventilatory outcomes than nasal continuous airway pressure (NCPAP) or noninvasive positive pressure ventilation (NIPP) on premature infants. MEDLINE, Embase, and CENTRAL were searched, and randomized controlled trials (RCTs) that compared NIV-NAVA with NCPAP or NIPP for preterm infants (gestational age: <37 weeks) were included. We evaluated the following outcomes in the neonatal intensive care unit: the desaturation rate, failure of noninvasive modality requiring intubation when received as the primary mode or the need for re-intubation after extubation from mechanical ventilation in the secondary mode (weaning), length of stay, and fraction of inspired oxygen. The mean difference and risk ratio were used to represent continuous and dichotomous outcomes, respectively. We included nine RCTs involving 339 preterm infants overall. NIV-NAVA showed similar clinical and ventilatory outcomes to NCPAP or NIPP, except for the maximum diaphragmatic electrical activity. The rate of failure of the noninvasive modality was not statistically different between NIV-NAVA and NCPAP. The pooled estimates for the maximum electrical activity were significantly reduced in NIV-NAVA compared with those in NIPP. The findings suggest that NIV-NAVA may be as safe and effective as NCPAP and NIPP for preterm neonates, particularly those who may not tolerate these alternative noninvasive methods. However, further trials are recommended for greater evidence.

Classifying multicenter approaches to invasive mechanical ventilation for infants with bronchopulmonary dysplasia using hierarchical clustering analysis

INTRODUCTION

Evidence-based ventilation strategies for infants with severe bronchopulmonary dysplasia (BPD) remain unknown. Determining whether contemporary ventilation approaches cluster as specific BPD strategies may better characterize care and enhance the design of clinical trials. The objective of this study was to test the hypothesis that unsupervised, multifactorial clustering analysis of point prevalence ventilator setting data would classify a discrete number of physiology-based approaches to mechanical ventilation in a multicenter cohort of infants with severe BPD.

METHODS

We performed a secondary analysis of a multicenter point prevalence study of infants with severe BPD treated with invasive mechanical ventilation. We clustered the cohort by mean airway pressure (MAP), positive end expiratory pressure (PEEP), set respiratory rate, and inspiratory time (Ti) using Ward's hierarchical clustering analysis (HCA).

RESULTS

Seventy-eight patients with severe BPD were included from 14 centers. HCA classified three discrete clusters as determined by an agglomerative coefficient of 0.97. Cluster stability was relatively strong as determined by Jaccard coefficient means of 0.79, 0.85, and 0.77 for clusters 1, 2, and 3, respectively. The median PEEP, MAP, rate, Ti, and PIP differed significantly between clusters for each comparison by Kruskall-Wallis testing (p < 0.0001).

CONCLUSIONS

In this study, unsupervised clustering analysis of ventilator setting data identified three discrete approaches to mechanical ventilation in a multicenter cohort of infants with severe BPD. Prospective trials are needed to determine whether these approaches to mechanical ventilation are associated with specific severe BPD clinical phenotypes and differentially modify respiratory outcomes.

Synchronized intermittent mandatory ventilation with volume guarantee and pressure support in neonates: Detailed analysis of ventilator parameters

OBJECTIVE

To analyse the relationship between peak inflating pressure, expired tidal volume, respiratory rate, and inspiratory time of volume-guaranteed ventilator inflations and pressure-supported spontaneous breaths during synchronized intermittent positive pressure mode with volume guarantee and pressure support (SIMV-VG-PS) in neonates.

METHODS

Ventilator parameters were downloaded every second from 16 babies ventilated with SIMV-VG-PS mode using Dräger Babylog VN500 ventilators over 137 days. Transcutaneous carbon dioxide (tcCO₂ ) data were also collected. Data were computationally analysed using Python. The average of each ventilator parameter was determined during each minute separately for ventilator inflations and for spontaneous breaths. These values were compared and their effect on tcCO₂ levels was also analysed.

RESULTS

The relationship between the peak inflating pressure of the volume guaranteed inflations (PIP_VG ) and pressure-supported spontaneous breaths (PIP_PS ) was highly variable. The PIP_PS /PIP_VG ratio differed significantly from the value (0.66) targeted by clinicians (group median: 0.80, range: 0.50-1.00). PIP_PS frequently exceeded PIP_VG . When PIP_PS /PIP_VG was >0.66, the expired tidal volume and the rate of the pressure-supported spontaneous breaths were also significantly (p < 0.0001) higher, but there was no difference in tcCO₂ levels. The flow-cycled spontaneous breaths had significantly shorter inspiratory times than ventilator inflations.

CONCLUSIONS

During SIMV-VG-PS it is difficult to ensure a pressure support level proportionate to the inflating pressure of ventilator inflations and to achieve the stability of tidal volumes.

Respiratory Management of the Preterm Infant: Supporting Evidence-Based Practice at the Bedside

Extremely preterm infants frequently require some form of respiratory assistance to facilitate the cardiopulmonary transition that occurs in the first hours of life. Current resuscitation guidelines identify as a primary determinant of overall newborn survival the establishment, immediately after birth, of adequate lung inflation and ventilation to ensure an adequate functional residual capacity. Any respiratory support provided, however, is an important contributing factor to the development of bronchopulmonary dysplasia. The risks correlated to invasive ventilatory techniques increase inversely with gestational age. Preterm infants are born at an early stage of lung development and are more susceptible to lung injury deriving from mechanical ventilation. Any approach aiming to reduce the global burden of preterm lung disease must implement lung-protective ventilation strategies that begin from the newborn’s first breaths in the delivery room. Neonatologists today must be able to manage both invasive and noninvasive forms of respiratory assistance to treat a spectrum of lung diseases ranging from acute to chronic conditions. We searched PubMed for articles on preterm infant respiratory assistance. Our narrative review provides an evidence-based overview on the respiratory management of preterm infants, especially in the acute phase of neonatal respiratory distress syndrome, starting from the delivery room and continuing in the neonatal intensive care unit, including a section regarding exogenous surfactant therapy.

First week of life respiratory management and pulmonary ventilation/perfusion matching in infants with bronchopulmonary dysplasia: a retrospective observational study

OBJECTIVE

To investigate the association between early neonatal respiratory management in infants with bronchopulmonary dysplasia (BPD) and the degree of pulmonary ventilation perfusion-matching (V/Q) at term.

