Longitudinal assessment of lung function in extremely prematurely born children

AMPK-driven Macrophage Responses Are Autophagy Dependent in Experimental Bronchopulmonary Dysplasia

The pathogenesis of bronchopulmonary dysplasia (BPD) remains incompletely understood. Recent studies suggest insufficient AMP-activated protein kinase (AMPK) activation as a potential cause of impaired autophagy in rodent and nonhuman primate models of BPD. Impaired autophagy is associated with enhanced inflammatory signaling in alveolar macrophages (AMs) and increased severity of murine BPD induced by neonatal hyperoxia exposure. The goal of this study was to determine the role of autophagy and AMPK activation in macrophage responses in murine BPD. C57BL/6J mice were exposed to neonatal hyperoxia starting on postnatal day (P)1 and treated with the AMPK activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) between P3 and P6. Mice were euthanized on P7, and markers of AMPK activation and autophagy were assessed by immunoblotting. Alveolarization was assessed using radial alveolar counts, mean linear intercept measurements, and quantification of alveolar septal myofibroblasts. Relative mRNA expression of M1-like and M2-like genes was assessed in AMs isolated from BAL fluid from wild-type, LysMCre--Becn1fl/fl, and LysMCre+-Becn1fl/fl mice after neonatal hyperoxia exposure. AICAR treatment resulted in AMPK activation and induction of autophagic activity in whole-lung and BAL cell lysates and attenuated hyperoxia-induced alveolar simplification in neonatal lungs. AICAR-treated control but not Beclin1-deficient AMs demonstrated significantly decreased expression of M1-like markers and significantly increased expression of M2-like markers. In conclusion, pharmacologic activation of AMPK by AICAR resulted in induction of autophagy and played a protective role, at least in part, through attenuation of proinflammatory signaling in AMs via autophagy-dependent mechanisms in a murine model of BPD.

Longitudinal changes in lung function in very prematurely born young people receiving high-frequency oscillation or conventional ventilation from birth

OBJECTIVE

To examine changes in lung function over time in extremely prematurely born adolescents.

WORKING HYPOTHESIS

Changes in lung function during adolescence would vary by ventilation mode immediately after birth.

STUDY DESIGN

Longitudinal follow-up study.

PATIENT SUBJECT SELECTION

Participants from the United Kingdom Oscillation Study who were randomized at birth to high-frequency oscillation (HFO) or conventional ventilation (CV) were assessed at 11-14 years (n = 319) and at 16-19 years (n = 159).

METHODOLOGY

Forced expiratory flow (FEF), forced expiratory volume in 1 s (FEV1), forced vital capacity (FVC), and lung volumes including functional residual capacity (FRC) were reported as z-scores. The diffusion capacity of the lungs for carbon monoxide (DLCO) was measured. Lung function trajectories were compared by mode of ventilation using mixed models. Changes in z-scores were scaled to 5-year average follow-up.

RESULTS

There were significant changes in the mean FEF75, FEF50, FEF25, FEV1, FVC, and DLCO z-scores within the CV and HFO cohorts, but no significant differences in the changes between the two groups. The mean FRC z-score increased in both groups, with an average change of greater than one z-score. The mean FEV1/FVC z-score increased significantly in the CV group, but not in the HFO group (difference in slopes: p = 0.02). Across the population, deterioration in lung function was associated with male sex, white ethnicity, lower gestational age at birth, postnatal corticosteroids, oxygen dependency at 36 weeks postmenstrual age, and lower birth weight, but not ventilation mode.

CONCLUSIONS

There was little evidence that the mode of ventilation affected changes in lung function over time.

The Next Frontier of Prematurity: Predicting Respiratory Morbidity During the First Two Years of Life in Extremely Premature Babies

Background

Advances in perinatal and neonatal medicine have led to an increasing number of infants surviving extreme prematurity (≤27 weeks gestational age, GA). The goal of this study was to examine the respiratory outcomes after neonatal intensive care unit (NICU) discharge of this vulnerable population. We hypothesized that the rates of respiratory hospitalizations are disproportionally higher in the subset of infants born ≤27 weeks GA relative to premature infants born 28-32 weeks GA.

