Effect of sustained inflation duration; resuscitation of near-term asphyxiated lambs

Positive Pressure Ventilation in Preterm Infants in the Delivery Room: A Review of Current Practices, Challenges, and Emerging Technologies

BACKGROUND

A major proportion of preterm neonates require positive pressure ventilation (PPV) immediately after delivery. PPV may be administered through a face mask (FM) or nasal prongs. Current literature indicates that either of these are associated with similar outcomes.

SUMMARY

Nonetheless, FM remains the most utilized and the best choice. However, most available FM sizes are too large for extremely preterm infants, which leads to mask leak and ineffective PPV. Challenges to providing effective PPV include poor respiratory drive, complaint chest wall, weak thoracic muscle, delayed liquid clearance, and surfactant deficiency in preterm infants. Mask leak, airway obstruction, poor technique, and inappropriate size are correctable causes of ineffective PPV. Visual assessment of chest rise is often used to assess the efficacy of PPV. However, its accuracy is debatable. Though end tidal CO2 may adjudge the effectiveness of PPV, clinical studies are limited. The compliance of a preterm lung is highly dynamic. The inflating pressure set on T-piece is constant throughout the resuscitation, but the lung volume and dynamics changes with every breath. This leads to huge fluctuations of tidal volume delivery and can trigger inflammatory cascade in preterm infants leading to brain and lung injury. Respiratory function monitoring in the delivery room has potential for guiding and optimizing delivery room resuscitation. This is, however, limited by high costs, complex information that is difficult to interpret during resuscitation, and absence of clinical trials.

KEY MESSAGES

This review summarizes the existing literature on PPV in preterm infants, the various aspects related to it such as the pathophysiology, interfaces, devices utilized to deliver it, appropriate technique, emerging technologies, and future directions.

Single versus continuous sustained inflations during chest compressions and physiological-based cord clamping in asystolic lambs

BACKGROUND

The feasibility and benefits of continuous sustained inflations (SIs) during chest compressions (CCs) during delayed cord clamping (physiological-based cord clamping; PBCC) are not known. We aimed to determine whether continuous SIs during CCs would reduce the time to return of spontaneous circulation (ROSC) and improve post-asphyxial blood pressures and flows in asystolic newborn lambs.

METHODS

Fetal sheep were surgically instrumented immediately prior to delivery at ~139 days' gestation and asphyxia induced until lambs reached asystole. Lambs were randomised to either immediate cord clamping (ICC) or PBCC. Lambs then received a single SI (SIsing; 30 s at 30 cmH2O) followed by intermittent positive pressure ventilation, or continuous SIs (SIcont: 30 s duration with 1 s break). We thus examined 4 groups: ICC +SIsing, ICC +SIcont, PBCC +SIsing, and PBCC +SIcont. Chest compressions and epinephrine administration followed international guidelines. PBCC lambs underwent cord clamping 10 min after ROSC. Physiological and oxygenation variables were measured throughout.

RESULTS

The time taken to achieve ROSC was not different between groups (mean (SD) 4.3±2.9 min). Mean and diastolic blood pressure was higher during chest compressions in PBCC lambs compared with ICC lambs, but no effect of SIs was observed. SIcont significantly reduced pulmonary blood flow, diastolic blood pressure and oxygenation after ROSC compared with SIsing.

CONCLUSION

We found no significant benefit of SIcont over SIsing during CPR on the time to ROSC or on post-ROSC haemodynamics, but did demonstrate the feasibility of continuous SIs during advanced CPR on an intact umbilical cord. Longer-term studies are recommended before this technique is used routinely in clinical practice.

Recent Update on Neonatal Resuscitation

Every 5 y, the International Liaison Committee on Resuscitation publishes consensus on cardiopulmonary resuscitation, and emergency cardiovascular science and treatment recommendations. The latest update on neonatal resuscitation guidelines was published in 2020. Here, the authors review the important changes in the recent recommendations, including initial steps of resuscitation, umbilical cord management, management of nonvigorous infants born through meconium-stained amniotic fluid, sustained inflation in preterm infants, epinephrine, vascular access, timing of discontinuation of resuscitative effort, and team briefing and debriefing.

Sustained Inflation Reduces Pulmonary Blood Flow during Resuscitation with an Intact Cord

The optimal timing of cord clamping in asphyxia is not known. Our aims were to determine the effect of ventilation (sustained inflation-SI vs. positive pressure ventilation-V) with early (ECC) or delayed cord clamping (DCC) in asphyxiated near-term lambs. We hypothesized that SI with DCC improves gas exchange and hemodynamics in near-term lambs with asphyxial bradycardia. A total of 28 lambs were asphyxiated to a mean blood pressure of 22 mmHg. Lambs were randomized based on the timing of cord clamping (ECC-immediate, DCC-60 s) and mode of initial ventilation into five groups: ECC + V, ECC + SI, DCC, DCC + V and DCC + SI. The magnitude of placental transfusion was assessed using biotinylated RBC. Though an asphyxial bradycardia model, 2-3 lambs in each group were arrested. There was no difference in primary outcomes, the time to reach baseline carotid blood flow (CBF), HR ≥ 100 bpm or MBP ≥ 40 mmHg. SI reduced pulmonary (PBF) and umbilical venous (UV) blood flow without affecting CBF or umbilical arterial blood flow. A significant reduction in PBF with SI persisted for a few minutes after birth. In our model of perinatal asphyxia, an initial SI breath increased airway pressure, and reduced PBF and UV return with an intact cord. Further clinical studies evaluating the timing of cord clamping and ventilation strategy in asphyxiated infants are warranted.

European Resuscitation Council Guidelines 2021: Newborn resuscitation and support of transition of infants at birth

The European Resuscitation Council has produced these newborn life support guidelines, which are based on the International Liaison Committee on Resuscitation (ILCOR) 2020 Consensus on Science and Treatment Recommendations (CoSTR) for Neonatal Life Support. The guidelines cover the management of the term and preterm infant. The topics covered include an algorithm to aid a logical approach to resuscitation of the newborn, factors before delivery, training and education, thermal control, management of the umbilical cord after birth, initial assessment and categorisation of the newborn infant, airway and breathing and circulation support, communication with parents, considerations when withholding and discontinuing support.

Impact of Acute and Chronic Hypoxia-Ischemia on the Transitional Circulation

The transition from intrauterine life to extrauterine existence encompasses significant cardiorespiratory adaptations. These include rapid lung aeration and increase in pulmonary blood flow (PBF). Perinatal asphyxia and fetal growth restriction can severely hamper this transition. Hypoxia is the common denominator in these 2 disease states, with the former characterized by acute insult and the latter by utero-placental insufficiency and a chronic hypoxemic state. Both may manifest as hemodynamic instability. In this review, we emphasize the role of physiologic-based cord clamping in supplementing PBF during transition. The critical role of lung aeration in initiating pulmonary gas exchange and increasing PBF is discussed. Physiologic studies in animal models have enabled greater understanding of the mechanisms and effects of various therapies on transitional circulation. With data from sheep models, we elaborate instrumentation for monitoring of cardiovascular and pulmonary physiology and discuss the combined effect of chest compressions and adrenaline in improving transition at birth. Lastly, physiologic adaptation influencing management in human neonatal cohorts with respect to cardiac and vascular impairments in hypoxic-ischemic encephalopathy and growth restriction is discussed. Impairments in right ventricular function and vascular mechanics hold the key to prognostication and understanding of therapeutic rationale in these critically ill cohorts. The right ventricle and pulmonary circulation seem to be especially affected and may be explored as therapeutic targets. The role of comprehensive assessments using targeted neonatal echocardiography as a longitudinal, reliable, and easily accessible tool, enabling precision medicine facilitating physiologically appropriate treatment choices, is discussed.