METHODS

30 preterm infants with a diagnosis of BPD who were initially treated with either controlled mechanical ventilation/continuous positive airway pressure (CMV/CPAP) (n = 14) or high-frequency oscillatory ventilation (HFOV) using a high lung-volume strategy (n = 16) were retrospectively included in this study. All infants underwent pulmonary V/Q single photon emission computed tomography at a median postmenstrual age of 37 weeks.

RESULTS

Infants treated with HFOV had significantly larger proportion of the lung with matched V/Q as compared to infants treated with CMV/CPAP, median (interquartile range) 60.4% (55.5-66.0%) and 45.8% (37.8-53.1%) respectively (p = 0.01).

CONCLUSIONS

In infants who needed mechanical ventilation the first week of life and later developed BPD an association was observed between treatment with a HFOV and better pulmonary V/Q matching at near-term age.

[Efficacy of volume-targeted ventilation versus high-frequency oscillatory ventilation in the treatment of neonatal respiratory distress syndrome]

OBJECTIVES

To study the clinical efficacy of volume-targeted ventilation (VTV) versus high-frequency oscillatory ventilation (HFOV) in the treatment of neonatal respiratory distress syndrome (NRDS).

METHODS

A retrospective cohort analysis was performed on the medical data of 140 neonates with severe NRDS who were admitted from September 2016 to February 2022, with 55 neonates in the VTV group and 85 in the HFOV group. The neonates in the VTV group received conventional mechanical ventilation and target tidal volume, and those in the HFOV group received HFOV. Arterial blood gas parameters were collected at 48 hours after admission, and related indices during hospitalization were recorded, including mortality rate, duration of invasive mechanical ventilation, duration of oxygen therapy, and the incidence rates of complications.

RESULTS

Compared with the VTV group, the HFOV group had significantly lower incidence rates of grade Ⅲ-Ⅳ periventricular-intraventricular hemorrhage and neonatal necrotizing enterocolitis (P<0.05), and there were no significant differences between the two groups in the duration of invasive mechanical ventilation, the duration of oxygen therapy, mortality rate, and the incidence rates of bronchopulmonary dysplasia, hypocapnia, hypercapnia, periventricular leukomalacia, and retinopathy of prematurity (P>0.05).

CONCLUSIONS

HFOV has a better clinical efficacy than VTV in the treatment of NRDS.

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.

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.

Volume-Targeted Ventilation

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

Meta-analysis of Lung Ultrasound Scores for Early Prediction of Bronchopulmonary Dysplasia

RATIONALE

Lung ultrasound scores (LUS) might be useful in monitoring neonates with chronic pulmonary insufficiency of prematurity and in predicting bronchopulmonary dysplasia (BPD). Given their ease of use, accuracy and lack of invasiveness, LUS have been the subject of several recent studies.

OBJECTIVE

We sought to clarify whether LUS provide an accurate and early (within the first two weeks of life) prediction of BPD in preterm infants of gestational age <32weeks.

METHODS

Systematic review and diagnostic accuracy meta-analysis following PRISMA-P, PRISMA and QUADAS guidelines. Studies designed to predict BPD in the first two weeks of life using LUS were selected. A classical LUS (calculated for 6 chest areas) and its extended version (eLUS, 10 chest areas) were tested.

RESULTS

Seven studies (1027 neonates) were meta-analyzed. LUS and eLUS showed good diagnostic accuracy in predicting BPD at 7 and 14 days of life (AUC 0.85-0.87, pooled sensitivity 70-80%, pooled specificity 80-87%). The diagnostic accuracy of LUS and eLUS did not differ at any timepoint (AUC difference always p >0.05). Repeating the analyses without outliers or with moderate-to-severe BPD as outcome yielded similar results. Meta-regressions showed that prenatal steroid prophylaxis and sex were not significant effect confounders.

CONCLUSIONS

LUS are accurate for early prediction of BPD and moderate-to-severe BPD, in an average population of preterm infants <32weeks' gestation. The diagnostic accuracy is similar for LUS and eLUS, so the use of the simpler score should be advocated. Registration. PROSPERO CRD42021233010.

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

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

Current respiratory support practices in premature infants: an observational study

This study aims to describe longitudinally the current invasive and non-invasive ventilation practices in premature infants in a single neonatal intensive care unit (NICU). It´s a retrospective chart review including 682 babies born at gestational age ≤35 weeks, admitted to the NICU at Erasme Hospital, between 1^st of January 2001 and 31^st of December 2011, the different ventilatory support used were analyzed. This population was stratified depending on gestational age and the recruitment period on 3 groups. All infants born <28 weeks of GA (group 1) needed some kind of respiratory support of which 22% non-invasive. Among babies born after 28 to 31 weeks (group 2), 10.2% didn´t need any ventilatory support and 42% needed a non-invasive respiratory support. In neonates from 32 to 35 weeks of GA (group 3) respiratory support was needed in 34.9%, 65% of which was non-invasive. The median duration of endotracheal ventilation was: 6, 1 and 2 days, and of non-invasive support: 41, 17 and 2 days in group 1, 2 and 3 respectively. One single premature baby could pass along the first weeks through all modes. In premature infants whose respiratory support was needed, the median age at the end of support was remarkably constant at 33 - 34 weeks of corrected age. We conclude that is an important diversity and a significant complementarity between modes of respiratory support for premature infants. Invasive ventilation decreased significantly for group 2, but is still remarkably long for group 1.

Effect of the measurement of the work of breathing on the respiratory outcome of preterms

RATIONALE

There are no validated criteria for the choice of the optimal type of noninvasive respiratory support (NRS) and most appropriate settings in preterms.

METHODS

The work of breathing (WOB) during oxygen (O2) alone, nasal continuous positive pressure (nCPAP) and high flow nasal cannula (HFNC) was compared in preterm babies (23-30 weeks' gestation, "physiological group") needing any type of noninvasive respiratory support ("baseline" NRS) at 4 weeks of life. Babies were thereafter treated with the NRS associated with the greatest reduction in WOB ("optimal NRS"). The respiratory outcome at 36 weeks" gestation of these babies was compared to a "control" group treated with NRS based on standard noninvasive parameters. Preterm babies were prospectively enrolled in 3 centers and randomized into the "physiological" or "control" group.

