Medical Progress Series: Bronchopulmonary Dysplasia at 50 Years-An Introduction

Lung Ultrasonography to Diagnose Bronchopulmonary Dysplasia of Premature Infants

Background: Bronchopulmonary dysplasia (BPD) is a common severe respiratory problem in premature infants, and imaging information has important reference value for its diagnosis. Recently, lung ultrasonography (LUS) has been successfully used for the diagnosis and differential diagnosis of neonatal lung diseases (NLDs), but the study of the diagnosis of BPD is still rare. Objectives: The purpose of this study was to investigate the ultrasonographic characteristics of BPD and its value for the diagnosis and differential diagnosis of premature infants’ BPD. Methods: From January 2015 to December 2019, 25 premature infants diagnosed with early-stage BPD and 32 infants diagnosed with late-stage BPD according to their medical history, clinical manifestation, and chest X-ray were included in this study. The LUS examinations were performed on each infant. The LUS findings were recorded and compared with those of 40 premature infants without lung diseases. Results: The gestational age of 25 early-stage BPD infants was 26+1 – 31+6 weeks, and their birth weight was between 730 and 1,810 g. The gestational age of 32 late-stage BPD infants was 26 - 32 weeks, and their birth weight was 750 - 1,760 g. The gestational age of 40 control infants was 25+6 - 32+1 weeks, and their birth weight was 810 - 2,050 g. There was no difference in the proportion of primary lung diseases (including RDS, TTN, pneumonia, etc.) between the three groups. The proportions of infants receiving invasive and/or non-invasive respiratory support at admission in the three groups of early BPD, late BPD, and normal control were 20/25 (80.0%), 26/32 (81.2%), and 33/40 (77.5%), respectively, with no significant difference (P > 0.05). The mechanical ventilation duration over one week in three groups was 15/20 (75%), 21/26 (80.7%), and 24/33 (72.7%), respectively, with no significant difference (P > 0.05). Nonspecific pleural line abnormalities were seen in all early and late BPD patients (100%), alveolar-interstitial syndrome (AIS) in 16 cases (64%) of early BPD and 32 cases of late BPD infants (100%), pleural insect erosion-like change (PIE-like change) in two cases of early-stage BPD infants (8.0%) and 20 cases (62.5%) of late-stage BPD infants, and air vesicle signs (AVS) only in 17 cases of late-stage BPD infants. The sensitivity and specificity of PIE-like change for the diagnosis of late-stage BPD were 62.5% and 92.0%, respectively, and the sensitivity and specificity of AVS for the diagnosis of late-stage BPD were 53.1 and 100%, respectively. Conclusions: Lung ultrasonography is not specific for the diagnosis of early-stage BPD, but has a high reference value and specificity for the diagnosis of late-stage BPD when combined with obvious pulmonary fibrosis and pulmonary vesicle formation, which is mainly manifested by AIS, PIE-like change, and AVS.

Using a home oxygen weaning protocol and pCO2 to evaluate outcomes for infants with bronchopulmonary dysplasia discharged on home oxygen

BACKGROUND

Predischarge capillary blood gas partial pressure of carbon dioxide (pCO₂ ) has been associated with increased adverse events including readmission. This study aimed to determine if predischarge pCO₂ or 36-week pCO₂ was associated with increased respiratory readmissions or other pulmonary healthcare utilization in the year after neonatal intensive care unit (NICU) discharge for infants with bronchopulmonary dysplasia (BPD) discharged with home oxygen, using a standardized outpatient oxygen weaning protocol.

METHODS

This was a secondary cohort analysis of infants born <32 weeks gestational age with BPD, referred to our clinic for home oxygen therapy from either from our level IV NICU or local level III NICUs between 2015 and 2017. Infants with major nonrespiratory comorbidities were excluded. Subject information was obtained from electronic health records.

RESULTS

Of 125 infants, 120 had complete 1-year follow-up. Twenty-three percent of infants experienced a respiratory readmission after NICU discharge. There was no significant association between predischarge or 36-week pCO₂ and respiratory readmissions, emergency room visits, new or increased bronchodilators, or diuretics. Higher 36-week pCO₂ was associated with a later corrected age when oxygen was discontinued (<6 months; median, 54 mmHg; interquartile range [IQR], 51-61; 6-11 months; median, 62 mmHg; IQR, 57-65; ≥12 months, median, 66 mmHg; IQR, 58-73; p = .006).

CONCLUSIONS

Neither predischarge pCO₂ nor 36-week pCO₂ was associated with 1-year respiratory readmissions. However higher pCO₂ at 36 weeks was associated with a longer duration of home oxygen. Neonatal illness measures like 36-week pCO₂ may be useful in communicating expectations for home oxygen therapy to families.

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.

Mouse genetic background impacts susceptibility to hyperoxia-driven perturbations to lung maturation

BACKGROUND

The laboratory mouse is widely used in preclinical models of bronchopulmonary dysplasia, where lung alveolarization is stunted by exposure of pups to hyperoxia. Whether the diverse genetic backgrounds of different inbred mouse strains impacts lung development in newborn mice exposed to hyperoxia has not been systematically assessed.

METHODS

Hyperoxia (85% O₂ , 14 days)-induced perturbations to lung alveolarization were assessed by design-based stereology in C57BL/6J, BALB/cJ, FVB/NJ, C3H/HeJ, and DBA/2J inbred mouse strains. The expression of components of the lung antioxidant machinery was assessed by real-time reverse transcriptase polymerase chain reaction and immunoblot.

RESULTS

Hyperoxia-reduced lung alveolar density in all five mouse strains to different degrees (C57BL/6J, 64.8%; FVB/NJ, 47.4%; BALB/cJ, 46.4%; DBA/2J, 45.9%; and C3H/HeJ, 35.9%). Hyperoxia caused a 94.5% increase in mean linear intercept in the C57BL/6J strain, whilst the C3H/HeJ strain was the least affected (31.6% increase). In contrast, hyperoxia caused a 65.4% increase in septal thickness in the FVB/NJ strain, where the C57BL/6J strain was the least affected (30.3% increase). The expression of components of the lung antioxidant machinery in response to hyperoxia was strain dependent, with the C57BL/6J strain exhibiting the most dramatic engagement. Baseline expression levels of components of the lung antioxidant systems were different in the five mouse strains studied, under both normoxic and hyperoxic conditions.

CONCLUSION

The genetic background of laboratory mouse strains dramatically influenced the response of the developing lung to hyperoxic insult. This might be explained, at least in part, by differences in how antioxidant systems are engaged by different mouse strains after hyperoxia exposure.

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.