Epidemiology of bronchopulmonary dysplasia

Impact of postnatal dexamethasone timing on preterm mortality and bronchopulmonary dysplasia: a propensity score analysis

BACKGROUND

Postnatal dexamethasone (PND) is used in high-risk preterm infants after the first week of life to facilitate extubation and prevent bronchopulmonary dysplasia (BPD) but the optimal treatment timing remains unclear. Our objective was to explore the association between the timing of PND commencement and mortality and respiratory outcomes.

METHODS

This was a retrospective National Neonatal Research Database study of 84 440 premature infants born <32 weeks gestational age from 2010 to 2020 in England and Wales. Propensity score weighting analysis was used to explore the impact of PND commenced at three time-points (2-3 weeks (PND2/3), 4-5 weeks (PND4/5) and after 5 weeks (PND6+) chronological age) on the primary composite outcome of death before neonatal discharge and/or severe BPD (defined as respiratory pressure support at 36 weeks) alongside other secondary respiratory outcomes.

RESULTS

3469 infants received PND. Compared with PND2/3, infants receiving PND6+ were more likely to die and/or develop severe BPD (OR 1.68, 95% CI 1.28-2.21), extubate at later postmenstrual age (mean difference 3.1 weeks, 95% CI 2.9-3.4 weeks), potentially require respiratory support at discharge (OR 1.34, 95% CI 1.06-1.70) but had lower mortality before discharge (OR 0.38, 95% CI 0.29-0.51). PND4/5 was not associated with severe BPD or discharge respiratory support.

CONCLUSIONS

PND treatment after 5 weeks of age was associated with worse respiratory outcomes although residual bias cannot be excluded. A definitive clinical trial to determine the optimal PND treatment window, based on early objective measures to identify high-risk infants, is needed.

Severity of preterm birth and the risk of pulmonary hypertension in childhood: A population-based cohort study in Sweden

BACKGROUND

Preterm birth (<37 completed gestational weeks) has been linked to pulmonary hypertension (PH), but the relationship to severity of preterm birth has not been studied.

OBJECTIVES

We investigated associations between extremely (<28 weeks), very (28-31 weeks), moderately (32-36 weeks) preterm birth, early-term birth (37-38 weeks) and later PH. Additionally, we explored associations between birthweight for gestational age and PH.

METHODS

This registry-based cohort study followed 3.1 million individuals born in Sweden (1987-2016) from 1 up to a maximum of 30 years of age. The outcome was diagnosis or death from PH in national health registers. Adjusted hazard ratios (HR) were estimated using Cox regression analysis. Unadjusted and confounder-adjusted incidence rate differences were also calculated.

RESULTS

Of 3,142,812 individuals, there were 543 cases of PH (1.2 per 100,000 person-years), 153 of which in individuals without malformations. Compared with individuals born at 39 weeks, adjusted HRs with 95% confidence interval (CI) for PH for extremely, moderately, and very preterm birth were 68.78 (95% CI 49.49, 95.57), 13.86 (95% CI 9.27, 20.72) and 3.42 (95% CI 2.46, 4.74), respectively, and for early-term birth 1.74 (1.31, 2.32). HRs were higher in subjects without malformations. There were 90 additional cases of PH per 100,000 person-years in the extremely preterm group (50 after excluding malformations). Very small for gestational age (below 2 SD from estimated birthweight for gestational age and sex) was also associated with increased risk of PH (adjusted HR 2.02, 95% CI 1.14, 3.57).

CONCLUSIONS

We found an inverse association between gestational age and later PH, but the incidence and absolute risks are low. The severity of preterm birth adds clinically relevant information to the assessment of cardiovascular risks in childhood.

Postnatal abnormality in brainstem neural conduction in neonatal bronchopulmonary dysplasia survivors

OBJECTIVE

To investigate postnatal neural conduction in the auditory brainstem in neonatal bronchopulmonary dysplasia (BPD) survivors.

METHODS

Thirty-two very preterm BPD survivors were studied at 57-58 weeks of postconceptional age. Brainstem auditory-evoked response was studied using maximum length sequence. Wave latencies and intervals were analyzed in detail. The controls were 37 normal term infants and 35 very preterm non-BPD infants.

RESULTS

Compared with normal term controls, BPD survivors showed significantly shortened I-III interval but significantly prolonged III-V interval and greater III-V/I-III interval ratio. Compared with very preterm non-BPD controls, BPD survivors showed a significant shortening in waves III latency and I-III interval, moderate prolonged III-V interval, and significantly greater III-V/I-III interval ratio. These differences were generally similar at all click rates used. The slopes of latency- and interval-click rate functions in BPD survivors did not differ significantly from the two control groups.

CONCLUSIONS

Brainstem neural conduction in BPD survivors differed from normal term and age-matched non-BPD infants; neural maturation is accelerated in caudal brainstem regions but delayed in rostral regions. Neonatal BPD survivors are associated with differential maturation in neural conduction at caudal and rostral brainstem regions, which may constitute an important risk for postnatal neurodevelopment in BPD survivors.

IMPACT

We found that brainstem neural conduction at PCA 57-58 weeks in neonatal BPD survivors differs from normal term and age-matched non-BPD infants. No major differences were found between normal term and very preterm non-BPD infants in brainstem auditory conduction. Neural conduction in BPD survivors is accelerated in caudal brainstem regions but delayed in rostral regions. Neonatal BPD survivors are associated with differential maturation in neural conduction at caudal and rostral brainstem regions. The abnormality may constitute an important risk for postnatal neurodevelopment in BPD survivors.

Nutrition of Infants with Bronchopulmonary Dysplasia before and after Discharge from the Neonatal Intensive Care Unit

Bronchopulmonary dysplasia (BPD) represents a severe sequela in neonates born very prematurely. The provision of adequate nutritional support in this high-risk population is challenging. The development of the lungs and physical growth are closely linked together in infants with BPD. Growth deficiency has been associated with pulmonary dysfunction, whereas improvement in respiratory status results in growth acceleration. Currently, there is not enough data regarding optimal nutritional strategies in this population. Nutrition in these infants should provide sufficient calories and nutrients to establish growth, avoid growth retardation and assist alveolarization of the lungs. Meticulous follow-up is mandatory during and after discharge from the Neonatal Intensive care Unit (NICU) to minimize growth retardation and improve lung function. Despite the significant literature supporting the contribution of growth and nutrition in the avoidance of BPD, there is limited research regarding interventions and management of infants with established BPD. Our aim was to review clinical strategies applied in everyday clinical practice and identify debates on the nutritional approach of newborns with BPD. Well-organized interventions and clinical trials regarding the somatic development and nutrition of infants with BPD are warranted.

Stem-Cell Therapy for Bronchopulmonary Dysplasia (BPD) in Newborns

Premature newborns are at a higher risk for the development of respiratory distress syndrome (RDS), acute lung injury (ALI) associated with lung inflammation, disruption of alveolar structure, impaired alveolar growth, lung fibrosis, impaired lung angiogenesis, and development of bronchopulmonary dysplasia (BPD) with severe long-term developmental adverse effects. The current therapy for BPD is limited to supportive care including high-oxygen therapy and pharmacotherapy. Recognizing more feasible treatment options to improve lung health and reduce complications associated with BPD is essential for improving the overall quality of life of premature infants. There is a reduction in the resident stem cells in lungs of premature infants with BPD, which strongly suggests a critical role of stem cells in BPD pathogenesis; this warrants the exploration of the potential therapeutic use of stem-cell therapy. Stem-cell-based therapies have shown promise for the treatment of many pathological conditions including acute lung injury and BPD. Mesenchymal stem cells (MSCs) and MSC-derived extracellular vesicles (EVs) including exosomes are promising and effective therapeutic modalities for the treatment of BPD. Treatment with MSCs and EVs may help to reduce lung inflammation, improve pulmonary architecture, attenuate pulmonary fibrosis, and increase the survival rate.

Temporal trends in respiratory care and bronchopulmonary dysplasia in very preterm infants over a 10-year period in Spain

OBJECTIVE

To evaluate trends in respiratory care practices and bronchopulmonary dysplasia (BPD) among very preterm infants born in Spain between 2010 and 2019.

STUDY DESIGN

This was a retrospective cohort study of data obtained from a national population-based database (SEN1500 network). Changes in respiratory care and BPD-free survival of infants with gestational age (GA) of 23⁰-31⁶ weeks and <1500 g were assessed over two 5-year periods. Temporal trends were examined by joinpoint and Poisson regression models and expressed as the annual per cent change and adjusted relative risk (RR) for the change per year.

RESULTS

A total of 17 952 infants were included. In the second period, infants were less frequently intubated in the delivery room and during neonatal intensive care unit stay. This corresponded with an increase in use of non-invasive ventilation techniques. There were no significant differences between the periods in BPD-free survival or survival without moderate-to-severe BPD. After adjusting for covariates, the RR for the change per year was significant for the following variables: never intubated (RR 1.03, 95% CI 1.02 to 1.04); intubation in the delivery room (RR 0.98, 95% CI 0.97 to 0.99); use of nasal intermittent positive pressure ventilation (RR 1.08, 95% CI 1.05 to 1.11); and BPD-free survival (only in the group with the lowest GA; RR 0.98, 95% CI 0.97 to 0.99).