Is Chest Compression Superimposed with Sustained Inflation during Cardiopulmonary Resuscitation an Alternative to 3:1 Compression to Ventilation Ratio in Newborn Infants?

Approximately 0.1% for term and 10-15% of preterm infants receive chest compression (CC) in the delivery room, with high incidence of mortality and neurologic impairment. The poor prognosis associated with receiving CC in the delivery room has raised concerns as to whether specifically-tailored cardiopulmonary resuscitation methods are needed. The current neonatal resuscitation guidelines recommend a 3:1 compression:ventilation ratio; however, the most effective approach to deliver chest compression is unknown. We recently demonstrated that providing continuous chest compression superimposed with a high distending pressure or sustained inflation significantly reduced time to return of spontaneous circulation and mortality while improving respiratory and cardiovascular parameters in asphyxiated piglet and newborn infants. This review summarizes the current available evidence of continuous chest compression superimposed with a sustained inflation.

[Newborn resuscitation and support of transition of infants at birth]

The European Resuscitation Council has produced these newborn life support guidelines, which are based on the International Liaison Committee on Resuscitation (ILCOR) 2020 Consensus on Science and Treatment Recommendations (CoSTR) for Neonatal Life Support. The guidelines cover the management of the term and preterm infant. The topics covered include an algorithm to aid a logical approach to resuscitation of the newborn, factors before delivery, training and education, thermal control, management of the umbilical cord after birth, initial assessment and categorisation of the newborn infant, airway and breathing and circulation support, communication with parents, considerations when withholding and discontinuing support.

Sustained Lung Inflations During Neonatal Resuscitation at Birth: A Meta-analysis

CONTEXT

The International Liaison Committee on Resuscitation prioritized review of sustained inflation (SI) of the lung at birth.

OBJECTIVE

To complete a systematic review and meta-analysis comparing strategies using 1 or more SI ≥1 second with intermittent inflations <1 second for newborns at birth.

DATA SOURCES

Medline, Embase, and Evidence-Based Medicine Reviews were searched from January 1, 1946, to July 20, 2020.

STUDY SELECTION

Studies were selected by pairs of independent reviewers in 2 stages.

DATA EXTRACTION

Reviewers extracted data, appraised risk of bias, and assessed certainty of evidence for each outcome.

RESULTS

Ten trials enrolling 1502 preterm newborns were included. Five studies included newborns who did not receive assisted ventilation at the outset. There were no differences between SI and control groups for death before discharge or key morbidities. For death within the first 2 days, comparing SI with the controls, risk ratio was 2.42 (95% confidence interval = 1.15-5.09). In subgroup analysis of preterm infants ≤28 + 0 weeks' gestation, for death before discharge, risk ratio was 1.38 (95% confidence interval = 1.00-1.91). Together, these findings suggest the potential for harm of SI.

LIMITATIONS

The certainty of evidence was very low for death in the delivery room and low for all other outcomes.

CONCLUSIONS

In this systematic review, we did not find benefit in using 1 or more SI >5 seconds for preterm infants at birth. SI(s) may increase death before discharge among the subgroup born ≤28 + 0 weeks' gestation. There is insufficient evidence to determine the likely effect of SI(s) on other key morbidities.

Delivery Room Management of Asphyxiated Term and Near-Term Infants

Approximately 800,000 newborns die annually due to birth asphyxia. The resuscitation of asphyxiated term newly born infants often occurs unexpected and is challenging for healthcare providers as it demands experience and knowledge in neonatal resuscitation. Current neonatal resuscitation guidelines often focus on resuscitation of extremely and/or very preterm infants; however, the recommendations for asphyxiated term newborn infants differ in some aspects to those for preterm infants (i.e., respiratory support, supplemental oxygen, and temperature management). Since the update of the neonatal resuscitation guidelines in 2015, several studies examining various resuscitation approaches to improve the outcome of asphyxiated infants have been published. In this review, we discuss current recommendations and recent findings and provide an overview of delivery room management of asphyxiated term newborn infants.

Sustained inflation: The lung recruitment maneuvers for neonates

Establishing effective respiration is vital in the transition from fetal to neonatal life. Respiratory support mainly facilitates and creates functional residual capacity and maintains adequate gas exchange. Sustained inflation (SI) delivers prolonged inflation and rapidly creates and establishes the functional residual capacity. The use of SI in preterm infants in the delivery room is still controversial. The optimum settings of SI remain unknown. Animal studies and clinical reports have demonstrated the advantages and disadvantages of SI. In this article, the current literature was reviewed to examine the efficacy of SI in infants.

Sustained Inflation vs Standard Resuscitation for Preterm Infants: A Systematic Review and Meta-analysis

IMPORTANCE

Most preterm infants require respiratory support to establish lung aeration after birth. Intermittent positive pressure ventilation and continuous positive airway pressure are standard therapies. An initial sustained inflation (inflation time >5 seconds) is a widely practiced alternative strategy.

OBJECTIVE

To conduct a systematic review and meta-analysis of sustained inflation vs intermittent positive pressure ventilation and continuous positive airway pressure for the prevention of hospital mortality and morbidity for preterm infants.

DATA SOURCES

MEDLINE (through PubMed), Embase, the Cumulative Index of Nursing and Allied Health Literature, and the Cochrane Central Register of Controlled Trials were searched through June 24, 2019.

STUDY SELECTION

Randomized clinical trials of preterm infants born at less than 37 weeks' gestation that compared sustained inflation (inflation time >5 seconds) vs standard resuscitation with either intermittent positive pressure ventilation or continuous positive airway pressure were included. Studies including other cointerventions were excluded.

DATA EXTRACTION AND SYNTHESIS

Two reviewers assessed the risk of bias of included studies. Meta-analysis of pooled outcome data used a fixed-effects model specific to rarer events. Subgroups were based on gestational age and study design (rescue vs prophylactic sustained inflation).

MAIN OUTCOMES AND MEASURES

Death before hospital discharge.

RESULTS

Nine studies recruiting 1406 infants met inclusion criteria. Death before hospital discharge occurred in 85 of 736 infants (11.5%) treated with sustained inflation and 62 of 670 infants (9.3%) who received standard therapy for a risk difference of 3.6% (95% CI, -0.7% to 7.9%). Although analysis of the primary outcome identified important heterogeneity based on gestational age subgroups, the 95% CI for the risk difference included 0 for each individual gestational age subgroup. There was no difference in the primary outcome between subgroups based on study design. Sustained inflation was associated with increased risk of death in the first 2 days after birth (risk difference, 3.1%; 95% CI, 0.9%-5.3%). No differences in the risk of other secondary outcomes were identified. The quality-of-evidence assessment was low owing to risk of bias and imprecision.

CONCLUSIONS AND RELEVANCE

There was no difference in the risk of the primary outcome of death before hospital discharge, and there was no evidence of efficacy for sustained inflation to prevent secondary outcomes. These findings do not support the routine use of sustained inflation for preterm infants after birth.

