Respiratory management for extremely premature infants born at 22 to 23 weeks of gestation in proactive centers in Sweden, Japan, and USA

Effect of high-frequency oscillatory ventilation with intermittent sigh breaths on carbon dioxide levels in neonates

BACKGROUND

High-frequency oscillatory ventilation (HFOV) minimizes ventilator-induced lung injuries. Spontaneous sigh breathing may augment the functional residual capacity, increase lung compliance, and recruit atelectatic alveoli.

PURPOSE

To evaluate the difference in the partial pressure of carbon dioxide (PaCO2) in neonates receiving invasive HFOV as the primary mode of respiratory support before versus after sigh breaths (Sighs).

METHODS

This prospective study was conducted between January and December 2023. Intubated preterm and term neonates who underwent HFOV with an available arterial line were enrolled in this study after informed parental consent was obtained. Sighs were set at a frequency of 3 breaths/min and pressure of 5 cmH2O above the mean airway pressure for 2 hours. Arterial blood gas was collected before and after Sighs and analyzed using 2 dependent tests.

RESULTS

Thirty neonates with a mean gestational age of 33.6±4.1 weeks and median date of intervention of 1.88 days (interquartile range, 0.87-3.79 days) were enrolled. The mean PaCO2 level was significantly lower in the HFOV with Sighs group (45.2±6.6 mmHg) versus the HFOV alone group (48.8±3.1 mmHg) with a mean difference (MD) of -3.6 mmHg (95% confidence interval [CI], -6.3 to -0.9; P=0.01). Subgroup analyses indicated the ability of Sighs to reduce the PaCO2 level in neonates with respiratory distress syndrome (n=15; MD [95% CI]=-4.2 [-8.2 to -0.2] mmHg; P= 0.04).

CONCLUSION

Sighing can reduce PaCO2 levels in neonates ventilated with HFOV, particularly those with respiratory distress syndrome.

Invasive ventilation at the boundary of viability: A respiratory pathophysiology study of infants born between 22 and 24 weeks of gestation

BACKGROUND

Invasive ventilation of infants born before 24 weeks of gestation is critical for survival and long-term respiratory outcomes, but currently there is a lack of evidence to guide respiratory management. We aimed to compare respiratory mechanics and gas exchange in ventilated extremely preterm infants born before and after 24 weeks of gestation.

METHODS

Secondary analysis of two prospective observational cohort studies, comparing respiratory mechanics and indices of gas exchange in ventilated infants born at 22-24 weeks of gestation (N=14) compared to infants born at 25-27 weeks (N=37). The ventilation/perfusion ratio (VA/Q), intrapulmonary shunt, alveolar dead space (VDalv) and adjusted alveolar surface area (SA) were measured in infants born at the Neonatal Unit of King's College Hospital NHS Foundation Trust, London, UK.

RESULTS

Compared to infants of 25-27 weeks, infants of 22-24 weeks had higher median (IQR) intrapulmonary shunt [18 (4 - 29) % vs 8 (2 - 12) %, p=0.044] and higher VDalv [0.9 (0.6 - 1.4) vs 0.6 (0.5 - 0.7) ml/kg, p=0.036], but did not differ in VA/Q. Compared to infants of 25-27 weeks, the infants of 22-24 weeks had a lower adjusted SA [509 (322- 687) vs 706 (564 - 800) cm2, p=0.044]. The infants in the two groups did not differ in any of the indices of respiratory mechanics.

CONCLUSION

Ventilated infants born before 24 completed weeks of gestation exhibit abnormal gas exchange, with higher alveolar dead space and intrapulmonary shunt and a decreased alveolar surface area compared to extreme preterms born after 24 weeks of gestation.

Lung recruitment with HFOV versus VTV/AC in preterm infants with RDS

OBJECTIVES

To compare the effect of lung recruitment using high frequency ventilation versus volume targeted ventilation on duration of intubation as well as its effect on lung inflammation in preterm infants with respiratory distress syndrome.

METHODS

The study was conducted on a total of 40 preterm infants, 34 weeks gestational age or less, having RDS that needed intubation and mechanical ventilation within the first 72 h after their birth at the NICU of Mansoura University Children's Hospital during the period from July 2020 to July 2022. Infants included were randomly assigned into two groups, Group A who were subjected to LRM using HFOV (20 cases) and Group B who were subjected to LRM using VTV/AC (20 cases). TGF-β1 level was measured in BAL samples of all studied infants at two time points; before lung recruitment maneuver and at day 5 after lung recruitment or just before extubation if extubation occurs earlier than 5 days.