Methodology

A retrospective longitudinal study of severe premature children (≤32 weeks GA, n = 183) was conducted. We subdivided our sample into extremely preterm infants (≤27 weeks GA; n = 101) and those born very preterm (28-32 weeks GA; n = 82). Our main outcome was the presence of respiratory hospitalizations within 24 months of NICU discharge.

Results

Extremely premature infants had more than three times higher odds of respiratory hospitalization at 24 months relative to infants born 28-32 weeks GA (adjusted odds ratio = 3.4; 95% confidence interval = 1.8, 6.4; p < 0.01). The increased risk of respiratory hospitalization in extremely premature infants was independent of GA. Regression models identified that the duration of supplemental oxygen and Black/African American ethnicity were significant predictors of respiratory hospitalizations in both prematurity groups independent of gender and birth weight.

Conclusions

The results support that babies born ≤27 weeks GA represent a distinct high-risk group of severely premature infants that needs novel preventive strategies and targeted interventions to improve their respiratory outcomes after NICU discharge.

Respiratory Follow Up of the Premature Neonates-Rationale and Practical Issues

The aim of the review was to present the state of knowledge about the respiratory pathology in former premature neonates (children that were born preterm-before 37 weeks of gestation-and are examined and evaluated after 40 weeks corrected age) other than chronic lung disease, in order to provide reasons for a respiratory follow-up program for this category of patients. After a search of the current evidence, we found that premature infants are prone to long-term respiratory consequences due to several reasons: development of the lung outside of the uterus, leading to dysmaturation of the structures, pulmonary pathology due to immaturity, infectious agents or mechanical ventilation and deficient control of breathing. The medium- to long-term respiratory consequences of being born before term are represented by an increased risk of respiratory infections (especially viral) during the first years of life, a risk of recurrent wheezing and asthma and a decrease in pulmonary volumes and airway flows. Late preterm infants have risks of pulmonary long-term consequences similar to other former premature infants. Due to all the above risks, premature neonates should be followed in an organized fashion, being examined at regular time intervals from discharge from the maternity hospital until adulthood-this could lead to an early detection of the risks and preventive therapies in order to improve their prognosis and assure a normal and productive life. The difficulties related to establishing such programs are represented by the insufficient standardization of the data gathering forms, clinical examinations and lung function tests, but it is our belief that if more premature infants are followed, the experience will allow standards to be established in these fields and the methods of data gathering and evaluation to be unified.

The high-risk factors of different severities of bronchopulmonary dysplasia (BPD) based on the national institute of child health and human development (NICHD) diagnosis criteria in 2018

Objective

To investigate the clinical characteristics of preterm infants with different severities of bronchopulmonary dysplasia (BPD) and disclose the high-risk factors of exacerbating BPD.

Methods

Collection of clinical data of 91 preterm infants admitted to the NICU and diagnosed with BPD, categorized in groups according to the disease severity: 41 mild cases,, 24 moderate cases, and 26 severe cases. Comparison and analysis of perinatal risk factors, treatment, complications and prognosis of the infants with different severity degrees.

Results

The severe group had a higher proportion of infants with congenital heart disease (CHD) higher than the moderate group (P < 0.05), and a higher ratio of pneumonia and mechanical ventilation (MV) ≥ seven days than the mild group (P < 0.05). The severe group also presented higher reintubation incidence than both the mild and moderate groups (P < 0.05). The groups presented different (P < 0.05) incidence rates of hemodynamically significant patent ductus arteriosus (hsPDA) . Ridit analysis suggested that the premature infants (PIs) with hsPDA, multiple microbial pulmonary infections, or Klebsiella pneumoniae pneumonia had more severe illness.

Conclusion

CHD, hsPDA, MV ≥ seven days, reintubation, pneumonia, especially multiple microbial pulmonary infections, and Klebsiella pneumoniae pneumonia are correlated with the severity of BPD and can be used as BPD progression predictor.