Improving Newborn Respiratory Outcomes With a Sustained Inflation: A Systematic Narrative Review of Factors Regulating Outcome in Animal and Clinical Studies

Respiratory support is critically important for survival of newborns who fail to breathe spontaneously at birth. Although there is no internationally accepted definition of a sustained inflation (SI), it has commonly been defined as a positive pressure inflation designed to establish functional residual capacity and applied over a longer time period than normally used in standard respiratory support (SRS). Outcomes vary distinctly between studies and to date there has been no comprehensive investigation of differences in SI approach and study outcome in both pre-clinical and clinical studies. A systematic literature search was performed and, after screening, identified 17 animal studies and 17 clinical studies evaluating use of a SI in newborns compared to SRS during neonatal resuscitation. Study demographics including gestational age, SI parameters (length, repetitions, pressure, method of delivery) and study outcomes were compared. Animal studies provide mechanistic understanding of a SI on the physiology underpinning the cardiorespiratory transition at birth. In clinical studies, there is considerable difference in study quality, delivery of SIs (number, pressure, length) and timing of primary outcome evaluation which limits direct comparison between studies. The largest difference is method of delivery, where the role of a SI has been observed in intubated animals, as the inflation pressure is directly applied to the lung, bypassing the obstructed upper airway in an apnoeic state. This highlights a potential limitation in clinical use of a SI applied non-invasively. Further research is required to identify if a SI may have greater benefits in subpopulations of newborns.

Efficacy of Intravenous, Endotracheal, or Nasal Adrenaline Administration During Resuscitation of Near-Term Asphyxiated Lambs

Objectives: Neonatal resuscitation guidelines recommend administering intravenous (IV) adrenaline if bradycardia persists despite adequate ventilation and chest compressions (CC). Rapid IV access is challenging, but little evidence exists for other routes of administration. We compared IV, endotracheal (ET), and intranasal routes for adrenaline administration during resuscitation of asphyxiated newborn lambs. Study design: Near-term lambs (n = 22) were delivered by caesarean section. Severe asphyxia was induced by clamping the umbilical cord while delaying ET ventilation until blood flow in the carotid artery ceased. Following a 30 s sustained inflation and ventilation for 30 s, we commenced uncoordinated CC at 90/min. We randomized four groups receiving repeated treatment doses (Tds) every 3rd min of (i) IV-Adrenaline (50 μg), (ii) ET-Adrenaline (500 μg), (iii) Nasal-Adrenaline via an atomizer (500 μg), and (iv) IV-saline. If return of spontaneous circulation (ROSC) was not achieved after three Tds by the assigned route, up to two rescue doses (Rds) of IV adrenaline were administered. Main outcome measures were achievement of ROSC and time from start of CC to ROSC, defined as heart rate >100/min, and mean carotid arterial pressure >30 mmHg. Results: In the IV-Adrenaline group, 5/6 lambs achieved ROSC after the first Td, whereas 1 lamb required two Tds before achieving ROSC. In the ET-Adrenaline group, 1/5 lambs required one Td, 1 lamb required three Tds, 2 lambs required 2 Rds, and 1 did not achieve ROSC. In the Nasal-Adrenaline group, 1/6 lambs required one Td, 2 required two Tds, whereas 3 lambs required either one (2 lambs) or two (1 lamb) Rds of adrenaline to achieve ROSC. In the IV-saline group, no lambs achieved ROSC until adrenaline Rds; 4/5 lambs required one Rd and 1 lamb required two Rds. Time to ROSC was shorter using IV-Adrenaline (2.4 ± 0.4 min) compared with ET-Adrenaline (10.3 ± 2.4 min), Nasal-Adrenaline (9.2 ± 2.2 min), and IV-saline (11.2 ± 1.2 min). Conclusion: IV adrenaline had superior efficacy compared with nasal or ET administration. Nasal administration had a similar effect as ET administration and is an easier route for early application. Nasal high-dose adrenaline administration for neonatal resuscitation merits further investigation.

Aeration strategy at birth influences the physiological response to surfactant in preterm lambs

BACKGROUND

The influence of pressure strategies to promote lung aeration at birth on the subsequent physiological response to exogenous surfactant therapy has not been investigated.

OBJECTIVES

To compare the effect of sustained inflation (SI) and a dynamic positive end-expiratory pressure (PEEP) manoeuvre at birth on the subsequent physiological response to exogenous surfactant therapy in preterm lambs.

METHODS

Steroid-exposed preterm lambs (124-127 days' gestation; n=71) were randomly assigned from birth to either (1) positive-pressure ventilation (PPV) with no recruitment manoeuvre; (2) SI until stable aeration; or (3) 3 min dynamic stepwise PEEP strategy (maximum 14-20 cmH₂O; dynamic PEEP (DynPEEP)), followed by PPV for 60 min using a standardised protocol. Surfactant (200 mg/kg poractant alfa) was administered at 10 min. Dynamic compliance, gas exchange and regional ventilation and aeration characteristics (electrical impedance tomography) were measured throughout and compared between groups, and with a historical group (n=38) managed using the same strategies without surfactant.

RESULTS

Compliance increased after surfactant only in the DynPEEP group (p<0.0001, repeated measures analysis of variance), being 0.17 (0.10, 0.23) mL/kg/cmH₂O higher at 60 min than the SI group. An SI resulted in the least uniform aeration, and unlike the no-recruitment and DynPEEP groups, the distribution of aeration and tidal ventilation did not improve with surfactant. All groups had similar improvements in oxygenation post-surfactant compared with the corresponding groups not treated with surfactant.

CONCLUSIONS

A DynPEEP strategy at birth may improve the response to early surfactant therapy, whereas rapid lung inflation with SI creates non-uniform aeration that appears to inhibit surfactant efficacy.

Novel interventions to reduce oxidative-stress related brain injury in neonatal asphyxia

Perinatal asphyxia-induced brain injury may present as hypoxic-ischemic encephalopathy in the neonatal period, and disability including cerebral palsy in the long term. The brain injury is secondary to both the hypoxic-ischemic event and the reoxygenation-reperfusion following resuscitation. Early events in the cascade of brain injury can be classified as either inflammation or oxidative stress through the generation of free radicals. The objective of this paper is to present efforts that have been made to limit the oxidative stress associated with hypoxic-ischemic encephalopathy. In the acute phase of ischemia/hypoxia and reperfusion/reoxygenation, the outcomes of asphyxiated infants can be improved by optimizing the initial delivery room stabilization. Interventions include limiting oxygen exposure, and shortening the time to return of spontaneous circulation through improved methods for supporting hemodynamics and ventilation. Allopurinol, melatonin, noble gases such as xenon and argon, and magnesium administration also target the acute injury phase. Therapeutic hypothermia, N-acetylcysteine2-iminobiotin, remote ischemic postconditioning, cannabinoids and doxycycline target the subacute phase. Erythropoietin, mesenchymal stem cells, topiramate and memantine could potentially limit injury in the repair phase after asphyxia. To limit the injurious biochemical processes during the different stages of brain injury, determination of the stage of injury in any particular infant remains essential. Currently, therapeutic hypothermia is the only established treatment in the subacute phase of asphyxia-induced brain injury. The effects and side effects of oxidative stress reducing/limiting medications may however be difficult to predict in infants during therapeutic hypothermia. Future neuroprotection in asphyxiated infants may indeed include a combination of therapies. Challenges include timing, dosing and administration route for each neuroprotectant.

Newborn self-inflating manual resuscitators: precision robotic testing of safety and reliability

AIM

A controlled bench test was undertaken to determine the performance variability among a range of neonatal self-inflating bags (SIB) compliant with current International Standards Organisation (ISO).

INTRODUCTION

Use of SIB to provide positive pressure ventilation during newborn resuscitation is a common emergency procedure. The United Nations programmes advocate increasing availability of SIB in low-income and middle-income nations and recommend devices compliant with ISO. No systematic study has evaluated variance in different models of neonatal SIB.