CONCLUSION

Our findings reveal significant changes in respiratory care practices between 2009 and 2019. Despite an increase in use of non-invasive respiratory strategies, BPD-free survival did not improve and even worsened in the group with the lowest GA (23⁰-25⁶).

Pharmacometabolomics Profiling of Preterm Infants Validates Patterns of Metabolism Associated With Response to Dexamethasone Treatment for Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is one of the most common health complications of premature birth. Corticosteroids are commonly used for treatment of BPD, but their use is challenging due to variability in treatment response. Previous pharmacometabolomics study has established patterns of metabolite levels with response to dexamethasone. We obtained additional patient samples for metabolomics analysis to find associations between the metabolome and dexamethasone response in a validation cohort. A total of 14 infants provided 15 plasma and 12 urine samples. The measure of treatment response was the calculated change in respiratory severity score (deltaRSS) from pre-to-post treatment. Each metabolite was assessed with paired analysis of pre and post-treatment samples using Wilcoxon signed rank test. Correlation analysis was conducted between deltaRSS and pre-to-post change in metabolite level. Paired association analysis identified 20 plasma and 26 urine metabolites with significant level difference comparing pre to post treatment samples (p < 0.05). 4 plasma and 4 urine metabolites were also significant in the original study. Pre-to-post treatment change in metabolite analysis identified 4 plasma and 8 urine metabolites significantly associated with deltaRSS (p < 0.05). Change in urine citrulline levels showed a similar correlation pattern with deltaRSS in the first study, with increasing level associated with improved drug response. These results help validate the first major findings from pharmacometabolomics of BPD including key metabolites within the urea cycle and trans-4-hydroxyproline as a potential marker for lung injury. Ultimately, this study furthers our understanding of the mechanisms of steroid response in BPD patients and helps to design future targeted metabolomics studies in this patient population.

Verification of immunology-related genetic associations in BPD supports ABCA3 and five other genes

BACKGROUND

Inflammatory processes are key drivers of bronchopulmonary dysplasia (BPD), a chronic lung disease in preterm infants. In a large sample, we verify previously reported associations of genetic variants of immunology-related genes with BPD.

METHODS

Preterm infants with a gestational age ≤32 weeks from PROGRESS and the German Neonatal Network (GNN) were included. Through a consensus case/control definition, 278 BPD cases and 670 controls were identified. We identified 49 immunity-related genes and 55 single-nucleotide polymorphisms (SNPs) previously associated with BPD through a comprehensive literature survey. Additionally, a quantitative genetic association analysis regarding oxygen supplements, mechanical ventilation, and continuous positive air pressure (CPAP) was performed.

RESULTS

Five candidate SNPs were nominally associated with BPD-related phenotypes with effect directions not conflicting the original studies: rs11265269-CRP, rs1427793-NUAK1, rs2229569-SELL, rs1883617-VNN2, and rs4148913-CHST3. Four of these genes are involved in cell adhesion. Extending our analysis to all well-imputed SNPs of all candidate genes, the strongest association was rs45538638-ABCA3 with CPAP (p = 4.9 × 10^-7, FDR = 0.004), an ABC transporter involved in surfactant formation.

CONCLUSIONS

Most of the previously reported associations could not be replicated. We found additional support for SNPs in CRP, NUAK1, SELL, VNN2, and ABCA3. Larger studies and meta-analyses are required to corroborate these findings.

IMPACT

Larger cohort for improved statistical power to detect genetic associations with bronchopulmonary dysplasia (BPD). Most of the previously reported genetic associations with BPD could not be replicated in this larger study. Among investigated immunological relevant candidate genes, additional support was found for variants in genes CRP, NUAK1, SELL, VNN2, and CHST3, four of them related to cell adhesion. rs45538638 is a novel candidate SNP in reported candidate gene ABC-transporter ABCA3. Results help to prioritize molecular candidate pathomechanisms in follow-up studies.

Differences in clinical and laboratory biomarkers for short and long-term respiratory outcomes in preterm neonates

BACKGROUND

Pulmonary outcome of premature neonates has focused more on short-term than long-term respiratory morbidities.

OBJECTIVE

Describe risk factors/biomarkers associated with short-term (bronchopulmonary dysplasia [BPD]) (supplemental oxygen use at 36 weeks postmenstrual age [PMA]) and longer-term (chronic respiratory morbidity [CRM]) (respiratory related symptoms, medications, medical/emergency visits, hospitalizations at 6-12 months corrected gestational age [CGA]) respiratory outcomes in a longitudinal cohort.

DESIGN/METHODS

Neonates born at 24-29-week gestation were prospectively followed to 6-12-month CGA. Associations between clinical and laboratory risk factors/biomarkers of BPD and CRM were explored.

RESULTS

Of 86 subjects, 94% survived. Outcomes were available for 89% at 36-week PMA (BPD present in 42% of infants) and 72% at 6-12-month CGA (CRM present in 47% of infants). For the 54 infants with known outcomes for both BPD and CRM, diagnoses were discordant in 41%. BPD was associated with lower birthweight and birthweight Z-score for GA, lower Apgar scores, more surfactant doses, higher SNAPPE-II scores, highest Day 1 inspired oxygen concentration, Day 7 oxygen use, prolonged ventilatory support, bacteremia, necrotizing enterocolitis, and treated patent ductus arteriosus. CRM was associated with lower Apgar scores, Day 7 oxygen use and higher urine vascular endothelial growth factor. Patterns of plasma and urine lipid oxidation products differed in the two outcomes.

CONCLUSION

In this hypothesis generating and exploratory study, BPD and CRM were associated with different risk factors/biomarker patterns. Concordance between these two outcomes was weak. Strategies for reducing CRM should be studied in cohorts identified by appropriate early risk factors/biomarkers.

Lung growth and pulmonary function after prematurity and bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) still carries a heavy burden of morbidity and mortality in survivors of extreme prematurity. The disease is characterized by simplification of the alveolar structure, involving a smaller number of enlarged alveoli due to decreased septation and a dysmorphic pulmonary microvessel growth. These changes lead to persistent abnormalities mainly affecting the smaller airways, lung parenchyma, and pulmonary vasculature, which can be assessed with lung function tests and imaging techniques. Several longitudinal lung function studies have demonstrated that most preterm-born subjects with BPD embark on a low lung function trajectory, never achieving their full airway growth potential. They are consequently at higher risk of developing a chronic obstructive pulmonary disease-like phenotype later in life. Studies based on computer tomography and magnetic resonance imaging, have also shown that in these patients there is a persistence of lung abnormalities like emphysematous areas, bronchial wall thickening, interstitial opacities, and mosaic lung attenuation also in adult age. This review aims to outline the current knowledge of pulmonary and vascular growth in survivors of BPD and the evidence of their lung function and imaging up to adulthood.

Recent Advances in Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a form of chronic lung disease that occurs in preterm infants, usually those receiving substantial respiratory support with either mechanical ventilation or supplementation with oxygen. The pathogenesis of BPD is multifactorial, and the clinical phenotype is variable. BPD is associated with substantial mortality and short- and long-term morbidity. The incidence of BPD has remained stable or increased, as advances in neonatal care have led to improved survival of more extremely preterm infants. Extensive basic science, translational, and clinical research focusing on BPD has improved the current understanding of the factors that contribute to BPD pathogenesis. However, despite a better understanding of its pathophysiology, BPD continues to be challenging to prevent and manage adequately. The current review aims to provide a clinically useful synopsis of evidence on the prevention and management of BPD in preterm infants.

The association between diuretic class exposures and enteral electrolyte use in infants developing grade 2 or 3 bronchopulmonary dysplasia in United States children's hospitals

OBJECTIVE

To evaluate the association between chronic diuretic exposures and enteral electrolyte use in infants developing severe bronchopulmonary dysplasia (sBPD).

STUDY DESIGN

Retrospective longitudinal cohort study in infants admitted to United States children's hospitals. We identified diuretic exposures and measured enteral NaCl and KCl use during pre-defined exposure risk-interval days. We used mixed-effects logistic regression to model the association between diuretic exposures and electrolyte use.

RESULTS

We identified 442,341 subject-days in 3252 infants. All common diuretic classes and class combinations were associated with increased NaCl and KCl use. Thiazide monotherapy was associated with greater electrolyte use than loop monotherapy. The addition of potassium-sparing diuretics was associated with a limited reduction in KCl use compared to thiazide monotherapy.

CONCLUSIONS

Chronic diuretic exposures are associated with increased NaCl and KCl use. Presumptions about the relative impact of different diuretic classes on electrolyte derangements may be inaccurate and require further study.

The Prediction of Bronchopulmonary Dysplasia in Very Low Birth Weight Infants through Clinical Indicators within 1 Hour of Delivery

BACKGROUND

Despite the advances in neonatology, the incidence of bronchopulmonary dysplasia (BPD) is increasing. It is important to prevent the development of BPD in the first place. The online BPD outcome estimator from National Institute of Children Health and Human Development and Neonatal Research Network is available. However, it is not applicable for Asians. Moreover, limits are set for birth weight and gestational weeks excluding those who may still have BPD. The aim of this study was to develop a prediction model for BPD using first hour perinatal and neonatal factors in Korean very low birth weight infants (VLBWIs).