RESULTS

Thirty babies were randomized. WOB with "baseline" NRS was higher than the "optimal" NRS and the consequent NRS chosen by physicians (p = 0.001). WOB was lower during HFNC than during O2 (p = 0.032) but WOB was comparable between nCPAP and HFNC, and between nCPAP and O2. Notably, WOB was near to normal during spontaneous breathing with O2. Respiratory outcome at 36 week' gestation was comparable between the 2 groups.

CONCLUSION

The optimization of NRS by means of the measurement of WOB in preterms requiring any type of NRS at 4 weeks of life was able to decrease the WOB but had no effect on the clinical outcome at 36 weeks' gestation.

A twelve-year neonatal and pediatric high-frequency oscillatory ventilation transport experience

OBJECTIVE

To describe the evolution over a 12-year period of a pediatric intensive care unit transport team's (PICU-TT) experience of pediatric and neonatal interhospital transportation on high-frequency oscillation ventilation (HFOV).

METHODS

This was a monocentric retrospective observational study from January 2006 to December 2017. All patients aged under 18 years old who were transported on HFOV by the Robert Debré Hospital PICU-TT were included.

RESULTS

Over a 12-year period, 125 patients were transported on HFOV, including 107 newborns and 18 children. Median (range) age and weight were 9 days (1 h-9 years) and 3.3 (0.6-39) kg, respectively. Initial median oxygenation index, SpO₂ /FiO₂ ratio and mean airway pressure were 32, 91, and 18 cmH₂ O, respectively, without significant difference between values before and after transport. Adverse events occurred during 28 transportations (22%) including three recovered cardiac arrests and one death. Overall survival rate at discharge was 74%, 78% in neonates and 56% in pediatrics, respectively. HFOV transportation rate increased over the last four years of the study for neonates and remained stable for older children. Extra-corporeal membrane oxygenation (ECMO) initiation rate on arrival decreased and survival rate increased significantly during the last four years of the study (p < .05).

CONCLUSION

This study showed the feasibility of HFOV transportation by a PICU-TT, despite some challenges. A trend towards using ECMO more than HFOV for the most severe respiratory and/or circulatory failures was seen over the 12-year period. The HFOV transportation rate has increased for less severe neonatal patients.

Synchronized Inflations Generate Greater Gravity-Dependent Lung Ventilation in Neonates

OBJECTIVE

To describe the regional distribution patterns of tidal ventilation within the lung during mechanical ventilation that is synchronous or asynchronous with an infant's own breathing effort.

STUDY DESIGN

Intubated infants receiving synchronized mechanical ventilation at The Royal Children's Hospital neonatal intensive care unit were studied. During four 10-minute periods of routine care, regional distribution of tidal volume (V_T; electrical impedance tomography), delivered pressure, and airway flow (Florian Respiratory Monitor) were measured for every inflation. Post hoc, each inflation was then classified as synchronous or asynchronous from video data of the ventilator screen, and the distribution of absolute V_T and delivered ventilation characteristics determined.

RESULTS

In total, 2749 inflations (2462 synchronous) were analyzed in 19 infants; mean (SD) age 28 (30) days, gestational age 35 (5) weeks. Synchronous inflations were associated with a shorter respiratory cycle (P = .004) and more homogenous V_T (center of ventilation) along the right (0%) to left (100%) lung plane; 45.3 (8.6)% vs 48.8 (9.4)% (uniform ventilation 46%). The gravity-dependent center of ventilation was a mean (95% CI) 2.1 (-0.5, 4.6)% toward the dependent lung during synchronous inflations. Tidal ventilation relative to anatomical lung size was more homogenous during synchronized inflations in the dependent lung.

CONCLUSIONS

Synchronous mechanical ventilator lung inflations generate more gravity-dependent lung ventilation and more uniform right-to-left ventilation than asynchronous inflations.

Evaluating peak inspiratory pressures and tidal volume in premature neonates on NAVA ventilation

Neurally adjusted ventilatory assist (NAVA) ventilation allows patients to determine their peak inspiratory pressure and tidal volume on a breath-by-breath basis. Apprehension exists about premature neonates' ability to self-regulate breath size. This study describes peak pressure and tidal volume distribution of neonates on NAVA and non-invasive NAVA. This is a retrospective study of stored ventilator data with exploratory analysis. Summary statistics were calculated. Distributional assessment of peak pressure and tidal volume were evaluated, overall and per NAVA level. Over 1 million breaths were evaluated from 56 subjects. Mean peak pressure was 16.4 ± 6.4 in the NAVA group, and 15.8 ± 6.4 in the NIV-NAVA group (t test, p < 0.001). Mean tidal volume was 3.5 ± 2.7 ml/kg.Conclusion:In neonates on NAVA, most pressures and volumes were within or lower than recommended ranges with pressure-limited or volume-guarantee ventilation. What is known: • Limiting peak inspiratory pressures or tidal volumes are the main strategies to minimize ventilator-induced lung injury in neonates. Neurally adjusted ventilatory assist allows neonates to regulate their own peak inspiratory pressures and tidal volumes on a breath-to-breath basis using neural feedback. What is new: • When neonates chose the size of their breaths based on neural feedback, the majority of peak inspiratory pressures and tidal volumes were within or lower than the recommended peak inspiratory pressure or tidal volume ranges with pressure-limited or volume guarantee ventilation.

Effect of pressure rise time on ventilator parameters and gas exchange during neonatal ventilation

BACKGROUND

Pressure rise time (PRT), also known as slope time to the peak inflating pressure can be set on some modern neonatal ventilators. On other ventilators, PRT is determined by the set circuit flow. Changing slope time can affect mean airway pressure (MAP), oxygenation, and carbon dioxide elimination. Our aim was to investigate the effect of PRT on ventilator parameters and gas exchange during volume-guaranteed ventilation.

METHODS

In a crossover study, 12 infants weighing greater than 2 kg were ventilated using a Dräger Babylog VN500 ventilator with synchronized intermittent positive pressure ventilation with volume guarantee (SIPPV-VG) and pressure support ventilation with volume guarantee (PSV-VG). During both modes PRTs between 0.08 and 0.40 seconds were used in 15-minute epochs. Data from the ventilator and patient monitors were downloaded with 1- and 100-Hz sampling rate and analyzed using the Python computer language.