METHODS

20 models of SIB were incrementally compressed by an automated robotic device simulating the geometry and force of a human hand across a range of precise distances in a newborn lung model. Significance was calculated using analysis of variance repeated measures to determine the relationship between distance of SIB compression and delivered ventilation. A pass/fail was derived from a composite score comprising: minimum tidal volume; coefficient of variation (across all compression distances); peak pressures generated and functional compression distance.

RESULTS

Ten out of the 20 models of SIB failed our testing methodology. Two models could not provide safe minimum tidal volumes (2.5-5 mL); six models exceeded safety inflation pressure limit >45 cm H₂O, representing 6% of their inflations; five models had excessive coefficient of variation (>30% averaged across compression distances) and three models did not deliver inflation volumes >2.5 mL until approximately 50% of maximum bag compression distance was reached. The study also found significant intrabatch variability and forward leakage.

CONCLUSION

Compliance of SIBs with ISO standards may not guarantee acceptable or safe performance to resuscitate newborn infants.

The SURV1VE trial-sustained inflation and chest compression versus 3:1 chest compression-to-ventilation ratio during cardiopulmonary resuscitation of asphyxiated newborns: study protocol for a cluster randomized controlled trial

Background

The need for cardiopulmonary resuscitation (CPR) is often unexpected, and the infrequent use of CPR in the delivery room (DR) limits the opportunity to perform rigorous clinical studies to determine the best method for delivering chest compression (CC) to newborn infants. The current neonatal resuscitation guidelines recommend using a coordinated 3:1 compression-to-ventilation (C:V) ratio (CC at a rate of 90/min and ventilations at a rate of 30/min). In comparison, providing CC during a sustained inflation (SI) (CC + SI) significantly improved hemodynamics, minute ventilation, and time to return of spontaneous circulation (ROSC) compared to 3:1 C:V ratio in asphyxiated piglets. Similarly, a small pilot trial in newborn infants showed similar results. Until now no study has examined different CC techniques during neonatal resuscitation in asphyxiated newborn infants in the DR. To date, no trial has been performed to directly compare CC + SI and 3:1 C:V ratio in the DR during CPR of asphyxiated newborn infants.

Methods

This is a large, international, multi-center, prospective, unblinded, cluster randomized controlled trial in asphyxiated newborn infants at birth. All term and preterm infants > 28^+ 0 by best obstetrical estimate who require CPR at birth due to bradycardia (< 60/min) or asystole are eligible. The primary outcome of this study is to compare the time to ROSC in infants born > 28^+ 0 weeks’ gestational age with bradycardia (< 60/min) or asystole immediately after birth who receive either CC + SI or 3:1 C:V ratio as the CPR strategy.

Discussion

Morbidity and mortality rates are extremely high for newborns requiring CC. We believe the combination of simultaneous CC and SI during CPR has the potential to significantly improve ROSC and survival. In addition, we believe that CC + SI might improve respiratory and hemodynamic parameters and potentially minimize morbidity and mortality in newborn infants. In addition, this will be the first randomized controlled trial to examine CC in the newborn period.

Trial registration

ClinicalTrials.gov, NCT02858583. Registered on 8 August 2016

Electronic supplementary material

The online version of this article (10.1186/s13063-019-3240-8) contains supplementary material, which is available to authorized users.

Chest Compressions in the Delivery Room

Annually, an estimated 13–26 million newborns need respiratory support and 2–3 million newborns need extensive resuscitation, defined as chest compression and 100% oxygen with or without epinephrine in the delivery room. Despite such care, there is a high incidence of mortality and neurologic morbidity. The poor prognosis associated with receiving chest compression alone or with medications in the delivery room raises questions as to whether improved cardiopulmonary resuscitation methods specifically tailored to the newborn could improve outcomes. This review discusses the current recommendations, mode of action, different compression to ventilation ratios, continuous chest compression with asynchronous ventilations, chest compression and sustained inflation optimal depth, and oxygen concentration during cardiopulmonary resuscitation.

Physiologically based cord clamping stabilises cardiac output and reduces cerebrovascular injury in asphyxiated near-term lambs

BACKGROUND

Physiologically based cord clamping (PBCC) has advantages over immediate cord clamping (ICC) during preterm delivery, but its efficacy in asphyxiated infants is not known. We investigated the physiology of PBCC following perinatal asphyxia in near-term lambs.

METHODS

Near-term sheep fetuses (139±2 (SD) days' gestation) were instrumented to measure umbilical, carotid, pulmonary and femoral arterial flows and pressures. Systemic and cerebral oxygenation was recorded using pulse oximetry and near-infrared spectroscopy, respectively. Fetal asphyxia was induced until mean blood pressure reached ~20 mm Hg, where lambs underwent ICC and initiation of ventilation (n=7), or ventilation for 15 min prior to umbilical cord clamping (PBCC; n=8). Cardiovascular parameters were measured and white and grey matter microvascular integrity assessed using qRT-PCR and immunohistochemistry.

RESULTS

PBCC restored oxygenation and cardiac output at the same rate and in a similar fashion to lambs resuscitated following ICC. However, ICC lambs had a rapid and marked overshoot in mean systemic arterial blood pressure from 1 to 10 min after ventilation onset, which was largely absent in PBCC lambs. ICC lambs had increased cerebrovascular injury, as indicated by reduced expression of blood-brain barrier proteins and increased cerebrovascular protein leakage in the subcortical white matter (by 86%) and grey matter (by 47%).

CONCLUSION

PBCC restored cardiac output and oxygenation in an identical time frame as ICC, but greatly mitigated the postasphyxia rebound hypertension measured in ICC lambs. This likely protected the asphyxiated brain from cerebrovascular injury. PBCC may be a more suitable option for the resuscitation of the asphyxiated newborn compared with the current standard of ICC.

Animal models in neonatal resuscitation research: What can they teach us?

Animal models have made and continue to make important contributions to neonatal medicine. For example, studies in fetal sheep have taught us much about the physiology of the fetal-to-neonatal transition. However, whereas animal models allow multiple factors to be investigated in a logical and systematic manner, no animal model is perfect for humans and so we need to understand the fundamental differences in physiology between the species in question and humans. Although most physiological systems are well conserved between species, some small differences exist and so wherever possible the knowledge generated from preclinical studies in animals should be tested in clinical trials. However, with the rise of evidence-based medicine the distinction between scientific knowledge generation and evidence gathering has been confused and the two have been lumped together. This misunderstands the contribution that scientific knowledge can provide. Science should be used to guide the gathering of evidence by informing the design of clinical trials, thereby increasing their likelihood of success. While scientific knowledge is not evidence, in the absence of evidence it is likely to be the best option for guiding clinical practice.

Sustained inflations versus UK standard inflations during initial resuscitation of prematurely born infants in the delivery room: a study protocol for a randomised controlled trial

BACKGROUND

Many infants born at less than 34 weeks of gestational age will require resuscitation in the delivery suite. Yet, different resuscitation techniques are specified in different national guidelines, likely reflecting a limited evidence base. One difference is the length of mechanical inflation initially delivered to infants either via a facemask or endotracheal tube. Some guidelines specify short inflations delivered at rates of 40-60/min, others recommend initial inflations lasting 2-3 s or sustained inflations lasting for ≥ 5 s for initial resuscitation. Research has shown that tidal volumes > 2.2 mL/kg (the anatomical dead space) are seldom generated unless the infant's respiratory effort coincides with an inflation (active inflation). When inflations lasting 1-3 s were used, the time to the first active inflation was inversely proportional to the inflation time. This trial investigates whether a sustained inflation or repeated shorter inflations is more effective in stimulating the first active inflation.