METHODS

Data were collected for 8,022 VLBWIs with gestational age (GA) ≥ 22 weeks who were born between January 1, 2013 and December 31, 2016, and admitted to the neonatal intensive care units of the KNN. Multiple logistic regression models reanalyzed by stepwise selection with significant clinical indicators for BPD. PROC package was used to calculate the area under curve (AUC) and corresponding 95% confidence intervals. Moreover, it was used to search the best cut-off value. External validation was performed with the 2017 Korean neonatal network (KNN) data.

RESULTS

After all missing data were excluded, 4,600 VLBWIs were included in the training dataset of the prediction model. Predictability of presence of BPD was 90.8% and prediction P value cut off was 0.550. Five-minute Apgar score, birth weight, GA, sex, surfactant use were significant indicators. Predictability of severe BPD was 81.5% and prediction P value cut off was 0.160. Five-minute Apgar score, birth weight, maternal PIH, chronic maternal hypertension, GA, sex, respiratory distress syndrome, need of resuscitation at birth were significant indicators. After external validation, sensitivity and specificity did not change significantly.

CONCLUSION

From this study, high predictability was obtained using clinical parameters obtained within one hour of life. P value for prediction of each grade of BPD and equation for calculation was presented. It can be helpful for the early prediction of BPD in Korean VLBWI. This study will contribute to the prediction of BPD in Asians especially Korean VLBWIs, not currently included in the NICHD BPD online BPD predictor. In addition, the predictive power may be continuously increased with the cumulative data of KNN.

Outcomes of neonates with tracheostomy secondary to bronchopulmonary dysplasia

Background

Bronchopulmonary dysplasia (BPD) is a disease that can affect preterm neonates. Infants with severe BPD may develop pulmonary hypertension (PHN) and may require chronic mechanical ventilation with tracheostomy. The outcomes of these infants have not been studied well. We proposed to review survival and outcomes of infants requiring tracheostomy secondary to severe BPD in our NICU at 24 months.

Methods

We reviewed infants’ charts who were diagnosed with BPD that underwent tracheostomy from January 2011 to May 2016 at our children’s hospital NICU. Data were recorded from hospital stay as well as from follow up clinics. Institutional review board approval was obtained prior to beginning of study.

Results

Forty-one babies (37 during initial hospitalization and 4 subsequently) requiring tracheostomy were identified from our database. Median gestational age at birth was 26 weeks (25–27 IQR), mean birthweight of 731 g (±245 SD) and 32% were small for gestational age (SGA). Median age of tracheostomy placement was 168 days (108–197 IQR), and median PMA 48 wks (40–56 IQR). 26% of infants requiring tracheostomy also had subglottic stenosis along with BPD. 34 infants (83%) survived to discharge from NICU. 66% (27/41) of our patients had a composite outcome of death, ventilator dependency and/or poor neurodevelopmental outcome at 2 years. We found that a higher respiratory severity score at the time of tracheostomy placement and later post-menstrual age at admission to level IV NICU was associated with a worse outcome. Small for gestational age infants were found to have worse outcomes as well. 41% (13/32) of infants had more than 3 hospital admissions after discharge.

Conclusions

In our cohort about 80% of infants with severe BPD and tracheostomy survived to discharge with need for prolonged home ventilation in more than half of the survivors. Later postmenstrual age at admission to level 4 NICU was associated with a worse outcome. Our retrospective data may be inadequate to determine the causal relationship between postmenstrual age at admission and outcome. These patients continue to have high morbidity and recurrent hospitalizations.

Short- and long-term outcomes of very low birth weight infants in Korea: Korean Neonatal Network update in 2019

Korea currently has the world's lowest birth rate but a rapidly inreasing number of preterm infants. The Korean Neonatal Network (KNN), launched by the Korean Society of Neonatology under the support of Korea Centers for Disease Control, has collected population-based data for very low birth weight infants (VLBWIs) born in Korea since 2013. In terms of the short-term outcomes of VLBWIs born from 2013 to 2016 registered in the KNN, the survival rate of all VLBWIs was 86%. Respiratory distress syndrome and bronchopulmonary dysplasia were observed in 78% and 30% of all VLBWIs, respectively. Necrotizing enterocolitis occurred in 7%, while 8% of the VLBWIs needed therapy for retinopathy of prematurity in the neonatal intensive care unit (NICU). Sepsis occurred in 21% during their NICU stay. Intraventricular hemorrhage (grade ≥III) was diagnosed in 10%. In terms of the long-term outcomes for VLBWIs born from 2013 to 2014 registered in the KNN, the post-discharge mortality rate was approximately 1.2%-1.5%, mainly owing to their underlying illness. Nearly half of the VLBWIs were readmitted to the hospital at least once in their first 1-2 years of life, mostly as a result of respiratory diseases. The overall prevalence of cerebral palsy was 6.2%-6.6% in Korea. Bilateral blindness was reported in 0.2%-0.3% of VLBWIs, while bilateral hearing loss was found in 0.8%-1.9%. Since its establishment, the KNN has published annual reports and papers that facilitate the improvement of VLBWI outcome and the formulation of essential healthcare policies in Korea.

The association between the microbes in the tracheobronchial aspirate fluid and bronchopulmonary dysplasia in preterm infants

OBJECTIVE

The study aimed to evaluate the association between microbes in the lower respiratory tract (LRT) and the srisk for severe bronchopulmonary dysplasia (sBPD) in premature infants.

METHODS

We conducted a retrospective, single-center study of preterm infants who were admitted to the neonatal intensive care unit (NICU) of Southern Medical University Affiliated Maternal & Child Health Hospital of Foshan, China, between January 2015 and December 2017. The microbes in the LRT were screened by using tracheobronchial aspirate fluid (TAF) culture.

RESULTS

One hundred and fifty-five infants were included in the analysis. Among 155 infants, 41 were diagnosed with sBPD, and 114 were diagnosed without sBPD. There were significant differences between infants with and without sBPD in regard to birth weight (BW), gestational age (GA), the duration of endotracheal ventilation and supplemental oxygen. The incidence of retinopathy (ROP) and sepsis was higher in the sBPD infants than in the infants without sBPD. There was a difference in the detection rate of Gram-negative bacteria (GNB) between the two groups. Stenotrophomonas maltophilia and Klebsiella pneumoniae were mainly detected in TAF.

CONCLUSIONS

The LRT microbes were different between infants with and without sBPD, and GNB is more frequently detected in sBPD infants.

Non-Invasive Ventilation in Neonatology

BACKGROUND

Invasive mechanical ventilation (IMV) has been replaced by early continuous positive airway pressure (CPAP) in the treatment of respiratory distress syndrome (RDS) in preterm infants aiming to reduce the rate of bronchopulmonary dysplasia (BPD). Subsequently, modern non-invasive ventilation strategies (NIV) were introduced into clinical practice with limited evidence of effects on pulmonary and neurodevelopmental outcomes.

METHODS

We performed a selective literature search in PubMed including randomized controlled trials (RCT) (n ≥ 200) and meta-analyses published in the field of NIV in neonatology and follow-up studies focusing on long term pulmonary and neurodevelopmental outcomes.

RESULTS

Individual studies do not show a significant risk reduction for the combined endpoint death or BPD in preterm infants caused by early CPAP in RDS when compared to primary intubation. One meta-analysis comparing four studies found CPAP significantly reduces the risk of BPD or death (relative risk: 0.91; 95% confidence interval [0.84;0.99]). Nasal intermittent positive pressure ventilation (NIPPV) as a primary ventilation strategy reduces the rate of intubations in infants with RDS (RR: 0.78 [0.64;0.94]) when compared to CPAP but does not affect the rate of BPD (RR: 0.78 [0.58;1.06]).

CONCLUSION

Early CPAP reduces the need for IMV and the risk of BPD or death in preterm infants with RDS. NIPPV may offer advantages over CPAP regarding intubation rates. Networking-based follow-up programs are required to assess the effect of NIV on long term pulmonary and neurodevelopmental outcomes.

Impact of early caffeine therapy in preterm newborns on infant lung function

OBJECTIVE

To know the effect of caffeine therapy on infant lung function in preterm infants with a gestational age less than 31 weeks.

MATERIAL AND METHODS

Forced vital capacity (FVC), forced expiratory volume at 0.5 seconds (FEV_0.5 ), and forced expiratory flows were measured by raised volume rapid thoracoabdominal compression technique; functional residual capacity was measured by plethysmography (FRC_pleth ). Compliance of the respiratory system was measured by a single interruption technique (Crs). The Student t test was used to compare lung function measurements between the two groups: treated versus nontreated with caffeine. A multivariate analysis was carried out considering each and every lung function parameter (z-score) as the dependent variable; and gender, gestational age, birth weight (z-score), corrected age, invasive mechanical ventilation (yes/no), and bronchopulmonary dysplasia (BPD) diagnosis (yes/no) as independent ones. Additionally, stratified analyses by BPD diagnosis were performed.

RESULTS

The multivariate analysis showed significant higher z-scores of FVC and FEV_0.5 in preterm infants treated with caffeine (P = .004 and P = .024, respectively). This result only being significant in the group of non-BPD infants (P = .021 and P = .042), after stratifying by BPD diagnosis. Differences were not found in z-scores of FEV0.5/FVC, FEF75, FEF25-75, FRCpleth, nor Crs.