RESULTS

During PSV-VG, longer PRTs were associated with longer inspiratory time (P < .0001) and with lower peak inflating pressure (PIP; P = .003), but the MAP was similar. During SIPPV-VG the PIP was not significantly different; however, MAP was lower with longer PRT (P = .001). With a short PRT (0.08 seconds), the PIP was higher during PSV-VG than during SIPPV-VG (19.8 vs 16.5 mbar; P = .042). There were no significant differences in tidal volume delivery, respiratory rate, minute volume, oxygen saturations, or end-tidal CO₂ with different PRTs in either mode.

CONCLUSIONS

During SIPPV-VG or PSV-VG, using short or long PRTs affects some ventilation parameters but does not significantly change oxygenation or carbon dioxide elimination.

A novel approach using volumetric dynamic airway computed tomography to determine positive end-expiratory pressure (PEEP) settings to maintain airway patency in ventilated infants with bronchopulmonary dysplasia

BACKGROUND

Positive end-expiratory pressure (PEEP) is a key mechanical ventilator setting in infants with bronchopulmonary dysplasia (BPD). Excessive PEEP can result in insufficient carbon dioxide elimination and lung damage, while insufficient PEEP can result in impaired gas exchange secondary to airway and alveolar collapse. Determining PEEP settings based on clinical parameters alone is challenging and variable.

OBJECTIVE

The purpose of this study was to describe our experience using dynamic airway CT to determine the lowest PEEP setting sufficient to maintain expiratory central airway patency of at least 50% of the inspiratory cross-sectional area in children with BPD requiring long-term ventilator support.

MATERIALS AND METHODS

We retrospectively identified all infants with BPD who underwent volumetric CT with a dynamic airway protocol for PEEP optimization from December 2014 through April 2019. Sixteen infants with BPD underwent 17 CT exams. Each CT exam consisted of acquisitions spanning the trachea and mainstem bronchi. We measured cross-sectional area of the trachea and mainstem bronchi and qualitatively assessed the amount of atelectasis. We documented changes in management as a result of the CT exam.

RESULTS

The average effective dose was 0.1-0.8 mSv/scan. Of 17 CT exams, PEEP was increased in 9, decreased in 3 and unchanged after 5 exams.

CONCLUSION

Dynamic airway CT shows promise to assist the clinician in determining PEEP settings to maintain airway patency in infants with BPD requiring long-term ventilator support. Further evaluation of the impact of this maneuver on gas exchange, cardiac output and other physiological measures is needed.

Porcine vs bovine surfactant therapy for preterm neonates with RDS: systematic review with biological plausibility and pragmatic meta-analysis of respiratory outcomes

BACKGROUND

Bovine surfactants are known to be clinically equivalent but it is unclear if porcine or bovine surfactants at their licensed dose should be preferred to treat respiratory distress syndrome in preterm neonates.

METHODS

We performed a comprehensive review of biochemical and pharmacological features of surfactants to understand the biological plausibility of any clinical effect. We then performed a pragmatic meta-analysis comparing internationally marketed porcine and bovine surfactants for mortality and respiratory outcomes. Search for randomised controlled trials with no language/year restrictions and excluding "grey" literature, unpublished or non-peer reviewed reports was conducted, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines and the most recent methodological recommendations.

RESULTS

Sixteen articles were included in the review and 14 in the meta-analysis (1491 neonates). 200 mg/kg poractant-α (a porcine surfactant) was associated with lower BPD/mortality (OR 0.632[95%CI:0.494, 0.809];p < 0.001),BPD (OR 0.688[95%CI:0.512, 0.925];p = 0.013), retreatment (OR 0.313[95%CI:0.187, 0.522];p < 0.0001), airleaks (OR 0.505[95%CI:0.308, 0.827];p = 0.006) and lung haemorrhage (OR 0.624[95%CI:0.388, 1];p = 0.051). Gestational age is associated with effect size for BPD (coefficient: 0.308 [95%CI:0.063, 0.554];p = 0.014) and surfactant retreatment (coefficient: -0.311 [95%CI:-0.595, - 0.028];p = 0.031).

CONCLUSION

200 mg/kg poractant-α is associated with better respiratory outcomes compared to bovine surfactants at their licensed dose. The effect of poractant-α on BPD and surfactant retreatment is greater at lowest and highest gestational ages, respectively.

TRIAL REGISTRATION

PROSPERO n.42017075251 .

Impact of delivered tidal volume on the occurrence of intraventricular haemorrhage in preterm infants during positive pressure ventilation in the delivery room

BACKGROUND AND OBJECTIVES

Delivery of inadvertent high tidal volume (V_T) during positive pressure ventilation (PPV) in the delivery room is common. High V_T delivery during PPV has been associated with haemodynamic brain injury in animal models. We examined if V_T delivery during PPV at birth is associated with brain injury in preterm infants <29 weeks' gestation.

METHODS

A flow-sensor was placed between the mask and the ventilation device. V_T values were compared with recently described reference ranges for V_T in spontaneously breathing preterm infants at birth. Infants were divided into two groups: V_T<6  mL/kg or V_T>6 mL/kg (normal and high V_T, respectively). Brain injury (eg, intraventricular haemorrhage (IVH)) was assessed using routine ultrasound imaging within the first days after birth.

RESULTS

A total of 165 preterm infants were included, 124 (75%) had high V_T and 41 (25%) normal V_T. The mean (SD) gestational age and birth weight in high and normal V_T group was similar, 26 (2) and 26 (1) weeks, 858 (251) g and 915 (250) g, respectively. IVH in the high V_T group was diagnosed in 63 (51%) infants compared with 5 (13%) infants in the normal V_T group (P=0.008).Severe IVH (grade III or IV) developed in 33/124 (27%) infants in the high V_T group and 2/41 (6%) in the normal V_T group (P=0.01).

CONCLUSIONS

High V_T delivery during mask PPV at birth was associated with brain injury. Strategies to limit V_T delivery during mask PPV should be used to prevent high V_T delivery.

