The administration of 100% oxygen and respiratory drive in very preterm infants 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.

Rescue nasopharyngeal tube for preterm infants non-responsive to initial ventilation after birth

BACKGROUND

Physiological changes during the insertion of a rescue nasopharyngeal tube (NPT) after birth are unclear.

METHODS

Observational study of very preterm infants in the delivery room. Data were extracted at predefined timepoints starting with first facemask placement after birth until 5 min after insertion of NPT. End-expiratory lung impedance (EELI), heart rate (HR) and SpO2/FiO2-ratio were analysed over time. Changes during the same time span of NIPPV via facemask and NIPPV via NPT were compared.

RESULTS

Overall, 1154 inflations in 15 infants were analysed. After NPT insertion, EELI increased significantly [0.33 AU/kg (0.19-0.57), p < 0.001]. Compared with the mask period, changes in EELI were not significantly larger during the NPT period [median difference (IQR) = 0.14 AU/kg (-0.14-0.53); p = 0.12]. Insertion of the NPT was associated with significant improvement in HR [52 (33-96); p = 0.001] and SpO2/FiO2-ratio [161 (69-169); p < 0.001] not observed during the mask period.

CONCLUSIONS

In very preterm infants non-responsive to initial facemask ventilation after birth, insertion of an NPT resulted in a considerable increase in EELI. This additional gain in lung volume was associated with an immediate improvement in clinical parameters. The use of a NPT may prevent intubation in selected non-responsive infants.

IMPACT

After birth, a nasopharyngeal tube may be considered as a rescue airway in newborn infants non-responsive to initial positive pressure ventilation via facemask. Although it is widely used among clinicians, its effect on lung volumes and physiological parameters remains unclear. Insertion of a rescue NPT resulted in a considerable increase in lung volume but this was not significantly larger than during facemask ventilation. However, insertion of a rescue NPT was associated with a significant and clinically important improvement in heart rate and oxygenation. This study highlights the importance of individual strategies in preterm resuscitation and introduces the NPT as a valid option.

Air or Oxygen for Infant Resuscitation: A Prospective Cohort Study of Moderate-Late Preterm Infants Requiring Delivery Room Resuscitation

INTRODUCTION

Due to concerns of oxidative stress and injury, most clinicians currently use lower levels of fractional inspired oxygen (FiO2, 0.21-0.3) to initiate respiratory support for moderate to late preterm (MLPT, 32-36 weeks gestation) infants at birth. Whether this practice achieves recommended oxygen saturation (SpO2) targets is unknown.

METHODS

We aimed to determine SpO2 trajectories of MLPT infants requiring respiratory support at birth. We conducted a prospective, opportunistic, observational study with consent waiver. Preductal SpO2 readings were obtained during the first 10 min of life from infants between 32 and 36 weeks gestation requiring respiratory support in the delivery room. Primary outcome was reaching a minimum SpO2 80% at 5 min of life. The study was prospectively registered (ACTRN12620001252909).

RESULTS

A total of 76 eligible infants were recruited between February 2021 and March 2022 from 5 hospitals in Australia. Most (n = 58, 76%) had respiratory support initiated with FiO2 0.21 (range 0.21-1.0) using CPAP (92%). Median SpO2 at 5 min was 81% (interquartile range [IQR] 67-90) and 93% (IQR 86-96) at 10 min. At 5 min, 18/43 (42%) infants had SpO2 below 80% and only 8/43 (19%) reached SpO2 80-85%.

CONCLUSIONS

Many MLPT infants requiring respiratory support do not achieve recommended SpO2 targets. In very preterm infants, SpO2 <80% at 5 min of life increases risk of death, intraventricular haemorrhage, and neurodevelopmental impairment. The implications on this practice on the health outcomes of MLPT infants are unclear and require further research.

Stimulating and maintaining spontaneous breathing during transition of preterm infants

Most preterm infants breathe at birth, but need additional respiratory support due to immaturity of the lung and respiratory control mechanisms. To avoid lung injury, the focus of respiratory support has shifted from invasive towards non-invasive ventilation. However, applying effective non-invasive ventilation is difficult due to mask leak and airway obstruction. The larynx has been overlooked as one of the causes for obstruction, preventing face mask ventilation from inflating the lung. The larynx remains mostly closed at birth, only opening briefly during a spontaneous breath. Stimulating and supporting spontaneous breathing could enhance the success of non-invasive ventilation by ensuring that the larynx remains open. Maintaining adequate spontaneous breathing and thereby reducing the need for invasive ventilation is not only important directly after birth, but also in the first hours after admission to the NICU. Respiratory distress syndrome is an important cause of respiratory failure. Traditionally, treatment of RDS required intubation and mechanical ventilation to administer exogenous surfactant. However, new ways have been implemented to administer surfactant and preserve spontaneous breathing while maintaining non-invasive support. In this narrative review we aim to describe interventions focused on stimulation and maintenance of spontaneous breathing of preterm infants in the first hours after birth.

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.