CONCLUSION

Lung function (FVC and FEV_0.5 ) is improved in infants born under 31 weeks of gestation when treated with caffeine. This improvement is driven by the group of infants who did not suffer from BPD. Overall, our results show that there is an early beneficial effect of caffeine treatment in infant lung function.

Prematurity as an Independent Risk Factor for the Development of Pulmonary Disease

OBJECTIVES

To determine if premature infants without bronchopulmonary dysplasia (BPD) are at similar risk for developing pulmonary morbidity as compared with those with BPD and if there are differences in management of care.

STUDY DESIGN

We retrospectively abstracted information from our electronic medical record from January 1, 2006, to December 31, 2015, for primary care patients born at <30 weeks of gestation (n = 811). Multivariate models determined the impact of BPD on a diagnosis of respiratory disease, respiratory medications, subspecialty visits, and emergency department use or hospitalizations after adjusting for gestational age, sex, insurance type, and race.

RESULTS

Infants with BPD were more likely to be diagnosed with asthma than those without BPD (75% vs 60%; OR, 1.8; 95% CI, 1.27-2.54), but not all respiratory conditions (OR, 1.56; 95% CI, 0.7-3.51), and were more likely to be referred to a pulmonologist (relative risk, 5.98; 95% CI, 4.1-8.74). Infants with BPD were more likely to be hospitalized for respiratory conditions than those without BPD (50% vs 30%; relative risk, 2.44; 95% CI, 1.73-3.45).

CONCLUSIONS

Although infants with BPD were more likely to have a diagnosis of asthma and be readmitted for respiratory conditions, 60% of infants without BPD were also diagnosed with asthma and 30% were readmitted. There were significant differences in the management of patients, including time to pulmonary referral and prescription rates for inhaled corticosteroids. Practitioners should consider all patients born prematurely at high risk for respiratory morbidity.

Interleukin-1 Receptor Antagonist Protects Newborn Mice Against Pulmonary Hypertension

Pulmonary hypertension secondary to bronchopulmonary dysplasia (BPD-PH) represents a major complication of BPD in extremely preterm infants for which there are currently no safe and effective interventions. The abundance of interleukin-1 (IL-1) is strongly correlated with the severity and long-term outcome of BPD infants and we have previously shown that IL-1 receptor antagonist (IL-1Ra) protects against murine BPD; therefore, we hypothesized that IL-1Ra may also be effective against BPD-PH. We employed daily injections of IL-1Ra in a murine model in which BPD/BPD-PH was induced by antenatal LPS and postnatal hyperoxia of 65% O₂. Pups reared in hyperoxia for 28 days exhibited a BPD-PH-like disease accompanied by significant changes in pulmonary vascular morphology: micro-CT revealed an 84% reduction in small vessels (4-5 μm diameter) compared to room air controls; this change was prevented by IL-1Ra. Pulmonary vascular resistance, assessed at day 28 of life by echocardiography using the inversely-related surrogate marker time-to-peak-velocity/right ventricular ejection time (TPV/RVET), increased in hyperoxic mice (0.27 compared to 0.32 in air controls), and fell significantly with daily IL-1Ra treatment (0.31). Importantly, in vivo cine-angiography revealed that this protection afforded by IL-1Ra treatment for 28 days is maintained at day 60 of life. Despite an increased abundance of mediators of pulmonary angiogenesis in day 5 lung lysates, namely vascular endothelial growth factor (VEGF) and endothelin-1 (ET-1), no difference was detected in ex vivo pulmonary vascular reactivity between air and hyperoxia mice as measured in precision cut lung slices, or by immunohistochemistry in alpha-smooth muscle actin (α-SMA) and endothelin receptor type-A (ET_A) at day 28. Further, on day 28 of life we observed cardiac fibrosis by Sirius Red staining, which was accompanied by an increase in mRNA expression of galectin-3 and CCL2 (chemokine (C-C motif) ligand 2) in whole hearts of hyperoxic pups, which improved with IL-1Ra. In summary, our findings suggest that daily administration of the anti-inflammatory IL-1Ra prevents the increase in pulmonary vascular resistance and the pulmonary dysangiogenesis of murine BPD-PH, thus pointing to IL-1Ra as a promising candidate for the treatment of both BPD and BPD-PH.

Elafin Treatment Rescues EGFR-Klf4 Signaling and Lung Cell Survival in Ventilated Newborn Mice

Mechanical ventilation with O₂-rich gas (MV-O₂) inhibits alveologenesis and lung growth. We previously showed that MV-O₂ increased elastase activity and apoptosis in lungs of newborn mice, whereas elastase inhibition by elafin suppressed apoptosis and enabled lung growth. Pilot studies suggested that MV-O₂ reduces lung expression of prosurvival factors phosphorylated epidermal growth factor receptor (pEGFR) and Krüppel-like factor 4 (Klf4). Here, we sought to determine whether apoptosis and lung growth arrest evoked by MV-O₂ reflect disrupted pEGFR-Klf4 signaling, which elafin treatment preserves, and to assess potential biomarkers of bronchopulmonary dysplasia (BPD). Five-day-old mice underwent MV with air or 40% O₂ for 8-24 hours with or without elafin treatment. Unventilated pups served as controls. Immunoblots were used to assess lung pEGFR and Klf4 proteins. Cultured MLE-12 cells were exposed to AG1478 (EGFR inhibitor), Klf4 siRNA, or vehicle to assess effects on proliferation, apoptosis, and EGFR regulation of Klf4. Plasma elastase and elafin levels were measured in extremely premature infants. In newborn mice, MV with air or 40% O₂ inhibited EGFR phosphorylation and suppressed Klf4 protein content in lungs (vs. unventilated controls), yielding increased apoptosis. Elafin treatment inhibited elastase, preserved lung pEGFR and Klf4, and attenuated the apoptosis observed in lungs of vehicle-treated mice. In MLE-12 studies, pharmacological inhibition of EGFR and siRNA suppression of Klf4 increased apoptosis and reduced proliferation, and EGFR inhibition decreased Klf4. Plasma elastase levels were more than twofold higher, without a compensating increase of plasma elafin, in infants with BPD, compared to infants without BPD. These findings indicate that pEGFR-Klf4 is a novel prosurvival signaling pathway in lung epithelium that MV disrupts. Elafin preserves pEGFR-Klf4 signaling and inhibits apoptosis, thereby enabling lung growth during MV. Together, our animal and human data raise the question: would elastase inhibition prevent BPD in high-risk infants exposed to MV-O₂?

Right ventricular myocardial performance index in pediatric patients with bronchopulmonary dysplasia-related pulmonary hypertension

INTRODUCTION

This study aims to assess the utility of right ventricular myocardial performance index (RVMPI) as a potential echocardiographic tool to evaluate and serially follow patients with bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH).

METHODS

We performed a retrospective chart review of all hemodynamic cardiac catheterizations performed January 2011 to December 2016 in patients born premature and with diagnosed BPD up to 4 years of age-excluding patients with significant congenital heart defects. Echocardiograms performed within 24 hours of the cardiac catheterization were reviewed, and a blinded RVMPI was calculated. The primary endpoint was correlation of invasive catheterization hemodynamics to noninvasive echocardiographic RVMPI measurement.

RESULTS

A total of 49 individual patients met complete study criteria, and 10 of those patients underwent repeat cardiac catheterization. Median age at the time of assessment was 8 months (25%-75%, 4-18 months), and the cohort had a calculated RVMPI mean of 0.39 (±0.19), with 73% (43/59) having a RVMPI >0.28. A statistically significant correlation was found between the RVMPI and the baseline hemodynamics during catheterization with regard to the initial mean pulmonary arterial pressure (r = 0.58; P < 0.01) as well as the calculated pulmonary vascular resistance (r = 0.34; P = 0.01).

CONCLUSIONS

This study demonstrates the utility of RVMPI for evaluation of PH in patients with prematurity and BPD. An increased RVMPI by noninvasive echocardiography was found to correlate with increased mean pulmonary arterial pressure and pulmonary vascular resistance measured during invasive cardiac catheterization. Large-scale validation of this study is being planned.

Intercenter variability and factors associated with survival without bronchopulmonary dysplasia in extremely preterm newborns

Background: Variability in clinical practice may influence morbidity and mortality in extremely preterm infants. We aimed to know if there are differences in survival and survival without bronchopulmonary dysplasia (BPD) in extremely preterm infants in Spanish tertiary hospitals and the potential associated factors.Methods: Fifteen hospitals from the SEN1500 network were studied. The overall rate of survival without BPD was 61.4%. Hospitals with extreme results were grouped for comparison (Group 1; N = 2480 versus Group 2; N = 2367). A bivariate analysis of the characteristics of patients and perinatal interventions was carried out and the probability of survival without BPD was studied by Cox regression.Results: Survival (79.0 versus 72.9%; p < .001) and survival without BPD (72.5 versus 49.1%; p < .001) were greater in Group 1. Higher gestational age, birth weight, and female sex were associated with better outcomes. Oxygen administration (aHR: 0.868 [95%CI: 0.782, 0.964]; p=.008) and intubation (aHR: 0.767 [95%CI: 0.701, 0.839]; p < .001) in delivery room were associated with lower survival without BPD. The occurrence of patent ductus arteriosus (PDA), sepsis and/or necrotizing enterocolitis (NEC) was independently associated with worse outcomes. After adjusting for confounders, the probabilities of survival without BPD were significantly higher among patients in Group 1: aHR: 1.557 [95% CI: 1.458, 1.662]; p < .001.Conclusions: Among the studied hospitals, we found great variability in clinical practice and in the rates of survival and survival without BPD. A more conservative approach to the use of oxygen and respiratory support seems to be related to an increase in survival without BPD. Complications such as PDA, sepsis, and/or NEC decrease survival without BPD. Other variables not included in the present study could be relevant and deserve further study.