Volume-targeted ventilation: one size does not fit all. Evidence-based recommendations for successful use

Despite level 1 evidence for important benefits of volume-targeted ventilation (VTV), many vulnerable extremely preterm infants continue to be exposed to traditional pressure-controlled ventilation. Lack of suitable equipment and a lack of appreciation of the fact that 'one size does NOT fit all' appear to contribute to the slow uptake of VTV. This review attempts to improve clinicians' understanding of the way VTV works and to provide essential information about evidence-based tidal volume (V_T) targets. Focus on underlying lung pathophysiology, individualised ventilator settings and V_Ttargets are keys to successful use of VTV thereby improving important clinical outcomes.

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.

Nasal high-frequency oscillatory ventilation and CO2 removal: A randomized controlled crossover trial

OBJECTIVE

To compare short-term application of nasal high-frequency oscillatory ventilation (nHFOV) with nasal continuous positive airway pressure (nCPAP).

WORKING HYPOTHESIS

nHFOV improves CO₂ removal with respect to nCPAP in preterm infants needing noninvasive respiratory support and persistent oxygen supply after the first 72 h of life.

STUDY DESIGN

Multicenter non-blinded prospective randomized crossover study.

PATIENT SELECTION

Thirty premature infants from eight tertiary neonatal intensive care units, of mean ± SD 26.4 ± 1.8 weeks of gestational age and 921 ± 177 g of birth weight.

METHODOLOGY

Infants were randomly allocated in a 1:1 ratio to receive a starting treatment mode of either nCPAP or nHFOV delivered by the ventilator CNO (Medin, Germany), using short binasal prongs of appropriate size. A crossover design with four 1-h treatment periods was used, such that each infant received both treatments twice. The primary outcome was the mean transcutaneous partial pressure of CO₂ (TcCO₂ ) value during the 2-h cumulative period of nHFOV compared with the 2-h cumulative period of nCPAP.

RESULTS

Significantly lower TcCO₂ values were observed during nHFOV compared with nCPAP: 47.5 ± 7.6 versus 49.9 ± 7.2 mmHg, respectively, P = 0.0007. A different TcCO₂ behavior was found according to the random sequence: in patients starting on nCPAP, TcCO₂ significantly decreased from 50.0 ± 8.0 to 46.6 ± 7.5 mmHg during nHFOV (P = 0.001). In patients starting on nHFOV, TcCO₂ slightly increased from 48.5 ± 7.8 to 49.9 ± 6.7 mmHg during nCPAP (P = 0.13).

CONCLUSIONS

nHFOV delivered through nasal prongs is more effective than nCPAP in improving the elimination of CO₂ .

Accuracy of near-patient vs. inbuilt spirometry for monitoring tidal volumes in an in-vitro paediatric lung model

Spirometric monitoring provides precise measurement and delivery of tidal volumes within a narrow range, which is essential for lung-protective strategies that aim to reduce morbidity and mortality in mechanically-ventilated patients. Conventional anaesthesia ventilators include inbuilt spirometry to monitor inspiratory and expiratory tidal volumes. The GE Aisys CS² anaesthesia ventilator allows additional near-patient spirometry via a sensor interposed between the proximal end of the tracheal tube and the respiratory tubing. Near-patient and inbuilt spirometry of two different GE Aisys CS² anaesthesia ventilators were compared in an in-vitro study. Assessments were made of accuracy and variability in inspiratory and expiratory tidal volume measurements during ventilation of six simulated paediatric lung models using the ASL 5000 test lung. A total of 9240 breaths were recorded and analysed. Differences between inspiratory tidal volumes measured with near-patient and inbuilt spirometry were most significant in the newborn setting (p < 0.001), and became less significant with increasing age and weight. During expiration, tidal volume measurements with near-patient spirometry were consistently more accurate than with inbuilt spirometry for all lung models (p < 0.001). Overall, the variability in measured tidal volumes decreased with increasing tidal volumes, and was smaller with near-patient than with inbuilt spirometry. The variability in measured tidal volumes was higher during expiration, especially with inbuilt spirometry. In conclusion, the present in-vitro study shows that measurements with near-patient spirometry are more accurate and less variable than with inbuilt spirometry. Differences between measurement methods were most significant in the smallest patients. We therefore recommend near-patient spirometry, especially for neonatal and paediatric patients.

Volume guaranteed? Accuracy of a volume-targeted ventilation mode in infants

OBJECTIVES

Volume-targeted ventilation (VTV) is widely used and may reduce lung injury, but this assumes the clinically set tidal volume (V_Tset) is accurately delivered. This prospective observational study aimed to determine the relationship between V_Tset, expiratory V_T (V_Te) and endotracheal tube leak in a modern neonatal -volume-targeted ventilator (VTV) and the resultant partial arterial pressure of carbon dioxide (PaCO₂) relationship with and without VTV.

DESIGN

Continuous inflations were recorded for 24 hours in 100 infants, mean (SD) 34 (4) weeks gestation and 2483 (985) g birth weight, receiving synchronised mechanical ventilation (SLE5000, SLE, UK) with or without VTV and either the manufacturer's V4 (n=50) or newer V5 (n=50) VTV algorithm. The V_Tset, V_Te and leak were determined for each inflation (maximum 90 000/infant). If PaCO₂ was sampled (maximum of 2 per infant), this was compared with the average V_Te data from the preceding 15 min.

RESULTS

A total of 7 497 137 inflations were analysed. With VTV enabled (77 infants), the V_Tset-V_Te bias (95% CI) was 0.03 (-0.12 to 0.19) mL/kg, with a median of 80% of V_Te being ±1.0 mL/kg of V_Tset. Endotracheal tube leak up to 30% influenced V_Tset-V_Te bias with the V4 (r²=-0.64, p<0.0001; linear regression) but not V5 algorithm (r²=0.04, p=0.21). There was an inverse linear relationship between V_Te and PaCO₂ without VTV (r²=0.26, p=0.004), but not with VTV (r²=0.04, p=0.10), and less PaCO₂ within 40-60 mm Hg, 53% versus 72%, relative risk (95% CI) 1.7 (1.0 to 2.9).

CONCLUSION

VTV was accurate and reliable even with moderate leak and PaCO₂ more stable. VTV algorithm differences may exist in other devices.

