Tracking of lung function from 10 to 35 years after being born extremely preterm or with extremely low birth weight

Ventilatory responses to independent and combined hypoxia, hypercapnia and hypobaria in healthy pre-term-born adults

Pre-term birth is associated with physiological sequelae that persist into adulthood. In particular, modulated ventilatory responsiveness to hypoxia and hypercapnia has been observed in this population. Whether pre-term birth per se causes these effects remains unclear. Therefore, we aimed to assess pulmonary ventilation and blood gases under various environmental conditions, comparing 17 healthy prematurely born individuals (mean ± SD; gestational age, 28 ± 2 weeks; age, 21 ± 4 years; peak oxygen uptake, 48.1 ± 11.2 ml kg-1 min-1) with 16 well-matched adults born at term (gestational age, 40 ± 1 weeks; age, 22 ± 2 years; peak oxygen uptake, 51.2 ± 7.7 ml kg-1 min-1). Participants were exposed to seven combinations of hypoxia/hypobaria (equivalent to ∼3375 m) and/or hypercapnia (3% CO2), at rest for 6 min. Pulmonary ventilation, pulse oxygen saturation and the arterial partial pressures of O2 and CO2 were similar in pre-term and full-term individuals under all conditions. Higher ventilation in hypoxia compared to normoxia was only observed at terrestrial altitude, despite an equivalent (normobaric) hypoxic stimulus administered at sea level (0.138F i O 2 ${F_{{\mathrm{i}}{{\mathrm{O}}_{\mathrm{2}}}}}$ ). Assessment of oscillations in key variables revealed that combined hypoxic hypercapnia induced greater underlying fluctuations in ventilation in pre-term individuals only. In general, higher pulse oxygen saturation fluctuations were observed with hypoxia, and lower fluctuations in end-tidal CO2 with hypercapnia, despite similar ventilatory oscillations observed between conditions. These findings suggest that healthy prematurely born adults display similar overall ventilation to their term-born counterparts under various environmental stressors, but that combined ventilatory stimuli could induce an irregular underlying ventilatory pattern. Moreover, barometric pressure may be an important factor when assessing ventilatory responsiveness to moderate hypoxic stimuli. KEY POINTS: Evidence exists for unique pulmonary and respiratory function under hypoxic conditions in adult survivors of pre-term birth. Whether pre-term birth per se causes these differences requires a comparison of conventionally healthy prematurely born adults with an appropriately matched sample of term-born individuals. According to the present data, there is no difference between healthy pre-term and well-matched term-born individuals in the magnitude of pulmonary ventilation or arterial blood gases during independent and combined hypobaria, hypoxia and hypercapnia. Terrestrial altitude (hypobaria) was necessary to induce differences in ventilation between normoxia and a hypoxic stimulus equivalent to ∼3375 m of altitude. Furthermore, peak power in pulse oxygen saturation was similar between hypobaric normoxia and normobaric hypoxia. The observed similarities between groups suggest that ventilatory regulation under various environmental stimuli is not impaired by pre-term birth per se. Instead, an integrated combination of neonatal treatment strategies and cardiorespiratory fitness/disease status might underlie previously observed chemosensitivity impairments.

Flexible bronchoscopy in preterm infants with bronchopulmonary dysplasia: findings and complications in a matched control study

Bronchopulmonary dysplasia (BPD) poses a significant challenge as the most common late morbidity of preterm infants. This study aimed to evaluate airway abnormalities in infants with BPD who underwent flexible bronchoscopy (FB) to gain insights into the prevalence of upper airway obstruction and associated complications. A retrospective case-control study was conducted on BPD patients who underwent FB at a tertiary center between 2013 and 2023. BPD patients were matched (1:3) with a reference group based on age, gender, and ethnicity, who also had undergone FB. Demographic data, comorbidities, indications for FB, findings, and complications during and after FB were collected. The study included 50 BPD patients (mean age 1.26 ± 0.9 years, 58% males), and 150 controls. As expected, BPD patients had a lower gestational age, lower birth weight, and longer hospitalizations and were treated with more medications. Abnormal bronchoscopy findings were significantly more common in the BPD group compared to the reference group, with an increased rate of turbinate hypertrophy (OR [95% CI]: 3.44 [1.27-9.37], P = 0.014), adenoid hypertrophy (OR: 2.7 [1.38-5.29], P = 0.004), lingual tonsils (OR: 5.44 [1.29-27.4], P = 0.0024), subglottic stenosis (OR: 6.95 [2.08-27.1], P = 0.002), and tracheomalacia (OR: 2.98 [1.06-8.19], P = 0.034). Complications including desaturation (OR: 3.89 [1.32-11.7], P = 0.013) and PICU admission (OR: 16.6 [2.58-322], P = 0.011) were more frequent in the BPD than in the reference group.

CONCLUSION

The study revealed a high prevalence of structural anomalies leading to upper airway obstruction and complications in infants with BPD undergoing FB. These findings emphasize the importance of careful consideration and preparation for bronchoscopic procedures in this vulnerable population.

WHAT IS KNOWN

• Bronchopulmonary dysplasia (BPD) represents the most prevalent late morbidity among preterm infants. • Preterm infants diagnosed with BPD frequently undergo diagnostic procedures, including flexible and rigid bronchoscopies, to identify structural pathologies within the respiratory tract.

