Increasing Respiratory Effort With 100% Oxygen During Resuscitation of Preterm Rabbits at Birth

Initial Oxygen Concentration for the Resuscitation of Infants Born at Less Than 32 Weeks' Gestation: A Systematic Review and Individual Participant Data Network Meta-Analysis

Importance

Resuscitation with lower fractional inspired oxygen (FiO2) reduces mortality in term and near-term infants but the impact of this practice on very preterm infants is unclear.

Objective

To evaluate the relative effectiveness of initial FiO2 on reducing mortality, severe morbidities, and oxygen saturations (SpO2) in preterm infants born at less than 32 weeks' gestation using network meta-analysis (NMA) of individual participant data (IPD).

Data Sources

MEDLINE, Embase, CENTRAL, CINAHL, ClinicalTrials.gov, and WHO ICTRP from 1980 to October 10, 2023.

Study Selection

Eligible studies were randomized clinical trials enrolling infants born at less than 32 weeks' gestation comparing at least 2 initial oxygen concentrations for delivery room resuscitation, defined as either low (≤0.3), intermediate (0.5-0.65), or high (≥0.90) FiO2.

Data Extraction and Synthesis

Investigators from eligible studies were invited to provide IPD. Data were processed and checked for quality and integrity. One-stage contrast-based bayesian IPD-NMA was performed with noninformative priors and random effects and adjusted for key covariates.

Main Outcomes and Measures

The primary outcome was all-cause mortality at hospital discharge. Secondary outcomes were morbidities of prematurity and SpO2 at 5 minutes.

Results

IPD were provided for 1055 infants from 12 of the 13 eligible studies (2005-2019). Resuscitation with high (≥0.90) initial FiO2 was associated with significantly reduced mortality compared to low (≤0.3) (odds ratio [OR], 0.45; 95% credible interval [CrI], 0.23-0.86; low certainty) and intermediate (0.5-0.65) FiO2 (OR, 0.34; 95% CrI, 0.11-0.99; very low certainty). High initial FiO2 had a 97% probability of ranking first to reduce mortality. The effects on other morbidities were inconclusive.

Conclusions and Relevance

High initial FiO2 (≥0.90) may be associated with reduced mortality in preterm infants born at less than 32 weeks' gestation compared to low initial FiO2 (low certainty). High initial FiO2 is possibly associated with reduced mortality compared to intermediate initial FiO2 (very low certainty) but more evidence is required.

The effect of vibrotactile stimulation on hypoxia-induced irregular breathing and apnea in preterm rabbits

BACKGROUND

Manual tactile stimulation is used to counteract apnea in preterm infants, but it is unknown when this intervention should be applied. We compared an anticipatory to a reactive approach using vibrotactile stimulation to prevent hypoxia induced apneas.

METHODS

Preterm rabbit kittens were prematurely delivered and randomized to either group. All kittens breathed spontaneously with a positive airway pressure of 8 cmH2O while they were imaged using phase contrast X-ray. Irregular breathing (IB) was induced using gradual hypoxia. The anticipatory group received stimulation at the onset of IB and the reactive group if IB transitioned into apnea. Breathing rate (BR), heart rate (HR) and functional residual capacity (FRC) were compared.

RESULTS

Anticipatory stimulation significantly reduced apnea incidence and maximum inter-breath intervals and increased BR following IB, compared to reactive stimulation. Recovery in BR but not HR was more likely with anticipatory stimulation, although both BR and HR were significantly higher at 120 s after stimulation onset. FRC values and variability were not different.

CONCLUSIONS

Anticipated vibrotactile stimulation is more effective in preventing apnea and enhancing breathing when compared to reactive stimulation in preterm rabbits. Stimulation timing is likely to be a key factor in reducing the incidence and duration of apnea.

IMPACT

Anticipated vibrotactile stimulation can prevent apnea and stimulate breathing effort in preterm rabbits. Anticipated vibrotactile stimulation increases the likelihood of breathing rate recovery following hypoxia induced irregular breathing, when compared to reactive stimulation. Automated stimulation in combination with predictive algorithms may improve the treatment of apnea in preterm infants.

The role of oxygen in the development and treatment of bronchopulmonary dysplasia

Oxygen (O2) is crucial for both the development and treatment of one of the most important consequences of prematurity: bronchopulmonary dysplasia (BPD). In fetal life, the hypoxic environment is important for alveolar development and maturation. After birth, O2 becomes a double-edged sword. While O2 is needed to prevent hypoxia, it also causes oxidative stress leading to a plethora of morbidities, including retinopathy and BPD. The advent of continuous O2 monitoring with pulse oximeters has allowed clinicians to recognize the narrow therapeutic margins of oxygenation for the preterm infant, but more knowledge is needed to understand what these ranges are at different stages of the preterm infant's life, including at birth, in the neonatal intensive care unit and after hospital discharge. Future research, especially in innovative technologies such as automated O2 control and remote oximetry, will improve the understanding and treatment of the O2 needs of infants with BPD.