Preventing bronchopulmonary dysplasia: new tools for an old challenge

Bronchopulmonary dysplasia (BPD) is the most prevalent chronic lung disease in infants and presents as a consequence of preterm birth. Due to the lack of effective preventive and treatment strategies, BPD currently represents a major therapeutic challenge that requires continued research efforts at the basic, translational, and clinical levels. However, not all very low birth weight premature babies develop BPD, which suggests that in addition to known gestational age and intrauterine and extrauterine risk factors, other unknown factors must be involved in this disease's development. One of the main goals in BPD research is the early prediction of very low birth weight infants who are at risk of developing BPD in order to initiate the adequate preventive strategies. Other benefits of determining the risk of BPD include providing prognostic information and stratifying infants for clinical trial enrollment. In this article, we describe new opportunities to address BPD's complex pathophysiology by identifying prognostic biomarkers and develop novel, complex in vitro human lung models in order to develop effective therapies. These therapies for protecting the immature lung from injury can be developed by taking advantage of recent scientific progress in -omics, 3D organoids, and regenerative medicine.

Neonatal Outcomes of Very Low Birth Weight Infants in Korean Neonatal Network from 2013 to 2016

BACKGROUND

This study was performed to determine survival and morbidity rates in very low birth weight infants (VLBWIs) in the Korean Neonatal Network (KNN), and to compare neonatal outcomes with those in other countries.

METHODS

Data were collected for 8,269 VLBWIs with gestational age (GA) ≥ 22 weeks who were born between January 1, 2013 and December 31, 2016, and admitted to the neonatal intensive care units of the KNN.

RESULTS

The survival rate of all VLBWIs and of infants with GA 22-23, 24-25, 26-27, 28-29, 30-32, and > 32 weeks were 86% (total), 33%, 65%, 84%, 94%, 97%, and 98%, respectively. The bronchopulmonary dysplasia (BPD) rates of all VLBWIs and of infants with GA 22-23, 24-25, 26-27, 28-29, 30-32, and > 32 weeks were 30% (total), 88%, 64%, 47%, 26%, 14%, and 5%, respectively. The intraventricular hemorrhage rates (≥ grade III) of all VLBWIs and of infants with GA 22-23, 24-25, 26-27, 28-29, 30-32, and > 32 weeks were 10% (total), 45%, 27%, 12%, 5%, 2%, and 1%, respectively. In an international comparison, the survival rate of VLBWIs with GA 24-27 weeks in KNN was lower, and the BPD rate of VLBWIs in the KNN was higher than that of the neonatal networks of other countries.

CONCLUSION

Despite overall improvements in neonatal outcomes, the survival and morbidity rates of more immature infants with GA 22-27 weeks need further improvement. Therefore, it would be necessary to develop more optimal treatment strategies and perform more active quality improvement to further improve neonatal outcomes of VLBWIs in Korea.

Prospective study of pulmonary hypertension in preterm infants with bronchopulmonary dysplasia

OBJECTIVE

To evaluate the prevalence, risk factors, and optimal timing of echocardiogram for pulmonary hypertension (PH) in infants with bronchopulmonary dysplasia (BPD).

DESIGN

In this prospective study, infants with gestational age (GA) <30 weeks admitted to a tertiary NICU between July 2015 and June 2017 who required positive pressure ventilation or oxygen therapy at ≥28 days of life were evaluated with serial echocardiograms at study enrollment (4-6 weeks of age), 32 weeks (only for ≤25 weeks), 36, and 40 weeks post-menstrual age (PMA) for PH.

RESULTS

Of 126 infants (mean birth weight 858 ± 221 g; mean GA 26.1 ± 1.6 wks), 48 (38%) developed PH at any time during their hospital stay. The first study echocardiogram was performed at a median age of 31 weeks PMA. The prevalence of PH was 36/126 (28.5%) at enrollment, at 6/30 (20%) at 32 weeks, 24/111 (21.6%) at 36 weeks, and 10/59 (17%) at 40 weeks. No new cases of PH were identified at 40 weeks. At 36 weeks, none of the infants with mild BPD had PH, whereas 20% of moderate and 32% of severe BPD infants had PH. After controlling for confounding variables severe BPD (OR 3.31, 95%CI 1.12, 9.74), and ventilator associated pneumonia (VAP) (OR 17.9, 95%CI 3.9, 82.11) remained independent risk factors for BPD-associated PH.

CONCLUSION

Echocardiographic screening for PH can be safely restricted to infants with moderate or severe BPD at 36 weeks PMA. We identified VAP as an independent risk factor for PH.

An update on the post-NICU discharge management of bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease which develops as a result of neonatal/perinatal lung injury. It is the commonest cause of chronic lung disease in infancy and the most frequent morbidity associated with prematurity. The incidence of BPD has continued to rise despite many advances in neonatal care and this increase has been attributed to the increased survival of younger and more premature babies. There have been many advances in the care of patients with early and evolving BPD, yet there is a paucity of data regarding outpatient management of patients with established BPD. There are limited adequately-powered high-quality studies/randomized controlled trials which assess commonly used therapies such as supplemental oxygen, bronchodilators, steroids and diuretics in patients with BPD, beyond short-term effects. Further research is needed to improve our understanding of the role of currently used treatments on the long-term outcomes of patients with established BPD, post-discharge from the neonatal intensive care unit.

Treatment of Hyperoxia-Induced Lung Injury with Lung Mesenchymal Stem Cells in Mice

Objective

Bronchopulmonary dysplasia (BPD) is a common chronic lung disease in preterm neonates and has no effective treatment. This study aimed to investigate the therapeutic effects of neonatal mouse lung resident mesenchymal stem cells (L-MSCs) on the hyperoxia-induced lung injury.

Methods

L-MSCs were separated and identified according to the MSC criterions. Hyperoxia-Induced Lung Injury (HILI) of neonatal KM mice was induced with hyperoxia (FiO₂ = 60%) and investigated with pathological methods. Neonatal KM mice were divided into 3 groups (hyperoxia + L-MSC group, hyperoxia + PBS group, and air control group). Mice in the hyperoxia + L-MSC group were treated with L-MSCs at 3, 7, and 14 days after birth. After hyperoxia exposure for 21 days, the lung pathology, Radial Alveolar Count (RAC), CD31 expression, and vascular endothelial growth factor (VEGF) expression were investigated.

Results

After hyperoxia exposure, the body weight, RAC, CD31 expression, and VEGF expression in the hyperoxia + L-MSC group were significantly better than those in the hyperoxia + PBS group but inferior to those in the air control group significantly. These indicate L-MSCs are partially protective on the lung injury of mice with hyperoxia-induced BPD.

Conclusion

L-MSCs are helpful for the prevention and treatment of BPD, and endogenous L-MSCs may play a role in the postinjury repair of the lung.

Leflunomide attenuates oxidative stress in fetal human lung endothelial cells via superoxide dismutase 2 and catalase

Hyperoxia-induced oxidative stress contributes to the pathogenesis of bronchopulmonary dysplasia (BPD), the most common respiratory morbidity of preterm infants. Importantly, the disease lack specific therapies and is associated with long-term cardio-pulmonary and neurodevelopmental morbidities, signifying the need to discover novel therapies and decrease the disease burden. We and others have demonstrated that leflunomide, a food and drug administration approved drug to treat humans with rheumatoid arthritis, increases the expression of the anti-oxidant enzymes, NAD(P)H quinone dehydrogenase 1 (NQO1), catalase, and superoxide dismutase (SOD). However, whether this drug can decrease oxidative stress in fetal human pulmonary arterial endothelial cells (HPAECs) is unknown. Therefore, we tested the hypothesis that leflunomide will decrease hyperoxia-induced oxidative stress by upregulating these anti-oxidant enzymes in HPAECs. Leflunomide decreased hydrogen peroxide (H₂O₂) levels and increased the mRNA and protein levels of catalase, NQO1, and SOD2 in HPAECs at basal conditions. Further, leflunomide-treated cells continued to have decreased H₂O₂ and increased SOD2 levels upon hyperoxia exposure. Leflunomide did not affect the expression of other anti-oxidant enzymes, including hemoxygenase-1 and SOD1. AhR-knockdown experiments suggested that leflunomide regulated NQO1 levels via AhR-dependent mechanisms and H₂O₂, catalase, and SOD2 levels via AhR-independent mechanisms. Collectively, the results support the hypothesis that leflunomide decreases oxidative stress in HPAECs via SOD2-and catalase-dependent, but AhR- and NQO1-independent mechanisms. Our findings indicate that leflunomide is a potential drug for the management of BPD in preterm infants.

