Early Cumulative Supplemental Oxygen Predicts Bronchopulmonary Dysplasia in High Risk Extremely Low Gestational Age Newborns

Urine Desmosine as a Novel Biomarker for Bronchopulmonary Dysplasia and Postprematurity Respiratory Disease in Extremely Preterm or Low Birth Weight Infants

OBJECTIVE

 This study aimed to evaluate whether elevated urine desmosine levels at 3 weeks of age were associated with severe radiological findings, bronchopulmonary dysplasia (BPD), and post-prematurity respiratory disease (PRD) in extremely preterm (EP) or extremely low birth weight (ELBW) infants.

STUDY DESIGN

 This study recruited 37 EP (22-27 completed weeks) or ELBW (<1,000 g) infants. Urine was collected between 21 and 28 postnatal days, and desmosine was measured using an enzyme-linked immunosorbent assay kit; the urine creatinine level was also measured. Bubbly/cystic lungs were characterized by emphysematous chest X-rays on postnatal day 28. Furthermore, provision of supplemental oxygen or positive-pressure respiratory support at 40 weeks' postmenstrual age defined BPD, and increased medical utilization at 18 months of corrected age defined PRD. The desmosine/creatinine threshold was determined by receiver operating characteristic analysis. The adjusted risk and 95% confidence interval (CI) for elevated urine desmosine/creatinine levels were estimated by logistic regression analysis.

RESULTS

 Elevated urine desmosine/creatinine levels higher than the threshold were significantly associated with bubbly/cystic lungs (8/13 [61.5%] vs. 2/24 [8.3%], p = 0.001), BPD (10/13 [76.9%] vs. 8/24 [33.3%], p = 0.02), and PRD (6/13 [46.2%] vs. 2/24 [8.3%], p = 0.01). After adjusting for gestational age, birth weight, and sex, the urine desmosine/creatinine levels were significantly higher in those who were highly at risk of bubbly/cystic lungs (odds ratio [OR], 13.2; 95% CI, 1.67-105) and PRD (OR, 13.8; 95% CI, 1.31-144).

CONCLUSION

 Elevated urine desmosine/creatinine levels on the third postnatal week were associated with bubbly/cystic lungs on day 28 and PRD at 18 months of corrected age in EP or ELBW infants.

KEY POINTS

· Urine desmosine was prospectively measured in 3-week-old EP/ELBW infants.. · Elevated urine desmosine levels were associated with emphysematous radiological findings on day 28, PRD at 18 months of corrected age.. · Urine desmosine may be a promising biomarker indicating lung damage in EP/ELBW infants..

Cord Blood Adductomics Reveals Oxidative Stress Exposure Pathways of Bronchopulmonary Dysplasia

Fetal and neonatal exposures to perinatal oxidative stress (OS) are key mediators of bronchopulmonary dysplasia (BPD). To characterize these exposures, adductomics is an exposure science approach that captures electrophilic addition products (adducts) in blood protein. Adducts are bound to the nucleophilic cysteine loci of human serum albumin (HSA), which has a prolonged half-life. We conducted targeted and untargeted adductomics to test the hypothesis that adducts of OS vary with BPD. We studied 205 preterm infants (≤28 weeks) and 51 full-term infants from an ongoing birth cohort. Infant plasma was collected at birth (cord blood), 1-week, 1-month, and 36-weeks postmenstrual age. HSA was isolated from plasma, trypsin digested, and analyzed using high-performance liquid chromatography-mass spectrometry to quantify previously annotated (known) and unknown adducts. We identified 105 adducts in cord and postnatal blood. A total of 51 known adducts (small thiols, direct oxidation products, and reactive aldehydes) were increased with BPD. Postnatally, serial concentrations of several known OS adducts correlated directly with supplemental oxygen exposure. The application of large-scale adductomics elucidated OS-mediated pathways of BPD. This is the first study to investigate the "neonatal-perinatal exposome" and to identify oxidative stress-related exposure biomarkers that may inform antioxidant strategies to protect the health of future generations of infants.

IL-17a-producing γδT cells and NKG2D signaling mediate bacterial endotoxin-induced neonatal lung injury: implications for bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease in preterm birth survivors characterized by inflammation, impaired alveolarization and dysmorphic vasculature. Activated IL-17A+ lymphocytes are key drivers of inflammation in preterm infants. We have shown that in immature mice chronic airway exposure to lipopolysaccharide (LPS) induces pulmonary inflammation, increased IL-17a expression, and hypoalveolarization, a BPD-like phenotype. The source of IL-17a and contribution to lung pathology is unknown. The natural-killer group 2, member D (NKG2D) receptor mediates activation and IL-17a production in γδ T cells by binding to stress molecules. LPS induces NKG2D ligand expression, including Rae-1 and MULT1. We hypothesized that IL-17a+ γδ T cells and NKG2D signaling mediate neonatal LPS-induced lung injury. Immature C57BL/6J (wild type), Nkg2d-/- or Tcrd-/- (lacking γδ T cells) mice were inoculated with 3ug/10ul of LPS from E. coli O26:B6 or 10ul of PBS intranasally on day of life 3, 5, 7, and 10. Selected mice were treated with neutralizing antibodies against IL-17a, or NKG2D intraperitoneally. Lung immune cells were assessed by flow cytometry and gene expression was analyzed by qPCR. Alveolar growth was assessed by lung morphometry. We established that anti-IL-17a antibody treatment attenuated LPS-induced hypoalveolarization. We found that LPS induced the fraction of IL-17a+NKG2D+ γδ T cells, a major source of IL-17a in the neonatal lung. LPS also induced lung mRNA expression of NKG2D, Rae-1, MULT1, and the DNA damage regulator p53. Anti-NKG2D treatment attenuated the effect of LPS on γδ T cell IL-17a expression, immune cell infiltration and hypoalveolarization. LPS-induced hypoalveolarization was also attenuated in Nkg2d-/- and Tcrd-/- mice. In tracheal aspirates of preterm infants IL-17A and its upstream regulator IL-23 were higher in infants who later developed BPD. Also, human ligands of NKG2D, MICA and MICB were present in the aspirates and MICA correlated with median FiO2. Our novel findings demonstrate a central role for activated IL-17a+ γδ T cells and NKG2D signaling in neonatal LPS-induced lung injury. Future studies will determine the role of NKG2D ligands and effectors, other NKG2D+ cells in early-life endotoxin-induced lung injury and inflammation with a long-term goal to understand how inflammation contributes to BPD pathogenesis.

Bronchopulmonary Dysplasia: A Five-Year Retrospective Cohort Study on Differences in Clinical Characteristics and Morbidities According to Severity Grading

INTRODUCTION

Bronchopulmonary dysplasia (BPD) is the most common complication associated with extreme prematurity. Although several criteria defining severity were developed over time, there are a few studies describing the differences in BPD phenotype and neonatal morbidities and complications between severity groups. We aimed to describe these differences in BPD patients of a neonatal intensive care unit (NICU).

METHODS

We conducted an observational retrospective cohort study through a medical record review over a five-year period. Participants were newborns admitted to an NICU who were diagnosed with BPD. We performed a descriptive statistical analysis of gestational complications and the use of antenatal corticosteroid therapy, birth-related data, and complications throughout the NICU stay, as well as the respiratory support used. We also compared different severity groups across these variables. The patients were divided into severe and non-severe BPD using the severity criteria of the 2001 NICHD/NHLBI/ORD consensus workshop.

RESULTS

A total of 101 newborns with BPD participated in the study and 73 had data on BPD severity. The median gestational age was 27 weeks, ranging from 23 to 32 weeks. Of these 73 newborns, 36 had mild BPD (49.3%), 10 had moderate BPD (13.7%), and 27 had severe BPD (37.0%). When comparing severe and non-severe BPD, we found that extreme prematurity, extremely low birth weight, and small size for gestational age were more frequent in the severe BPD group (p-value=0.012, p-value<0.001, and p-value=0.012, respectively). Infants with severe BPD had a longer duration of invasive ventilation than those with mild or moderate BPD (p-value<0.001). Late sepsis, necrotizing enterocolitis, severe brain injury, and retinopathy of prematurity were more frequent in severe BPD (p-value=0.017, p-value=0.045, p-value=0.033, p-value=0.003, respectively).

DISCUSSION

Previously published evidence describing causal links between BPD development and comorbidities exists but data on their impact on BPD severity are scarce. In our study, severe BPD seemed to be associated with a higher frequency of comorbidities and complications. Further studies are needed to ascertain the impact of each morbidity on the severity of BPD and if measures to prevent them could lead to potentially milder BPD disease.

Prediction Models for Bronchopulmonary Dysplasia in Preterm Infants: A Systematic Review and Meta-Analysis

OBJECTIVE

To review systematically and assess the accuracy of prediction models for bronchopulmonary dysplasia (BPD) at 36 weeks of postmenstrual age.