WHAT IS NEW

• A significantly higher prevalence of structural anomalies leading to upper airway obstruction was observed in the BPD group compared to controls. • The incidence of complications during flexible bronchoscopy was higher in the BPD group than in controls.

Impaired lung function and associated risk factors in children born prematurely: a systematic review and meta-analysis

BACKGROUND

Immature lung development and respiratory morbidity place preterm-born children at high risk of long-term pulmonary sequelae. This systematic review and meta-analysis aims to quantify lung function in preterm-born children and identify risk factors for a compromised lung function.

METHODS

We searched MEDLINE, Embase, Cochrane Library, Web of Science and Scopus for relevant studies published on preterm cohorts born since 1990. Studies comparing forced expiratory volume in 1 s (FEV1) in preterm-born children aged ≥5 years to term-born controls or normative data were included. Study quality was assessed using the Newcastle-Ottawa Scale for cohort studies. Standardised mean differences in FEV1 and secondary spirometry outcomes per study were pooled using meta-analysis. The impact of different demographic and neonatal variables on studies' FEV1 effect sizes was investigated by meta-regression analyses. Certainty of evidence was assessed using the Grading of Recommendations, Assessment, Development, and Evaluations framework.

RESULTS

We identified 42 studies with unique cohorts including 4743 preterm children and 9843 controls. Median gestational age in the studies was 28.0 weeks and age at assessment ranged from 6.7 to 16.7 years. Preterm children had lower FEV1 than controls (-0.58 sd, 95% CI -0.69- -0.47 sd, p<0.001) resulting in a relative risk of 2.9 (95% CI 2.4-3.4) for abnormal outcome, with high certainty of evidence. FEV1 was significantly associated with gestational age, birthweight, bronchopulmonary dysplasia and invasive mechanical ventilation in univariate meta-regression analyses (R2=36-96%).

CONCLUSION

This systematic review shows robust evidence of impaired lung function in preterm-born children with a high certainty of evidence.

Effects of preterm birth on the pattern of altitude acclimatization at rest and during moderate-intensity exercise across three days at 3,375 m

Preterm birth elicits long-lasting physiological effects in various organ systems, potentially modulating exercise and environmental stress responses. To establish whether prematurely-born adults respond uniquely during early high-altitude acclimatization at rest and during exercise, 17 healthy adults born preterm (gestational age < 32 wk) and 17 term-born, age- and aerobic-capacity-matched, control participants completed a three-day high-altitude sojourn (3,375 m). Oxygen uptake, pulmonary ventilation, and hemodynamic responses, as well as pulse oxygen saturation, brain tissue saturation index (TSI), and skeletal muscle TSI, were measured daily at rest and during moderate-intensity steady-state exercise bouts. In general, the prematurely-born group displayed comparable acclimatization responses at rest, with similar ventilation and cardiac output observed between groups throughout. Resting brain TSI was, however, higher in the preterm group upon arrival at high altitude (72 ± 7% vs. 68 ± 3%; d = 1.20). Absolute exercising oxygen uptake was lower in the preterm participants (P = 0.047), with this group displaying lower exercising cardiac output underpinned by reduced stroke volume (both P = 0.035). Nevertheless, exercising minute ventilation (V̇e) did not differ between groups (P = 0.237) while brain TSI (70 ± 6% vs. 66 ± 3%; d = 1.35) and pulse oxygen saturation (85 ± 3% vs. 82 ± 5%; d = 1.52) were higher with prematurity upon arrival to high altitude. These findings suggest that healthy prematurely-born adults exhibit comparable early acclimatization patterns to their term-born counterparts and better maintain cerebral oxygenation at rest. Together, these data suggest that prematurely-born adults should not be discouraged from high-altitude sojourns involving physical activity.NEW & NOTEWORTHY The acclimatization pattern across three days at 3,375 m, at rest and during moderate-intensity exercise, was similar between healthy adults born prematurely and their term-born counterparts. Preterm adults free from respiratory complications were found to better maintain brain tissue and capillary oxygen saturation at high altitudes, whereas the term-born group experienced larger altitude-induced reductions. Despite apparent cardiac limitations, preterm individuals tolerated exercise similarly to their term-born peers. These findings underscore the notion that preterm birth per se does not predispose healthy adults to decreased altitude tolerance during exercise.

Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD) is a chronic lung disease, associated with premature birth, that arises during the infantile period. It is an evolving disease process with an unchanged incidence due to advancements in neonatal care which allow for the survival of premature infants of lower gestational ages and birth weights. Currently, there are few effective interventions to prevent BPD. However, careful attention to BPD phenotypes and comprehensive care provided by an interdisciplinary team have improved care. Interventions early in the disease course hold promise for improving long-term survival and outcomes in adulthood for this high-risk population.