RESULTS

Lung recruitment maneuver had no significant effect on time to extubation. Both groups showed no significant difference in rate of prematurity complications nor delta change of TFG-β1 level in tracheal aspirate of those preterm infants measured before lung recruitment and five days after recruitment or at extubation when extubation occurred earlier.

CONCLUSIONS

Lung recruitment maneuver was not associated with significant difference between both groups of preterm infants. The results obtained from our study, being the first of its kind to compare the effect of lung recruitment, provide a promising research area for further investigations.

Viability of Extremely Premature neonates: clinical approaches and outcomes

Viability refers to an infant's ability to survive outside the womb, which is influenced by both developmental maturity and the quality of medical care received. The concept of periviability, which has evolved alongside medical advancements, describes the stage between viability and nonviability, typically spanning from 200/7 to 25 6/7 weeks of gestation. While the chances of survival are extremely low at the earlier end of this range, the possibility of surviving without significant long-term complications improves towards the later end. The effectiveness of various antenatal and postnatal care practices, particularly those considered to be part of an active approach, plays a crucial role in influencing survival rates and mitigating morbidities. However, the decision to provide such active care is heavily influenced by national guidelines as well as international standards. The variability in guideline recommendations from one country to another, coupled with differences based on gestational age or accompanying risk factors, prevents the establishment of a standardized global approach. This variability results in differing practices depending on the country or institution where the birth occurs. Consequently, healthcare providers must navigate these discrepancies, which often leads to complex ethical dilemmas regarding the balance between potential survival and the associated risks. This review article explores the evolution of the definition of viability, the vulnerabilities faced by periviable infants, and the advancements in medical care that have improved survival rates. Additionally, it examines the viability and periviability definitions, the care and outcomes of periviable infants and recommendations in guidelines.

Finding treasure in the journey: a single center quality improvement bundle to reduce bronchopulmonary dysplasia

BACKGROUND

Reducing bronchopulmonary dysplasia (BPD) utilizing a single intervention has been challenging. The quality improvement (QI) bundle approach may better address BPD multifactorial risk factors.

METHODS

A single-center interdisciplinary quality improvement (QI) initiative to enhance respiratory care for preterm infants born less than 30 weeks gestation.

GLOBAL AIM

To reduce BPD in preterm infants.

SMART AIM

Introduce and implement a comprehensive, evidence-based respiratory care bundle within 12 months, targeting areas needing improvement in our practices.

RESULTS

Our preplanned improvement targets were achieved for all process measures. Overall BPD incidence did not change (45% vs. 44.3%). After the QI intervention, inborn infants had a lower BPD rate, though not statistically significant (38.7% vs. 30.3%, p = 0.22), with a significant reduction in grade 1 BPD (24.5% vs. 12.4%, p = 0.032).

CONCLUSION

Structured interdisciplinary QI work tailored to local settings can improve respiratory care and possibly amend the outcomes of infants at risk for BPD.

Challenges of parenting children born before 24 weeks of gestation

AIM

To assess experience of care, well-being of parents and children's development in a cohort of extremely premature infants born <24 weeks of gestation in Sweden from 2007 to 2018.

METHODS

A survey based on multiple questionnaires answered by 124/349 (35.5%) parents.

RESULTS

The median age of parents and children was 43 and 9 years, respectively; 74.2% were mothers. Parents expressed high healthcare satisfaction. Following discharge from neonatal care, the satisfaction with the infant's treatment, support from personnel and being respected as a parent significantly declined but remained high. The criteria for suspected developmental deviation according to the screening test early symptomatic syndromes eliciting neurodevelopmental clinical examinations-questionnaire was fulfilled by 84.3%, 55.6% had suspected avoidant restrictive food intake disorder and 47.9% had visual perception problems. Parents experienced severe fatigue (48.6%) despite strong social support and family self-efficacy. Economic support was provided to 30.6%, and 37.9% of children were enrolled in habilitation services.

CONCLUSION

This study highlighted the substantial challenges faced by parents of infants born before 24 weeks of gestation, including decreased satisfaction post-discharge, fatigue and concerns about children's well-being. The findings underscore the need for comprehensive family-centred support and long-term multi-professional follow-up centres.

Outcomes of infants with birthweights less than 501 g compared to infants weighing 501-750 g at a center utilizing first intention high frequency jet ventilation

Background

Data on clinical outcomes of infants with birthweights less than 501 g (ELBW<501) are limited.

Objective

To evaluate management strategies and clinical outcomes of ELBW<501infants compared to infants weighing 501-750 g (ELBW501-750).