STUDY DESIGN

Searches were conducted in MEDLINE and EMBASE. Studies published between 1990 and 2022 were included if they developed or validated a prediction model for BPD or the combined outcome death/BPD at 36 weeks in the first 14 days of life in infants born preterm. Data were extracted independently by 2 authors following the Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (ie, CHARMS) and PRISMA guidelines. Risk of bias was assessed using the Prediction model Risk Of Bias ASsessment Tool (ie, PROBAST).

RESULTS

Sixty-five studies were reviewed, including 158 development and 108 externally validated models. Median c-statistic of 0.84 (range 0.43-1.00) was reported at model development, and 0.77 (range 0.41-0.97) at external validation. All models were rated at high risk of bias, due to limitations in the analysis part. Meta-analysis of the validated models revealed increased c-statistics after the first week of life for both the BPD and death/BPD outcome.

CONCLUSIONS

Although BPD prediction models perform satisfactorily, they were all at high risk of bias. Methodologic improvement and complete reporting are needed before they can be considered for use in clinical practice. Future research should aim to validate and update existing models.

Machine learning to predict late respiratory support in preterm infants: a retrospective cohort study

Bronchopulmonary dysplasia (BPD) has been a critical morbidity in preterm infants. To improve our definition and prediction of BPD is challenging yet indispensable. We aimed to apply machine learning (ML) to investigate effective models by using the recently-proposed and data-driven definition to predict late respiratory support modalities at 36 weeks' post menstrual age (PMA). We collected data on very-low-birth-weight infants born between 2016 and 2019 from the Taiwan Neonatal Network database. Twenty-four attributes associated with their early life and seven ML algorithms were used in our analysis. The target outcomes were overall mortality, death before 36 weeks' PMA, and severity of BPD under the new definition, which served as a proxy for respiratory support modalities. Of the 4103 infants initially considered, 3200 were deemed eligible. The logistic regression algorithm yielded the highest area under the receiver operating characteristic curve (AUROC). After attribute selection, the AUROC of the simplified models remain favorable (e.g., 0.801 when predicting no BPD, 0.850 when predicting grade 3 BPD or death before 36 weeks' PMA, and 0.881 when predicting overall mortality). By using ML, we developed models to predict late respiratory support. Estimators were developed for clinical application after being simplified through attribute selection.

Early-life hyperoxia-induced Flt3L drives neonatal lung dendritic cell expansion and proinflammatory responses

Premature infants with chronic lung disease, bronchopulmonary dysplasia (BPD), develop recurrent cough and wheezing following respiratory viral infections. The mechanisms driving the chronic respiratory symptoms are ill-defined. We have shown that hyperoxic exposure of neonatal mice (a model of BPD) increases the activated lung CD103+ dendritic cells (DCs) and these DCs are required for exaggerated proinflammatory responses to rhinovirus (RV) infection. Since CD103+ DC are essential for specific antiviral responses and their development depends on the growth factor Flt3L, we hypothesized that early-life hyperoxia stimulates Flt3L expression leading to expansion and activation of lung CD103+ DCs and this mediates inflammation. We found that hyperoxia numerically increased and induced proinflammatory transcriptional signatures in neonatal lung CD103+ DCs, as well as CD11bhi DCs. Hyperoxia also increased Flt3L expression. Anti-Flt3L antibody blocked CD103+ DC development in normoxic and hyperoxic conditions, and while it did not affect the baseline number of CD11bhi DCs, it neutralized the effect of hyperoxia on these cells. Anti-Flt3L also inhibited hyperoxia-induced proinflammatory responses to RV. In tracheal aspirates from preterm infants mechanically-ventilated for respiratory distress in the first week of life levels of FLT3L, IL-12p40, IL-12p70 and IFN-γ were higher in infants who went on to develop BPD and FLT3L levels positively correlated with proinflammatory cytokines levels. This work highlights the priming effect of early-life hyperoxia on lung DC development and function and the contribution of Flt3L in driving these effects.

Regular lung recruitment maneuvers during high-frequency oscillatory ventilation in extremely preterm infants: a randomized controlled trial

BACKGROUND

Lung recruitment maneuvers (LRMs) improve lung volume at initiation of high-frequency oscillatory ventilation (HFOV), but it is unclear when to repeat LRMs. We evaluated the efficiency of scheduled LRMs.

METHODS

In a randomized controlled trial, extremely preterm infants on HFOV received either LRMs at 12-hour intervals and when clinically indicated (intervention) or only when clinically indicated (control). The primary outcome was the cumulative oxygen saturation index (OSI) over HFOV time, limited to 7 days. Additionally, LRMs were analyzed with respect to OSI improvement.

RESULTS

Fifteen infants were included in each group. The mean (SD) postmenstrual age and weight at HFOV start were 23 + 6 (0 + 5) weeks and 650 (115) g in the intervention group and 24 + 4 (0 + 6) weeks (p = 0.03) and 615 (95) g (p = 0.38) in the control group. The mean (SD) cumulative OSI amounted to 4.95 (1.72) in the intervention versus 5.30 (2.08) in the control group (p = 0.61). The mean (SD) number of LRMs in 12 h was 1.3 (0.2) in the intervention versus 1.1 (0.5) in the control group (p = 0.13). Performing LRM when FiO2 > 0.6 resulted in a mean OSI reduction of 3.6.

CONCLUSION

Regular versus clinically indicated LRMs were performed with equal frequency in preterm infants during HFOV, and consequently, no difference in lung volume was observed. LRMs seem to be most efficient at high FiO2.

TRIAL REGISTRATION

ClinicalTrials.gov ID: NCT04289324 (28/02/2020).

Low flow nasal cannula requirement among preterm infants: predictors and description of clinical course

OBJECTIVE

We aim to identify potential risk factors associated with longer duration of supplemental oxygen use in preterm infants at risk for bronchopulmonary dysplasia (BPD) to better inform families and weaning protocols.

STUDY DESIGN

This is a retrospective study of infants with a birth gestational age (GA) < 32 0/7 weeks admitted to the neonatal intensive care unit (NICU) between October 2017 and September 2019.

RESULTS

A total of 172 infants met criteria for inclusion and analysis, of which 69 (40.1%) infants required LFNC. Risk factors for longer duration included lower birth GA or birth weight, increased ventilator days, and diagnosis of a patent ductus arteriosus (PDA). BPD was diagnosed in 69.6% who required LFNC, of which 47.8% were discharged on home oxygen.

CONCLUSION

Younger birth GA, lower birth weight, increased ventilator days, and presence of a PDA were identified as risk factors for longer LFNC duration.

Safety of sildenafil in premature infants at risk of bronchopulmonary dysplasia: Rationale and methods of a phase II randomized trial

Bronchopulmonary dysplasia (BPD) is a disease of chronic respiratory insufficiency stemming from premature birth and iatrogenic lung injury leading to alveolar simplification, impaired alveolar-capillary development, interstitial fibrosis, and often pulmonary hypertension. BPD is the most common pulmonary sequela of prematurity and is often fatal; however, there remains no FDA-approved therapies to treat or prevent BPD. Sildenafil is increasingly used off-label in premature infants despite scant safety and efficacy data. Sildenafil reduces lung injury and preserves normal vasculature in preclinical models, and improves outcomes in children with pulmonary hypertension, and thus is a promising candidate for BPD. Following phase I studies, we developed the phase II SIL02 trial to describe the safety, pharmacokinetics and preliminary effectiveness of intravenous and enteral sildenafil in premature infants at risk for BPD. SIL02 is a randomized, double-blind, placebo-controlled, 3-cohort, sequential dose-escalating trial of enteral or intravenous (IV) sildenafil dosed every 8 h for up to 34 days. The target IV doses were 0.125, 0.5 and 1 mg/kg/dose in cohorts 1, 2 and 3, respectively; while the enteral doses will be double the IV doses. Eligible infants must be < 29 weeks' gestation at birth and requiring respiratory support at 7–28 days' postnatal age. Adverse events and preliminary effectiveness will be compared by treatment group. Using the final population PK model, empirical Bayesian estimates will be generated for each patient. Preliminary effectiveness will be measured by the incidence of moderate to severe BPD or death at 36 weeks and change in the BPD risk estimation.

Clinical factors associated with abnormal general movements of preterm newborns during hospitalization in a neonatal intensive care unit

INTRODUCTION

There is no clarity about which clinical variables during hospitalization in the Neonatal Intensive Care Unit (NICU) are associated with abnormal General Movements (GMs).

OBJECTIVE

To describe the trajectory of GMs of preterm newborns and explore the association between clinical variables and the presence of abnormal GMs during the NICU stay.

METHODS

Fifty-eight preterm newborns (33 males), with a mean gestational age at birth of 31,93 week's postmenstrual age, were evaluated using the GMs assessment by Hadders-Algra method. Clinical variables recorded weekly throughout the hospitalization period. The weekly association between clinical variables and the presence of abnormal GMs was tested using the Generalized Estimating Equations (GEE) model.