Outcome-based Definition of the Lower Limit of Normal in Spirometry: A Study of 26,000 Young Adult Men

Rationale: The definition of the lower limit of normal (LLN) of spirometric variables is not well established. Objectives: To investigate the relationship between spirometric abnormalities defined with different thresholds of the LLN and clinical outcomes and to explore the possibility of using different LLN thresholds according to the pretest probability of disease. Methods: We studied the associations between prebronchodilator spirometric abnormalities (forced expiratory volume in the first second [FEV1] < LLN, forced vital capacity [FVC] < LLN, airflow obstruction, spirometric restriction) defined with different thresholds of the LLN (10th, 5th, 2.5th, 1st percentile) and multiple outcomes (prevalence of spirometric abnormalities, respiratory symptoms, all-cause and respiratory mortality) in 26,091 30- to 46-year-old men who participated in a general population survey in Norway in 1988-1990 and were followed for 26 years. Analyses were performed with both local and Global Lung Function Initiative (GLI)-2012 reference equations, stratified by pretest risk (presence or absence of respiratory symptoms), and adjusted for age, body mass index, smoking, and education. Results: In the total population, the prevalence of airflow obstruction was 11.6% with GLI-LLN10, 11.0% with Local-LLN5, 6.1% with GLI-LLN5, 7.6% with Local-LLN2.5, and 3.5% with GLI-LLN2.5. The prevalence of spirometric restriction was 5.9% with GLI-LLN10, 5.2% with Local-LLN5, and 2.8% with GLI-LLN5. Increasingly lower thresholds of the LLN were associated with increasingly higher odds of respiratory symptoms and hazard of mortality for all spirometric abnormalities with both reference equations. Spirometric abnormalities defined with Local-LLN2.5 in asymptomatic subjects were associated with lower hazard of all-cause mortality (hazard ratio [HR], 1.50; 95% confidence interval [CI], 1.15-1.95 for FEV1 < LLN) than those defined with Local-LLN5 in the general population (HR, 1.67; 95% CI, 1.50-1.87 for FEV1 < LLN) and symptomatic subjects (HR, 1.67; 95% CI, 1.46-1.91 for FEV1 < LLN). Overall, the prevalence of spirometric abnormalities and associations with outcomes obtained with Local-LLN5 were comparable to those obtained with GLI-LLN10 and those obtained with Local-LLN2.5 to GLI-LLN5. Conclusions: There is a relationship between statistically based thresholds of the LLN of spirometric variables and clinical outcomes. Different thresholds of the LLN may be used in different risk subgroups of subjects, but the choice of the threshold needs to be evaluated together with the choice of reference equations.

Changes in Lung Function Among Infants Born Extremely Preterm over a 20-Year Period in the Post-Surfactant Era: A Retrospective Study

Lung function was assessed at 8 years in 308 infants born extremely preterm between 1994 and 2013. Although lung function of those infants born at 22 through 25 weeks remained unchanged, those who were born at 26-27 weeks showed a significant improvement over the past 2 decades.

Pulmonary function and bronchopulmonary dysplasia classification: insights from the Spanish Registry

In 2016, the Spanish Research Group on Bronchopulmonary Dysplasia (BPD) (GEIDIS) established a national registry with participation of 66 hospitals to collect information on clinical characteristics and long-term outcomes of BPD infants into adulthood. The aim of this observational study is to examine forced spirometry data in early childhood and to assess their correlation with the respiratory support required at 36 weeks postmenstrual age (PMA). The study analyzed data from preterm infants with BPD born between January 2016 and December 2017 who underwent forced spirometry at 5-7 years of age. Statistical analyses were conducted to investigate the relationships between spirometry results, perinatal factors, and the required respiratory support at 36 weeks PMA. The study involved 143 patients with a median gestational age (GA) of 27.3 weeks (range 25.7-28.7) and a median weight of 880 g (range 740-1135). Abnormal spirometry results were observed in 39.2% (56) of the patients. Among patients diagnosed with BPD type 3, those requiring over 30% oxygen at 36 weeks PMA exhibited an increased risk of abnormal spirometry results (OR 4.48; 95% CI 1.11-18.13) compared to those requiring positive pressure with less than 30% oxygen. In addition, this subgroup had a higher risk of developing a restrictive-mixed pattern compared to those with BPD type 1 (OR 10.65; 95% CI 2.06-54.98) and BPD type 2 (OR 6.76; 95% CI 1.09-42.06). No significant differences were found in the incidence of an obstructive pattern between BPD types.      Conclusion: The requirement of more than 30% oxygen at 36 weeks PMA serves as a risk indicator for pulmonary function impairment in school-aged children with BPD. These findings suggest persistent airway and parenchymal injury in this specific patient population, and highlight the importance of careful monitoring to evaluate their long-term effects on lung function. What is Known: • Premature patients with bronchopulmonary dysplasia (BPD) may present abnormalities in pulmonary function tests during school age. However, the predictive accuracy of consensus BPD severity classification remains uncertain. What is New: • The requirement of more than 30% oxygen at 36 weeks postmenstrual age (PMA) indicates a potential risk of pulmonary function impairment in school-aged children with BPD. Additionally, a significant correlation has been observed between a restrictive-mixed pattern with exposure to mechanical ventilation and the development of severe forms of BPD.

Health-related quality of life in two birth cohorts of extremely preterm born adults

AIM

Investigate potential long-term cohort influences on health-related quality of life (HRQoL) in adults born extremely preterm (EP) during the 1980-90s, in view of advancements in neonatal care within that timeframe.