METHODS

This non-blinded, randomised controlled trial performed at a single tertiary neonatal unit is recruiting 40 infants born at < 34 weeks of gestational age. A 15-s sustained inflation is being compared to five repeated inflations of 2-3 s during the resuscitation at delivery. A respiratory function monitor is used to record airway pressure, flow, expiratory tidal volume and end tidal carbon dioxide (ETCO₂) levels. The study is performed as emergency research without prior consent and was approved by the NHS London-Riverside Research Ethics Committee. The primary outcome is the minute volume in the first minute of resuscitation with secondary outcomes of the time to the first active inflation and ETCO₂ level during the first minute of recorded resuscitation.

DISCUSSION

This is the first study to compare a sustained inflation to the current UK practice of five initial inflations of 2-3 s.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT02967562 . Registered on 15 November 2016.

Achieving and maintaining lung volume in the preterm infant: from the first breath to the NICU

The main goal for the neonatologist is to facilitate the adaptation to extra-uterine life during initial transition, while minimizing lung injury opening and protecting the premature lung from the first breath onwards. An appropriate management from birth should lead to the achievement of an early functional residual capacity (FRC), and the following steps should aim at maintaining an adequate lung volume. To date, different strategies are available to optimize fetal-neonatal transition and promote lung recruitment. New ventilation approaches, such as sustained lung inflation (SLI) and "open lung strategy", well-established ventilation techniques with a more tailored application and less invasive modalities to administer surfactant have been recently introduced in clinical practice with promising results.

CONCLUSIONS

given the current status of neonatal care, it seems that lung injury and BPD could be reduced with multiple strategies starting early in the delivery room. Literature underlines the importance of a respiratory tailored management of preterm infants from birth and during the whole NICU stay. What is Known: • Experimental and clinical studies have shown that the transition from fetal to adult type cardiorespiratory circulation needs an adequate lung ventilation. An appropriate management in the delivery room should lead to the achievement of an early FRC, and through the following steps, the neonatologist should aim at maintaining an adequate lung volume. • Literature underlines the importance of a respiratory tailored management of preterm infants during the whole NICU stay to maintain the benefits of a successful postnatal adaption. What is New: • Herewith, we describe the most relevant and recent interventions which can be performed from the delivery room to the NICU stay to guarantee an adequate tradition to postnatal life and an effective cardiorespiratory stability.

Continuous Chest Compressions During Sustained Inflations in a Perinatal Asphyxial Cardiac Arrest Lamb Model

OBJECTIVE

Continuous chest compressions are more effective during resuscitation in adults. Sustained inflation rapidly establishes functional residual capacity in fluid-filled lungs at birth. We sought to compare the hemodynamics and success in achieving return of spontaneous circulation in an asphyxial cardiac arrest lamb model with transitioning fetal circulation and fluid-filled lungs between subjects receiving continuous chest compressions during sustained inflation and those receiving conventional 3:1 compression-to-ventilation resuscitation.

DESIGN

Prospective, randomized, animal model study.

SETTING

An experimental laboratory.

SUBJECTS

Fourteen newborn term gestation lambs.

INTERVENTIONS

Lambs were randomized into two groups: 3:1 compression-to-ventilation (control) and continuous chest compressions during sustained inflation. The umbilical cord was occluded to induce asphyxia and asystole. The control group was resuscitated per NRP guidelines. In the sustained inflation + continuous chest compressions group, sustained inflation at 35 cm H2O was provided for 30 seconds with 1-second interruptions before another sustained inflation was provided. One hundred twenty chest compressions/min started after the initial sustained inflation. The first dose of IV epinephrine was given at 6 minutes if return of spontaneous circulation was not achieved and then every 3 minutes until return of spontaneous circulation or for a total of four doses.

MEASUREMENT AND RESULTS

All lambs achieved return of spontaneous circulation in a comparable median time (interquartile range) of 390 seconds (225-405 s) and 345 seconds (204-465 s) in the sustained inflation + continuous chest compressions and control groups, respectively. Four of seven (sustained inflation + continuous chest compressions) and three of six (control) lambs required epinephrine to achieve return of spontaneous circulation. Diastolic blood pressures were lower in the sustained inflation + continuous chest compressions (4 ± 2 mm Hg) compared to the control group (7 ± 2 mm Hg), p < 0.05. PaCO2, PaO2, and lactate were similar between the groups during the study period.

CONCLUSION

In this perinatal cardiac arrest lamb model with transitioning fetal circulation and fluid-filled lungs, sustained inflation + continuous chest compressions is as effective as 3:1 compression-to-ventilation resuscitation in achieving return of spontaneous circulation. Half the lambs achieved return of spontaneous circulation without epinephrine. continuous chest compressions during sustained inflation reduced diastolic pressures but did not alter gas exchange or carotid blood flow compared to 3:1 compression-to-ventilation resuscitation.

Management and investigation of neonatal encephalopathy: 2017 update

This review discusses an approach to determining the cause of neonatal encephalopathy, as well as current evidence on resuscitation and subsequent management of hypoxic-ischaemic encephalopathy (HIE). Encephalopathy in neonates can be due to varied aetiologies in addition to hypoxic-ischaemia. A combination of careful history, examination and the judicious use of investigations can help determine the cause. Over the last 7 years, infants with moderate to severe HIE have benefited from the introduction of routine therapeutic hypothermia; the number needed to treat for an additional beneficial outcome is 7 (95% CI 5 to 10). More recent research has focused on optimal resuscitation practices for babies with cardiorespiratory depression, such as delayed cord clamping after establishment of ventilation and resuscitation in air. Around a quarter of infants with asystole at 10 min after birth who are subsequently cooled have normal outcomes, suggesting that individualised decision making on stopping resuscitation is needed, based on access to intensive treatment unit and early cooling. The full benefit of cooling appears to have been exploited in our current treatment protocols of 72 hours at 33.5°C; deeper and longer cooling showed adverse outcome. The challenge over the next 5-10 years will be to assess which adjunct therapies are safe and optimise hypothermic brain protection in phase I and phase II trials. Optimal care may require tailoring treatments according to gender, genetic risk, injury severity and inflammatory status.

Hemodynamics and gas exchange during chest compressions in neonatal resuscitation

PURPOSE

Current knowledge about pulmonary/systemic hemodynamics and gas exchange during neonatal resuscitation in a model of transitioning fetal circulation with fetal shunts and fluid-filled alveoli is limited. Using a fetal lamb asphyxia model, we sought to determine whether hemodynamic or gas-exchange parameters predicted successful return of spontaneous circulation (ROSC).

METHODS

The umbilical cord was occluded in 22 lambs to induce asphyxial cardiac arrest. Following five minutes of asystole, resuscitation as per AHA-Neonatal Resuscitation Program guidelines was initiated. Hemodynamic parameters and serial arterial blood gases were assessed during resuscitation.

RESULTS

ROSC occurred in 18 lambs (82%) at a median (IQR) time of 120 (105-180) seconds. There were no differences in hemodynamic parameters at baseline and at any given time point during resuscitation between the lambs that achieved ROSC and those that did not. Blood gases at arrest prior to resuscitation were comparable between groups. However, lambs that achieved ROSC had lower PaO2, higher PaCO2, and lower lactate during resuscitation. Increase in diastolic blood pressures induced by epinephrine in lambs that achieved ROSC (11 ±4 mmHg) did not differ from those that were not resuscitated (10 ±6 mmHg). Low diastolic blood pressures were adequate to achieve ROSC.