RESULTS

Preterm infants were recorded for up to sixteen weeks and more than half of the infants (56.9 %) had abnormal movements in at least one week during hospitalization. The absence of peri-intraventricular hemorrhage (PIVH) grades I-II and non-invasive ventilatory support and/or oxygen therapy on the day of the evaluation reduced, respectively, by 77.3 % (OR = 0.23; p > 0.0001) and 64.3 % (OR = 0.36; p > 0.0001) the chance of having an abnormal classification. In addition, each day of increased invasive mechanical ventilation increased the chance of having an abnormal classification by 1.11 times (OR = 0.025; p > 0.0001).

CONCLUSION

PIVH grades I-II, longer durations of mechanical ventilation and the presence of non-invasive ventilatory support and/or oxygen therapy are associated with abnormal movements during stay in the neonatal period. The data suggest that development outcome of infants having these conditions should be closely monitored.

Mesenchymal stem cell bioenergetics and apoptosis are associated with risk for bronchopulmonary dysplasia in extremely low birth weight infants

Oxidant stress contributes significantly to the pathogenesis of bronchopulmonary dysplasia (BPD) in extremely low birth weight (ELBW) infants. Mitochondrial function regulates oxidant stress responses as well as pluripotency and regenerative ability of mesenchymal stem cells (MSCs) which are critical mediators of lung development. This study was conducted to test whether differences in endogenous MSC mitochondrial bioenergetics, proliferation and survival are associated with BPD risk in ELBW infants. Umbilical cord-derived MSCs of ELBW infants who later died or developed moderate/severe BPD had lower oxygen consumption and aconitase activity but higher extracellular acidification-indicative of mitochondrial dysfunction and increased oxidant stress-when compared to MSCs from infants who survived with no/mild BPD. Hyperoxia-exposed MSCs from infants who died or developed moderate/severe BPD also had lower PINK1 expression but higher TOM20 expression and numbers of mitochondria/cell, indicating that these cells had decreased mitophagy. Finally, these MSCs were also noted to proliferate at lower rates but undergo more apoptosis in cell cultures when compared to MSCs from infants who survived with no/mild BPD. These results indicate that mitochondrial bioenergetic dysfunction and mitophagy deficit induced by oxidant stress may lead to depletion of the endogenous MSC pool and subsequent disruption of lung development in ELBW infants at increased risk for BPD.

Increased antibiotic exposure in early life is associated with adverse outcomes in very low birth weight infants

BACKGROUND

The use of antibiotics in the early lives of premature infants may alter the microbiota and influence their clinical outcomes. However, whether the administration of probiotics can influence these outcomes remains unknown. In our study, probiotics were routinely administered unless contraindicated. We explored whether increased antibiotic exposure with the routine use of probiotics was associated with necrotizing enterocolitis (NEC) or bronchopulmonary dysplasia (BPD).

METHODS

A retrospective cohort study was conducted, enrolling very low birth weight (VLBW) infants admitted between January 1, 2016, and March 31, 2020, to a medical center. Days of antibiotic exposure in the first 14 days of life were recorded. The primary outcomes were NEC and BPD. Adjusted odds ratios (aORs) and 95% confidence intervals (CIs) were calculated using multivariable regression analyses to assess risk factors.

RESULTS

Of 185 VLBW infants admitted to the medical center, 132 met the inclusion criteria. Each additional day of antibiotic treatment was associated with increased odds of NEC (aOR, 1.278; 95% CI, 1.025-1.593) and BPD (aOR, 1.630; 95% CI, 1.233-2.156). The association remained in the NEC analysis after adjustment for probiotic use.

CONCLUSION

Increased antibiotic exposure in the early lives of VLBW infants was associated with increased risks of NEC and BPD. The probiotics did not influence the outcomes. Our findings suggest that clinicians should be alerted to the adverse outcomes of antibiotic use in infants with VLBWs.

Gelsolin Attenuates Neonatal Hyperoxia-Induced Inflammatory Responses to Rhinovirus Infection and Preserves Alveolarization

Prematurity and bronchopulmonary dysplasia (BPD) increase the risk of asthma later in life. Supplemental oxygen therapy is a risk factor for chronic respiratory symptoms in infants with BPD. Hyperoxia induces cell injury and release of damage-associated molecular patterns (DAMPs). Cytoskeletal filamentous actin (F-actin) is a DAMP which binds Clec9a, a C-type lectin selectively expressed on CD103+ dendritic cells (DCs). Co-stimulation of Clec9a and TLR3 induces maximal proinflammatory responses. We have shown that neonatal hyperoxia (a model of BPD) increases lung IL-12+Clec9a+CD103+ DCs, pro-inflammatory responses and airway hyperreactivity following rhinovirus (RV) infection. CD103+ DCs and Clec9a are required for these responses. Hyperoxia increases F-actin levels in bronchoalveolar lavage fluid (BALF). We hypothesized that the F-actin severing protein gelsolin attenuates neonatal hyperoxia-induced Clec9a+CD103+ DC-dependent pro-inflammatory responses to RV and preserves alveolarization. We exposed neonatal mice to hyperoxia and treated them with gelsolin intranasally. Subsequently we inoculated the mice with RV intranasally. Alternatively, we inoculated normoxic neonatal mice with BALF from hyperoxia-exposed mice (hyperoxic BALF), RV and gelsolin. We analyzed lung gene expression two days after RV infection. For in vitro studies, lung CD11c+ cells were isolated from C57BL/6J or Clec9a^gfp-/- mice and incubated with hyperoxic BALF and RV. Cells were analyzed by flow cytometry. In neonatal mice, gelsolin blocked hyperoxia-induced Il12p40, TNF-α and IFN-γ mRNA and protein expression in response to RV infection. Similar effects were observed when gelsolin was co-administered with hyperoxic BALF and RV. Gelsolin decreased F-actin levels in hyperoxic BALF in vitro and inhibited hyperoxia-induced D103lo DC expansion and inflammation in vivo. Gelsolin also attenuated hyperoxia-induced hypoalveolarization. Further, incubation of lung CD11c+ cells from WT and Clec9a^gfp-/- mice with hyperoxic BALF and RV, showed Clec9a is required for maximal hyperoxic BALF and RV induced IL-12 expression in CD103+ DCs. Finally, in tracheal aspirates from mechanically ventilated human preterm infants the F-actin to gelsolin ratio positively correlates with FiO2, and gelsolin levels decrease during the first two weeks of mechanical ventilation. Collectively, our findings demonstrate a promising role for gelsolin, administered by inhalation into the airway to treat RV-induced exacerbations of BPD and prevent chronic lung disease.

Mechanical ventilation characteristics and their prediction performance for the risk of moderate and severe bronchopulmonary dysplasia in infants with gestational age <30 weeks and birth weight <1,500 g

INTRODUCTION

Moderate and severe bronchopulmonary dysplasia (BPD) is a common pulmonary complication in premature infants, which seriously affects their survival rate and quality of life. This study aimed to describe the mechanical ventilation characteristics and evaluate their prediction performance for the risk of moderate and severe BPD in infants with gestational age <30 weeks and birth weight <1,500 g on postnatal Day 14.

METHODS

In this retrospective cohort study, 412 infants with gestational age <30 weeks and birth weight <1,500 g were included in the analysis, including 104 infants with moderate and severe BPD and 308 infants without moderate and severe BPD (as controls). LASSO regression was used to optimize variable selection, and Logistic regression was applied to build a predictive model. Nomograms were developed visually using the selected variables. To validate the model, receiver operating characteristic (ROC) curve, calibration plot, and clinical impact curve were used.

RESULTS

From the original 28 variables studied, six predictors, namely birth weight, 5 min apgar score, neonatal respiratory distress syndrome (≥Class II), neonatal pneumonia, duration of invasive mechanical ventilation (IMV) and maximum of FiO₂ (fraction of inspiration O₂) were identified by LASSO regression analysis. The model constructed using these six predictors and a proven risk factor (gestational age) displayed good prediction performance for moderate and severe BPD, with an area under the ROC of 0.917 (sensitivity = 0.897, specificity = 0.797) in the training set and 0.931 (sensitivity = 0.885, specificity = 0.844) in the validation set, and was well calibrated (P _{Hosmer-Lemeshow test}= 0.727 and 0.809 for the training and validation set, respectively).

CONCLUSION

The model included gestational age, birth weight, 5 min apgar score, neonatal respiratory distress syndrome (≥Class II), neonatal pneumonia, duration of IMV and maximum of FiO₂ had good prediction performance for predicting moderate and severe BPD in infants with gestational age <30 weeks and birth weight <1,500 g on postnatal Day 14.

Lung Ultrasound for Prediction of Bronchopulmonary Dysplasia in Extreme Preterm Neonates: A Prospective Diagnostic Cohort Study

OBJECTIVES

To evaluate the diagnostic and predictive ability of lung ultrasound at 3 time points in the first 2 weeks after birth for predicting bronchopulmonary dysplasia (BPD) among infants <29 weeks of gestational age.