METHODS

Two cohorts of EP-born adults (82-85 cohort and 91-92 cohort) enrolling matched term controls, were compared. Participants were assessed at 18 years and again in their mid-twenties using the Child Health Questionnaire Children Form-87 (CHQ-CF87) and the Short Form Health Survey (SF-36).

RESULTS

At 18 years, 77 (90%) EP-born and 75 (93%) term controls had data, followed by 67 (78%) EP-born and 66 (82%) term controls in their mid-twenties. At 18 years, there were no differences across the birth decades, and EP-born and term-born reported relatively similar HRQoL scores. In the mid-twenties, birth decade did also not significantly impact HRQoL scores, although the EP-born 82-85 cohort scored numerically poorer than the 91-92 cohort in three domains. Term controls scored similarly across birth decade in all domains. Regarding influence from neonatal factors, postnatal corticosteroids had a negative impact in some domains.

CONCLUSION

No significant differences in HRQoL were observed between EP-born adults from the 82-85 cohort versus the 91-92 cohort, although the EP-born 82-85 cohort tended to score poorer in their mid-twenties.

Expiratory airflow limitation in adults born extremely preterm: A systematic review and meta-analysis

Extreme preterm (EP) birth, denoting delivery before the onset of the third trimester, interrupts intrauterine development and causes significant early-life pulmonary trauma, thereby posing a lifelong risk to respiratory health. We conducted a systematic review and meta-analysis to investigate adult lung function following EP birth (gestational age <28 weeks); comparing forced expiratory volume in first second (FEV1), forced vital capacity (FVC), and FEV1/FVC to reference values. Subgroup differences were explored based on timing of birth relative to surfactant use (1991) and bronchopulmonary dysplasia (BPD) status. Systematic searches were performed in Medline, EMBASE, Web of Science and Cochrane Central. Quality assessments were carried out using a modified Newcastle-Ottawa Scale for cohort studies. Sixteen studies encompassing 1036 EP-born adults were included, with 14 studies (n = 787) reporting data as %predicted, and 11 (n = 879) as z-score (not mutually exclusive). Overall mean [95 % confidence interval (CI)] %FEV1 was 85.30 (82.51; 88.09), %FVC was 94.33 (91.74; 96.91), and FEV1/FVC was 79.54 (77.71 to 81.38), all three with high heterogeneity. Overall mean (95 %CI) zFEV1 was -1.05 (-1.21; -0.90) and zFVC was. -0.45 (-0.59; -0.31), both with moderate heterogeneity. Subgroup analyses revealed no difference in FEV1 before versus after widespread use of surfactant, but more impairments after neonatal BPD. This meta-analysis revealed significant airflow limitation in EP-born adults, mostly explained by those with neonatal BPD. FEV1 was more reduced than FVC, and FEV1/FVC was at the lower limit of normal. Although at a group level, most adult EP-born individuals do not meet COPD criteria, these findings are concerning.

Long-term pulmonary outcomes in BPD throughout the life-course

Respiratory disease is one of the most common complications of preterm birth. Survivors of prematurity have increased risks of morbidities and mortalities independent of prematurity, and frequently require multiple medications, home respiratory support, and subspecialty care to maintain health. Although advances in neonatal and pulmonary care have improved overall survival, earlier gestational age, lower birth weight, chorioamnionitis and late onset sepsis continue to be major factors in the development of bronchopulmonary dysplasia. These early life events associated with prematurity can have respiratory consequences that persist into adulthood. Furthermore, after initial hospital discharge, air pollution, respiratory tract infections and socioeconomic status may modify lung growth trajectories and influence respiratory outcomes in later life. Given that the incidence of respiratory disease associated with prematurity remains stable or increased, there is a need for pediatric and adult providers to be familiar with the natural history, manifestations, and common complications of disease.

Unravelling the respiratory health path across the lifespan for survivors of preterm birth

Many survivors of preterm birth will have abnormal lung development, reduced peak lung function and, potentially, an increased rate of physiological lung function decline, each of which places them at increased risk of chronic obstructive pulmonary disease across the lifespan. Current rates of preterm birth indicate that by the year 2040, around 50 years since the introduction of surfactant therapy, more than 700 million individuals will have been born prematurely-a number that will continue to increase by about 15 million annually. In this Personal View, we describe current understanding of the impact of preterm birth on lung function through the life course, with the aim of putting this emerging health crisis on the radar for the respiratory community. We detail the potential underlying mechanisms of prematurity-associated lung disease and review current approaches to prevention and management. Furthermore, we propose a novel way of considering lung disease after preterm birth, using a multidimensional model to determine individual phenotypes of lung disease-a first step towards optimising management approaches for prematurity-associated lung disease.

Prophylactic sildenafil to prevent bronchopulmonary dysplasia: A systematic review and meta-analysis

BACKGROUND

Bronchopulmonary dysplasia (BPD) persists as one of the foremost factors contributing to mortality and morbidity in extremely preterm infants. The effectiveness of administering sildenafil early on to prevent BPD remains uncertain. The aim of this study was to investigate the efficacy and safety of prophylactically administered sildenafil during the early life stages of preterm infants to prevent mortality and BPD.