Weaning oxygen in infants with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is a form of chronic lung disease commonly seen in preterm infants as the sequelae following respiratory distress syndrome. The management of evolving BPD aims to minimise lung injury and prevent the impact of hypoxia and hyperoxia. Proposed morbidities include respiratory instability, pulmonary hypertension, suboptimal growth, altered cerebral oxygenation and long-term neurodevelopmental impairment. The ongoing management and associated morbidity present a significant burden for carers and healthcare systems. Long-term oxygen therapy may be required for variable duration, though there is a lack of consensus and wide variation in practise when weaning supplemental oxygen. Furthermore, a shift in care towards earlier discharge and community care underlines the importance of a structured discharge and weaning process that eliminates the potential risks associated with hypoxia and hyperoxia. This review article describes recent evidence outlining oxygen saturation reference ranges in young infants, on which structured guidance can be based.

15-Year trends in respiratory care of extremely preterm infants: Contributing factors and consequences on health and growth during hospitalization

OBJECTIVES

To review 15-year trends in respiratory care of extremely preterm infants managed in a tertiary perinatal center; to identify the factors contributing to their evolution; and to determine whether these changes had an impact on infant mortality, severe morbidity, and growth.

METHODS

Retrospective cohort study of infants born at 23 to 26 weeks' gestation between 2003 and 2017. Changes in respiratory care were assessed in three 5-year periods. Logistic regression was used to examine the factors associated with prolonged duration (ie, greater than the median) of invasive mechanical ventilation (IMV), noninvasive ventilation (NIV), and overall respiratory support (ORS), and those associated with adequate weight and head circumference growth.

RESULTS

Of the 396 actively treated neonates, 268 (68%) survived to discharge. Between the first and third periods, IMV duration decreased from 22 (6-37) to 4 (1-14.0) days (P < .001), that of NIV increased from 24 (14-34) to 56 (44-66) days (P < .001), and that of ORS from 50 (34-68) to 63 (52-77) days (P < .001). Study period (2003-2007 vs 2013-2017) was the main factor associated with prolonged IMV (P < .001). Use of high-flow nasal cannula was the main factor associated with prolonged NIV (P = .02) and ORS (P = .02). NIV duration was associated with adequate postnatal weight (P = .003) and head circumference (P = .03) growth. Severe morbidities in survivors, including bronchopulmonary dysplasia, and survival at hospital discharge were comparable across the study periods.

CONCLUSIONS

Respiratory management was characterized by a marked reduction in IMV. NIV withdrawal protocols are necessary to limit ORS duration while respecting postnatal growth requirements.

Small for gestational age birth may increase airflow limitation in bronchopulmonary dysplasia

OBJECTIVES

To determine significant indices for assessing the pulmonary function of infants according to bronchopulmonary dysplasia (BPD) severity and to evaluate whether small for gestational age (SGA) could affect pulmonary function in BPD.

METHODS

We evaluated 117 preterm infants who had undergone tidal breathing flow-volume loop and multiple-breath washout analyses within 7 months after birth. We categorized preterm infants according to BPD severity into mild/moderate BPD (n = 86), severe BPD (n = 21), and without BPD (n = 10) and the presence of SGA or appropriate gestational age (AGA) using the Fenton growth chart. We evaluated nine healthy term infants as controls.

RESULTS

The tidal breathing ratio (time to peak expiratory flow/expiratory time [t_PEF /t_E ]) was significantly lower in infants with severe BPD than in those with mild/moderate BPD. Lung clearance index (LCI) was not different based on BPD severity. In the correlation analysis after adjusting for gestational age and sex, t_PEF /t_E was correlated with the duration of mechanical ventilation (r = -0.347, P < .001) and the duration of oxygen supply (r = -0.248, P = .013) in infants with BPD. The proportion of "lower t_PEF /t_E ," defined as below the cut-off value, was greater in SGA infants (P = .017), while no significant difference was seen in the percentage of "higher LCI," defined as above the cut-off value between SGA and AGA infants.

CONCLUSIONS

In infants with BPD, t_PEF /t_E could be a useful pulmonary index which shows lower values in severe BPD. The finding of SGA in infants with BPD could be associated with poor pulmonary function related to the t_PEF /t_E values.