STUDY DESIGN

This was a prospective, diagnostic cohort study. Lung ultrasound was performed on days 3, 7, and 14 after birth and lung ultrasound scores (LUS) were calculated in blinded fashion. Diagnostic test characteristics and area under receiver operating characteristic (AUROC) curves were calculated.

RESULTS

A total of 152 infants were enrolled with mean (SD) gestational age of 25.8 (1.5) weeks gestation. Of them, 87 (57%) infants were diagnosed with BPD. The LUS were significantly higher in infants diagnosed with BPD compared with those without BPD at all scan time points (P < .01). The score of >10 at all 3 time points had higher sensitivity (0.89, 0.89, and 0.77), specificity (0.87, 0.90, and 0.92), and corresponding clinically important positive and negative likelihood ratios. The AUROC for LUS at the 3 time points were 0.96, 0.97, and 0.95 on day 3, 7, and 14, respectively. Compared with the model using clinical characteristics, LUS alone had higher AUROC (P < .05 for all 3 time points).

CONCLUSIONS

In this cohort, LUS in the first 2 weeks after birth had a very high predictive value for the diagnosis of BPD among infants of <29 weeks of gestation.

TRIAL REGISTRATION

ClinicalTrials.govNCT04756297.

Bronchopulmonary dysplasia precursors influence risk of white matter injury and adverse neurodevelopmental outcome in preterm infants

BACKGROUND

Cumulative supplemental oxygen (CSO) and cumulative mean airway pressure (CMAP) are associated with bronchopulmonary dysplasia (BPD) in preterm infants, but their relationships to white matter injury (WMI) and neurodevelopment have not been evaluated.

METHODS

Preterm infants <32 weeks' gestation were prospectively imaged with 3 T MRI near term. CSO and CMAP were retrospectively summed over the first 14 and 28 days. Neurodevelopment was assessed at 30 months adjusted using the Bayley-III. ROC and linear regression were used to evaluate the relationship between CSO, CMAP, and BPD with WMI and neurodevelopmental performance, respectively.

RESULTS

Of the 87 infants, 30 (34.5%) had moderate-severe BPD, which was associated with WMI (OR 5.5, 95% CI 1.1-34.9, p = 0.012). CSO and CMAP predicted WMI as well as BPD (AUC 0.68-0.77). CSO was independently associated with decreased language and cognitive performance (mean difference at 14 days: -11.0, 95% CI -19.8 to -2.2, p = 0.015 and -9.8, 95% CI -18.9 to -0.7, p = 0.035, respectively) at 30 months adjusted.

CONCLUSIONS

BPD precursors predict WMI as well as BPD. Cumulative supplemental oxygen over the first 14 days of life is independently associated with lower language and cognitive performances. These data suggest that early respiratory status influences the risk of adverse neurodevelopment in preterm infants.

IMPACT

Respiratory precursors to bronchopulmonary dysplasia (BPD), cumulative supplemental oxygen and mean airway pressure, over the first 14-28 days performed as well as BPD for the prediction of white matter injury on MRI in preterm infants. Cumulative supplemental oxygen was independently associated with lower language and cognitive performance on the Bayley-III at 30 months adjusted. These data suggest that early respiratory status may help explain why BPD is independently associated with adverse neurodevelopmental outcomes in the preterm population and highlights the importance of interventions targeting respiratory status as a potential avenue to improve neurodevelopmental outcomes.

Patent ductus arteriosus, systemic NT-proBNP concentrations and development of bronchopulmonary dysplasia in very preterm infants: retrospective data analysis from a randomized controlled trial

BACKGROUND

Patent ductus arteriosus (PDA) is a common complication in very preterm infants. It is known that there is an association between PDA and development of bronchopulmonary dysplasia (BPD) or death before the postmenstrual age (PMA) of 36 weeks, but this association remains one of the most controversial aspects of the problem. The study aimed to evaluate the relationship between PDA, serum NT-proBNP levels at 2-3 and 8-9 days of life, and BPD/death in very preterm infants.

METHODS

Data of 52 preterm infants with a gestational age < 32 weeks, chronological age < 72 h, and PDA diameter > 1.5 mm, enrolled in a randomized controlled trial, were used for the retrospective analysis. All patients underwent daily echocardiographic and two serum NT-proBNP measurements within the first 10 days after birth. Two groups of infants were formed retrospectively at PMA of 36 weeks depending on the outcome, BPD (n = 18)/death (n = 7) or survival without BPD (n = 27). Receiver operator characteristic (ROC) curve was used to evaluate the predictive performance of serum NT-proBNP levels for BPD/death occurrence.

RESULTS

The percentage of infants who received pharmacological treatment for PDA did not differ between the groups. Based on the area under the ROC curve, serum NT-proBNP levels on the 2-3 day of life (AUC = 0.71; 95% confidence interval (CI): 0.56-0.9; p = 0.014)) and on the 8-9 day of life (AUC = 0.76; 95% CI: 0.6-0.9; p = 0.002) could reliably predict BPD/death in very preterm infants who had PDA diameter > 1.5 mm in the first 72 h of life. Hemodynamically significant PDA (hsPDA) was significantly more often detected in newborns with BPD/death, however, treatment of infants with hsPDA did not reduce the incidence of BPD/death.

CONCLUSIONS

In very preterm infants with PDA > 1.5 mm at the age of 24-48 h, serum NT-proBNP concentration could reliably predict the development of BPD or death, regardless of the persistence of PDA, with the highest diagnostic value at 8-9 days.

TRIAL REGISTRATION

This study is registered in ClinicalTrials.gov - NCT03860428 on March 4, 2019.

Low caloric intake and high fluid intake during the first week of life are associated with the severity of bronchopulmonary dysplasia in extremely low birth weight infants

OBJECTIVE

To study whether there is an association between nutritional intake during the first week of life and severity of bronchopulmonary dysplasia (BPD) in extremely low birth weight (ELBW) infants.

METHODS

In a retrospective cohort study, medical records of all ELBW infants admitted to our Neonatal Intensive Care Unit (2010-2017) were reviewed for infants' demographics, clinical characteristics, nutritional intake during their first week of life, and BPD risk factors.

RESULTS

During the study period 226 infants were identified of whom 67% (151/226) had moderate-severe BPD and the rest served as controls. Overall infants with moderate-severe BPD were younger, smaller, and spent more time on mechanical ventilation than their controls [(mean±standard deviation) 24.7±1.7 vs. 26.8±2.0 weeks gestational age (p < 0.001); 678±154 vs. 837±129 grams (p < 0.001); and 37.9±23.6 vs. 13.7±15.3 days (p < 0.001) respectively]. During the first week of life, the average caloric, carbohydrate, protein and lipid intakes were significantly lower, and the average fluid intake was significantly higher in the moderate-severe BPD than the control group. After adjustment for confounders, fluid intake, and days on mechanical ventilation were significantly associated with moderate-severe BPD with an odds ratio [OR (95% confidence interval)] of 1.03 (1.01-1.04), and 1.05 (1.03-1.07) respectively. Daily caloric intake was associated with an increased risk for moderate-severe BPD [OR: 0.94 (0.91-0.97)].

CONCLUSION

Low caloric intake, and high fluid intake during the first week of life are associated with the severity of BPD in ELBW infants.

Trends in Bronchopulmonary Dysplasia Among Extremely Preterm Infants in Japan, 2003-2016

OBJECTIVE

To investigate recent trends in bronchopulmonary dysplasia (BPD) and its risk factors among extremely preterm infants.

STUDY DESIGN

Demographic and clinical data were reviewed for 19 370 infants born at 22-27 weeks of gestation registered in the affiliated hospitals of the Neonatal Research Network of Japan between 2003 and 2016. We investigated the overall survival and prevalence of bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age and risk factors for developing BPD among the survivors.

RESULTS

Among 19 370 infants, 2244 (11.6%) died by 36 weeks' postmenstrual age. The mortality rate decreased from 19.0% (99% CI, 15.7%-22.8%) in 2003 to 8.0% (99% CI, 6.2%-10.3%) in 2016. Among 17 126 survivors, BPD developed in 7792 (45.5%) infants, and its proportion significantly increased from 41.4% (99% CI, 36.5%-46.4%) in 2003 to 52.0% (99% CI, 48.2%-55.9%) in 2016. A multivariable analysis of the survivors showed a positive association of BPD with ≥4 weeks' supplemental oxygen or invasive ventilation, birth weight <750 g, small for gestational age, ≥4 weeks' noninvasive positive pressure ventilation, chorioamnionitis, <26 weeks' gestational age, <20 cases per year of center patient volume, or treated patent ductus arteriosus. Although the median duration of invasive ventilation was shortened, the proportions of factors associated adversely with BPD generally showed increasing trends over time.