METHODS

MEDLINE, Embase, Cochrane Central Register of Controlled Trials, Cumulative Index to Nursing and Allied Health Literature, and Ichushi were searched. Published randomized controlled trials (RCTs), non-RCTs, interrupted time series, cohort studies, case-control studies, and controlled before-and-after studies were included. Two reviewers independently screened the title, abstract, and full text, extracted data, assessed the risk of bias, and evaluated the certainty of evidence (CoE) following the Grading of Recommendations Assessment and Development and Evaluation approach. The random-effects model was used for a meta-analysis of RCTs.

RESULTS

This review included three RCTs (162 infants). There were no significant differences between the prophylactic sildenafil and placebo groups in mortality (risk ratio [RR]: 1.32; 95% confidence interval [CI]: 0.16-10.75; very low CoE), BPD (RR: 1.20; 95% CI: 0.79-1.83; very low CoE), and all other outcome assessed (all with very low CoE). The sample sizes were less than the optimal sizes for all outcomes assessed, indicating the need for further trials.

CONCLUSIONS

The prophylactic use of sildenafil in individuals at risk of BPD did not indicate any advantageous effects in terms of mortality, BPD, and other outcomes, or increased side effects.

Obstructive and restrictive spirometry from school age to adulthood: three birth cohort studies

Background

Spirometric obstruction and restriction are two patterns of impaired lung function which are predictive of poor health. We investigated the development of these phenotypes and their transitions through childhood to early adulthood.

Methods

In this study, we analysed pooled data from three UK population-based birth cohorts established between 1989 and 1995. We applied descriptive statistics, regression modelling and data-driven modelling to data from three population-based birth cohorts with at least three spirometry measures from childhood to adulthood (mid-school: 8-10 years, n = 8404; adolescence: 15-18, n = 5764; and early adulthood: 20-26, n = 4680). Participants were assigned to normal, restrictive, and obstructive spirometry based on adjusted regression residuals. We considered two transitions: from 8-10 to 15-18 and from 15-18 to 20-26 years.

Findings

Obstructive phenotype was observed in ∼10%, and restrictive in ∼9%. A substantial proportion of children with impaired lung function in school age (between one third in obstructive and a half in restricted phenotype) improved and achieved normal and stable lung function to early adulthood. Of those with normal lung function in school-age, <5% declined to adulthood. Underweight restrictive and obese obstructive participants were less likely to transit to normal. Maternal smoking during pregnancy and current asthma diagnosis increased the risk of persistent obstruction and worsening. Significant associate of worsening in restrictive phenotypes was lower BMI at the first lung function assessment. Data-driven methodologies identified similar risk factors for obstructive and restrictive clusters.

Interpretation

The worsening and improvement in obstructive and restrictive spirometry were observed at all ages. Maintaining optimal weight during childhood and reducing maternal smoking during pregnancy may reduce spirometry obstruction and restriction and improve lung function.

Funding

MRC Grant MR/S025340/1.

Evidence for Wnt signaling's central involvement in perinatal nicotine exposure-induced offspring lung pathology and its modulation by electroacupuncture

OBJECTIVE

Many factors during pregnancy can induce intrauterine growth restriction (IUGR), resulting in various adverse perinatal outcomes such as low birth weight and multiple organ disorders. Among these factors, prenatal smoke/nicotine exposure is a common cause of IUGR, often associated with altered fetal lung development. The classical Wnt signaling pathway plays a vital role in lung development, and its alterations are commonly associated with developmental lung pathologies. The purpose of this study was to determine whether electroacupuncture (EA) at "Zusanli" (ST 36) points protects perinatal nicotine exposure (PNE)-induced offspring lung dysplasia through Wnt/β-catenin signaling pathway and to identify specific Wnt signaling pathway targets of EA.

METHODS

Following a well-established protocol, nicotine (1 mg/kg/ body weight) was administered subcutaneously to pregnant Sprague Dawley rat dams from gestational day 6 to postnatal day 21. In the EA group, dams were treated with EA at both ST 36 acupoints, while in another experimental group, Wnt/β-catenin signaling pathway agonist was injected subcutaneously (2 mg/kg/ body weight). Offspring body weight (PND 1, 7, 14, and 21), lung weight, Wnt signaling markers, pulmonary function, and lung morphology were determined at sacrifice on PND 21. Specifically, Western blotting and Real-time PCR were used to detect the protein and mRNA levels of critical Wnt signaling markers Wnt2, Wnt7b, FZD4, FZD7, LRP5, and LRP6 in the offspring lung. The protein levels of β-catenin in lung tissue of offspring rats were detected by ELISA that of LEF-1 by Western blotting.

