Lung function and respiratory outcomes in teenage boys and girls born very prematurely

Chorioamnionitis and respiratory outcomes in prematurely born children: a systematic review and meta analysis

INTRODUCTION

To conduct a systematic review and meta-analysis of the association between chorioamnionitis and respiratory outcomes of prematurely born children.

CONTENT

Pubmed, Medline and Embase were searched for relevant studies. Studies were included if they assessed prematurely born children, who had been exposed to chorioamnionitis and had either lung function testing or assessment of wheeze or asthma following NICU discharge. Two reviewers independently screened the search results, applied inclusion criteria and assessed methodological quality. One reviewer extracted the data and these were checked by a second reviewer.

SUMMARY

1,237 studies were identified, but only eight which included 35,000 infants, fulfilled the inclusion criteria. One study looked at both lung function results and wheeze or asthma in childhood. Four of five studies found an association between wheeze/asthma in childhood and exposure to chorioamnionitis: the overall Odds Ratio (OR) for developing wheeze/asthma in childhood was OR 1.71 (95 % CI: 1.55-1.89). Four studies looked at lung function in childhood, three of which showed no statistically significant association between chorioamnionitis exposure and altered lung function. One study found lower lung function in those exposed to chorioamnionitis and lower expiratory flows with increasing levels of chorioamnionitis (forced expiratory flow at 50 % of exhaled forced vital capacity (=FEF50) p=0.012, forced expiratory flow at 25-75 % of the forced vital capacity is exhaled (=FEF25-75) p=0.014).

OUTLOOK

There was a significant association between chorioamnionitis and the development of wheeze or asthma in childhood, but overall not in impairment of lung function.

Sex differences in preterm respiratory morbidity: A recent whole-population study

AIM

To determine whether there were differences between male and female infants in respiratory morbidity in a whole population of extremely preterm infants, including infants born below 24 weeks of gestation.

METHODS

Retrospective whole-population study of all infants <28 weeks of gestation admitted to a neonatal unit in England from 2014 to 2019. Bronchopulmonary dysplasia (BPD) development was defined as any respiratory support at 36 weeks postmenstrual age.

RESULTS

The 11 844 infants had a median (IQR) gestational age of 26.0 (24.9-27.1) weeks and a birth weight of 0.81 (0.67-0.96) kg. The duration of invasive ventilation was longer in male compared to female infants who were born at 24-27 completed weeks of gestation (p < 0.001), but not significantly different between male and female infants born at 22 and 23 weeks of gestation (p = 0.446). The incidence of BPD was higher in male compared to female infants born at 24-27 weeks of gestation (p < 0.001) but not different between male and female infants born at 22 and 23 weeks of gestation (p = 0.148).

CONCLUSION

Respiratory morbidity was more pronounced in male compared to female extremely preterms, only in gestations 24-27 completed weeks. Male predominance was absent in infants born below 24 weeks of gestation.

Lung function deficits and bronchodilator responsiveness at 12 years of age in children born very preterm compared with controls born at term

INTRODUCTION

Very preterm birth is associated with lung function impairment later in life, but several aspects have not been studied. We aimed to comprehensively assess lung function at school age in very preterm infants and term controls, with special emphasis on bronchopulmonary dysplasia (BPD), sex, and bronchodilator response.

METHODS

At 12 years of age, 136 children born very preterm (85 with and 51 without BPD) and 56 children born at term performed spirometry, body plethysmography, impulse oscillometry, measurement of diffusion capacity, and multiple breath washout, before and after bronchodilator inhalation.

RESULTS

Airway symptoms and a diagnosis of asthma were more common in children born very preterm. These children had more airflow limitation, seen as lower forced expiratory volume in 1 s (FEV1 ) (p < .001), FEV1 /forced vital capacity (FVC) (p = .011), and mean forced expiratory flow between 25% and 75% of FVC (p < .001), and a higher total and peripheral airway resistance compared with term-born controls. There was no difference in total lung capacity but air trapping and lung clearance index were higher in children born very preterm. Diffusion capacity was lower in children born very preterm, especially in those with a diagnosis of BPD. In most other tests, the differences between preterm-born children with or without BPD were smaller than between children born preterm versus at term. Boys born preterm had more lung function deficits than preterm-born girls. In children born very preterm, airway obstruction was to a large extent reversible.