The Respiratory Management of the Extreme Preterm in the Delivery Room

The fetal-to-neonatal transition poses an extraordinary challenge for extremely low birth weight (ELBW) infants, and postnatal stabilization in the delivery room (DR) remains challenging. The initiation of air respiration and the establishment of a functional residual capacity are essential and often require ventilatory support and oxygen supplementation. In recent years, there has been a tendency towards the soft-landing strategy and, subsequently, non-invasive positive pressure ventilation has been generally recommended by international guidelines as the first option for stabilizing ELBW in the delivery room. On the other hand, supplementation with oxygen is another cornerstone of the postnatal stabilization of ELBW infants. To date, the conundrum concerning the optimal initial inspired fraction of oxygen, target saturations in the first golden minutes, and oxygen titration to achieve desired stability saturation and heart rate values has not yet been solved. Moreover, the retardation of cord clamping together with the initiation of ventilation with the patent cord (physiologic-based cord clamping) have added additional complexity to this puzzle. In the present review, we critically address these relevant topics related to fetal-to-neonatal transitional respiratory physiology, ventilatory stabilization, and oxygenation of ELBW infants in the delivery room based on current evidence and the most recent guidelines for newborn stabilization.

The quest for optimum oxygenation during newborn delivery room resuscitation: Is it the baby or is it us?

Achieving "normal oxygenation" in sick newborn infants requiring resuscitation is one of the most difficult and incompletely informed practices in neonatal care. Suboptimal oxygenation, whether too little or too much, has profound repercussions, including death. In the last two decades, clinicians have lost equipoise for the use of higher oxygen strategies due to concerns of hyperoxia but emerging evidence suggests that lower oxygen strategies may also be as detrimental, especially in infants with pulmonary pathologies such as those born at the cusp of viability. Practice at the coalface using rapidly evolving recommendations has also uncovered continuing complexities in the quest to achieve optimum oxygenation during the first critical minutes of life. There are adjustable factors, such as the practical impediments to acquiring knowledge, equipment and expertise as well as unadjustable factors, such as inherent infant pathology, that necessitates agile clinical manipulation to "first do no harm". This review will address the deficiencies in knowledge that currently impede our quest to determine the best and safest means to deliver oxygen to sick infants during the first critical minutes of life and suggest practical solutions for current practice while awaiting definitive evidence from large scale, well defined, randomized controlled studies.

Technology in the delivery room supporting the neonatal healthcare provider's task

Very preterm infants are a unique and highly vulnerable group of patients that have a narrow physiological margin within which interventions are safe and effective. The increased understanding of the foetal to neonatal transition marks the intricacy of the rapid and major physiological changes that take place, making delivery room stabilisation and resuscitation an increasingly complex and sophisticated activity for caregivers to perform. While modern, automated technologies are progressively implemented in the neonatal intensive care unit (NICU) to enhance the caregivers in providing the right care for these patients, the technology in the delivery room still lags far behind. Diligent translation of well-known and promising technological solutions from the NICU to the delivery room will allow for better support of the caregivers in performing their tasks. In this review we will discuss the current technology used for stabilisation of preterm infants in the delivery room and how this could be optimised in order to further improve care and outcomes of preterm infants in the near future.

Higher CPAP levels improve functional residual capacity at birth in preterm rabbits

BACKGROUND

Preterm infants are commonly supported with 4-8 cm H₂O continuous positive airway pressures (CPAP), although higher CPAP levels may improve functional residual capacity (FRC).

METHODS

Preterm rabbits delivered at 29/32 days (~26-28 weeks human) gestation received 0, 5, 8, 12, 15 cm H₂O of CPAP or variable CPAP of 15 to 5 or 15 to 8 cm H₂O (decreasing ~2 cm H₂O/min) for up to 10 min after birth.

RESULTS

FRC was lower in the 0 (6.8 (1.0-11.2) mL/kg) and 5 (10.1 (1.1-16.8) mL/kg) compared to the 15 (18.8 (10.9-22.4) mL/kg) cm H₂O groups (p = 0.003). Fewer kittens achieved FRC > 15 mL/kg in the 0 (20%), compared to 8 (36%), 12 (60%) and 15 (73%) cm H₂O groups (p = 0.008). While breathing rates were not different (p = 0.096), apnoea tended to occur more often with CPAP < 8 cm H₂O (p = 0.185). CPAP belly and lung bulging rates were similar whereas pneumothoraces were rare. Lowering CPAP from 15 to 5, but not 15 to 8 cm H₂O, decreased FRC and breathing rates.