RESULTS

Compared to the control group, the body and lung weights of the offspring rats were significantly decreased in the nicotine-only exposed group. The pulmonary function determined as FVC, PEF, TV, and Cdyn was also significantly decreased, while PIF was significantly increased. The protein levels and mRNA expression of Wnt2, Wnt7b, FZD4, FZD7, LRP5, and LRP6 in the lung tissue of the PNE offspring rats were significantly increased. With EA administration at ST 36 acupoints concomitant with nicotine administration, the body and lung weights, pulmonary function (FVC, PEF, PIF, TV, and Cdyn), protein and mRNA levels Wnt signaling pathway markers (Wnt2, Wnt7b, FZD4, FZD7, LRP5, LRP6, β-catenin, and LEF-1) normalized and were not different from the control group. Notably, Wnt agonists agonist administration blocked the protective effects of EA against PNE-induced lung morphological, molecular, and function changes, highlighting the central significance of Wnt pathway signaling in PNE-induced offspring pulmonary pathology and its modulation by EA at ST 36 acupoints.

CONCLUSION

Concomitant maternal EA at ST 36 acupoints from gestational day 6 to PND 21 protects against offspring PNE-induced lung phenotype. The protective effect is achieved by regulating the expression of Wnt ligand proteins (Wnt2 and Wnt7b) and receptor proteins (FZD4, FZD7, LRP5, and LRP6) upstream of the Wnt/β-catenin signaling pathway intermediates β-catenin, and LEF-1.

Risk factors for poorer respiratory outcomes in adolescents and young adults born preterm

RATIONALE

The respiratory outcomes for adult survivors of preterm birth in the postsurfactant era are wide-ranging with prognostic factors, especially those encountered after the neonatal period, poorly understood.

OBJECTIVES

To obtain comprehensive 'peak' lung health data from survivors of very preterm birth and identify neonatal and life-course risk factors for poorer respiratory outcomes in adulthood.

METHODS

127 participants born ≤32 weeks gestation (64%, n=81 with bronchopulmonary dysplasia (BPD), initially recruited according to a 2 with-BPD:1 without-BPD strategy), and 41 term-born controls completed a lung health assessment at 16-23 years, including lung function, imaging and symptom review. Risk factors assessed against poor lung health included neonatal treatments, respiratory hospitalisation in childhood, atopy and tobacco smoke exposure.

MEASUREMENTS AND MAIN RESULTS

Young adults born prematurely had greater airflow obstruction, gas trapping and ventilation inhomogeneity, in addition to abnormalities in gas transfer and respiratory mechanics, compared with term. Beyond lung function, we observed greater structural abnormalities, respiratory symptoms and inhaled medication use. A previous respiratory admission was associated with airway obstruction; mean forced expiratory volume in 1 s/forced vital capacity z-score was -0.561 lower after neonatal confounders were accounted for (95% CI -0.998 to -0.125; p=0.012). Similarly, respiratory symptom burden was increased in the preterm group with a respiratory admission, as was peribronchial thickening (6% vs 23%, p=0.010) and bronchodilator responsiveness (17% vs 35%, p=0.025). Atopy, maternal asthma and tobacco smoke exposure did not influence lung function or structure at 16-23 years in our preterm cohort.

CONCLUSIONS

Even after accounting for the neonatal course, a respiratory admission during childhood remained significantly associated with reduced peak lung function in the preterm-born cohort, with the largest difference seen in those with BPD. A respiratory admission during childhood should, therefore, be considered a risk factor for long-term respiratory morbidity in those born preterm, especially for individuals with BPD.

Evidence of abnormality in glutathione metabolism in the airways of preterm born children with a history of bronchopulmonary dysplasia

Preterm-born children are at risk of long-term pulmonary deficits, including those who developed bronchopulmonary dysplasia (BPD) in infancy, however the underlying mechanisms remain poorly understood. We characterised the exhaled breath condensate (EBC) metabolome from preterm-born children, both with and without BPD. Following spirometry, EBC from children aged 7-12 years, from the Respiratory Health Outcomes in Neonates study, were analysed using Time-of-Flight Mass Spectrometry. Metabolite Set Enrichment Analysis (MSEA) linked significantly altered metabolites to biological processes. Linear regression models examined relationships between metabolites of interest and participant demographics. EBC was analysed from 214 children, 144 were born preterm, including 34 with BPD. 235 metabolites were detected, with 38 above the detection limit in every sample. Alanine and pyroglutamic acid were significantly reduced in the BPD group when compared to preterm controls. MSEA demonstrated a reduction in glutathione metabolism. Reduced quantities of alanine, ornithine and urea in the BPD group were linked with alteration of the urea cycle. Linear regression revealed significant associations with BPD when other characteristics were considered, but not with current lung function parameters. In this exploratory study of the airway metabolome, preterm-born children with a history of BPD had changes consistent with reduced antioxidant mechanisms suggesting oxidative stress.

Microbial signatures in amniotic fluid at preterm birth and association with bronchopulmonary dysplasia

BACKGROUND

Microbiome dysbiosis can have long-lasting effects on our health and induce the development of various diseases. Bronchopulmonary dysplasia (BPD) is a multifactorial disease with pre- and postnatal origins including intra-amniotic infection as main risk factor. Recently, postnatal pathologic lung microbiota colonization was associated with BPD. The objectives of this prospective observational cohort study were to describe differences in bacterial signatures in the amniotic fluid (AF) of intact pregnancies without clinical signs or risk of preterm delivery and AF samples obtained during preterm deliveries and their variations between different BPD disease severity stages.