Riociguat prevents hyperoxia-induced lung injury and pulmonary hypertension in neonatal rats without effects on long bone growth

Bronchopulmonary dysplasia (BPD) remains the most common and serious chronic lung disease of premature infants. Severe BPD complicated with pulmonary hypertension (PH) increases the mortality of these infants. Riociguat is an allosteric soluble guanylate cyclase stimulator and is approved by the FDA for treating PH in adults. However, it has not been approved for use in neonates due to concern for adverse effects on long bone growth. To address this concern we investigated if administration of riociguat is beneficial in preventing hyperoxia-induced lung injury and PH without side effects on long bone growth in newborn rats. Newborn rats were randomized to normoxia (21% O₂) or hyperoxia (85% O₂) exposure groups within 24 hours of birth, and received riociguat or placebo by once daily intraperitoneal injections during continuous normoxia or hyperoxia exposure for 9 days. In the hyperoxia control group, radial alveolar count, mean linear intercept and vascular density were significantly decreased, the pathological hallmarks of BPD, and these were accompanied by an increased inflammatory response. There was also significantly elevated vascular muscularization of peripheral pulmonary vessels, right ventricular systolic pressure and right ventricular hypertrophy indicating PH. However, administration of riociguat significantly decreased lung inflammation, improved alveolar and vascular development, and decreased PH during hyperoxia by inducing cGMP production. Additionally, riociguat did not affect long bone growth or structure. These data indicate that riociguat is beneficial in preventing hyperoxia-induced lung injury and PH without affecting long bone growth and structure and hence, suggests riociguat may be a potential novel agent for preventing BPD and PH in neonates.

Polysomnography for the management of oxygen supplementation therapy in infants with chronic lung disease of prematurity

Aim: Some infants with bronchopulmonary dysplasia (BPD) may require oxygen supplementation at home but a role for overnight polysomnography (PSG) in the management of home oxygen therapy has been rarely described. Methods: Forty-one infants with BPD born at less than 30 weeks gestational age were discharged with continuous home oxygen supplementation therapy between 2010 and 2013. PSG data were recorded on oxygen supplementation versus room air at median corrected age of 2 months (range 1-5 months) (first PSG after discharge to home). Those infants who continued oxygen supplementation therapy at home had at least one more PSG before oxygen therapy was discontinued (last PSG). We also collected PSG data in 10 healthy term infants (median age 3.5 months; range 2-4 months). Results: In infants with BPD in room air, increased numbers of central apneas, hypopneas, and SaO2 desaturations were the predominant PSG features with a median apnea-hypopnea index (AHI) of 16.8 events per hour (range 0-155). On oxygen supplementation therapy, median AHI dramatically improved (2.2, range 0-22; p < .001) and was not different from control infants (2.0, range 0-3.9; p = .31). AHI on room air at the last PSG when home oxygen was ceased was 4.1 per hour (range 0-13.8) slightly higher than in healthy infants. Conclusion: Central sleep disordered breathing in infants with BPD dramatically normalizes with low flow nasal cannula home oxygen therapy and improves with age. Mild central sleep disordered breathing remains detectable, although much improved, when compared with healthy infants at the time when the decision to cease home oxygen therapy was made by the physician.

Bronchopulmonary dysplasia: clinical aspects and preventive and therapeutic strategies

BACKGROUND

Bronchopulmonary dysplasia (BPD) is the result of a complex process in which several prenatal and/or postnatal factors interfere with lower respiratory tract development, leading to a severe, lifelong disease. In this review, what is presently known regarding BPD pathogenesis, its impact on long-term pulmonary morbidity and mortality and the available preventive and therapeutic strategies are discussed.

MAIN BODY

Bronchopulmonary dysplasia is associated with persistent lung impairment later in life, significantly impacting health services because subjects with BPD have, in most cases, frequent respiratory diseases and reductions in quality of life and life expectancy. Prematurity per se is associated with an increased risk of long-term lung problems. However, in children with BPD, impairment of pulmonary structures and function is even greater, although the characterization of long-term outcomes of BPD is difficult because the adults presently available to study have received outdated treatment. Prenatal and postnatal preventive measures are extremely important to reduce the risk of BPD.

CONCLUSION

Bronchopulmonary dysplasia is a respiratory condition that presently occurs in preterm neonates and can lead to chronic respiratory problems. Although knowledge about BPD pathogenesis has significantly increased in recent years, not all of the mechanisms that lead to lung damage are completely understood, which explains why therapeutic approaches that are theoretically effective have been only partly satisfactory or useless and, in some cases, potentially negative. However, prevention of prematurity, systematic use of nonaggressive ventilator measures, avoiding supraphysiologic oxygen exposure and administration of surfactant, caffeine and vitamin A can significantly reduce the risk of BPD development. Cell therapy is the most fascinating new measure to address the lung damage due to BPD. It is desirable that ongoing studies yield positive results to definitively solve a major clinical, social and economic problem.

Long-term pulmonary and cardiovascular morbidities of neonatal hyperoxia exposure in mice

Pulmonary hypertension (PH) frequently occurs in infants with bronchopulmonary dysplasia (BPD), causing increased mortality and right ventricular (RV) dysfunction that persists into adulthood. A first step in developing better therapeutic options is identifying and characterizing an appropriate animal model. Previously, we characterized the short-term morbidities of a model in which C57BL/6J wild-type (WT) mice were exposed to 70% O2 (hyperoxia) during the neonatal period. Here, we aimed to determine the long-term morbidities using lung morphometry, echocardiography (Echo), and cardiac magnetic resonance imaging (cMRI). The major highlight of this study is the use of the state-of-the art imaging technique, cMRI, in mice to characterize the long-term cardiac effects of neonatal hyperoxia exposure. To this end, WT mice were exposed to 21% O2 (normoxia) or hyperoxia for two weeks of life, followed by recovery in normoxia for six weeks. Alveolarization, pulmonary vascularization, pulmonary hypertension, and RV function were quantified at eight weeks. We found that hyperoxia exposure resulted in persistent alveolar and pulmonary vascular simplification. Furthermore, the Echo and cMRI studies demonstrated that hyperoxia-exposed mice had signs of PH and RV dysfunction as indicated by increased RV pressure, mass, and end-systolic and -diastolic volumes, and decreased RV stroke volume and ejection fractions. Taken together, our results demonstrate that neonatal hyperoxia exposure in mice cause cardiopulmonary morbidities that persists into adulthood and provides evidence for the use of this model to develop novel therapies for BPD infants with PH.

Sleep disordered breathing in bronchopulmonary dysplasia

BACKGROUND

There are limited data on the effect of bronchopulmonary dysplasia (BPD) on sleep disordered breathing (SDB). We hypothesized that both the severity of prematurity and BPD would increase the likelihood of SDB in early childhood. Our secondary aim was to evaluate the association of demographic factors on the development of SDB.

METHODS

This is a retrospective study of patient factors and overnight polysomnogram (PSG) data of children enrolled in our BPD registry between 2008 and 2015. Association between PSG results and studied variables was assessed using multiple linear regression analysis.

RESULTS

One-hundred-forty children underwent at least one sleep study on room air. The mean respiratory disturbance index (RDI) was elevated at 9.9 events/hr (SD: 10.1). The mean obstructive apnea-hypopnea index (OAHI) was 6.5 (9.1) events/hr and the mean central event rate of 3.0 (3.7) events/hr. RDI had decreased by 22% or 1.5 events/hour (95%CI: 0.6, 1.9) with each year of age (P = 0.005). Subjects with more severe respiratory disease had 38% more central events (P = 0.02). Infants exposed to secondhand smoke had 2.4% lower (P = 0.04) oxygen saturation nadirs and a pattern for more desaturation events. Non-white subjects were found to have 33% higher OAHI (P = 0.05), while white subjects had a 61% higher rate of central events (P < 0.001).

CONCLUSIONS

RDI was elevated in a selected BPD population compared to norms for non-preterm children. BPD severity, smoke exposure, and race may augment the severity of SDB. RDI improved with age but was still elevated by age 4, suggesting that this population is at risk for the sequelae of SDB.

Hypothermia at neonatal intensive care unit admission was not associated with respiratory disease or death in very preterm infants

AIM

This study investigated the association between hypothermia and respiratory distress syndrome (RDS), bronchopulmonary dysplasia (BPD) or death in very preterm infants admitted to a Danish neonatal intensive care unit (NICU).

METHODS

We studied 675 infants born at Aalborg University Hospital before 32 weeks and admitted to the NICU from April 1997 to December 2011. Hypothermia was defined as a core temperature of <36.5°C on admission. The primary outcome was severe RDS or death within the first three days of life, and the secondary outcome was BPD or death before 36 postmenstrual weeks. The multivariable logistic regression was adjusted for early-onset infection, gestational age, Apgar score, sex, treatment year and birth weight.

RESULTS

Infants with hypothermia had a twofold increase (OR) in the odds for RDS or death (2.03), but the adjusted OR was not statistically significant (1.36). They also demonstrated a twofold increase (OR) in the odds for BPD or death (2.28), but again the adjusted OR was not statistically significant (1.03).

CONCLUSION

After adjusting for confounders, we found that the association between hypothermia on admission to the NICU and RDS or death, or BPD or death was statistically insignificant.