CONCLUSION

In all, 15 cm H₂O of CPAP improved lung aeration and reduced apnoea, but did not increase the risk of lung over-expansion, pneumothorax or CPAP belly immediately after birth. FRC and breathing rates were maintained when CPAP was decreased to 8 cm H₂O.

IMPACT

Although preterm infants are commonly supported with 4-8 cm H₂O CPAP at birth, preclinical studies have shown that higher PEEP levels improve lung aeration. In this study, CPAP levels of 15 cm H₂O improved lung aeration and reduced apnoea in preterm rabbit kittens immediately after birth. In all, 15 cm H₂O CPAP did not increase the risk of lung over-expansion (indicated by bulging between the ribs), pneumothorax, or CPAP belly. These results can be used when designing future studies on CPAP strategies for preterm infants in the delivery room.

Tactile stimulation in the delivery room: past, present, future. A systematic review

In current resuscitation guidelines, tactile stimulation is recommended for infants with insufficient respiratory efforts after birth. No recommendations are made regarding duration, onset, and method of stimulation. Neither is mentioned how tactile stimulation should be applied in relation to the gestational age. The aim was to review the physiological mechanisms of respiratory drive after birth and to identify and structure the current evidence on tactile stimulation during neonatal resuscitation. A systematic review of available data was performed using PubMed, covering the literature up to April 2021. Two independent investigators screened the extracted references and assessed their methodological quality. Six studies were included. Tactile stimulation management, including the onset of stimulation, overall duration, and methods as well as the effect on vital parameters was analyzed and systematically presented. Tactile stimulation varies widely between, as well as within different centers and no consensus exists which stimulation method is most effective. Some evidence shows that repetitive stimulation within the first minutes of resuscitation improves oxygenation. Further studies are warranted to optimize strategies to support spontaneous breathing after birth, assessing the effect of stimulating various body parts respectively within different gestational age groups.

Oxygen saturation and heart rate in healthy term and late preterm infants with delayed cord clamping

Blood oxygen in the fetus is substantially lower than in the newborn infant. In the minutes after birth, arterial oxygen saturation rises from around 50-60% to 90-95%. Initial respiratory efforts generate negative trans-thoracic pressures that drive liquid from the airways into the lung interstitium facilitating lung aeration, blood oxygenation, and pulmonary artery vasodilatation. Consequently, intra- (foramen ovale) and extra-cardiac (ductus arteriosus) shunting changes and the sequential circulation switches to a parallel pulmonary and systemic circulation. Delaying cord clamping preserves blood flow through the ascending vena cava, thus increasing right and left ventricular preload. Recently published reference ranges have suggested that delayed cord clamping positively influenced the fetal-to-neonatal transition. Oxygen saturation in babies with delayed cord clamping plateaus significantly earlier to values of 85-90% than in babies with immediate cord clamping. Delayed cord clamping may also contribute to fewer episodes of brady-or-tachycardia in the first minutes after birth, but data from randomized trials are awaited. IMPACT: Delaying cord clamping during fetal to neonatal transition contributes to a significantly earlier plateauing of oxygen saturation and fewer episodes of brady-and/or-tachycardia in the first minutes after birth. We provide updated information regarding the changes in SpO2 and HR during postnatal adaptation of term and late preterm infants receiving delayed compared with immediate cord clamping. Nomograms in newborn infants with delayed cord clamping will provide valuable reference ranges to establish target SpO2 and HR in the first minutes after birth.

Face mask versus nasal prong or nasopharyngeal tube for neonatal resuscitation in the delivery room: a systematic review and meta-analysis

IMPORTANCE

The current neonatal resuscitation guidelines recommend positive pressure ventilation via face mask or nasal prongs at birth. Using a nasal interface may have the potential to improve outcomes for newborn infants.

OBJECTIVE

To determine whether nasal prong/nasopharyngeal tube versus face mask during positive pressure ventilation of infants born <37 weeks' gestation in the delivery room reduces in-hospital mortality and morbidity.

DATA SOURCES

MEDLINE (through PubMed), Google Scholar and EMBASE, Clinical Trials.gov and the Cochrane Central Register of Controlled Trials through August 2019.