CONCLUSIONS

Hemodynamic parameters in a neonatal lamb asphyxia model with transitioning circulation did not predict success of ROSC. Lactic acidosis, higher PaO2 and lower PaCO2 observed in the lambs that did not achieve ROSC may represent a state of inadequate tissue perfusion and/or mitochondrial dysfunction.

Tidal volume delivery during continuous chest compressions and sustained inflation

OBJECTIVE

To determine the distending pressure needed to achieve sufficient tidal volume (V_T) delivery during continuous chest compressions (CC) superimposed by sustained inflation (SI) (CC+SI).

DESIGN

Randomised animal/manikin trial.

SETTING

University laboratory.

SUBJECTS

Cadaver piglets/manikin.

INTERVENTIONS

SI distending pressures of 5, 10, 15, 20, 25 and 30 cm H₂O were delivered in random order during CC+SI for 2 min each.

MAIN OUTCOME MEASURES

V_T, gas flow and airway pressure. Spearman's r for distending pressure and V_T.

RESULTS

Distending pressure and V_T correlated in cadaver piglets (r=0.83, p<0.001), manikin (r=0.98, p<0.001) and combined data (r=0.49, p<0.001). V_T was delivered during chest recoil during CC in both models. In cadaver piglets, a distending pressure ∼25 cm H₂O was needed to achieve an adequate V_T.

CONCLUSIONS

Chest recoil generates V_T depending on an adequate distending pressure. This has previously been demonstrated in adult animals. A pressure of ∼25 cm H₂O is needed to achieve an adequate V_T delivery.

Understanding the Full Spectrum of Organ Injury Following Intrapartum Asphyxia

Birth asphyxia is a significant global health problem, responsible for ~1.2 million neonatal deaths each year worldwide. Those who survive often suffer from a range of health issues including brain damage-manifesting as cerebral palsy (CP)-respiratory insufficiency, cardiovascular collapse, and renal dysfunction, to name a few. Although the majority of research is directed toward reducing the brain injury that results from intrapartum birth asphyxia, the multi-organ injury observed in surviving neonates is of equal importance. Despite the advent of hypothermia therapy for the treatment of hypoxic-ischemic encephalopathy (HIE), treatment options following asphyxia at birth remain limited, particularly in low-resource settings where the incidence of birth asphyxia is highest. Furthermore, although cooling of the neonate results in improved neurological outcomes for a small proportion of treated infants, it does not provide any benefit to the other organ systems affected by asphyxia at birth. The aim of this review is to summarize the current knowledge of the multi-organ effects of intrapartum asphyxia, with particular reference to the findings from our laboratory using the precocial spiny mouse to model birth asphyxia. Furthermore, we reviewed the current treatments available for neonates who have undergone intrapartum asphyxia, and highlight the emergence of maternal dietary creatine supplementation as a preventative therapy, which has been shown to provide multi-organ protection from birth asphyxia-induced injury in our preclinical studies. This cheap and effective nutritional supplement may be the key to reducing birth asphyxia-induced death and disability, particularly in low-resource settings where current treatments are unavailable.

Effects of Breathing and Apnoea during Sustained Inflations in Resuscitation of Preterm Infants

BACKGROUND

A sustained inflation (SI) at birth in preterm babies may be ineffective unless the infants breathe. Gain in lung volume is associated with breathing during delivery room non-invasive management.

OBJECTIVE

To describe the breathing patterns of preterm infants during an SI and correlate to a calculated gain in lung volume.

METHODS

Retrospective observational study. Data collected from a respiratory function monitor during SI (25 cmH2O for 15 s then PEEP at 5 cmH2O) through a face mask in preterm infants (gestational age [GA] ≤31 weeks). Spontaneous breaths, inspiratory time (TI), inspiratory/expiratory tidal volume (Vti/Vte), and gain in lung volume were determined.

RESULTS

30 SIs in 20 infants (mean GA 27 weeks; birth weight 825 g) were analysed and stratified in 2 groups according to spontaneous breathing: SIs without spontaneous breaths (apnoea: n = 11) and SIs with spontaneous breaths (breathing: n = 19). Mean GA was lower in the apnoea group versus the breathing group (25 vs. 27+5 weeks; p = 0.01). Mean birth weight was lower in the apnoea group versus the breathing group (683 vs. 860 g; p = ns). In the breathing group, the mean number of spontaneous breaths was 4 with a mean TI of 0.52 min, the mean Vti/kg was 5.9 mL/kg, and the mean Vte was 2.7 mL/kg. The calculated mean gain in lung volume was 7.5 mL/kg in the apnoea group and 17.8 mL/kg in the breathing group (p = 0.039).

CONCLUSIONS

Actively breathing infants during an SI at birth showed a gain in lung volume higher than apnoeic infants. Spontaneous breathing during SI seems to be related to GA.

Sustained Lung Inflation: Physiology and Practice

Lung aeration is the most critical task newborns must accomplish after birth. Almost all extremely preterm infants require respiratory support during this process, but the best method to promote lung aeration in preterm infants is unknown. The current standard practice is intermittent positive pressure ventilation with positive end-expiratory pressure. Sustained inflation is a promising alternative strategy for lung liquid clearance and aeration. Here we review the physiologic rationale for sustained inflation and the available clinical evidence for sustained inflation in preterm infants.

Novel Approaches to Neonatal Resuscitation and the Impact on Birth Asphyxia

Historically, recommendations for neonatal resuscitation were largely based on dogma, but there is renewed interest in performing resuscitation studies at birth. The emphasis for resuscitation following birth asphyxia is administering effective ventilation, as adequate lung aeration leads not only to an increase in oxygenation but also increased pulmonary blood flow and heart rate. To aerate the lung, an initial sustained inflation can increase heart rate, oxygenation, and blood pressure recovery much faster when compared with standard ventilation. Hyperoxia should be avoided, and extra oxygen given to restore cardiac function and spontaneous breathing should be titrated based on oxygen saturations.

Optimizing lung aeration at birth using a sustained inflation and positive pressure ventilation in preterm rabbits

BACKGROUND

A sustained inflation (SI) facilitates lung aeration, but the most effective pressure and duration are unknown. We investigated the effect of gestational age (GA) and airway liquid volume on the required inflation pressure and SI duration.

METHODS

Rabbit kittens were delivered at 27, 29, and 30 d gestation, intubated and airway liquid was aspirated. Either no liquid (control) or 30 ml/kg of liquid was returned to the airways. Lung gas volumes were measured by plethysmography and phase-contrast X-ray-imaging. Starting at 22 cmH2O, airway pressure was increased until airflow commenced and pressure was then held constant. The SI was truncated when 20 ml/kg air had entered the lung and ventilation continued with intermittent positive pressure ventilation (iPPV).

RESULTS

Higher SI pressures and longer durations were required in 27-d kittens compared to 30-d kittens. During iPPV, 27-d kittens needed higher pressures and had lower functional residual capacity (FRC) compared to 30-d kittens. Adding lung liquid increased SI duration, reduced FRC, and increased resistance and pressures during iPPV in 29- and 30-d kittens.

CONCLUSION

Immature kittens required higher starting pressures and longer SI durations to achieve a set inflation volume. Larger airway liquid volumes adversely affected lung function during iPPV in older but not young kittens.