Methods

A retrospective study of all ELBW<501 and ELBW501-750 infants born between 2012 and 2022 at a center utilizing first intention high frequency jet ventilation was performed. Patient characteristics, clinical and outcome data were compared between the two groups.

Results

A total of 358 infants (92 ELBW<501 infants and 266 ELBW501-750) were included. The survival rate for the ELBW<501 group was 60.9% compared to 86.5% for ELBW501-750. ELBW<501 infants required more frequent use of 2.0 mm endotracheal tubes, required higher FiO2 and longer duration of mechanical ventilation. Compared to ELBW501-750 group, the ELBW<501 group were more likely to be SGA (68.2% vs. 16.5%) and more premature (23.2 vs. 24.3 weeks) with lower survival, longer length of stay, higher incidence of ROP and lower weight at discharge but comparable rates of IVH, grade 3 BPD, discharged on supplemental oxygen, and tracheostomy.

Conclusion

ELBW<501 infants are at risk for significant morbidity and mortality. However, with specialized obstetric and neonatal care, survival rates of 60% are possible with respiratory outcomes comparable to ELBW501-750 infants. However, the increased risk of severe ROP for ELBW<501 requiring either surgical or medical intervention is concerning and warrants optimal surveillance.

Weaning from mechanical ventilation and assessment of extubation readiness

Tremendous advancements in neonatal respiratory care have contributed to the improved survival of extremely preterm infants (gestational age ≤ 28 weeks). While mechanical ventilation is often considered one of the most important breakthroughs in neonatology, it is also associated with numerous short and long-term complications. For those reasons, clinical research has focused on strategies to avoid or reduce exposure to mechanical ventilation. Nonetheless, in the extreme preterm population, 70-100% of infants born 22-28 weeks of gestation are exposed to mechanical ventilation, with nearly 50% being ventilated for ≥ 3 weeks. As contemporary practices have shifted towards selectively reserving mechanical ventilation for those patients, mechanical ventilation weaning and extubation remain a priority yet offer a heightened challenge for clinicians. In this review, we will summarize the evidence for different strategies to expedite weaning and assess extubation readiness in preterm infants, with a particular focus on extremely preterm infants.

Non-invasive versus invasive respiratory support in preterm infants

Respiratory insufficiency is almost ubiquitous in infants born preterm, with its incidence increasing with lower gestational age. A wide range of respiratory support management strategies are available for these infants, separable into non-invasive and invasive forms of respiratory support. Here we review the history and evolution of respiratory care for the preterm infant and then examine evidence that has emerged to support a non-invasive approach to respiratory management where able. Continuous positive airway pressure (CPAP) is the non-invasive respiratory support mode currently with the most evidence for benefit. CPAP can be delivered safely and effectively and can commence in the delivery room. Particularly in early life, time spent on non-invasive respiratory support, avoiding intubation and mechanical ventilation, affords benefit for the preterm infant by virtue of a lessening of lung injury and hence a reduction in incidence of bronchopulmonary dysplasia. In recent years, enthusiasm for application of non-invasive support has been further bolstered by new techniques for administration of exogenous surfactant. Methods of less invasive surfactant delivery, in particular with a thin catheter, have allowed neonatologists to administer surfactant without resort to endotracheal intubation. The benefits of this approach appear to be sustained, even in those infants subsequently requiring mechanical ventilation. This cements the notion that any reduction in exposure to mechanical ventilation leads to alleviation of injury to the vulnerable preterm lung, with a long-lasting effect. Despite the clear advantages of non-invasive respiratory support, there will continue to be a role for intubation and mechanical ventilation in some preterm infants, particularly for those born <25 weeks' gestation. It is currently unclear what role early non-invasive support has in this special population, with more studies required.

Neonatal high frequency ventilation: Current trends and future directions

High frequency ventilation (HFV) in neonates has been in use for over forty years. Some early HFV ventilators are no longer available, but high frequency oscillatory ventilation (HFOV) and jet ventilators (HFJV) continue to be commonly employed. Advanced HFOV models available outside of the United States are much quieter and easier to use, and are available as options on many conventional ventilators, providing important improvements such as tidal volume measurement and targeting. HFJV excels in treating air leak and non-homogenous lung disease and is often used for other diseases as well. High frequency non-invasive ventilation (hfNIV) is a novel application of HFV that remains under investigation. Similar to bubble CPAP, hfNIV has been applied with a variety of high-frequency ventilators. Efficacy and safety of hfNIV with any device have not yet been established. This article describes the current approaches to these HFV therapies and stresses the importance of understanding how each device works and what disease processes may respond best to the technology employed.