CONCLUSION

At 12 years of age, children born very preterm had lower lung function than children born at term in most aspects and there was only little difference between children with or without BPD. Airway obstruction improved markedly after bronchodilator inhalation.

Endothelial to mesenchymal transition in neonatal hyperoxic lung injury: role of sex as a biological variable

Bronchopulmonary dysplasia (BPD) is characterized by an arrest in alveolarization, abnormal vascular development, and variable interstitial fibroproliferation in the premature lung. Endothelial to mesenchymal transition (EndoMT) may be a source of pathological fibrosis in many organ systems. Whether EndoMT contributes to the pathogenesis of BPD is not known. We tested the hypothesis that pulmonary endothelial cells will show increased expression of EndoMT markers upon exposure to hyperoxia and that sex as a biological variable will modulate differences in expression. Wild-type (WT) and Cdh5-PAC CreERT2 (endothelial reporter) neonatal male and female mice (C57BL6) were exposed to hyperoxia (0.95 [Formula: see text]) either during the saccular stage of lung development (95% [Formula: see text]; postnatal day 1-5 [PND1-5]) or through the saccular and early alveolar stages of lung development (75% [Formula: see text]; PND1-14). Expression of EndoMT markers was measured in whole lung and endothelial cell mRNA. Sorted lung endothelial cells (from room air- and hyperoxia-exposed lungs) were subjected to bulk RNA-Seq. We show that exposure of the neonatal lung to hyperoxia leads to upregulation of key markers of EndoMT. Furthermore, using lung sc-RNA-Seq data from neonatal lung we were able to show that all endothelial cell subpopulations including the lung capillary endothelial cells show upregulation of EndoMT-related genes. Markers related to EndoMT are upregulated in the neonatal lung upon exposure to hyperoxia and show sex-specific differences. Mechanisms mediating EndoMT in the injured neonatal lung can modulate the response of the neonatal lung to hyperoxic injury and need further investigation.NEW & NOTEWORTHY We show that neonatal hyperoxia exposure increased EndoMT markers in the lung endothelial cells and this biological process exhibits sex-specific differences.

Lung function at 16-19 years in males and females born very prematurely

OBJECTIVES

To determine if there were differences in lung function at 16-19 years of age between males and females born very prematurely.

WORKING HYPOTHESIS

Females compared with males would have superior lung function and exercise capacity.

STUDY DESIGN

Cohort study.

PATIENT-SUBJECT SELECTION

Those born at less than 29 weeks of gestational age.

METHODOLOGY

Lung function testing (spirometry, oscillometry, diffusion capacity, lung clearance index, and plethysmography), a shuttle sprint test for exercise capacity, and a respiratory symptoms questionnaire.

RESULTS

Amongst 150 participants, males had poorer lung function compared with females with mean z score differences (95% CI [confidence interval]) after adjustment: forced expiratory flow at 75% (FEF₇₅ ) (-0.60 [-0.97,-0.24]), forced expiratory flow at 50% (FEF₅₀ ) (-0.39 [-0.72,-0.07]), forced expiratory flow at 25%-75% (FEF_25-75 ) (-0.62 [-0.98,-0.26]), the ratio of the forced expiratory volume in the first one second to the forced vital capacity of the lungs (FEV₁ :FVC ratio) (-0.71 [-1.09,-0.34]), diffusing capacity of the lungs for carbon monoxide (DLCO) (-0.41 [-0.78,-0.03]), diffusing capacity of the lung for carbon monoxide divided by alveolar volume (DLCO/VA) (-0.57 [-0.86,-0.28]). Exercise capacity and self-reported exercise were both significantly better in males than females (46% males achieving between 1250 and 1500 m shuttle sprint distance vs. 4.8% females) and 74% males versus 67% females undertaking some exercise. There were no significant differences by sex in the prevalence of either wheeze or current asthma.

CONCLUSIONS

Males had poorer lung function than females at age 16-19 years, but their exercise capacity was superior to females.