Recombinant CCN1 prevents hyperoxia-induced lung injury in neonatal rats

BackgroundCystein-rich protein 61 (Cyr61/CCN1) is a member of the CCN family of matricellular proteins that has an important role in tissue development and remodeling. However, the role of CCN1 in the pathogenesis of bronchopulmonary dysplasia (BPD) is unknown. Accordingly, we have investigated the effects of CCN1 on a hyperoxia-induced lung injury model in neonatal rats.MethodsIn experiment 1, newborn rats were randomized to room air (RA) or 85% oxygen (O₂) for 7 or 14 days, and we assessed the expression of CCN1. In experiment 2, rat pups were exposed to RA or O₂ and received placebo or recombinant CCN1 by daily intraperitoneal injection for 10 days. The effects of CCN1 on hyperoxia-induced lung inflammation, alveolar and vascular development, vascular remodeling, and right ventricular hypertrophy (RVH) were observed.ResultsIn experiment 1, hyperoxia downregulated CCN1 expression. In experiment 2, treatment with recombinant CCN1 significantly decreased macrophage and neutrophil infiltration, reduced inflammasome activation, increased alveolar and vascular development, and reduced vascular remodeling and RVH in the hyperoxic animals.ConclusionThese results demonstrate that hyperoxia-induced lung injury is associated with downregulated basal CCN1 expression, and treatment with CCN1 can largely reverse hyperoxic injury.

Pulmonary hypertension associated with bronchopulmonary dysplasia in preterm infants

Bronchopulmonary dysplasia (BPD) and BPD-associated pulmonary hypertension (BPD-PH) are chronic inflammatory cardiopulmonary diseases with devastating short- and long-term consequences for infants born prematurely. The immature lungs of preterm infants are ill-prepared to achieve sufficient gas exchange, thus usually necessitating immediate commencement of respiratory support and oxygen supplementation. These therapies are life-saving, but they exacerbate the tissue damage that is inevitably inflicted on a preterm lung forced to perform gas exchange. Together, air-breathing and necessary therapeutic interventions disrupt normal lung development by aggravating pulmonary inflammation and vascular remodelling, thus frequently precipitating BPD and PH via an incompletely understood pathogenic cascade. BPD and BPD-PH share common risk factors, such as low gestational age at birth, fetal growth restriction and perinatal maternal inflammation; however, these risk factors are not unique to BPD or BPD-PH. Occurring in 17-24% of BPD patients, BPD-PH substantially worsens the morbidity and mortality attributable to BPD alone, thus darkening their outlook; for example, BPD-PH entails a mortality of up to 50%. The absence of a safe and effective therapy for BPD and BPD-PH renders neonatal cardiopulmonary disease an area of urgent unmet medical need. Besides the need to develop new therapeutic strategies, a major challenge for clinicians is the lack of a reliable method for identifying babies at risk of developing BPD and BPD-PH. In addition to discussing current knowledge on pathophysiology, diagnosis and treatment of BPD-PH, we highlight emerging biomarkers that could enable clinicians to predict disease-risk and also optimise treatment of BPD-PH in our tiniest patients.

Stem cells and Bronchopulmonary Dysplasia - The five questions: Which cells, when, in which dose, to which patients via which route?

Preterm birth is the leading cause of death in newborns and children. Despite advances in perinatology, immature infants continue to face serious risks such chronic respiratory impairment from bronchopulmonary dysplasia (BPD). Current treatment options are insufficient and novel approaches are desperately needed. In recent years stem cells have emerged as potential candidates to treat BPD with mesenchymal stem/stromal cells (MSCs) being particularly promising. MSCs originate from several stem cell niches including bone marrow, skin, or adipose, umbilical cord, and placental tissues. Although the first MSCs clinical trials in BPD are ongoing, multiple questions remain open. In this review, we discuss the question of the optimal cell source (live cells or cell products), route and timing of the transplantation. Furthermore, we discuss MSCs possible capacities including migration, homing, pro-angiogenesis, anti-inflammatory, and tissue-regenerative potential as well.

Intratracheal Administration of Budesonide-Surfactant in Prevention of Bronchopulmonary Dysplasia in Very Low Birth Weight Infants: A Systematic Review and Meta-Analysis

Despite the near universal adaptation of gentle mechanical ventilation, surfactant use and non-invasive respiratory support, bronchopulmonary dysplasia (BPD) remains one of the most common respiratory morbidities in very low birth weight (VLBW) infants. Thus, the objective of this review was to evaluate the efficacy of intra-tracheal administration of budesonide-surfactant mixture in preventing bronchopulmonary dysplasia (BPD) in very low birth weight (VLBW) infants. MEDLINE, EMBASE, and PubMed were searched for randomized clinical trials in which intra-tracheal administration of budesonide-surfactant was used to prevent BPD in infants. The primary outcomes were BPD and composite outcome of death or BPD. Meta-analysis of the two clinical trials revealed that infants who received intra-tracheal instillation of budesonide-surfactant mixture demonstrated 43% reduction in the risk of BPD (RR: 0.57; 95%CI: 0.43-0.76, NNT = 5). Although mortality was not different between the groups (OR: 0.61; 95%CI: 0.34-1.04), a 40% reduction was observed in the composite outcome of death or BPD in the budesonide-surfactant group (RR: 0.60; 95%CI: 0.49-0.74, NNT = 3). Thus, this review concludes that intra-tracheal administration of budesonide-surfactant combination was associated with decreased incidence of BPD alone or composite outcome of death or BPD in VLBW infants though there is a need for larger trials before it can be recommended as a standard of care.

Influence of own mother's milk on bronchopulmonary dysplasia and costs

BACKGROUND

Human milk from the infant's mother (own mother's milk; OMM) feedings reduces the risk of several morbidities in very low birthweight (VLBW) infants, but limited data exist regarding its impact on bronchopulmonary dysplasia (BPD).

OBJECTIVE

To prospectively study the impact of OMM received in the neonatal intensive care unit (NICU) on the risk of BPD and associated costs.

DESIGN/METHODS

A 5-year prospective cohort study of the impact of OMM dose on growth, morbidity and NICU costs in VLBW infants. OMM dose was the proportion of enteral intake that consisted of OMM from birth to 36 weeks postmenstrual age (PMA) or discharge, whichever occurred first. BPD was defined as the receipt of oxygen and/or positive pressure ventilation at 36 weeks PMA. NICU costs included hospital and physician costs.

RESULTS

The cohort consisted of 254 VLBW infants with mean birth weight 1027±257 g and gestational age 27.8±2.5 weeks. Multivariable logistic regression demonstrated a 9.5% reduction in the odds of BPD for every 10% increase in OMM dose (OR 0.905 (0.824 to 0.995)). After controlling for demographic and clinical factors, BPD was associated with an increase of US$41 929 in NICU costs.

CONCLUSIONS

Increased dose of OMM feedings from birth to 36 weeks PMA was associated with a reduction in the odds of BPD in VLBW infants. Thus, high-dose OMM feeding may be an inexpensive, effective strategy to help reduce the risk of this costly multifactorial morbidity.

Respiratory Support for Very Low Birth Weight Infants Receiving Dexamethasone

OBJECTIVE

To assess how neonatal intensive care units followed the American Academy of Pediatrics guidelines for use of dexamethasone in preterm infants by evaluating respiratory support at the time of dexamethasone administration.

STUDY DESIGN

This is an observational study of infants discharged from one of 290 neonatal intensive care units from 2003 to 2010. The cohort included very low birth weight (<1500 g birth weight) infants born at ≤32 weeks gestational age. The main outcome was respiratory support at time of exposure to dexamethasone. Significant respiratory support was defined as invasive respiratory support (conventional or high-frequency ventilation) with a fraction of inspired oxygen (FiO₂) > 0.3.

RESULTS

Of 81 292 infants; 7093 (9%) received dexamethasone. At the time that dexamethasone was initiated, 4604 (65%) of infants were on significant respiratory support.

CONCLUSIONS

In accordance with the American Academy of Pediatrics recommendations, a majority of infants were on significant respiratory support when receiving dexamethasone, yet a substantial number of infants still received dexamethasone on less than significant respiratory support. Further research on reducing dexamethasone use in premature infants is required to decrease the risk of neurodevelopmental impairment.

Mesenchymal stem/stromal cells-a key mediator for regeneration after perinatal morbidity?

Perinatal complications in both term- and preterm-born infants are a leading cause of neonatal morbidities and mortality. Infants face different challenges in the neonatal intensive care unit with long-term morbidities such as perinatal brain injury and bronchopulmonary dysplasia being particularly devastating. While advances in perinatal medicine have improved our understanding of the pathogenesis, effective therapies to prevent and/or reduce the severity of these disorders are still lacking. The potential of mesenchymal stem/stromal cell (MSC) therapy has emerged during the last two decades, and an increasing effort is conducted to address brain- and lung-related morbidities in neonates at risk. Various studies support the notion that MSCs have protective effects. MSCs are an easy source and may be readily available after birth in a clinical setting. MSCs' mechanisms of action are diverse, including migration and homing, release of growth factors and immunomodulation, and the potential to replace injured cells. Here, we review the pathophysiology of perinatally acquired brain and lung injuries and focus on MSCs as potential candidates for therapeutic strategies summarizing preclinical and clinical evidence.