Total liquid ventilation in an ovine model of extreme prematurity: a randomized study

BACKGROUND

This study aimed at comparing cardiorespiratory stability during total liquid ventilation (TLV)-prior to lung aeration-with conventional mechanical ventilation (CMV) in extremely preterm lambs during the first 6 h of life.

METHODS

23 lambs (11 females) were born by c-section at 118-120 days of gestational age (term = 147 days) to receive 6 h of TLV or CMV from birth. Lung samples were collected for RNA and histology analyses.

RESULTS

The lambs under TLV had higher and more stable arterial oxygen saturation (p = 0.001) and cerebral tissue oxygenation (p = 0.02) than the lambs in the CMV group in the first 10 min of transition to extrauterine life. Although histological assessment of the lungs was similar between the groups, a significant upregulation of IL-1a, IL-6 and IL-8 RNA in the lungs was observed after TLV.

CONCLUSIONS

Total liquid ventilation allowed for remarkably stable transition to extrauterine life in an extremely preterm lamb model. Refinement of our TLV prototype and ventilation algorithms is underway to address specific challenges in this population, such as minimizing tracheal deformation during the active expiration.

IMPACT

Total liquid ventilation allows for remarkably stable transition to extrauterine life in an extremely preterm lamb model. Total liquid ventilation is systematically achievable over the first 6 h of life in the extremely premature lamb model. This study provides additional incentive to pursue further investigation of total liquid ventilation as a transition tool for the most extreme preterm neonates.

Single center experience with first-intention high-frequency jet vs. volume-targeted ventilation in extremely preterm neonates

Objectives

To examine whether first-intention high-frequency jet ventilation (HFVJ), compared to volume-targeted ventilation (VTV), in extremely preterm infants is associated with lower incidence of bronchopulmonary dysplasia (BPD) and other adverse clinical outcomes.

Study design

We conducted a retrospective cohort study evaluating neonates with gestational age (GA) ≤28 weeks, who received first-intention HFJV (main exposure) or VTV (comparator), between 11/2020 and 3/2023, with a subgroup analysis including neonates with GA ≤26 weeks and oxygenation index (OI) >5.

Results

We identified 117 extremely preterm neonates, 24 (GA 25.2 ± 1.6 weeks) on HFJV, and 93 (GA 26.4 ± 1.5 weeks, p = 0.001) on VTV. The neonates in the HFJV group had higher oxygenation indices on admission, higher inotrope use, and remained intubated for a longer period. Despite these differences, there were no statistically significant differences in rates of BPD, survival, or other adverse outcomes between the two groups. In subgroup analysis of 18 neonates on HFJV and 39 neonates on VTV, no differences were recorded in the GA, and duration of mechanical ventilation, while neonates in the HFJV group had significantly lower rates of BPD (50% compared to 83%, p = 0.034), and no significant differences in other adverse outcomes compared to neonates in the VTV group. In neonates ≤26 weeks of GA with OI >5, HFJV was significantly associated with lower rates of BPD (OR 0.21, 95% CI 0.05-0.92), and combined BPD or death (OR 0.18, 95% CI 0.03-0.85), after adjusting for birth weight, and Arterial-alveolar gradient on admission.

Conclusions

In extremely preterm neonates ≤26 weeks of GA with OI >5, first-intention HFJV, in comparison to VTV, is associated with lower rates of BPD.

Optimal timing of extubation in preterm infants

In neonatal intensive care, endotracheal intubation is usually performed as an urgent or semi-urgent procedure in infants with critical or unstable conditions related to progressive respiratory failure. Extubation is not. Patients undergoing extubation are typically stable, with improved respiratory function. The key elements to facilitating extubation are to recognize improvement in respiratory status, promote weaning of mechanical ventilation, and accurately identify readiness for removal of the endotracheal tube. Therefore, extubation should be a planned and well-organized procedure. In this review, we will appraise the evidence for existing predictors of extubation readiness and provide patient-specific, pathophysiology-derived strategies to optimize the timing and success of extubation in neonates, with a focus on extremely preterm infants.

Patent ductus arteriosus (PDA) and response to late surfactant treatment in premature infants

OBJECTIVE

To determine the clinical/echocardiography (ECHO) phenotype of patients with hypoxic respiratory failure (HRF) and response to late surfactant, according to patent ductus arteriosus (PDA) status.

STUDY DESIGN

This retrospective study included infants ≤26+6 weeks gestation who received ≥1 surfactant dose after 6 postnatal days and where PDA status was available by ECHO. Response to surfactant was appraised based on change in respiratory severity score over 48 h. The relationship between PDA status and response to surfactant was evaluated via univariate analysis.