STUDY SELECTION

Randomised controlled trials comparing nasal prong/nasopharyngeal tube versus face mask during positive pressure ventilation of infants born <37 weeks' gestation in the delivery room.

DATA ANALYSIS

Risk of bias was assessed using the Covidence Collaboration Tool, results were pooled into a meta-analysis using a random effects model.

MAIN OUTCOME

In-hospital mortality.

RESULTS

Five RCTs enrolling 873 infants were combined into a meta-analysis. There was no statistical difference in in-hospital mortality (risk ratio (RR 0.98, 95% CI 0.63 to 1.52, p=0.92, I²=11%), rate of chest compressions in the delivery room (RR 0.37, 95% CI 0.10 to 1.33, p=0.13, I²=28%), rate of intraventricular haemorrhage (RR 1.54, 95% CI 0.88 to 2.70, p=0.13, I²=0%) or delivery room intubations in infants ventilated with a nasal prong/tube (RR 0.63, 95% CI 0.39,1.02, p=0.06, I²=52%).

CONCLUSION

In infants born <37 weeks' gestation, in-hospital mortality and morbidity were similar following positive pressure ventilation during initial stabilisation with a nasal prong/tube or a face mask.

Oxygen saturation (SpO2) targeting for newborn infants at delivery: Are we reaching for an impossible unknown?

For more than 200 years, pure oxygen was given ad libitum to newborn infants requiring resuscitation. Due to oxidative stress and injury concerns, a paradigm shift towards using "less" oxygen, including air (21% oxygen) instead of pure (100%) oxygen, occurred about twenty years ago. A decade later, clinicians were advised to adjust fractional inspired oxygen (FiO₂) to target oxygen saturations (SpO₂) that were derived from spontaneously breathing, healthy, mature infants. Whether these recommendations are achievable, beneficial, harmful or redundant is uncertain. The underlying pathology leading to resuscitation varies between infants and may considerably alter an infant's response to supplemental oxygen. In this review, we summarize available evidence for the use of SpO₂ monitoring at delivery for newborn infants, elucidate existing knowledge and service gaps, and suggest future research recommendations that will lead to the safest clinical strategies for this standard and important practice.

Seeing the fetus from a DOHaD perspective: discussion paper from the advanced imaging techniques of DOHaD applications workshop held at the 2019 DOHaD World Congress

Advanced imaging techniques are enhancing research capacity focussed on the developmental origins of adult health and disease (DOHaD) hypothesis, and consequently increasing awareness of future health risks across various subareas of DOHaD research themes. Understanding how these advanced imaging techniques in animal models and human population studies can be both additively and synergistically used alongside traditional techniques in DOHaD-focussed laboratories is therefore of great interest. Global experts in advanced imaging techniques congregated at the advanced imaging workshop at the 2019 DOHaD World Congress in Melbourne, Australia. This review summarizes the presentations of new imaging modalities and novel applications to DOHaD research and discussions had by DOHaD researchers that are currently utilizing advanced imaging techniques including MRI, hyperpolarized MRI, ultrasound, and synchrotron-based techniques to aid their DOHaD research focus.

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.

Hyperoxia and Lungs: What We Have Learned From Animal Models

Although oxygen (O₂) is essential for aerobic life, it can also be an important source of cellular damage. Supra-physiological levels of O₂ determine toxicity due to exacerbated reactive oxygen species (ROS) production, impairing the homeostatic balance of several cellular processes. Furthermore, injured cells activate inflammation cascades, amplifying the tissue damage. The lung is the first (but not the only) organ affected by this condition. Critically ill patients are often exposed to several insults, such as mechanical ventilation, infections, hypo-perfusion, systemic inflammation, and drug toxicity. In this scenario, it is not easy to dissect the effect of oxygen toxicity. Translational investigations with animal models are essential to explore injuring stimuli in controlled experimental conditions, and are milestones in understanding pathological mechanisms and developing therapeutic strategies. Animal models can resemble what happens in critical care or anesthesia patients under mechanical ventilation and hyperoxia, but are also critical to explore the effect of O₂ on lung development and the role of hyperoxic damage on bronchopulmonary dysplasia. Here, we set out to review the hyperoxia effects on lung pathology, contributing to the field by describing and analyzing animal experimentation's main aspects and its implications on human lung diseases.