Of mice and men: correlations between microRNA-17∼92 cluster expression and promoter methylation in severe bronchopulmonary dysplasia

We previously demonstrated that decreased miR-17∼92 cluster expression was 1) present in lungs from human infants who died with bronchopulmonary dysplasia (BPD); 2) inversely correlated with DNA methyltransferase (DNMT) expression and promoter methylation; and 3) correlated with a subsequent diagnosis of BPD at 36 wk gestational age. We tested the hypothesis that plasma miR-17 levels would be lowest in infants who ultimately develop severe BPD. Secondly, we utilized our well-characterized murine model of severe BPD that combines perinatal inflammation with postnatal hyperoxia to test the hypothesis that alterations in lung miR-17∼92, DNMT, and promoter methylation in our model would mirror our findings in tissues from premature human infants. Plasma was obtained during the first 5 days of life from premature infants born ≤32 wk gestation. Lung tissues were harvested from mice exposed to maternal inflammation and neonatal hyperoxia for 14 days after birth. miR-17∼92 cluster expression and DNA methyltransferase expression were measured by qRT-PCR, and promoter methylation was assessed by Methyl-Profiler assay. Plasma miR-17 levels are significantly lower in the first week of life in human infants who develop severe BPD compared with mild or moderate BPD. Data from our severe BPD murine model reveal that lung miR-17∼92 cluster expression is significantly attenuated, and levels inversely correlated with DNMT expression and miR-17∼92 cluster promoter methylation. Collectively, our data support a plausible role for epigenetically altered miR-17∼92 cluster in the pathogenesis of severe BPD.

Aggressive Posterior Retinopathy of Prematurity Is Associated with Multiple Infectious Episodes and Thrombocytopenia

BACKGROUND

The most severe form of rapidly progressing retinopathy of prematurity (ROP) is termed aggressive posterior ROP (APROP). APROP frequently causes severe visual impairment in affected preterm infants despite timely and appropriate laser treatment.

OBJECTIVES

We investigated the postnatal characteristics associated with APROP development in a national Swedish cohort.

METHODS

This retrospective, 1:1 matched case-control study included all infants that developed APROP in zone 1 (n = 9) between 2008 and 2012. Control infants, matched for gestational age and birth weight, developed ROP no worse than stage 2 (n = 9). We retrieved data from medical records on infant birth characteristics, postnatal morbidities, and blood analyses from birth to the first ROP treatment. Infectious episodes included sepsis, C-reactive protein ≥10 mg/l, and other clinical signs of infection that required antibiotic treatment. A platelet count <100 × 109/l was considered to be thrombocytopenia.

RESULTS

All APROP cases postnatally developed at least two infectious episodes, one in the first month and one around the time of ROP diagnosis. All APROP cases exhibited thrombocytopenia in the first month, and 6/9 exhibited thrombocytopenia around the time of ROP diagnosis. Compared to the controls, APROP cases more frequently developed necrotizing enterocolitis (8/9 vs. 1/9; p < 0.01) and sepsis (9/9 vs. 3/9; p < 0.01), and they had significantly lower median platelet counts (90 × 109/l, range 4-459, vs. 158 × 109/l, range 20-500; p < 0.001).

CONCLUSION

Multiple infectious episodes and thrombocytopenia, particularly around the time of ROP diagnosis, were associated with APROP development.

Oxygen and parenteral nutrition two main oxidants for extremely preterm infants: 'It all adds up'

OBJECTIVES

To assess the effect of early exposure to O2 and parenteral nutrition (PN) on oxidative stress at 36 weeks post-menstrual age (PMA) and on bronchopulmonary dysplasia (BPD) in extremely preterm infants.

STUDY DESIGN

A prospective observational study including 116 infants <29 weeks of gestation. Baseline clinical characteristics, FiO2 on day 7, duration of PN and clinical outcomes data were collected. In 39 infants, whole blood glutathione (GSH) and oxidized glutathione (GSSG) at 36 weeks PMA were measured and the redox potential was calculated using Nernst equation. Student's t-test, Chi-square, Spearman correlation, ANOVA, and logistic regression analyses were used as appropriate. P <  0.05 was considered significant.

RESULTS

FiO2 ≥25% was associated with higher level of GSSG (0.29 ± 0.04 versus 0.18 ± 0.02 nmol/mg of protein), a more oxidized redox potential (-191 ± 2 versus -198 ± 2 mV) and more BPD (90% versus 45%). PN duration >14 days was also associated with higher level of GSSG (0.26 ± 0.03 versus 0.13 ± 0.02 nmol/mg of protein), a more oxidized redox potential (-193 ± 5 versus -203 ± 2 mV) and more BPD (89% versus 24%). In logistic regression model, each 1% increase in FiO2 and each day increase in PN duration resulted in an increase in the OR for BPD by 1.57 (1.09 -2.28) and 1.17 (1.03 -1.33) respectively.

CONCLUSION

Early O2 supplement and PN have additive effects that were associated with prolonged oxidative stress and increased risk of BPD. Strategies targeting judicious use of O2 and decreasing the duration or developing a safer formulation of PN can be targeted to decrease BPD.

S-Nitrosoglutathione Attenuates Airway Hyperresponsiveness in Murine Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is characterized by lifelong obstructive lung disease and profound, refractory bronchospasm. It is observed among survivors of premature birth who have been treated with prolonged supplemental oxygen. Therapeutic options are limited. Using a neonatal mouse model of BPD, we show that hyperoxia increases activity and expression of a mediator of endogenous bronchoconstriction, S-nitrosoglutathione (GSNO) reductase. MicroRNA-342-3p, predicted in silico and shown in this study in vitro to suppress expression of GSNO reductase, was decreased in hyperoxia-exposed pups. Both pretreatment with aerosolized GSNO and inhibition of GSNO reductase attenuated airway hyperresponsiveness in vivo among juvenile and adult mice exposed to neonatal hyperoxia. Our data suggest that neonatal hyperoxia exposure causes detrimental effects on airway hyperreactivity through microRNA-342-3p–mediated upregulation of GSNO reductase expression. Furthermore, our data demonstrate that this adverse effect can be overcome by supplementing its substrate, GSNO, or by inhibiting the enzyme itself. Rates of BPD have not improved over the past two decades; nor have new therapies been developed. GSNO-based therapies are a novel treatment of the respiratory problems that patients with BPD experience.

Inflammatory and oxidative stress airway markers in premature newborns of hypertensive mothers

Although oxidative stress and inflammation are important mechanisms in the pathophysiology of preeclampsia and preterm diseases, their contribution to the respiratory prognosis of premature infants of hypertensive mothers is not known. Our objective was to determine the levels of oxidative stress and inflammation markers in the airways of premature infants born to hypertensive and normotensive mothers, in the first 72 h of life, and to investigate whether they are predictors of bronchopulmonary dysplasia (BPD)/death. This was a prospective study with premature infants less than 34 weeks' gestation on respiratory support who were stratified into 2 groups: 32 premature infants of hypertensive mothers and 41 of normotensive women, with a mean gestational age of 29 weeks. Exclusion criteria were as follows: diabetes mellitus, chorioamnionitis, malformation, congenital infection, and death within 24 h after birth. The outcome of interest was BPD/death. Malondialdehyde (MDA), nitric oxide (NO), and interleukin 8 (IL-8) were measured in airway aspirates from the first and third days of life and did not differ between the groups. Univariate and multivariate statistical analyses were performed. The concentrations of MDA, NO, and IL-8 were not predictors of BPD/death. Premature infants who developed BPD/death had higher levels of IL-8 in the first days of life. The gestational age, mechanical ventilation, and a small size for gestational age were risk factors for BPD/death. In conclusion, the biomarkers evaluated were not increased in premature infants of hypertensive mothers and were not predictors of BPD/death.

Attenuation of miR-17∼92 Cluster in Bronchopulmonary Dysplasia

RATIONALE

Bronchopulmonary dysplasia remains a significant cause of neonatal morbidity; however, the identification of novel targets to predict or prevent the development of bronchopulmonary dysplasia remains elusive. Proper microRNA (miR)-17∼92 cluster is necessary for normal lung development, and alterations in expression are reported in other pulmonary diseases. The overall hypothesis for our work is that altered miR-17∼92 cluster expression contributes to the molecular pathogenesis of bronchopulmonary dysplasia.

OBJECTIVES

The current studies tested the hypothesis that alterations in miR-17∼92 cluster and DNA methyltransferase expression are present in bronchopulmonary dysplasia.

METHODS

miR-17∼92 cluster expression, promoter methylation, and DNA methyltransferase expression were determined in autopsy lung samples obtained from premature infants who died with bronchopulmonary dysplasia, or from term/near-term infants who died from nonrespiratory causes. Expression of miR-17∼92 cluster members miR-17 and -19b was measured in plasma samples collected in the first week of life from a separate cohort of preterm infants at a second institution in whom bronchopulmonary dysplasia was diagnosed subsequently.

MEASUREMENTS AND MAIN RESULTS

Autopsy tissue data indicated that miR-17∼92 expression is significantly lower in bronchopulmonary dysplasia lungs and is inversely correlated with promoter methylation and DNA methyltransferase expression when compared with that of control subjects without bronchopulmonary dysplasia. Plasma sample analyses indicated that miR-17 and -19b expression was decreased in infants who subsequently developed bronchopulmonary dysplasia.

CONCLUSIONS

Our data are the first to demonstrate altered expression of the miR-17∼92 cluster in bronchopulmonary dysplasia. The consistency between our autopsy and plasma findings further support our working hypothesis that the miR-17∼92 cluster contributes to the molecular pathogenesis of bronchopulmonary dysplasia.