Variation in Positive End-Expiratory Pressure Levels for Mechanically Ventilated Extremely Low Birth Weight Infants

OBJECTIVE

To test the hypothesis that significant positive end-expiratory pressure (PEEP) level variation exists between neonatal centers.

STUDY DESIGN

We performed a secondary analysis cohort study of the Nasal Intermittent Positive-Pressure Ventilation trial. Our study population was extremely low birth weight infants requiring mechanical ventilation within 28 days of life. The exposure was neonatal center; 34 international centers participated in the trial. Subjects from centers with fewer than 5 eligible cases were excluded. The main outcome was the maximal PEEP level used during the first course of mechanical ventilation. Infant characteristics judged a priori to directly influence clinical PEEP level selection and all characteristics associated with PEEP at P <.05 in bivariable analyses were included with and without center in multivariable linear regression models. Variation in PEEP level use between centers following adjustment for infant characteristics was assessed.

RESULTS

A total of 278 extremely low birth weight infants from 17 centers were included. Maximal PEEP ranged from 3 to 9 cm H₂O, mean = 5.7 (SD = 0.9). Significant variation between centers remained despite adjustment for infant characteristics (P < .0001). Further, center alone explained a greater proportion of the PEEP level variation than all infant characteristics combined.

CONCLUSIONS

Marked variation in PEEP levels for extremely low birth weight infants exists between neonatal centers. Research providing evidence-based guidance for this important aspect of respiratory care in preterm infants at high risk of lung injury is needed.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT00433212.

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.

Mechanical ventilation strategies

Although only a small proportion of full term and late preterm infants require invasive respiratory support, they are not immune from ventilator-associated lung injury. The process of lung damage from mechanical ventilation is multifactorial and cannot be linked to any single variable. Atelectrauma and volutrauma have been identified as the most important and potentially preventable elements of lung injury. Respiratory support strategies for full term and late preterm infants have not been as thoroughly studied as those for preterm infants; consequently, a strong evidence base on which to make recommendations is lacking. The choice of modalities of support and ventilation strategies should be guided by the specific underlying pathophysiologic considerations and the ventilatory approach must be individualized for each patient based on the predominant pathophysiology at the time.

Pulmonary diagnostics

Term infants with respiratory distress may have extremely varied etiologies of their illnesses. These range from anatomical malformations to infectious or inflammatory conditions to genetic, metabolic, or neurological abnormalities. This article reviews the present array of diagnostic studies available to the clinician, including the physical examination, imaging (radiography, computed tomography, magnetic resonance imaging, ultrasound, and nuclear scanning techniques), lung mechanics and function testing, evaluation of gas exchange (blood gases, pulse oximetry, transcutaneous monitoring, and end-tidal carbon monoxide measurements), and anatomical studies (bronchoscopy and lung biopsy). These tests and procedures are reviewed and a stepwise approach recommended.

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.

Tidal Volume Delivery during the Anesthetic Management of Neonates Is Variable

OBJECTIVES

To describe expiratory tidal volume (V_T) during routine anesthetic management of neonates at a single tertiary neonatal surgical center, as well as the proportion of V_T values within the range of 4.0-8.0 mL/kg.

STUDY DESIGN

A total of 26 neonates needing surgery under general anesthesia were studied, of whom 18 were intubated postoperatively. V_T was measured continuously during normal clinical care using a dedicated neonatal respiratory function monitor (RFM), with clinicians blinded to values. V_T, pressure, and cardiorespiratory variables were recorded regularly while intubated intraoperatively, during postoperative transport, and for 15 minutes after returning to the neonatal intensive care unit (NICU). In addition, paired V_T values from the anesthetic machine were documented intraoperatively.

RESULTS

A total of 2597 V_T measures were recorded from 26 neonates. Intraoperative and postoperative transport expiratory V_T values were highly variable compared with the NICU V_T (P < .0001, Kruskal-Wallis test), with 51% of inflations outside the 4.0-8.0 mL/kg range (35% and 38% of V_T >8.0 mL/kg, respectively), compared with 29% in the NICU (P < .001, χ² test). The use of a flow-inflating bag resulted in a median (range) V_T of 8.5 mL/kg (range, 5.3-11.4 mL/kg) vs 5.6 ml/kg (range, 4.3-7.9 mL/kg) using a Neopuff T-piece system (P < .0001, Mann-Whitney U test). The mean anesthetic machine expiratory V_T was 3.2 mL/kg (95% CI, -4.5 to 10.8 mL/kg) above RFM.

CONCLUSIONS

V_T is highly variable during the anesthetic care of neonates, and potentially injurious V_T is frequently delivered; thus, we suggest close V_T monitoring using a dedicated neonatal RFM.

Non-invasive high-frequency oscillatory ventilation in neonates: review of physiology, biology and clinical data

Non-invasive high-frequency oscillatory ventilation (NHFOV) consists of the application of a bias flow generating a continuous distending positive pressure with superimposed oscillations, which have constant frequency and active expiratory phase. NHFOV matches together the advantages of high-frequency ventilation (no need for synchronisation, high efficacy in removing CO₂) and nasal continuous positive airway pressure (CPAP) (non-invasive interface, increase in functional residual capacity allowing oxygenation to improve). There is enough clinical expertise demonstrating that NHFOV may be tried in some selected cases, in whom CPAP or conventional non-invasive ventilation have failed. Nonetheless, there are no clear data about its clinical usefulness and there is a need for randomised controlled studies. Our purpose is to review the physiology and biological effects of NHFOV, to present the current clinical evidence on its use, to provide some guiding principles to clinicians and suggest directions for further research.

Neurally adjusted ventilatory assist (NAVA) in preterm newborn infants with respiratory distress syndrome-a randomized controlled trial

Neurally adjusted ventilatory assist (NAVA) improves patient-ventilator synchrony during invasive ventilation and leads to lower peak inspiratory pressures (PIP) and oxygen requirements. The aim of this trial was to compare NAVA with current standard ventilation in preterm infants in terms of the duration of invasive ventilation. Sixty infants born between 28 + 0 and 36 + 6 weeks of gestation and requiring invasive ventilation due to neonatal respiratory distress syndrome (RDS) were randomized to conventional ventilation or NAVA. The median durations of invasive ventilation were 34.7 h (quartiles 22.8-67.9 h) and 25.8 h (15.6-52.1 h) in the NAVA and control groups, respectively (P = 0.21). Lower PIPs were achieved with NAVA (P = 0.02), and the rapid reduction in PIP after changing the ventilation mode to NAVA made following the predetermined extubation criteria challenging. The other ventilatory and vital parameters did not differ between the groups. Frequent apneas and persistent pulmonary hypertension were conditions that limited the use of NAVA in 17 % of the patients randomized to the NAVA group. Similar cumulative doses of opiates were used in both groups (P = 0.71).