Early origins of respiratory disease

Chronic respiratory morbidity is unfortunately common in childhood, particularly in those born very prematurely or with congenital anomalies affecting pulmonary development and those with sickle cell disease. Our research group, therefore, has focused on the early origins of chronic respiratory disease. This has included assessing antenatal diagnostic techniques and potentially therapeutic interventions in infants with congenital diaphragmatic hernia. Undertaking physiological studies, we have increased the understanding of the premature baby's response to resuscitation and evaluated interventions in the delivery suite. Mechanical ventilation modes have been optimised and randomised controlled trials (RCTs) with short- and long-term outcomes undertaken. Our studies highlighted respiratory syncytial virus lower respiratory tract infections (LRTIs) and other respiratory viral LRTIs had an adverse impact on respiratory outcomes of prematurely born infants, who we demonstrated have a functional and genetic predisposition to respiratory viral LRTIs. We have described the long-term respiratory outcomes for children with sickle cell disease and importantly identified influencing factors. In conclusion, it is essential to undertake long term follow up of infants at high risk of chronic respiratory morbidity if effective preventative strategies are to be developed.

Gender dimension in cardio-pulmonary continuum

Cardio-pulmonary diseases, which were once regarded as a man's illness, have been one of the leading causes of morbidity and mortality for both men and women in many countries in recent years. Both gender and sex influence the functional and structural changes in the human body and therefore play an important role in disease clinical manifestation, treatment choice, and/or response to treatment and prognosis of health outcomes. The gender dimension integrates sex and gender analysis in health sciences and medical research, however, it is still relatively overlooked suggesting the need for empowerment in the medical research community. Latest advances in the field of cardiovascular research have provided supportive evidence that the application of biological variables of sex has led to the understanding that heart disease in females may have different pathophysiology compared to males, particularly in younger adults. It has also resulted in new diagnostic techniques and a better understanding of symptomatology, while gender analysis has informed more appropriate risk stratification and prevention strategies. The existing knowledge in the pulmonary field shows the higher prevalence of pulmonary disorders among females, however, the role of gender as a socio-cultural construct has yet to be explored for the implementation of targeted interventions. The purpose of this review is to introduce the concept of gender dimension and its importance for the cardiopulmonary continuum with a focus on shared pathophysiology and disease presentation in addition to interrelation with chronic kidney disease. The review presents basic knowledge of what gender dimension means, and the application of sex and gender aspects in cardiovascular medicine with a specific focus on early pulmonary development, pulmonary hypertension, and chronic obstructive pulmonary disease (COPD). Early vascular aging and inflammation have been presented as a potential pathophysiological link, with further interactions between the cardiopulmonary continuum and chronic kidney disease. Finally, implications for potential future research have been provided to increase the impact of gender dimension on research excellence that would add value to everybody, foster toward precision medicine and ultimately improve human health.

Sex Differences in Patent Ductus Arteriosus Incidence and Response to Pharmacological Treatment in Preterm Infants: A Systematic Review, Meta-Analysis and Meta-Regression

A widely accepted concept in perinatal medicine is that boys are more susceptible than girls to complications of prematurity. However, whether this ‘male disadvantage of prematurity’ also involves persistent patent ductus arteriosus (PDA) has been scarcely investigated. Our aim was to conduct a systematic review and meta-analysis on studies addressing sex differences in the risk of developing PDA among preterm infants. We also investigated whether the response to pharmacological treatment of PDA differs between boys and girls. PubMed/Medline and Embase databases were searched. The random-effects male/female risk ratio (RR) and 95% confidence interval (CI) were calculated. We included 146 studies (357,781 infants). Meta-analysis could not demonstrate sex differences in risk of developing any PDA (37 studies, RR 1.03, 95% CI 0.97 to 1.08), hemodynamically significant PDA (81 studies, RR 1.00, 95% CI 0.97 to 1.02), or in the rate of response to pharmacological treatment (45 studies, RR 1.01, 95% CI 0.98 to 1.04). Subgroup analysis and meta-regression showed that the absence of sex differences was maintained over the years and in different geographic settings. In conclusion, both the incidence of PDA in preterm infants and the response rate to pharmacological treatment of PDA are not different between preterm boys and girls.

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.

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.

2020 year in review: Neonatal pulmonology

Pediatric Pulmonology publishes original research, reviews, and case reports related to a wide range of children's respiratory disorders. This review summarizes the past year's publications in the topic area of neonatal pulmonology, in the context of selected literature from other journals relevant to the discipline.