Feasibility and Effect of Physiological-Based CPAP in Preterm Infants at Birth

Background: Preterm infants are commonly supported with 5-8 cmH₂O CPAP. However, animal studies demonstrate that high initial CPAP levels (12-15 cmH₂O) which are then reduced (termed physiological based (PB)-CPAP), improve lung aeration without adversely affecting cardiovascular function. We investigated the feasibility of PB-CPAP and the effect in preterm infants at birth. Methods: Preterm infants (24-30 weeks gestation) were randomized to PB-CPAP or 5-8 cmH₂O CPAP for the first 10 min after birth. PB-CPAP consisted of 15 cmH₂O CPAP that was decreased when infants were stabilized (heart rate ≥100 bpm, SpO₂ ≥85%, FiO₂ ≤ 0.4, spontaneous breathing) to 8 cmH₂O with steps of ~2/3 cmH₂O/min. Primary outcomes were feasibility and SpO₂ in the first 5 min after birth. Secondary outcomes included physiological and breathing parameters and short-term neonatal outcomes. Planned enrollment was 42 infants. Results: The trial was stopped after enrolling 31 infants due to a low inclusion rate and recent changes in the local resuscitation guideline that conflict with the study protocol. Measurements were available for analysis in 28 infants (PB-CPAP n = 8, 5-8 cmH₂O n = 20). Protocol deviations in the PB-CPAP group included one infant receiving 3 inflations with 15 cmH₂O PEEP and two infants in which CPAP levels were decreased faster than described in the study protocol. In the 5-8 cmH₂O CPAP group, three infants received 4, 10, and 12 cmH₂O CPAP. During evaluations, caregivers indicated that the current PB-CPAP protocol was difficult to execute. The SpO₂ in the first 5 min after birth was not different [61 (49-70) vs. 64 (47-74), p = 0.973]. However, infants receiving PB-CPAP achieved higher heart rates [121 (111-130) vs. 97 (82-119) bpm, p = 0.016] and duration of mask ventilation was shorter [0:42 (0:34-2:22) vs. 2:58 (1:36-6:03) min, p = 0.020]. Infants in the PB-CPAP group required 6:36 (5:49-11:03) min to stabilize, compared to 9:57 (6:58-15:06) min in the 5-8 cmH2O CPAP group (p = 0.256). There were no differences in short-term outcomes. Conclusion: Stabilization of preterm infants with PB-CPAP is feasible but tailoring CPAP appeared challenging. PB-CPAP did not lead to higher SpO₂ but increased heart rate and shortened the duration of mask ventilation, which may reflect faster lung aeration.

[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.

The Effect of Initial High vs. Low FiO2 on Breathing Effort in Preterm Infants at Birth: A Randomized Controlled Trial

Background: Infants are currently stabilized at birth with initial low FiO₂ which increases the risk of hypoxia and suppression of breathing in the first minutes after birth. We hypothesized that initiating stabilization at birth with a high O₂ concentration, followed by titration, would improve breathing effort when compared to a low O₂ concentration, followed by titration. Methods: In a bi-center randomized controlled trial, infants <30 weeks gestation were stabilized at birth with an initial O₂ concentration of 30 or 100%, followed by oxygen titration. Primary outcome was minute volume of spontaneous breathing. We also assessed tidal volumes, mean inspiratory flow rate (MIFR) and respiratory rate with a respiratory function monitor in the first 5 min after birth, and evaluated the duration of mask ventilation in the first 10 min after birth. Pulse oximetry was used to measure heart rate and SpO₂ values in the first 10 min. Hypoxemia was defined as SpO₂ < 25th percentile and hyperoxemia as SpO₂ >95%. 8-iso-prostaglandin F2α (8iPGF2α) was measured to assess oxidative stress in cord blood and 1 and 24 h after birth. Results: Fifty-two infants were randomized and recordings were obtained in 44 infants (100% O₂-group: n = 20, 30% O₂-group: n = 24). Minute volumes were significantly higher in the 100% O₂-group (146.34 ± 112.68 mL/kg/min) compared to the 30% O₂-group (74.43 ± 52.19 mL/kg/min), p = 0.014. Tidal volumes and MIFR were significantly higher in the 100% O₂-group, while the duration of mask ventilation given was significantly shorter. Oxygenation in the first 5 min after birth was significantly higher in infants in the 100% O₂-group [85 (64-93)%] compared to the 30% O₂-group [58 (46-67)%], p < 0.001. The duration of hypoxemia was significantly shorter in the 100% O₂-group, while the duration of hyperoxemia was not different between groups. There was no difference in oxidative stress marker 8iPGF2α between the groups. Conclusion: Initiating stabilization of preterm infants at birth with 100% O₂ led to higher breathing effort, improved oxygenation, and a shorter duration of mask ventilation as compared to 30% O₂, without increasing the risk for hyperoxia or oxidative stress. Clinical Trial Registration: This study was registered in www.trialregister.nl, with registration number NTR6878.