Comparison of Two Respiratory Support Strategies for Stabilization of Very Preterm Infants at Birth: A Matched-Pairs Analysis

Objective: Respiratory support for stabilizing very preterm infants at birth varies between centers. We retrospectively compared two strategies that involved either increasing continuous positive airway pressures (CPAP), or increasing oxygen supplementation. Methods: Matched-pairs of infants (<28 weeks of gestation) were born either at the Leiden University Medical Center [low-pressure: CPAP 5-8 cmH₂O and/or positive pressure ventilation (PPV) and fraction of inspired oxygen (FiO₂) 0.3-1.0; n = 27], or at the University Hospital of Cologne (high-pressure: CPAP 12-35 cmH₂O, no PPV and FiO₂ 0.3-0.4; n = 27). Respiratory support was initiated non-invasively via facemask at both units. Infants (n = 54) were matched between centers for gestational age and birth weight, to compare physiological and short-term clinical outcomes. Results: In the low-pressure group, 20/27 (74%) infants received 1-2 sustained inflations (20, 25 cm H₂O) and 22/27 (81%) received PPV (1:19-3:01 min) using pressures of 25-27 cm H₂O. Within 3 min of birth [median (IQR)], mean airway pressures [12 (6-15) vs. 19 (16-23) cmH₂O, p < 0.001] and FiO₂ [0.30 (0.28-0.31) vs. 0.22 (0.21-0.30), p < 0.001] were different in low- vs. high-pressure groups, respectively. SpO₂ and heart rates were similar. After 3 min, higher FiO₂ levels [0.62 (0.35-0.98) vs. 0.28 (0.22-0.38), p = 0.005] produced higher SpO₂ levels [77 (50-92) vs. 53 (42-69)%, p < 0.001] in the low-pressure group, but SpO₂/FiO₂ and heart rates were similar. While intubation rates during admission were significantly different (70 vs. 30%, p = 0.013), pneumothorax rates (4 vs. 19%, p = 0.125) and the occurrence of spontaneous intestinal perforations (0 vs. 15%, p = 0.125) were similar between groups. Conclusion: Infants (<28 weeks) can be supported non-invasively at birth with either higher or lower pressures and while higher-pressure support may require less oxygen, it does not eliminate the need for oxygen supplementation. Future studies need to examine the effect of high pressures and pressure titration in the delivery room.

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

Background: Spontaneous breathing is essential for successful non-invasive respiratory support delivered by a facemask at birth. As hypoxia is a potent inhibitor of spontaneous breathing, initiating respiratory support with a high fraction of inspired O₂ may reduce the risk of hypoxia and increase respiratory effort at birth. Methods: Preterm rabbit kittens (29 days gestation, term ~32 days) were delivered and randomized to receive continuous positive airway pressure with either 21% (n = 12) or 100% O₂ (n = 8) via a facemask. If apnea occurred, intermittent positive pressure ventilation (iPPV) was applied with either 21% or 100% O₂ in kittens who started in 21% O₂, and remained at 100% O₂ for kittens who started the experiment in 100% O₂. Respiratory rate (breaths per minute, bpm) and variability in inter-breath interval (%) were measured from esophageal pressure recordings and functional residual capacity (FRC) was measured from synchrotron phase-contrast X-ray images. Results: Initially, kittens receiving 21% O₂ had a significantly lower respiratory rate and higher variability in inter-breath interval, indicating a less stable breathing pattern than kittens starting in 100% O₂ [median (IQR) respiratory rate: 16 (4-28) vs. 38 (29-46) bpm, p = 0.001; variability in inter-breath interval: 33.3% (17.2-50.1%) vs. 27.5% (18.6-36.3%), p = 0.009]. Apnea that required iPPV, was more frequently observed in kittens in whom resuscitation was started with 21% compared to 100% O₂ (11/12 vs. 1/8, p = 0.001). After recovering from apnea, respiratory rate was significantly lower and variability in inter-breath interval was significantly higher in kittens who received iPPV with 21% compared to 100% O₂. FRC was not different between study groups at both timepoints. Conclusion: Initiating resuscitation with 100% O₂ resulted in increased respiratory activity and stability, thereby reducing the risk of apnea and need for iPPV after birth. Further studies in human preterm infants are mandatory to confirm the benefit of this approach in terms of oxygenation. In addition, the ability to avoid hyperoxia after initiation of resuscitation with 100% oxygen, using a titration protocol based on oxygen saturation, needs to be clarified.