CONCLUSIONS

The mortality rate of extremely preterm infants has decreased, but the rate of BPD has increased in survivors between 2003 and 2016. Despite the decreasing duration of invasive ventilation over time, increasing rates of BPD suggest that differences in the patient population or other management strategies influence the development of BPD.

Lymphocyte-Specific Biomarkers Associated With Preterm Birth and Bronchopulmonary Dysplasia

Many premature babies who are born with neonatal respiratory distress syndrome (RDS) go on to develop Bronchopulmonary Dysplasia (BPD) and later Post-Prematurity Respiratory Disease (PRD) at one year corrected age, characterized by persistent or recurrent lower respiratory tract symptoms frequently related to inflammation and viral infection. Transcriptomic profiles were generated from sorted peripheral blood CD8+ T cells of preterm and full-term infants enrolled with consent in the NHLBI Prematurity and Respiratory Outcomes Program (PROP) at the University of Rochester and the University at Buffalo. We identified outcome-related gene expression patterns following standard methods to identify markers for oxygen utilization and BPD as outcomes in extremely premature infants. We further identified predictor gene sets for BPD based on transcriptomic data adjusted for gestational age at birth (GAB). RNA-Seq analysis was completed for CD8+ T cells from 145 subjects. Among the subjects with highest risk for BPD (born at <29 weeks gestational age (GA); n=72), 501 genes were associated with oxygen utilization. In the same set of subjects, 571 genes were differentially expressed in subjects with a diagnosis of BPD and 105 genes were different in BPD subjects as defined by physiologic challenge. A set of 92 genes could predict BPD with a moderately high degree of accuracy. We consistently observed dysregulation of TGFB, NRF2, HIPPO, and CD40-associated pathways in BPD. Using gene expression data from both premature and full-term subjects (n=116), we identified a 28 gene set that predicted the PRD status with a moderately high level of accuracy, which also were involved in TGFB signaling. Transcriptomic data from sort-purified peripheral blood CD8+ T cells from 145 preterm and full-term infants identified sets of molecular markers of inflammation associated with independent development of BPD in extremely premature infants at high risk for the disease and of PRD among the preterm and full-term subjects.

New BPD-prevalence and risk factors for bronchopulmonary dysplasia/mortality in extremely low gestational age infants ≤28 weeks

OBJECTIVE

To evaluate prevalence and risk factors of moderate-severe Bronchopulmonary dysplasia (BPD)/Death in extremely low gestation age neonates (ELGANs).

STUDY DESIGN

Study of 266 ELGANs born at gestational age (GA) ≤ 28 weeks (w). Primary Outcome measure-composite outcome of moderate-severe BPD/Death using the National Institute of Child Health and Human Development NICHD's (2001) BPD definition.

RESULT

Cohort's mean GA and birth-weight (BW) were 25.3 ± 1.4w and 724 ± 14 g respectively with an overall mortality of 19% and moderate-severe BPD of 67%. Prevalence of moderate-severe BPD/death decreased significantly with increasing GA (86-93%) at 23-24 w; to <60% at 27-28w (OR 0.63; 95% CI; 0.52-0.77). On univariate analysis, other risk factors included BW(OR 1.005; 95% CI; 1.003-1.007), Sepsis (OR 2.9; 95% CI, 1.3-6.4), PDA needing treatment (OR 2.2; 95% CI, 1.3-3.9); air leaks (OR 2.7; 95% CI; 1.02-7.3) FiO₂ requirement >25%(OR 1.06; 95% CI; 1.01-1.11); and mechanical ventilation(MV) on Day7 (OR5.5; 95% CI; 2.8-10.8). Only need for Day7 MV was independently predictive of composite outcome (OR1.97; 95% CI; 1.3-3.1).

CONCLUSION

Risk factor identification will enable initiatives to implement lung protective strategies and develop prospective models for BPD prediction and prognostication.

Early Neonatal Oxygen Exposure Predicts Pulmonary Morbidity and Functional Deficits at 1 Year

OBJECTIVE

To evaluate the predictive value of cumulative oxygen exposure thresholds over the first 2 postnatal weeks, linking them to bronchopulmonary dysplasia (BPD) and 1-year pulmonary morbidity and lung function in extremely low gestational age newborns.

STUDY DESIGN

Infants (N = 704) enrolled in the Prematurity and Respiratory Outcomes Program, a multicenter prospective cohort study, that survived to discharge were followed through their neonatal intensive care unit hospitalization to 1-year corrected age. Cumulative oxygen exposure (Oxygen_AUC14) thresholds were derived from univariate models of BPD, stratifying infants into high-, intermediate-, and low-oxygen exposure groups. These groups were then used in multivariate logistic regressions to prospectively predict post-prematurity respiratory disease (PRD), respiratory morbidity score (RMS) in the entire cohort, and pulmonary function z scores (N = 108 subset of infants) at 1-year corrected age.

RESULTS

Over the first 14 postnatal days, infants exposed to high oxygen averaged ≥33.1% oxygen, infants exposed to intermediate oxygen averaged 29.1%-33.1%, and infants exposed to low oxygen were below both cutoffs. In multivariate models, infants exposed to high oxygen showed increased PRD and RMS, whereas infants exposed to intermediate oxygen demonstrated increased moderate/severe RMS. Infants in the high/intermediate groups had decreased forced expiratory volume at 0.5 seconds/forced vital capacity ratio.

CONCLUSIONS

Oxygen_AUC14 establishes 3 thresholds of oxygen exposure that risk stratify infants early in their neonatal course, thereby predicting short-term (BPD) and 1-year (PRD, RMS) respiratory morbidity. Infants with greater Oxygen_AUC14 have altered pulmonary function tests at 1 year of age, indicating early evidence of obstructive lung disease and flow limitation, which may predispose extremely low gestational age newborns to increased long-term pulmonary morbidity.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01435187.

Pulmonary mechanics and structural lung development after neonatal hyperoxia in mice

BACKGROUND

Supplemental oxygen exposure administered to premature infants is associated with chronic lung disease and abnormal pulmonary function. This study used mild (40%), moderate (60%), and severe (80%) oxygen to determine how hyperoxia-induced changes in lung structure impact pulmonary mechanics in mice.

METHODS

C57BL/6J mice were exposed to room air or hyperoxia from birth through postnatal day 8. Baseline pulmonary function and methacholine challenge was assessed at 4 and 8 weeks of age, accompanied by immunohistochemical assessments of both airway (smooth muscle, tethering) and alveolar (simplification, elastin deposition) structure.

RESULTS

Mild/moderate hyperoxia increased baseline airway resistance (40% only) and airway hyperreactivity (40 and 60%) at 4 weeks accompanied by increased airway smooth muscle deposition, which resolved at 8 weeks. Severe hyperoxia increased baseline compliance, baseline resistance, and total elastin/surface area ratio without increasing airway hyperreactivity, and was accompanied by increased alveolar simplification, decreased airway tethering, and changes in elastin distribution at both time points.

CONCLUSIONS

Mild to moderate hyperoxia causes changes in airway function and airway hyperreactivity with minimal parenchymal response. Severe hyperoxia drives its functional changes through alveolar simplification, airway tethering, and elastin redistribution. These differential responses can be leveraged to further develop hyperoxia mouse models.

Present and Future of Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is the most common respiratory disorder among infants born extremely preterm. The pathogenesis of BPD involves multiple prenatal and postnatal mechanisms affecting the development of a very immature lung. Their combined effects alter the lung's morphogenesis, disrupt capillary gas exchange in the alveoli, and lead to the pathological and clinical features of BPD. The disorder is ultimately the result of an aberrant repair response to antenatal and postnatal injuries to the developing lungs. Neonatology has made huge advances in dealing with conditions related to prematurity, but efforts to prevent and treat BPD have so far been only partially effective. Seeing that BPD appears to have a role in the early origin of chronic obstructive pulmonary disease, its prevention is pivotal also in long-term respiratory outcome of these patients. There is currently some evidence to support the use of antenatal glucocorticoids, surfactant therapy, protective noninvasive ventilation, targeted saturations, early caffeine treatment, vitamin A, and fluid restriction, but none of the existing strategies have had any significant impact in reducing the burden of BPD. New areas of research are raising novel therapeutic prospects, however. For instance, early topical (intratracheal or nebulized) steroids seem promising: they might help to limit BPD development without the side effects of systemic steroids. Evidence in favor of stem cell therapy has emerged from several preclinical trials, and from a couple of studies in humans. Mesenchymal stromal/stem cells (MSCs) have revealed a reparatory capability, preventing the progression of BPD in animal models. Administering MSC-conditioned media containing extracellular vesicles (EVs) have also demonstrated a preventive action, without the potential risks associated with unwanted engraftment or the adverse effects of administering cells. In this paper, we explore these emerging treatments and take a look at the revolutionary changes in BPD and neonatology on the horizon.

rhIGF-1/BP3 Preserves Lung Growth and Prevents Pulmonary Hypertension in Experimental Bronchopulmonary Dysplasia