CONCLUSIONS

NAVA was a safe and feasible ventilation mode for the majority of preterm infants suffering from RDS, but the traditional extubation criteria were not clinically applicable during NAVA.

WHAT IS KNOWN

• NAVA improves patient-ventilator synchrony during invasive ventilation. • Lower airway pressures and oxygen requirements are achieved with NAVA during invasive ventilation in preterm infants by comparison with conventional ventilation. What is new: • Infants suffering from PPHN did not tolerate NAVA in the acute phase of their illness. • The traditional extubation criteria relying on inspiratory pressures and spontaneous breathing efforts were not clinically applicable during NAVA.

Individualized lung recruitment during high-frequency ventilation in preterm infants is not associated with lung hyperinflation and air leaks

Lung recruitment during high-frequency ventilation (HFV) in preterm infants with respiratory distress syndrome (RDS) has been associated with an increased risk of lung hyperinflation and air leaks. Individualizing the lung recruitment procedure to the severity of lung disease of each patient might reduce these risks. In this prospective cohort study, we evaluated chest X-ray (CXR) characteristics during individualized oxygenation-guided lung recruitment with HFV in preterm infants with RDS, before and after surfactant therapy. Two pediatric radiologists scored radiolucency, the presence of lung hyperinflation, and/or air leaks following lung recruitment during HFV in 69 infants before and 39 infants after surfactant treatment. Following lung recruitment, the median radiolucency score was 2, with 44 (64 %) infants having a score ≤2. Only mild to moderate hyperinflation was seen in 13 (19 %) infants, with no air leaks. After the surfactant, the radiolucency score improved in 62 % of 39 paired CXRs (p < 0.001). Mild to moderate hyperinflation was seen in nine (24 %) patients. During the entire admission, only four (6 %) of the patients developed air leaks.

CONCLUSION

The risk of significant hyperinflation and air leaks is low when using an individualized oxygenation-guided recruitment procedure during HFV in preterm infants with RDS.

WHAT IS KNOWN

• Lung recruitment during high-frequency ventilation in preterm infants with respiratory distress syndrome is associated with an increased risk of lung hyperinflation and air leaks. What is New: • The risk of lung hyperinflation and air leaks is low when using an individualized oxygenation-guided lung recruitment procedure during high-frequency ventilation in preterm infants with respiratory distress syndrome.

Protocolized versus non-protocolized weaning for reducing the duration of invasive mechanical ventilation in newborn infants

BACKGROUND

Mechanical ventilation is a life-saving intervention for critically ill newborn infants with respiratory failure admitted to a neonatal intensive care unit (NICU). Ventilating newborn infants can be challenging due to small tidal volumes, high breathing frequencies, and the use of uncuffed endotracheal tubes. Mechanical ventilation has several short-term, as well as long-term complications. To prevent complications, weaning from the ventilator is started as soon as possible. Weaning aims to support the transfer from full mechanical ventilation support to spontaneous breathing activity.

OBJECTIVES

To assess the efficacy of protocolized versus non-protocolized ventilator weaning for newborn infants in reducing the duration of invasive mechanical ventilation, the duration of weaning, and shortening the NICU and hospital length of stay. To determine efficacy in predefined subgroups including: gestational age and birth weight; type of protocol; and type of protocol delivery. To establish whether protocolized weaning is safe and clinically effective in reducing the duration of mechanical ventilation without increasing the risk of adverse events.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled trials (CENTRAL; the Cochrane Library; 2015, Issue 7); MEDLINE In-Process and other Non-Indexed Citations and OVID MEDLINE (1950 to 31 July 2015); CINAHL (1982 to 31 July 2015); EMBASE (1988 to 31 July 2015); and Web of Science (1990 to 15 July 2015). We did not restrict language of publication. We contacted authors of studies with a subgroup of newborn infants in their study, and experts in the field regarding this subject. In addition, we searched abstracts from conference proceedings, theses, dissertations, and reference lists of all identified studies for further relevant studies.

SELECTION CRITERIA

Randomized, quasi-randomized or cluster-randomized controlled trials that compared protocolized with non-protocolized ventilator weaning practices in newborn infants with a gestational age of 24 weeks or more, who were enrolled in the study before the postnatal age of 28 completed days after the expected date of birth.

DATA COLLECTION AND ANALYSIS

Four authors, in pairs, independently reviewed titles and abstracts identified by electronic searches. We retrieved full-text versions of potentially relevant studies.

MAIN RESULTS

Our search yielded 1752 records. We removed duplicates (1062) and irrelevant studies (843). We did not find any randomized, quasi-randomized or cluster-randomized controlled trials conducted on weaning from mechanical ventilation in newborn infants. Two randomized controlled trials met the inclusion criteria on type of study and type of intervention, but only included a proportion of newborns. The study authors could not provide data needed for subgroup analysis; we excluded both studies.

AUTHORS' CONCLUSIONS

Based on the results of this review, there is no evidence to support or refute the superiority or inferiority of weaning by protocol over non-protocol weaning on duration of invasive mechanical ventilation in newborn infants.

Effect of Minimally Invasive Surfactant Therapy on Lung Volume and Ventilation in Preterm Infants

OBJECTIVE

To assess the changes in (regional) lung volume and gas exchange during minimally invasive surfactant therapy (MIST) in preterm infants with respiratory distress syndrome.

STUDY DESIGN

In this prospective observational study, infants requiring a fraction of inspired oxygen (FiO2) ≥ 0.30 during nasal continuous positive airway pressure of 6 cmH2O were eligible for MIST. Surfactant (160-240 mg/kg) was administered in supine position in 1-3 minutes via an umbilical catheter placed 2 cm below the vocal cords. Changes in end-expiratory lung volume (EELV), tidal volume, and its distribution were recorded continuously with electrical impedance tomography before and up to 60 minutes after MIST. Changes in transcutaneous oxygen saturation (SpO2) and partial carbon dioxide pressure, FiO2, respiratory rate, and minute ventilation were recorded.