High vs. Low Initial Oxygen to Improve the Breathing Effort of Preterm Infants at Birth: Study Protocol for a Randomized Controlled Trial

Background: Although most preterm infants breathe at birth, their respiratory drive is weak and supplemental oxygen is often needed to overcome hypoxia. This could in turn lead to hyperoxia. To reduce the risk of hyperoxia, currently an initial low oxygen concentration (21-30%) is recommended during stabilization at birth, accepting the risk of a hypoxic period. However, hypoxia inhibits respiratory drive in preterm infants. Starting with a higher level of oxygen could lead to a shorter duration of hypoxia by stimulating breathing effort of preterm infants, and combined with subsequent titration based on oxygen saturation, prolonged hyperoxia might be prevented. Study design: This multi-center randomized controlled trial will include 50 infants with a gestational age between 24 and 30 weeks. Eligible infants will be randomized to stabilization with an initial FiO₂ of either 1.0 or 0.3 at birth. Hereafter, FiO₂ will be titrated based on the oxygen saturation target range. In both groups, all other interventions during stabilization and thereafter will be similar. The primary outcome is respiratory effort in the first 5 min after birth expressed as average minute volume/kg. Secondary outcomes include inspired tidal volumes/kg, rate of rise to maximum tidal volume/kg, percentage of recruitment breaths with tidal volumes above 8 mL/kg, duration of hypoxia and hyperoxia and plasma levels of markers of oxidative stress (8-iso-prostaglandin F2α). Discussion: Current resuscitation guidelines recommend oxygen titration if infants fail to achieve the 25th percentile of the SpO₂ reference ranges. It has become clear that, using this approach, most preterm infants are at risk for hypoxia in the first 5 min after birth, which could suppress the breathing effort. In addition, for compromised preterm infants who need respiratory support at birth, higher SpO₂ reference ranges in the first minutes after birth might be needed to prevent prolonged hypoxia. Enhancing breathing effort by achieving an adequate level of oxygenation could potentially lead to a lower incidence of intubation and mechanical ventilation in the delivery room, contributing to a lower risk on lung injury in high-risk preterm infants. Measuring 8-iso-prostaglandin F2α could lead to a reflection of the true amount of oxygen exposure in both study groups.

Oxygen Requirements for Acutely and Critically Ill Patients

Oxygen administration is often assumed to be required for all patients who are acutely or critically ill. However, in many situations, this assumption is not based on evidence. Injured body tissues and cells throughout the body respond both beneficially and adversely to delivery of supplemental oxygen. Available evidence indicates that oxygen administration is not warranted for patients who are not hypoxemic, and hyperoxia may contribute to increased tissue damage and mortality. Nurses must be aware of implications related to oxygen administration for all types of acutely and critically ill patients. These implications include having knowledge of oxygenation processes and pathophysiology; assessing global, tissue, and organ oxygenation status; avoiding either hypoxia or hyperoxia; and creating partnerships with respiratory therapists. Nurses can contribute to patients' oxygen status well-being by being proficient in determining each patient's specific oxygen needs and appropriate oxygen administration.

The Breathing Effort of Very Preterm Infants at Birth

OBJECTIVE

To compare the respiratory effort of very preterm infants receiving positive pressure ventilation (PPV) with infants breathing on continuous positive airway pressure (CPAP), directly after birth.

STUDY DESIGN

Recorded resuscitations of very preterm infants receiving PPV or CPAP after birth were analyzed retrospectively. The respiratory effort (minute volume and recruitment breaths [>8 mL/kg], heart rate, oxygen saturation, and oxygen requirement were analyzed for the first 2 minutes and in the fifth minute after birth.

RESULTS

Respiratory effort was analyzed in 118 infants, 87 infants receiving PPV and 31 infants receiving CPAP (median gestational age, 28 weeks [IQR, 26-29] vs 29 weeks [IQR, 29-30; P < .001); birth weight, 1059 g [IQR, 795-1300] vs 1205 g [IQR, 956-1418; P = .06]). The minute volume of spontaneous breaths of infants receiving PPV was lower at 2 minutes (37 mL/kg/minute [IQR, 15-69] vs 188 mL/kg/minute [IQR, 128-297; P < .001]) and at 5 minutes (112 mL/kg/minute [IQR, 46-229] vs 205 mL/kg/minute [IQR, 174-327; P < .001]). Recruitment breaths occurred less in the PPV group at 2 minutes (0 breaths/minute [IQR, 0-1] vs 4 breaths/minute [IQR, 1-8; P < .001]) and 5 minutes (0 breaths/minute [IQR, 0-3] vs 2 breaths/minute [IQR, 0-11; P = .01). The heart rate was lower in the PPV group (94 beats/minute [IQR, 68-128] vs 124 beats/minute [IQR, 100-144; P = .02]) as was oxygen saturation (50% [IQR, 35%-66%] vs 67% [IQR, 34%-80%; P = .04]), but not different at 5 minutes (heart rate, 149 beats/minute [IQR, 131-162] vs 150 beats/minute [IQR, 132-160; P = NS]; oxygen saturation , 91% [IQR, 80%-95%] vs 92% [IQR, 89%-97%; P = NS]). The oxygen requirement was higher (at 2 minutes, 30% [IQR, 21%-53%] vs 21% [IQR, 21%-29%; P = .05]; at 5 minutes, 39% [IQR, 22%-91%] vs 22% [IQR, 21%-31%; P = .003]).

CONCLUSION

Very preterm infants breathe at birth when receiving PPV, but the respiratory effort was significantly lower when compared with infants receiving CPAP only. The reduced breathing effort observed likely justified applying PPV in most infants.