Rationale: Antenatal factors, such as chorioamnionitis, preeclampsia, and postnatal injury, are associated with an increased risk for bronchopulmonary dysplasia (BPD) and pulmonary hypertension (PH) after preterm birth. IGF-1 (insulin-like growth factor-1) is markedly decreased in normal preterm infants, but whether IGF-1 treatment can prevent BPD or PH is unknown.Objectives: To evaluate whether postnatal treatment with rhIGF-1 (recombinant human IGF-1)/BP3 (binding peptide 3) improves lung growth and prevents PH in two antenatal models of BPD induced by intraamniotic exposure to endotoxin (ETX) or sFlt-1 (soluble fms-like tyrosine kinase 1), and in a postnatal model due to prolonged hyperoxia.Methods: ETX or sFlt-1 were administered into the amniotic sac of pregnant rats at Embryonic Day 20 to simulate antenatal models of chorioamnionitis and preeclampsia, respectively. Pups were delivered by cesarean section at Embryonic Day 22 and treated with rhIGF-1/BP3 (0.02-20 mg/kg/d intraperitoneal) or buffer for 2 weeks. Study endpoints included radial alveolar counts (RACs), vessel density, and right ventricular hypertrophy (RVH). Direct effects of rhIGF-1/BP3 (250 ng/ml) on fetal lung endothelial cell proliferation and tube formation and alveolar type 2 cell proliferation were studied by standard methods in vitro.Measurements and Main Results: Antenatal ETX and antenatal sFlt-1 reduced RAC and decreased RVH in infant rats. In both models, postnatal rhIGF-1/BP3 treatment restored RAC and RVH to normal values when compared with placebo injections. rhIGF-1/BP3 treatment also preserved lung structure and prevented RVH after postnatal hyperoxia. In vitro studies showed that rhIGF-1/BP3 treatment increased lung endothelial cell and alveolar type 2 cell proliferation.Conclusions: Postnatal rhIGF-1/BP3 treatment preserved lung structure and prevented RVH in antenatal and postnatal BPD models. rhIGF-1/BP3 treatment may provide a novel strategy for the prevention of BPD in preterm infants.

Urine gastrin-releasing peptide in the first week correlates with bronchopulmonary dysplasia and post-prematurity respiratory disease

RATIONALE

Bronchopulmonary dysplasia (BPD) is associated with post-prematurity respiratory disease (PRD) in survivors of extreme preterm birth. Identifying early biomarkers that correlate with later development of BPD and PRD may provide insights for intervention. In a preterm baboon model, elevated gastrin-releasing peptide (GRP) is associated with BPD, and GRP inhibition mitigates BPD occurrence.

OBJECTIVE

We performed a prospective cohort study to investigate whether urine GRP levels obtained in the first postnatal week were associated with BPD, PRD, and other urinary biomarkers of oxidative stress.

METHODS

Extremely low gestational age infants (23-28 completed weeks) were enrolled in a US multicenter observational study, The Prematurity and Respiratory Outcomes Program (http://clinicaltrials.gov/ct2/show/NCT01435187). We used multivariable logistic regression to examine the association between urine GRP in the first postnatal week and multiple respiratory outcomes: BPD, defined as supplemental oxygen use at 36 + 0 weeks postmenstrual age, and post-PRD, defined by positive quarterly surveys for increased medical utilization over the first year (PRD score).

RESULTS

A total of 109 of 257 (42%) infants had BPD, and 120 of 217 (55%) had PRD. On adjusted analysis, GRP level more than 80 was associated with BPD (adjusted odds ratio [aOR], 1.83; 95% confidence interval [CI], 1.03-3.25) and positive PRD score (aOR, 2.46; 95% CI, 1.35-4.48). Urine GRP levels correlated with duration of NICU ventilatory and oxygen support and with biomarkers of oxidative stress: allantoin and 8-hydroxydeoxyguanosine.

CONCLUSIONS

Urine GRP in the first postnatal week was associated with concurrent urine biomarkers of oxidative stress and with later diagnoses of BPD and PRD.

A multidisciplinary quality improvement effort to reduce bronchopulmonary dysplasia incidence

BACKGROUND

Bronchopulmonary Dysplasia (BPD) is the most common prematurity complication. Although several practices have been proposed for BPD prevention, none of these in isolation prevent BPD.

METHODS

Our initiative focused on two key drivers: oxygen management and noninvasive ventilation strategies. We created best practice guidelines and followed outcome measures using Shewhart control charts.

RESULTS

PDSAs of protocols preceded a large-scale rollout of a "0.21 by 28" campaign in 2014 leading to a special cause reduction in the "any BPD" rate, and a decrease in severe BPD (from 57 to 29%). At the end of 2017, we reinvigorated the project, which led to dramatic decreases in the "any BPD" rate to 41% and the "severe BPD" rate to 21%.

CONCLUSIONS

A multidisciplinary QI initiative focused on process improvement geared towards the pathophysiological contributors of BPD has successfully reduced the rate of BPD in an all referral level IV NICU.

Intermittent hypoxia and bronchial hyperreactivity

The premature neonate is at high risk for childhood airway hyperreactivity and episodes of wheezing. Intermittent hypoxic events are frequently observed during the first weeks and months of life in these infants. Intermittent hypoxemia has been associated with adverse outcomes in extremely premature infants; including the diagnosis of bronchopulmonary dysplasia, reported wheezing, and use of prescription asthma medications. We review the incidence of intermittent hypoxia, their potential role in short and longer term respiratory morbidity, and the translational newborn models now being used to investigate common pathways by which intermittent hypoxia contributes to respiratory disease.

Bronchopulmonary dysplasia

In the absence of effective interventions to prevent preterm births, improved survival of infants who are born at the biological limits of viability has relied on advances in perinatal care over the past 50 years. Except for extremely preterm infants with suboptimal perinatal care or major antenatal events that cause severe respiratory failure at birth, most extremely preterm infants now survive, but they often develop chronic lung dysfunction termed bronchopulmonary dysplasia (BPD; also known as chronic lung disease). Despite major efforts to minimize injurious but often life-saving postnatal interventions (such as oxygen, mechanical ventilation and corticosteroids), BPD remains the most frequent complication of extreme preterm birth. BPD is now recognized as the result of an aberrant reparative response to both antenatal injury and repetitive postnatal injury to the developing lungs. Consequently, lung development is markedly impaired, which leads to persistent airway and pulmonary vascular disease that can affect adult lung function. Greater insights into the pathobiology of BPD will provide a better understanding of disease mechanisms and lung repair and regeneration, which will enable the discovery of novel therapeutic targets. In parallel, clinical and translational studies that improve the classification of disease phenotypes and enable early identification of at-risk preterm infants should improve trial design and individualized care to enhance outcomes in preterm infants.

Antioxidants & bronchopulmonary dysplasia: Beating the system or beating a dead horse?

Preterm birth is a primary cause of worldwide childhood mortality. Bronchopulmonary dysplasia, characterized by impaired alveolar and lung vascular development, affects 25-50% of extremely low birth weight (BW; <1 kg) infants. Abnormalities in lung function persist into childhood in affected infants and are second only to asthma in terms of childhood respiratory disease healthcare costs. While advances in the medical care of preterm infants have reduced mortality, the incidence of BPD has not decreased in the past 10 years. Reactive oxygen intermediates play a key role in the development of lung disease but, despite promising preclinical therapies, antioxidants have failed to translate into meaningful clinical interventions to decrease the incidence of lung disease in premature infants. In this review we will summarize the state of the art research developments in regards to antioxidants and premature lung disease and discuss the limitations of antioxidant therapies in order to more fully comprehend the reasons why therapeutic antioxidant administration failed to prevent BPD. Finally we will review promising therapeutic strategies and targets.

Bronchopulmonary dysplasia: risk prediction models for very-low- birth-weight infants

OBJECTIVE

Our objective is to develop risk prediction models for moderate/severe bronchopulmonary dysplasia (BPD) and BPD and/or death in very-low-birth-weight infants (VLBWI) at birth, 3, 7, and 14 postnatal days.

STUDY DESIGN

It is a multicenter study including 16,407 infants weighing 500-1500 g (2001-2015) from the Neocosur Network. BPD was defined as oxygen dependency at 36 weeks. Variables were selected using forward logistic regression models. Predictive values were evaluated using the ROC curve.

RESULTS

In total, 2580 (15.7%) presented BPD and 6121 (37.3%) BPD/death. The AUC values for the BPD models were 0.788, 0.818, 0.827, and 0.894 respectively. For BPD/death, the AUC values were 0.860, 0.869, 0.867, and 0.906. BW and gestational age had higher contribution at birth; at later ages, the length of oxygen therapy and ventilation had the highest contribution. All AUC values were statistically significant when compared with a neutral value of 0.5 (p-value < 0.001).

CONCLUSIONS

We developed high predictive power models for moderate/severe BPD and BPD/death at four postnatal ages.