RESULT

We studied late surfactant (n = 71 doses) administration in 35 preterm infants born at a mean weight and GA at birth were 595 g (508, 696) and 23.3 (22.7, 25) weeks, respectively of whom 16 (46%) had a diagnosis of PDA. Positive response to late surfactant treatment was independently associated with absence of PDA [OR 26 (2, 334), p = 0.01] whereas presence of PDA was independently associated with negative response [OR 12 (1.1, 126), p = 0.04].

CONCLUSIONS

In neonates ≤26+6 weeks gestation, with HRF, response to surfactant after postnatal day 6 is influenced by PDA status. Future trials should consider PDA status which may enhance diagnostic precision and refine patient selection for late surfactant treatment.

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

INTRODUCTION

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Phenotypic changes in low-density lipoprotein particles as markers of adverse clinical outcomes in COVID-19

BACKGROUND AND AIMS

Low-density lipoprotein (LDL) plasma concentration decline is a biomarker for acute inflammatory diseases, including coronavirus disease-2019 (COVID-19). Phenotypic changes in LDL during COVID-19 may be equally related to adverse clinical outcomes.

METHODS

Individuals hospitalized due to COVID-19 (n = 40) were enrolled. Blood samples were collected on days 0, 2, 4, 6, and 30 (D0, D2, D4, D6, and D30). Oxidized LDL (ox-LDL), and lipoprotein-associated phospholipase A2 (Lp-PLA2) activity were measured. In a consecutive series of cases (n = 13), LDL was isolated by gradient ultracentrifugation from D0 and D6 and was quantified by lipidomic analysis. Association between clinical outcomes and LDL phenotypic changes was investigated.

RESULTS

In the first 30 days, 42.5% of participants died due to Covid-19. The serum ox-LDL increased from D0 to D6 (p < 0.005) and decreased at D30. Moreover, individuals who had an ox-LDL increase from D0 to D6 to over the 90th percentile died. The plasma Lp-PLA2 activity also increased progressively from D0 to D30 (p < 0.005), and the change from D0 to D6 in Lp-PLA2 and ox-LDL were positively correlated (r = 0.65, p < 0.0001). An exploratory untargeted lipidomic analysis uncovered 308 individual lipids in isolated LDL particles. Paired-test analysis from D0 and D6 revealed higher concentrations of 32 lipid species during disease progression, mainly represented by lysophosphatidyl choline and phosphatidylinositol. In addition, 69 lipid species were exclusively modulated in the LDL particles from non-survivors as compared to survivors.

CONCLUSIONS

Phenotypic changes in LDL particles are associated with disease progression and adverse clinical outcomes in COVID-19 patients and could serve as a potential prognostic biomarker.

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.

Respiratory management in the premature neonate

INTRODUCTION

Advances in neonatal care have made possible the increased survival of extremely preterm infants. Even though there is widespread recognition of the harmful effects of mechanical ventilation on the developing lung, its use has become imperative in the management of micro-/nano-preemies. There is an increased emphasis on the use of less-invasive approaches such as minimally invasive surfactant therapy and non-invasive ventilation that have been proven to result in improved outcomes.

AREAS COVERED

Here, we review the evidence-based practices surrounding the respiratory management of extremely preterm infants including delivery room interventions, invasive and non-invasive ventilation approaches, and specific ventilator strategies in respiratory distress syndrome and bronchopulmonary dysplasia. Adjuvant relevant respiratory pharmacotherapies used in preterm neonates are also discussed.

EXPERT OPINION

Early use of non-invasive ventilation and use of less invasive surfactant administration are key strategies in the management of respiratory distress syndrome in preterm infants. Ventilator management in bronchopulmonary dysplasia must be tailored according to the individual phenotype. There is strong evidence to start caffeine early to improve respiratory outcomes, but evidence is lacking on the use of other pharmacological agents in preterm neonates, and an individualized approach has to be considered for their use.

Ventilator Management in Extremely Preterm Infants

Advances in ventilation strategies for infants in the NICU have led to increased survival of extremely preterm infants. More than 75% of infants born at less than or equal to 27 weeks' gestation require initial mechanical ventilation for survival due to developmental immaturity of their lungs and respiratory drive. Various ventilators using different technologies and involving multiple management strategies are available for use in this population. Centers across the world have successfully used conventional, high-frequency oscillatory and high-frequency jet ventilation to manage respiratory failure in extremely preterm infants. This review explores the existing evidence for each mode of ventilation and the importance of individualizing ventilator management strategies when caring for extremely preterm infants.