Return of spontaneous Circulation Is Not Affected by Different Chest Compression Rates Superimposed with Sustained Inflations during Cardiopulmonary Resuscitation in Newborn Piglets

Objective

Recently, sustained inflations (SI) during chest compression (CC) have been suggested as an alternative to the current approach during neonatal resuscitation. However, the optimal rate of CC during SI has not yet been established. Our aim was to determine whether different CC rates during SI reduce time to return of spontaneous circulation (ROSC) and improve hemodynamic recovery in newborn piglets with asphyxia-induced bradycardia.

Intervention and measurements

Term newborn piglets were anesthetized, intubated, instrumented and exposed to 45-min normocapnic hypoxia followed by asphyxia. Resuscitation was initiated when heart rate decreased to 25% of baseline. Piglets were randomized into three groups: CC superimposed by SI at a rate of 90 CC per minute (SI+CC 90, n = 8), CC superimposed by SI at a rate of 120 CC per minute (SI+CC 120, n = 8), or a sham group (n = 6). Cardiac function, carotid blood flow, cerebral oxygenation and respiratory parameters were continuously recorded throughout the experiment.

Main results

Both treatment groups had similar time of ROSC, survival rates, hemodynamic and respiratory parameters during cardiopulmonary resuscitation. The hemodynamic recovery in the subsequent 4h was similar in both groups and was only slightly lower than sham-operated piglets at the end of experiment.

Conclusion

Newborn piglets resuscitated by SI+CC 120 did not show a significant advantage in ROSC, survival, and hemodynamic recovery as compared to those piglets resuscitated by SI+CC 90.

Sustained inflation: Prophylactic or rescue maneuver?

Application of nasal continuous positive airway pressure (nCPAP) in the delivery room is a valid alternative to mechanical ventilation in the management of respiratory failure of preterm infants, with reduced occurrence of bronchopulmonary dysplasia and death. nCPAP at birth is still burdened by a high failure rate. Sustained inflation appears to be an intriguing approach to allow the respiratory transition at birth by clearing the lung fluid, thus obtaining an adequate functional residual capacity. This may enhance nCPAP success. Sustained inflation reduces the need for mechanical ventilation in the first 72 h of life, with no changes in the incidence of bronchopulmonary dysplasia and death. The efficacy of sustained inflation seems to be related to the presence of open glottis with active breathing of the infant. Further studies are needed to recommend the application of sustained inflation during delivery room management of preterm infants at risk of respiratory distress or with clinical signs of respiratory failure.

The interrelationship of recruitment maneuver at birth, antenatal steroids, and exogenous surfactant on compliance and oxygenation in preterm lambs

BACKGROUND

To describe the interrelationship between antenatal steroids, exogenous surfactant, and two approaches to lung recruitment at birth on oxygenation and respiratory system compliance (Cdyn) in preterm lambs.

METHODS

Lambs (n = 63; gestational age 127 ± 1 d) received either surfactant at 10-min life (Surfactant), antenatal corticosteroids (Steroid), or neither (Control). Within each epoch lambs were randomly assigned to a 30-s 40 cmH2O sustained inflation (SI) or an initial stepwise positive end-expiratory pressure (PEEP) open lung ventilation (OLV) maneuver at birth. All lambs then received the same management for 60-min with alveolar-arterial oxygen difference (AaDO2) and Cdyn measured at regular time points.

RESULTS

Overall, the OLV strategy improved Cdyn and AaDO2 (all epochs except Surfactant) compared to SI (all P < 0.05; two-way ANOVA). Irrespective of strategy, Cdyn was better in the Steroid group in the first 10 min (all P < 0.05). Thereafter, Cdyn was similar to Steroid epoch in the OLV + Surfactant, but not SI + Surfactant group. OLV influenced the effect of steroid and surfactant (P = 0.005) on AaDO2 more than SI (P = 0.235).

CONCLUSIONS

The antenatal state of the lung influences the type and impact of a recruitment maneuver at birth. The effectiveness of surfactant maybe enhanced using PEEP-based time-dependent recruitment strategies rather than approaches solely aimed at initial lung liquid clearance.

Sustained lung inflation in late preterm infants: a randomized controlled trial

OBJECTIVE

To assess the need for respiratory support in late preterm infants treated with sustained lung inflation (SLI) at birth.

STUDY DESIGN

In this controlled trial, we randomly assigned infants born at 34(+0) to 36(+6) weeks of gestation to receive SLI (25 cmH2O for 15 s) at birth, followed by continuous positive airway pressure (CPAP) or assistance according to the recommendations of the American Academy of Pediatrics. The primary outcome was the need for any type of respiratory support. The secondary outcomes included neonatal intensive care unit (NICU) admission for respiratory distress and length of stay. The risk ratios (RRs) and 95% confidence intervals (CIs) of the outcomes were calculated for the SLI group in reference to the control group.

RESULTS

A total of 185 infants were enrolled: 93 in the SLI group and 92 in the control group. No difference was found in the need for any type of respiratory support between the infants treated with SLI and the control group (10.6 vs 8.7%, RR 1.24, 95% CI 0.51 to 2.99). The NICU admission for respiratory distress and the length of stay did not differ between the groups.

CONCLUSION

Providing SLI at birth in late preterm infants does not affect their need for respiratory support.

Neonatal resuscitation adhering to oxygen saturation guidelines in asphyxiated lambs with meconium aspiration

BACKGROUND

The Neonatal Resuscitation Program (NRP) recommends upper and lower limits of preductal saturations (SpO2) extrapolated from studies in infants resuscitated in room air. These limits have not been validated in asphyxia and lung disease.

METHODS

Seven control term lambs delivered by cesarean section were ventilated with 21% O2. Thirty lambs with asphyxia with meconium aspiration were randomly assigned to resuscitation with 21% O2 (n = 6), 100% O2 (n = 6), or initiation with 21% O2 followed by variable FIO2 to maintain NRP target SpO2 ranges (n = 18). Hemodynamic and ventilation parameters were recorded for 15 min.

RESULTS

Control lambs maintained preductal SpO2 near the lower limit of NRP target range. Asphyxiated lambs had low SpO2 (38 ± 2%), low arterial pH (6.99 ± 0.01), and high PaCO2 (96 ± 7 mm Hg) at birth. Resuscitation with 21% O2 resulted in SpO2 values below the target range with low pulmonary blood flow (Qp) compared to variable FIO2 group. The increase in PaO2 and Qp with variable FIO2 resuscitation was similar to control lambs.

CONCLUSION

Maintaining SpO2 as recommended by NRP by actively adjusting inspired O2 leads to effective oxygenation and higher Qp in asphyxiated lambs with lung disease. Our findings support the current NRP SpO2 guidelines for O2 supplementation during resuscitation of an asphyxiated neonate.

Maternal Creatine Supplementation during Pregnancy Prevents Long-Term Changes in Diaphragm Muscle Structure and Function after Birth Asphyxia

Using a model of birth asphyxia, we previously reported significant structural and functional deficits in the diaphragm muscle in spiny mice, deficits that are prevented by supplementing the maternal diet with 5% creatine from mid-pregnancy. The long-term effects of this exposure are unknown. Pregnant spiny mice were fed control or 5% creatine-supplemented diet for the second half of pregnancy, and fetuses were delivered by caesarean section with or without 7.5 min of in-utero asphyxia. Surviving pups were raised by a cross-foster dam until 33±2 days of age when they were euthanized to obtain the diaphragm muscle for ex-vivo study of twitch tension and muscle fatigue, and for structural and enzymatic analyses. Functional analysis of the diaphragm revealed no differences in single twitch contractile parameters between any groups. However, muscle fatigue, induced by stimulation of diaphragm strips with a train of pulses (330 ms train/sec, 40 Hz) for 300 sec, was significantly greater for asphyxia pups compared with controls (p<0.05), and this did not occur in diaphragms of creatine + asphyxia pups. Birth asphyxia resulted in a significant increase in the proportion of glycolytic, fast-twitch fibres and a reduction in oxidative capacity of Type I and IIb fibres in male offspring, as well as reduced cross-sectional area of all muscle fibre types (Type I, IIa, IIb/d) in both males and females at 33 days of age. None of these changes were observed in creatine + asphyxia animals. Thus, the changes in diaphragm fatigue and structure induced by birth asphyxia persist long-term but are prevented by maternal creatine supplementation.