Predicting the likelihood of bronchopulmonary dysplasia in premature neonates

Introduction: Bronchopulmonary dysplasia (BPD) is the most common serious pulmonary morbidity in premature infants. Despite ongoing advances in neonatal care, the incidence of BPD has not improved. A potential explanation for this phenomenon is the limited ability for accurate early prediction of the risk of BPD. BPD continues to represent a therapeutic challenge and no single effective therapy exists for this condition. Areas covered: Here, we review risk factors of BPD derived from clinical data, biological fluid biomarkers, respiratory management data, and scientific advancements using 'omics' technologies, and their ability to predict the pathogenesis of BPD in preterm neonates. Risk factors and biomarkers were identified via literature search with a focus on the last 5 years of data. Expert opinion: The most accurate predictive tools utilize risk factors that encompass a variety of categories. Numerous predictive models have been proposed but suffer from a lack of adequate validation. An ideal model should include multiple, easily measurable variables validated across a heterogeneous population. In addition to evaluating recent BPD prediction models, we suggest approaches to enhance future models.

Rodent models of respiratory control and respiratory system development-Clinical significance

The newborn infant's respiratory system must rapidly adapt to extra-uterine life. Neonatal rat and mouse models have been used to investigate early development of respiratory control and reactivity in both health and disease. This review highlights several rodent models of control of breathing and respiratory system development (including pulmonary function), discusses their translational strengths and limitations, and underscores the importance of creating clinically relevant models applicable to the human infant.

Imbalance of Ly-6Chi and Ly-6Clo Monocytes/Macrophages Worsens Hyperoxia-Induced Lung Injury and Is Rescued by IFN-γ

Inflammation in response to oxygen exposure is a major contributing factor in neonatal lung injury leading to bronchopulmonary dysplasia. Although increased levels of proinflammatory cytokines are seen in airway samples and blood from bronchopulmonary dysplasia patients, the innate immune responses in this common neonatal lung condition have not been well characterized. We previously reported that depletion of murine CD11b-expressing mononuclear phagocytes at birth led to severe acute hyperoxia-induced lung injury (HILI) and significant mortality. In this study, we further define the mononuclear phagocyte populations that are present in the neonatal lung and characterize their responses to hyperoxia exposure. We used myeloid depleter mice (CD11b-DTR and CCR2-DTR) to contrast the effects of depleting different monocyte/macrophage subpopulations on the innate immune response to hyperoxia. Using RNA sequencing and subsequent data analysis, we identified an IFN-γ-mediated role for interstitial monocytes/macrophages in acute HILI, in which decreased IFN-γ expression led to increased disease severity and increased Mmp9 mRNA expression. Importantly, intranasal administration of rIFN-γ largely rescued CD11b-DTR⁺ mice from severe HILI and decreased Mmp9 mRNA expression in Ly-6C^lo and Ly-6C^hi interstitial monocyte/macrophages. We conclude that the proinflammatory effects of hyperoxia exposure are, at least in part, because of the modulation of effectors downstream of IFN-γ by pulmonary monocytes/macrophages.

Human milk as a protective factor for bronchopulmonary dysplasia: a systematic review and meta-analysis

OBJECTIVE

To summarise current evidence evaluating the effects of human milk on the risk of bronchopulmonary dysplasia (BPD) in preterm infants.

DESIGN

We searched for studies on human milk and BPD in English and Chinese databases on 26 July 2017. Furthermore, the references of included studies were also screened. The inclusion criteria in this meta-analysis were the following: (1) preterm infants (<37 weeks); (2) human milk; (3) comparing with formula feeding; (4) the outcome included BPD; and (5) the type of study was randomised controlled trial (RCT) or cohort study.

RESULT

A total of 17 cohort studies and 5 RCTs involving 8661 preterm infants met our inclusion criteria. The ORs and 95% CIs of six groups were as follows: 0.78 (0.68 to 0.88) for exclusive human milk versus exclusive formula group, 0.77 (0.68 to 0.87) for exclusive human milk versus mainly formula group, 0.76 (0.68 to 0.87) for exclusive human milk versus any formula group, 0.78 (0.68 to 0.88) for mainly human milk versus exclusive formula group, 0.83 (0.69 to 0.99) for mainly human milk versus mainly formula group and 0.82 (0.73 to 0.93) for any human milk versus exclusive formula group. Notably, subgroup of RCT alone showed a trend towards protective effect of human milk on BPD but no statistical significance.

CONCLUSION

Both exclusive human milk feeding and partial human milk feeding appear to be associated with lower risk of BPD in preterm infants. The quality of evidence is low. Therefore, more RCTs of this topic are needed.

Neonatal intermittent hypoxemia events are associated with diagnosis of bronchopulmonary dysplasia at 36 weeks postmenstrual age

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a chronic lung disease and major pulmonary complication after premature birth. We have previously shown that increased intermittent hypoxemia (IH) events have been correlated to adverse outcomes and mortality in extremely premature infants. We hypothesize that early IH patterns are associated with the development of BPD.

METHODS

IH frequency, duration, and nadirs were assessed using oxygen saturation (SpO₂) waveforms in a retrospective cohort of 137 extremely premature newborns (<28 weeks gestation). Daily levels of inspired oxygen and mean airway pressure exposures were also recorded.

RESULTS

Diagnosis of BPD at 36 weeks postmenstrual age was associated with increased daily IH, longer IH duration, and a higher IH nadir. Significant differences were detected through day 7 to day 26 of life. Infants who developed BPD had lower mean SpO₂ despite their exposure to increased inspired oxygen and increased mean airway pressure.

CONCLUSIONS

BPD was associated with more frequent, longer, and less severe IH events in addition to increased oxygen and pressure exposure within the first 26 days of life. Early IH patterns may contribute to the development of BPD or aid in identification of neonates at high risk.

Surfactant status and respiratory outcome in premature infants receiving late surfactant treatment

BACKGROUND

Many premature infants with respiratory failure are deficient in surfactant, but the relationship to occurrence of bronchopulmonary dysplasia (BPD) is uncertain.

METHODS

Tracheal aspirates were collected from 209 treated and control infants enrolled at 7-14 days in the Trial of Late Surfactant. The content of phospholipid, surfactant protein B, and total protein were determined in large aggregate (active) surfactant.

RESULTS

At 24 h, surfactant treatment transiently increased surfactant protein B content (70%, p < 0.01), but did not affect recovered airway surfactant or total protein/phospholipid. The level of recovered surfactant during dosing was directly associated with content of surfactant protein B (r = 0.50, p < 0.00001) and inversely related to total protein (r = 0.39, p < 0.0001). For all infants, occurrence of BPD was associated with lower levels of recovered large aggregate surfactant, higher protein content, and lower SP-B levels. Tracheal aspirates with lower amounts of recovered surfactant had an increased proportion of small vesicle (inactive) surfactant.

CONCLUSIONS

We conclude that many intubated premature infants are deficient in active surfactant, in part due to increased intra-alveolar metabolism, low SP-B content, and protein inhibition, and that the severity of this deficit is predictive of BPD. Late surfactant treatment at the frequency used did not provide a sustained increase in airway surfactant.

Early inspired oxygen and intermittent hypoxemic events in extremely premature infants are associated with asthma medication use at 2 years of age

OBJECTIVE

Extremely premature infants are at risk for childhood wheezing. Early respiratory support and intermittent hypoxemia (IH) events may be associated with adverse breathing outcomes.

STUDY DESIGN

A single-center retrospective cohort study of 137 premature infants <28 weeks gestational age characterized the associations of cumulative oxygen, cumulative mean airway pressure, IH, and oxygen saturation (SpO₂) on the primary outcome of prescription asthma medication use at 2-year follow-up. Relative risk was calculated by generalized estimating equations.

RESULTS

Reported asthma medication use was 46%. At 1-3 days of age, elevated cumulative oxygen exposure, increased daily IH, and lower mean SpO₂ (adjusted for gestational age and sex) and increased cumulative mean airway pressure exposure (unadjusted) were associated with asthma medication use.

CONCLUSION

Increased oxygen and frequent IH events during just the first 3 days of age may help identify extremely premature newborns at risk for symptomatic childhood wheezing requiring prescription asthma medications.

Recent advances in antenatal factors predisposing to bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) remains a major cause of late morbidities and death after preterm birth. BPD is characterized by an arrest of vascular and alveolar growth and high risk for pulmonary hypertension; yet mechanisms contributing to its pathogenesis and early strategies to prevent BPD are poorly understood. Strong epidemiologic studies have shown that the "new BPD" reflects the long-lasting impact of antenatal factors on lung development, partly due to placental dysfunction, as reflected in recent data from animal models. Improved understanding of mechanisms through which antenatal stress alters placental function and contributes to BPD may lead to preventive therapies.