METHODS

AF samples were collected under sterile conditions during fetal intervention from intact pregnancies (n = 17) or immediately before preterm delivery < 32 weeks (n = 126). Metabarcoding based approaches were used for the molecular assessment of bacterial 16S rRNA genes to describe bacterial community structure.

RESULTS

The absolute amount of 16S rRNA genes was significantly increased in AF of preterm deliveries and detailed profiling revealed a reduced alpha diversity and a significant change in beta diversity with a reduced relative abundance of 16S rRNA genes indicative for Lactobacillus and Acetobacter while Fusobacterium, Pseudomonas, Ureaplasma and Staphylococcus 16S rRNA gene prevailed. Although classification of BPD by disease severity revealed equivalent absolute 16S rRNA gene abundance and alpha and beta diversity in no, mild and moderate/severe BPD groups, for some 16S rRNA genes differences were observed in AF samples. Bacterial signatures of infants with moderate/severe BPD showed predominance of 16S rRNA genes belonging to the Escherichia-Shigella cluster while Ureaplasma and Enterococcus species were enriched in AF samples of infants with mild BPD.

CONCLUSIONS

Our study identified distinct and diverse intrauterine 16S rRNA gene patterns in preterm infants immediately before birth, differing from the 16S rRNA gene signature of intact pregnancies. The distinct 16S rRNA gene signatures at birth derive from bacteria with varying pathogenicity to the immature lung and are suited to identify preterm infants at risk. Our results emphasize the prenatal impact to the origins of BPD.

The role of oxygen in the development and treatment of bronchopulmonary dysplasia

Oxygen (O2) is crucial for both the development and treatment of one of the most important consequences of prematurity: bronchopulmonary dysplasia (BPD). In fetal life, the hypoxic environment is important for alveolar development and maturation. After birth, O2 becomes a double-edged sword. While O2 is needed to prevent hypoxia, it also causes oxidative stress leading to a plethora of morbidities, including retinopathy and BPD. The advent of continuous O2 monitoring with pulse oximeters has allowed clinicians to recognize the narrow therapeutic margins of oxygenation for the preterm infant, but more knowledge is needed to understand what these ranges are at different stages of the preterm infant's life, including at birth, in the neonatal intensive care unit and after hospital discharge. Future research, especially in innovative technologies such as automated O2 control and remote oximetry, will improve the understanding and treatment of the O2 needs of infants with BPD.

Gestational age at birth and hospitalisations for infections among individuals aged 0-50 years in Norway: a longitudinal, register-based, cohort study

Background

Preterm birth is associated with increased risk of childhood infections. Whether this risk persists into adulthood is unknown and limited information is available on risk patterns across the full range of gestational ages.

Methods

In this longitudinal, register-based, cohort study, we linked individual-level data on all individuals born in Norway (January 01, 1967-December 31, 2016) to nationwide hospital data (January 01, 2008-December 31, 2017). Gestational age was categorised as 23-27, 28-31, 32-33, 34-36, 37-38, 39-41, and 42-44 completed weeks. The analyses were stratified by age at follow-up: 0-11 months and 1-5, 6-14, 15-29, and 30-50 years. The primary outcome was hospitalisation due to any infectious disease, with major infectious disease groups as secondary outcomes. Adjusted hospitalisation rate ratios (RRs) for any infection and infectious disease groups were estimated using negative binomial regression. Models were adjusted for year of birth, maternal age at birth, parity, and sex, and included an offset parameter adjusted for person-time at risk.

Findings

Among 2,695,830 individuals with 313,940 hospitalisations for infections, we found a pattern of higher hospitalisation risk in lower gestational age groups, which was the strongest in childhood but still evident in adulthood. Comparing those born very preterm (28-31) and late preterm (34-36) to full-term (39-41 weeks), RRs (95% confidence interval) for hospitalisation for any infectious disease at ages 1-5 were 3.3 (3.0-3.7) and 1.7 (1.6-1.8), respectively. At 30-50 years, the corresponding estimates were 1.4 (1.2-1.7) and 1.2 (1.1-1.3). The patterns were similar for the infectious disease groups, including bacterial and viral infections, respiratory tract infections (RTIs), and infections not attributable to RTIs.

Interpretation

Increasing risk of hospitalisations for infections in lower gestational age groups was most prominent in children but still evident in adolescents and adults. Possible mechanisms and groups that could benefit from vaccinations and other prevention strategies should be investigated.

Funding

St. Olav's University Hospital and Norwegian University of Science and Technology, Norwegian Research Council, Liaison Committee for education, research and innovation in Central Norway, European Commission, Academy of Finland, Sigrid Jusélius Foundation, Foundation for Pediatric Research, and Signe and Ane Gyllenberg Foundation.