Sustained lung inflation at birth: what do we know, and what do we need to know?

A sustained inflation has been advocated as a potential method of augmenting lung aeration at birth. Clinical trials have suggested that a sustained inflation may lead to a reduced need for intubation and ventilation in the first few days of life, without cardiovascular compromise or increased lung injury. Despite this, a sustained inflation is not currently a standard of practice, mainly due to a lack of clarity regarding the optimal delivery method. Animal trials have sought to refine delivery techniques. This review will outline current recommendations regarding a sustained inflation, discuss potential strategies for its optimal delivery and suggest priorities for future research.

Delayed Umbilical Cord Clamping in the 21st Century: Indications for Practice

BACKGROUND

Health care providers have debated the timing of umbilical cord clamping since the days of Aristotle. Delayed cord clamping was the mainstay of practice until about the 1950s when it was changed to immediate clamping on the basis of a series of blood volume studies combined with the introduction of active management of the third stage of labor. However, in recent years, several systematic reviews advise that delayed cord clamping should be used in all births for at least 30 to 60 seconds.

PURPOSE

The purpose of this article is to discuss the physiology of umbilical cord clamping, the potential benefits and adverse effects of delayed cord clamping, and how this affects the advanced practice nurse.

SEARCH STRATEGY

A search of PubMed, Cochrane Reviews, and Clinical Key was used to find relevant research on the topic of umbilical cord clamping.

RESULTS

Potential benefits of delayed cord clamping include decreased frequency of iron-deficiency anemia in the first year of life with improved neurodevelopmental outcomes in term infants, reduced need for blood transfusions, possible autologous transfusion of stem cells, and a decreased incidence of intraventricular hemorrhage. Apprehension exists regarding the feasibility of the practice as well as the potential hindrance of immediate resuscitation.

IMPLICATIONS FOR PRACTICE

There is a need to begin to look for populations for which delayed cord clamping can be implemented.

IMPLICATIONS FOR FUTURE RESEARCH

Recommendations are inconsistent on the patient population and timing; therefore, further studies are needed to understand the multiple variables that affect timing of umbilical cord clamping.

Single Sustained Inflation followed by Ventilation Leads to Rapid Cardiorespiratory Recovery but Causes Cerebral Vascular Leakage in Asphyxiated Near-Term Lambs

Background

A sustained inflation (SI) rapidly restores cardiac function in asphyxic, bradycardic newborns but its effects on cerebral haemodynamics and brain injury are unknown. We determined the effect of different SI strategies on carotid blood flow (CaBF) and cerebral vascular integrity in asphyxiated near-term lambs.

Methods

Lambs were instrumented and delivered at 139 ± 2 d gestation and asphyxia was induced by delaying ventilation onset. Lambs were randomised to receive 5 consecutive 3 s SI (multiple SI; n = 6), a single 30 s SI (single SI; n = 6) or conventional ventilation (no SI; n = 6). Ventilation continued for 30 min in all lambs while CaBF and respiratory function parameters were recorded. Brains were assessed for gross histopathology and vascular leakage.

Results

CaBF increased more rapidly and to a greater extent during a single SI (p = 0.01), which then decreased below both other groups by 10 min, due to a higher cerebral oxygen delivery (p = 0.01). Blood brain barrier disruption was increased in single SI lambs as indicated by increased numbers of blood vessel profiles with plasma protein extravasation (p = 0.001) in the cerebral cortex. There were no differences in CaBF or cerebral oxygen delivery between the multiple SI and no SI lambs.

Conclusions

Ventilation with an initial single 30 s SI improves circulatory recovery, but is associated with greater disruption of blood brain barrier function, which may exacerbate brain injury suffered by asphyxiated newborns. This injury may occur as a direct result of the initial SI or to the higher tidal volumes delivered during subsequent ventilation.

Respiratory adaptation and surfactant composition of unanesthetized male and female lambs differ for up to 8 h after preterm birth

BACKGROUND

Male preterm infants are more likely to experience respiratory distress syndrome than females. Our objectives were to determine if sex-related differences in physiological adaptation after preterm birth increase with time after birth and if the use of continuous positive airway pressure (CPAP) reduces these differences.

METHODS

Unanesthetized lambs (9F, 8M) were delivered at 0.90 of term. Blood gases, metabolites, and cardiovascular and respiratory parameters were monitored in spontaneously breathing lambs for 8 h. Supplemental oxygen was administered via a face mask at 4 cmH2O CPAP. At 8 h, lung compliance was determined, and bronchoalveolar lavage fluid (BALF) was analyzed for total protein and surfactant phospholipids. Surfactant protein (SP) gene expression and protein expression of SP-A and pro-SP-C were determined in lung tissue.

RESULTS

For 8 h after delivery, males had significantly lower arterial pH and higher Paco2, and a greater percentage of males were dependent on supplemental oxygen than females. Inspiratory effort was greater and lung compliance was lower in male lambs. Total protein concentration in BALF, SP gene expression, and SP-A protein levels were not different between sexes; pro-SP-C was 24% lower in males.

CONCLUSION

The use of CPAP did not eliminate the male disadvantage, which continues for up to 8 h after preterm birth.

An individualized approach to sustained inflation duration at birth improves outcomes in newborn preterm lambs

A sustained first inflation (SI) at birth may aid lung liquid clearance and aeration, but the impact of SI duration relative to the volume-response of the lung is poorly understood. We compared three SI strategies: 1) variable duration defined by attaining volume equilibrium using real-time electrical impedance tomography (EIT; SIplat); 2) 30 s beyond equilibrium (SIlong); 3) short 30-s SI (SI30); and 4) positive pressure ventilation without SI (no-SI) on spatiotemporal aeration and ventilation (EIT), gas exchange, lung mechanics, and regional early markers of injury in preterm lambs. Fifty-nine fetal-instrumented lambs were ventilated for 60 min after applying the allocated first inflation strategy. At study completion molecular and histological markers of lung injury were analyzed. The time to SI volume equilibrium, and resultant volume, were highly variable; mean (SD) 55 (34) s, coefficient of variability 59%. SIplat and SIlong resulted in better lung mechanics, gas exchange and lower ventilator settings than both no-SI and SI30. At 60 min, alveolar-arterial difference in oxygen was a mean (95% confidence interval) 130 (13, 249) higher in SI30 vs. SIlong group (two-way ANOVA). These differences were due to better spatiotemporal aeration and tidal ventilation, although all groups showed redistribution of aeration towards the nondependent lung by 60 min. Histological lung injury scores mirrored spatiotemporal change in aeration and were greatest in SI30 group ( P < 0.01, Kruskal-Wallis test). An individualized volume-response approach to SI was effective in optimizing aeration, homogeneous tidal ventilation, and respiratory outcomes, while an inadequate SI duration had no benefit over positive pressure ventilation alone.