Male Disadvantage in Oxidative Stress-Associated Complications of Prematurity: A Systematic Review, Meta-Analysis and Meta-Regression

A widely accepted concept is that boys are more susceptible than girls to oxidative stress-related complications of prematurity, including bronchopulmonary dysplasia (BPD), retinopathy of prematurity (ROP), necrotizing enterocolitis (NEC), intraventricular hemorrhage (IVH), and periventricular leukomalacia (PVL). We aimed to quantify the effect size of this male disadvantage by performing a systematic review and meta-analysis of cohort studies exploring the association between sex and complications of prematurity. Risk ratios (RRs) and 95% CIs were calculated by a random-effects model. Of 1365 potentially relevant studies, 41 met the inclusion criteria (625,680 infants). Male sex was associated with decreased risk of hypertensive disorders of pregnancy, fetal distress, and C-section, but increased risk of low Apgar score, intubation at birth, respiratory distress, surfactant use, pneumothorax, postnatal steroids, late onset sepsis, any NEC, NEC > stage 1 (RR 1.12, CI 1.06–1.18), any IVH, severe IVH (RR 1.28, CI 1.22–1.34), severe IVH or PVL, any BPD, moderate/severe BPD (RR 1.23, CI 1.18–1.27), severe ROP (RR 1.14, CI 1.07–1.22), and mortality (RR 1.23, CI 1.16–1.30). In conclusion, preterm boys have higher clinical instability and greater need for invasive interventions than preterm girls. This leads to a male disadvantage in mortality and short-term complications of prematurity.

Intrauterine growth retardation and lung function of very prematurely born young people

OBJECTIVES

To assess if intrauterine growth retardation (IUGR) was associated with reduced lung function at 16-19 years.

WORKING HYPOTHESIS

Very prematurely born young people who had IUGR would have reduced lung function postpuberty.

STUDY DESIGN

Prospective follow-up study.

PATIENT-SUBJECT SELECTION

One hundred and fifty-nine 16-19 year olds born before 29 weeks of gestation; 37 had IUGR.

METHODOLOGY

Lung function tests were performed: spirometry was used to assess forced expiratory volume in one second (FEV1), forced expiratory flow at 75%, 50% and 25% of expired vital capacity (FEF75, FEF50 and FEF25), peak expiratory flow (PEF) and forced vital capacity (FVC). Functional residual capacity (FRCpleth) total lung capacity (TLCpleth) and residual volume (RVpleth) were measured. Alveolar function was assessed by diffusion capacity within the lungs of carbon monoxide (DLCO). Impulse oscillometry was used to assess respiratory resistance and lung clearance index to assess ventilation homogeneity. Exercise capacity was assessed using a shuttle sprint test.

RESULTS

After adjustment for BMI, the mean FEV-1/FVC, FEF75, FEF25-75, FRCpleth and RVpleth were poorer in those who had had IUGR, with differences between 0.56 and 0.75 z-scores. After further adjustment for BPD and postnatal corticosteroid use, only the difference in RVpleth z-scores remained statistically significant, adjusted difference (95% CI): 0.66 (0.18,1.13). Exercise capacity was lower in those with IUGR and this was more pronounced in males (p=0.04).

CONCLUSIONS

At 16-19 years of age, those who had IUGR had poorer lung function and exercise capacity compared with those with adequate intrauterine growth.

Sex and Gender Differences in Lung Disease

Sex differences in the anatomy and physiology of the respiratory system have been widely reported. These intrinsic sex differences have also been shown to modulate the pathophysiology, incidence, morbidity, and mortality of several lung diseases across the life span. In this chapter, we describe the epidemiology of sex differences in respiratory diseases including neonatal lung disease (respiratory distress syndrome, bronchopulmonary dysplasia) and pediatric and adult disease (including asthma, cystic fibrosis, idiopathic pulmonary fibrosis, chronic obstructive pulmonary disease, lung cancer, lymphangioleiomyomatosis, obstructive sleep apnea, pulmonary arterial hypertension, and respiratory viral infections such as respiratory syncytial virus, influenza, and SARS-CoV-2). We also discuss the current state of research on the mechanisms underlying the observed sex differences in lung disease susceptibility and severity and the importance of considering both sex and gender variables in research studies' design and analysis.