RESULTS

A total of 16 preterm infants were included. One patient did not finish study protocol because of severe apnea 10 minutes after MIST. In the remaining infants (gestational age 29.8 ± 2.8 weeks, body weight 1545 ± 481 g) EELV showed a rapid and sustained increase, starting in the dependent lung regions, followed by the nondependent regions approximately 5 minutes later. Oxygenation, expressed as the SpO2/FiO2 ratio, increased from 233 (IQR 206-257) to 418 (IQR 356-446) after 60 minutes (P < .001). This change was significantly correlated with the change in EELV (ρ = 0.70, P < .01). Tidal volume and minute volume decreased significantly after MIST, but transcutaneous partial carbon dioxide pressure was comparable with pre-MIST values. Ventilation distribution remained unchanged.

CONCLUSIONS

MIST results in a rapid and homogeneous increase in EELV, which is associated with an improvement in oxygenation.

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.

Less invasive ventilation in extremely low birth weight infants from 1997 to 2011: survey versus evidence

Evidence for target values of arterial oxygen saturation (SaO2), CO2, and pH has changed substantially over the last 20 years. A representative survey concerning treatment strategies in extremely low-birth-weight infants (ELBW) was sent to all German neonatal intensive care units (NICUs) treating ELBW infants in 1997. A follow-up survey was conducted in 2011 and sent to all NICUs in Germany, Austria, and Switzerland. During the observation period, NICUs targeting SaO2 of 80, 85, and 90 % have increased, while units aiming for 94 and 96 % decreased (all p < 0.001). Similarly, NICUs aiming for pH 7.25 or lower increased, while 7.35 or higher decreased (both p < 0.001). Furthermore, more units targeted a CO2 of 50 mmHg (7.3 kPa) or higher (p < 0.001), while fewer targeted 40 or 35 mmHg (p < 0.001). Non-invasive ventilation (NIV) was used in 80.2 % of NICUs in 2011. The most frequently used ventilation modes were synchronized intermittent mandatory ventilation (SIMV) (67.5 %) and intermittent positive pressure ventilation (IPPV) (59.7 %) in 1997 and SIMV (77.2 %) and synchronized intermittent positive pressure ventilation (SIPPV) (26.8 %) in 2011. NICUs reporting frequent or always use of IPPV decreased to 11.0 % (p < 0.001). SIMV (77.2 %) and SIPPV (26.8 %) did not change from 1997 to 2011, while high-frequency oscillation (HFO) increased from 9.1 to 19.7 % (p = 0.018). Differences between countries, level of care, and size of the NICU were minimal.

CONCLUSIONS

Target values for SaO2 decreased, while CO2 and pH increased significantly during the observation period. Current values largely reflect available evidence at time of the surveys.

WHAT IS KNOWN

• Evidence concerning target values of oxygen saturation, CO 2 , and pH in extremely low-birth-weight infants has grown substantially. • It is not known to which extent this knowledge is transferred into clinical practice and if treatment strategies have changed.

WHAT IS NEW

• Target values for oxygen saturation in ELBW infants decreased between 1997 and 2011 while target values for CO 2 and pH increased. • Similar treatment strategies existed in different countries, hospitals of different size, or university versus nonuniversity hospitals in 2011.

The use of mechanical ventilation protocols in Canadian neonatal intensive care units

OBJECTIVES

To identify the proportion of Canadian neonatal intensive care units with existing mechanical ventilation protocols and to determine the characteristics and respiratory care practices of units that have adopted such protocols.

METHODS

A structured survey including 36 questions about mechanical ventilation protocols and respiratory care practices was mailed to the medical directors of all tertiary care neonatal units in Canada and circulated between December 2012 and March 2013.

RESULTS

Twenty-four of 32 units responded to the survey (75%). Of the respondents, 91% were medical directors and 71% worked in university hospitals. Nine units (38%) had at least one type of mechanical ventilation protocol, most commonly for the acute and weaning phases. Units with pre-existing protocols were more commonly university-affiliated and had higher ratios of ventilated patients to physicians or respiratory therapists, although this did not reach statistical significance. The presence of a mechanical ventilation protocol was highly correlated with the coexistence of a protocol for noninvasive ventilation (P<0.001, OR 4.5 [95% CI 1.3 to 15.3]). There were overall wide variations in ventilation practices across units. However, units with mechanical ventilation protocols were significantly more likely to extubate neonates from the assist control mode (P=0.039, OR 8.25 [95% CI 1.2 to 59]).

CONCLUSION

Despite the lack of compelling evidence to support their use in neonates, a considerable number of Canadian neonatal intensive care units have adopted mechanical ventilation protocols. More research is needed to better understand their role in reducing unnecessary variations in practice and improving short- and long-term outcomes.

Ventilator-induced lung injury in preterm infants

In preterm infants, the need for intubation and mechanical ventilation is associated with ventilator-induced lung injuries and subsequent bronchopulmonary dysplasia. The aim of the present review was to improve the understanding of the mechanisms of injury that involve cytokine-mediated inflammation to contribute to the development of new preventive strategies. Relevant articles were retrieved from the PubMed database using the search terms "ventilator-induced lung injury preterm", "continuous positive airway pressure", "preterm", and "bronchopulmonary dysplasia". The resulting data and other relevant information were divided into several topics to ensure a thorough, critical view of ventilation-induced lung injury and its consequences in preterm infants. The role of pro-inflammatory cytokines (particularly interleukins 6 and 8 and tumor necrosis factor alpha) as mediators of lung injury was assessed. Evidence from studies conducted with animals and human newborns is described. This evidence shows that brief periods of mechanical ventilation is sufficient to induce the release of pro-inflammatory cytokines. Other forms of mechanical and non-invasive ventilation were also analyzed as protective alternatives to conventional mechanical ventilation. It was concluded that non-invasive ventilation, intubation followed by early surfactant administration and quick extubation for nasal continuous positive airway pressure, and strategies that regulate tidal volume and avoid volutrauma (such as volume guarantee ventilation) protect against ventilator-induced lung injury in preterm infants.