Predicting Lung Health Trajectories for Survivors of Preterm Birth

Rates of preterm birth (<37 weeks of gestation) are increasing worldwide. Improved perinatal care has markedly increased survival of very (<32 weeks gestation) and extremely (<28 weeks gestation) preterm infants, however, long term respiratory sequalae are common among survivors. Importantly, individual's lung function trajectories are determined early in life and tend to track over the life course. Preterm infants are impacted by antenatal, postnatal and early life perturbations to normal lung growth and development, potentially resulting in significant shifts from the "normal" lung function trajectory. This review summarizes what is currently known about the long-term lung function trajectories in survivors of preterm birth. Further, this review highlights how antenatal, perinatal and early life factors are likely to contribute to individual lung health trajectories across the life course.

Recent advances in our understanding of the mechanisms of lung alveolarization and bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) is the most common cause of morbidity and mortality in preterm infants. A key histopathological feature of BPD is stunted late lung development, where the process of alveolarization-the generation of alveolar gas exchange units-is impeded, through mechanisms that remain largely unclear. As such, there is interest in the clarification both of the pathomechanisms at play in affected lungs, and the mechanisms of de novo alveoli generation in healthy, developing lungs. A better understanding of normal and pathological alveolarization might reveal opportunities for improved medical management of affected infants. Furthermore, disturbances to the alveolar architecture are a key histopathological feature of several adult chronic lung diseases, including emphysema and fibrosis, and it is envisaged that knowledge about the mechanisms of alveologenesis might facilitate regeneration of healthy lung parenchyma in affected patients. To this end, recent efforts have interrogated clinical data, developed new-and refined existing-in vivo and in vitro models of BPD, have applied new microscopic and radiographic approaches, and have developed advanced cell-culture approaches, including organoid generation. Advances have also been made in the development of other methodologies, including single-cell analysis, metabolomics, lipidomics, and proteomics, as well as the generation and use of complex mouse genetics tools. The objective of this review is to present advances made in our understanding of the mechanisms of lung alveolarization and BPD over the period 1 January 2017-30 June 2019, a period that spans the 50th anniversary of the original clinical description of BPD in preterm infants.

Pediatric Pulmonology year in review 2018: Asthma, physiology/pulmonary function testing, and respiratory infections

Pediatric Pulmonology publishes original research, reviews, and case reports related to a wide range of children's respiratory disorders. In our "Year in Review" series, we summarize publications in our major topic areas from 2018, in the context of selected literature in these areas from other journals relevant to our discipline. This review covers selected articles on asthma, physiology/lung function testing, and respiratory infections.

2018 year in review: Part 2 of 4: Neonatal lung disease

Pediatric Pulmonology publishes original research, reviews and case reports related to a wide range of children's respiratory disorders. This review (Part 2 of a 4-part series) summarizes the past year's publications in the topic area of neonatal lung diseases, in the context of selected literature from other journals relevant to the discipline.

Neonatal Pulmonary Magnetic Resonance Imaging of Bronchopulmonary Dysplasia Predicts Short-Term Clinical Outcomes

RATIONALE

Bronchopulmonary dysplasia (BPD) is a serious neonatal pulmonary condition associated with premature birth, but the underlying parenchymal disease and trajectory are poorly characterized. The current National Institute of Child Health and Human Development (NICHD)/NHLBI definition of BPD severity is based on degree of prematurity and extent of oxygen requirement. However, no clear link exists between initial diagnosis and clinical outcomes.

OBJECTIVES

We hypothesized that magnetic resonance imaging (MRI) of structural parenchymal abnormalities will correlate with NICHD-defined BPD disease severity and predict short-term respiratory outcomes.

METHODS

A total of 42 neonates (20 severe BPD, 6 moderate, 7 mild, 9 non-BPD control subjects; 40 ± 3-wk postmenstrual age) underwent quiet-breathing structural pulmonary MRI (ultrashort echo time and gradient echo) in a neonatal ICU-sited, neonatal-sized 1.5 T scanner, without sedation or respiratory support unless already clinically prescribed. Disease severity was scored independently by two radiologists. Mean scores were compared with clinical severity and short-term respiratory outcomes. Outcomes were predicted using univariate and multivariable models, including clinical data and scores.