Chronic lung disease in preterm infants receiving various modes of noninvasive ventilation at ≤30 weeks' postmenstrual age

Objective: To determine the incidence of chronic lung disease (CLD) in mechanically ventilated infants who were born at <29 weeks' gestational age (GA), extubated to continuous positive airway pressure (CPAP) or nasal intermittent positive pressure ventilation (NIPPV), and treated with CPAP/NIPPV alone, changed to heated humidified high flow nasal cannula (HHHFNC), or exposed to a combination of CPAP/NIPPV and HHHFNC at ≤30 weeks' postmenstrual age (PMA).Study design: Retrospective cohort study of infants born at <29 weeks' GA admitted to tertiary Canadian neonatal intensive care units between 2011 and 2015. Infants were grouped according to the type of noninvasive ventilation they received at ≤30 weeks' PMA: CPAP/NIPPV alone, HHHFNC alone, or a combination of both.Results: Of the 2378 eligible infants, 1091 (46%) were on CPAP/NIPPV alone, 173 (7.3%) were on HHHFNC alone, and 1114 (47%) were on a combination of CPAP/NIPPV and HHHFNC at ≤30 weeks' PMA until weaned to room air or low flow nasal cannula. After adjustment for confounders, infants in both the CPAP/NIPPV (odds ratio [95% confidence interval]; 2.37 [1.18, 4.79]) and Combination (3.47 [2.06, 5.86]) groups had higher odds of developing CLD than infants in the HHHFNC group.Conclusions: Our results demonstrate that infants transitioned to HHHFNC ≤30 weeks' PMA after extubation to CPAP/NIPPV were associated with a lower odds of CLD than infants maintained on CPAP/NIPPV or a combination of CPAP/NIPPV and HHHFNC.

Ancestry and genetic associations with bronchopulmonary dysplasia in preterm infants

Bronchopulmonary dysplasia in premature infants is a common and often severe lung disease with long-term sequelae. A genetic component is suspected but not fully defined. We performed an ancestry and genome-wide association study to identify variants, genes, and pathways associated with survival without bronchopulmonary dysplasia in 387 high-risk infants treated with inhaled nitric oxide in the Trial of Late Surfactant study. Global African genetic ancestry was associated with increased survival without bronchopulmonary dysplasia among infants of maternal self-reported Hispanic white race/ethnicity [odds ratio (OR) = 4.5, P = 0.01]. Admixture mapping found suggestive outcome associations with local African ancestry at chromosome bands 18q21 and 10q22 among infants of maternal self-reported African-American race/ethnicity. For all infants, the top individual variant identified was within the intron of NBL1, which is expressed in midtrimester lung and is an antagonist of bone morphogenetic proteins ( rs372271081 , OR = 0.17, P = 7.4 × 10^-7). The protective allele of this variant was significantly associated with lower nitric oxide metabolites in the urine of non-Hispanic white infants ( P = 0.006), supporting a role in the racial differential response to nitric oxide. Interrogating genes upregulated in bronchopulmonary dysplasia lungs indicated association with variants in CCL18, a cytokine associated with fibrosis and interstitial lung disease, and pathway analyses implicated variation in genes involved in immune/inflammatory processes in response to infection and mechanical ventilation. Our results suggest that genetic variation related to lung development, drug metabolism, and immune response contribute to individual and racial/ethnic differences in respiratory outcomes following inhaled nitric oxide treatment of high-risk premature infants.

Maternal Black Race and Persistent Wheezing Illness in Former Extremely Low Gestational Age Newborns: Secondary Analysis of a Randomized Trial

OBJECTIVE

To evaluate the relationship between maternal self-reported race/ethnicity and persistent wheezing illness in former high-risk, extremely low gestational age newborns, and to quantify the contribution of socioeconomic, environmental, and biological factors on this relationship.

STUDY DESIGN

We assessed persistent wheezing illness determined at 18-24 months corrected (for prematurity) age in survivors of a randomized trial. Parents/caregivers were surveyed for wheeze and inhaled asthma medication use quarterly to 12 months, and at 18 and 24 months. We used multivariable analysis to evaluate the relationship of maternal race to persistent wheezing illness, and identified mediators for this relationship via formal mediation analysis.

RESULTS

Of 420 infants (25.2 ± 1.2 weeks of gestation and 714 ± 166 g at birth, 57% male, 34% maternal black race), 189 (45%) had persistent wheezing illness. After adjustment for gestational age, birth weight, and sex, infants of black mothers had increased odds of persistent wheeze compared with infants of nonblack mothers (OR = 2.9, 95% CI 1.9, 4.5). Only bronchopulmonary dysplasia, breast milk diet, and public insurance status were identified as mediators. In this model, the direct effect of race accounted for 69% of the relationship between maternal race and persistent wheeze, whereas breast milk diet, public insurance status, and bronchopulmonary dysplasia accounted for 8%, 12%, and 10%, respectively.

CONCLUSIONS

Among former high-risk extremely low gestational age newborns, infants of black mothers have increased odds of developing persistent wheeze. A substantial proportion of this effect is directly accounted for by race, which may reflect unmeasured environmental influences, and acquired and innate biological differences.

TRIAL REGISTRATION

ClinicalTrials.gov: NCT01022580.

[Clinical features and prognosis of preterm infants with varying degrees of bronchopulmonary dysplasia]

OBJECTIVE

To study the clinical features and prognosis of preterm infants with varying degrees of bronchopulmonary dysplasia (BPD).

METHODS

The clinical data of 144 preterm infants with a gestational age of <32 weeks who were admitted to the neonatal intensive care unit from March 2014 to March 2016 and were diagnosed with BPD were collected. According to the severity of BPD, these preterm infants were divided into mild group with 81 infants and moderate/severe group with 63 infants. The two groups were compared in terms of perinatal risk factors, treatment, comorbidities, complications, and prognosis of the respiratory system.

RESULTS

Compared with the mild BPD group, the moderate/severe BPD group had a significantly higher gestational age and rate of small-for-gestational-age (SGA) infants (P&lt;0.05), as well as a significantly higher rate of severe preeclampsia and a significantly lower rate of threatened preterm labor (P&lt;0.05). Compared with the mild BPD group, the moderate/severe BPD group had a significantly higher percentage of infants who needed mechanical ventilation at 2 weeks after birth, longer duration of mechanical ventilation, total time of oxygen therapy, and length of hospital stay, and higher incidence rates of pneumonia and cholestasis (P&lt;0.05), as well as a significantly lower application rate of caffeine citrate (P&lt;0.05). The multivariate logistic regression analysis showed that SGA birth (OR=5.974, P&lt;0.05), pneumonia (OR=2.590, P&lt;0.05), and mechanical ventilation required at 2 weeks after birth (OR=4.632, P&lt;0.05) were risk factors for increased severity of BPD. The pulmonary function test performed at the corrected gestational age of 40 weeks showed that compared with the mild BPD group, the moderate/severe BPD group had significantly lower ratio of time to peak tidal expiratory flow to total expiratory time, ratio of volume to peak tidal expiratory flow to total expiratory volume, and tidal expiratory flow at 25% remaining expiration (P&lt;0.05). The infants were followed up to the corrected gestational age of 1 year, and the moderate/severe BPD group had significantly higher incidence rates of recurrent hospital admission for pneumonia and recurrent wheezing (P&lt;0.05).

CONCLUSIONS

SGA birth, pneumonia, and prolonged mechanical ventilation are associated with increased severity of BPD. Infants with moderate or severe BPD have poor pulmonary function and may experience recurrent infection and wheezing.

A Time-Based Analysis of Inflammation in Infants at Risk of Bronchopulmonary Dysplasia

OBJECTIVE

To precisely delineate the timing and contribution of inflammation to bronchopulmonary dysplasia (BPD) in preterm infants during the neonatal period.

STUDY DESIGN

Longitudinal study of blood inflammatory biomarkers (interleukin [IL]-6, IL-8, and granulocyte colony-stimulating factor) measured between birth and 42 days of age, at high temporal (daily) resolution, in infants born at or below 30 weeks of gestation. Cytokine predictors of BPD at 36 weeks postmenstrual age were adjusted for infant-specific and time-dependent factors, using hierarchical mixed effects regressions models.

RESULTS

A total of 1518 data points were obtained in 62 infants (mean gestational age of 27 weeks). Infants who developed BPD later on presented increased inflammation after birth compared with infants without BPD. Inflammation was sustained, with gradual attenuation over 2 weeks (IL-8: OR: 6.5 [95% CI: 1.8-24]; granulocyte colony-stimulating factor: 3.3 [1.5-7.6]) and was higher in boys and in infants of lower birth weight. This inflammation preceded the clinical increased requirement in supplemental oxygen characteristic of BPD, and preceded the peak occurrence of neonatal sepsis or necrotizing enterocolitis.

CONCLUSIONS

Systemic inflammation occurs early in the neonatal period and precedes clinical symptoms in infants with BPD. These data provide a discrete vulnerability window period, supporting a role for targeted intensive care interventions during the early phase of BPD.