MEASUREMENTS AND MAIN RESULTS

MRI scores significantly correlated with severities and predicted respiratory support at neonatal ICU discharge (P < 0.0001). In multivariable models, MRI scores were by far the strongest predictor of respiratory support duration over clinical data, including birth weight and gestational age. Notably, NICHD severity level was not predictive of discharge support.

CONCLUSIONS

Quiet-breathing neonatal pulmonary MRI can independently assess structural abnormalities of BPD, describe disease severity, and predict short-term outcomes more accurately than any individual standard clinical measure. Importantly, this nonionizing technique can be implemented to phenotype disease, and has potential to serially assess efficacy of individualized therapies.

Effect of dexamethasone exposure on the neonatal unit on the school age lung function of children born very prematurely

The objective of this study was to determine the impact of postnatal dexamethasone treatment on the neonatal unit on the school age lung function of very prematurely born children. Children born prior to 29 weeks of gestational age had been entered into a randomised trial of two methods of neonatal ventilation (United Kingdom Oscillation Study). They had comprehensive lung function measurements at 11 to 14 years of age. One hundred and seventy-nine children born at a mean gestational age of 26.9 (range 23–28) weeks were assessed at 11 to 14 years; 50 had received postnatal dexamethasone. Forced expiratory flow at 75% (FEF₇₅), 50%, 25% and 25–75% of the expired vital capacity, forced expiratory volume in one second, peak expiratory flow and forced vital capacity and lung volumes including total lung capacity and residual volume were assessed. Lung function outcomes were compared between children who had and had not been exposed to dexamethasone after adjustment for neonatal factors using linear mixed effects regression. After adjustment for confounders all the mean spirometry results were between 0.38 and 0.87 standard deviations lower in those exposed to dexamethasone compared to the unexposed. For example, the mean FEF₇₅ z-score was 0.53 lower (95% CI 0.21 to 0.85). The mean lung function was lower as the number of courses of dexamethasone increased. In conclusion, postnatal dexamethasone exposure was associated with lower mean lung function at school age in children born extremely prematurely. Our results suggest the larger the cumulative dose the greater the adverse effect on lung function at follow-up.

The increased purchase of asthma medication for individuals born preterm seems to wane with age: A register-based longitudinal national cohort study

Introduction

Preterm birth is associated with increased risk of respiratory symptoms in childhood, often treated with asthma medication. We designed a follow-up study to previous research and investigated whether the association of gestational age with purchasing asthma medication diminishes in adulthood.

Methods

We conducted a register-based study of a national cohort of all infants born in Denmark in 1980–2009 evaluating longitudinal data on individually prescribed asthma medication (both inhaled ß-2 receptor agonist and different controller treatment over 2-year periods) available from 1995–2011. We analyzed the effect of gestational age considering age, birth year, and perinatal variables using logistic regression with a Generalized Estimating Equations model. All data were unambiguously linked through the Civil Registration System.

Results

We included 1,819,743 individuals in our study population. We found an inverse dose-response relationship between gestational age and asthma medication in earlier age-groups with a gradual decrease in odds ratios with increasing age and loss of statistical significance in early adulthood (18–31 years). For our oldest generations, there was a significant effect of gestational age (p-value = 0.04), which became insignificant when adjusting for confounding and mediating factors (p = 0.44). There were significant interactions between gestational age and age (p<0.0001) and gestational age and birth year, but these were most important during childhood (0–11 years) and for our youngest generations (born after 1995).

Conclusion

The strong association between gestational age and purchase of prescription asthma medication weakens with age into early adulthood, in consistence with the results from our previous study. The risk for purchasing medication to treat asthma-like symptoms was higher in more recent birth years, but the effect of gestational age was small beyond 11 years of age. Gestational age per se did not seem to be significant for the development of asthma-like symptoms: most of its effect could be explained by other perinatal factors.