An Update on Lung Function of Extremely and Very Preterm Infants in Later Life: The Role of Early Nutritional Interventions

Birth occurring at ≤32 weeks' gestation ("very preterm") or at ≤28 weeks' gestation ("extremely preterm") potentially poses considerable health problems for the neonate, including respiratory sequelae, not only during the immediate newborn period, but throughout childhood and into adulthood. With the progressive improvements in neonatal care, the survival of extremely preterm and very preterm neonates has improved substantially. However, a considerable percentage of these infants suffer dysfunctions that may trigger, at some stage later in life, the onset of respiratory morbidities. The interruption of the normal development of the respiratory tract caused by preterm birth, in combination with postnatal lung injury caused by various interventions, e.g., mechanical ventilation and oxygen therapy, increases the risk ofthe development of long-term respiratory deficits in survivors. Those infants that are most affected are those who develop chronic lung disease of prematurity (also called bronchopulmonary dysplasia, BPD), but impaired lung function can develop irrespective of BPD diagnosis. Apart from indicating abnormal lung function in survivors of extreme prematurity, recent long-term follow-up studies also emphasize the crucial role of early nutritional intake as an effective strategy, which promotes lung growth and repair. This article will update the associations between extremely/very preterm birth with long-term respiratory outcomes. It will also discuss the protective effect of nutritional interventions, focusing on recently published follow-up data.

Development and Disorders of the Airway in Bronchopulmonary Dysplasia

Bronchopulmonary dysplasia (BPD), a disorder characterized by arrested lung development, is a frequent cause of morbidity and mortality in premature infants. Parenchymal lung changes in BPD are relatively well-characterized and highly studied; however, there has been less emphasis placed on the role that airways disease plays in the pathophysiology of BPD. In preterm infants born between 22 and 32 weeks gestation, the conducting airways are fully formed but still immature and therefore susceptible to injury and further disruption of development. The arrest of maturation results in more compliant airways that are more susceptible to deformation and damage. Consequently, neonates with BPD are prone to developing airway pathology, particularly for patients who require intubation and positive-pressure ventilation. Airway pathology, which can be divided into large and small airways disease, results in increased respiratory morbidity in neonates with chronic lung disease of prematurity.

Increasing airway obstruction through life following bronchopulmonary dysplasia: a meta-analysis

Background

Few studies exist investigating lung function trajectories of those born preterm; however growing evidence suggests some individuals experience increasing airway obstruction throughout life. Here we use the studies identified in a recent systematic review to provide the first meta-analysis investigating the impact of preterm birth on airway obstruction measured by the forced expiratory volume in 1 s (FEV1) to forced vital capacity (FVC) ratio.

Methods

Cohorts were included for analysis if they reported FEV1/FVC in survivors of preterm birth (<37 weeks' gestation) and control populations born at term. Meta-analysis was performed using a random effect model, expressed as standardised mean difference (SMD). Meta-regression was conducted using age and birth year as moderators.

Results

55 cohorts were eligible, 35 of which defined groups with bronchopulmonary dysplasia (BPD). Compared to control populations born at term, lower values of FEV1/FVC were seen in all individuals born preterm (SMD -0.56), with greater differences seen in those with BPD (SMD -0.87) than those without BPD (SMD -0.45). Meta-regression identified age as a significant predictor of FEV1/FVC in those with BPD with the FEV1/FVC ratio moving -0.04 sds away from the term control population for every year of increased age.

Conclusions

Survivors of preterm birth have significantly increased airway obstruction compared to those born at term with larger differences in those with BPD. Increased age is associated with a decline in FEV1/FVC values suggesting increased airway obstruction over the life course.

Myocardial function including estimates of myocardial work in young adults born very preterm or with extremely low birthweight - a cohort study

BACKGROUND

Preterm birth and low birthweight have been associated with increased risk of heart failure and cardiovascular disease in young adulthood. However, results from clinical studies of myocardial function are not consistent. Echocardiographic strain analyses allow detection of early stages of cardiac dysfunction, and non-invasive estimates of myocardial work can provide additional information on cardiac function. We aimed to evaluate left ventricular (LV) myocardial function including measures of myocardial work in young adults born very preterm (gestational age < 29 weeks) or with extremely low birthweight (< 1000 g) (PB/ELBW), compared with term-born age- and sex matched controls.

METHODS

63 PB/ELBW and 64 controls born in Norway in the periods 1982-1985, 1991-1992, and 1999-2000 were examined with echocardiography. LV ejection fraction (EF) and LV global longitudinal strain (GLS) were measured. Myocardial work was estimated from LV pressure-strain loops after determination of GLS and construction of a LV pressure curve. Diastolic function was evaluated by determination of the presence or absence of elevated LV filling pressure, including measures of left atrial longitudinal strain.

RESULTS

The PB/ELBW with mean birthweight 945 (standard deviation (SD) 217) grams, mean gestational age 27 (SD 2) weeks, and mean age 27 (SD 6) years had LV systolic function mainly within normal range. Only 6% had EF < 50% or impaired GLS >-16%, but 22% had borderline impaired GLS between - 16% and - 18%. Mean GLS in PB/ELBW (-19.4% (95% confidence interval (CI) -20.0, -18.9)) was impaired compared to controls (-20.6% (95% CI -21.1, -20.1)), p = 0.003. Lower birthweight was associated to more impaired GLS (Pearson correlation coefficient - 0.2). Means of EF, measures of diastolic function including left atrial reservoir strain, global constructive and wasted work, global work index and global work efficiency was similar in PB/ELBW and controls.

CONCLUSION

The young adults born very preterm or with extremely low birthweight had impaired LV-GLS compared to controls, although systolic function mainly within normal range. Lower birthweight was associated with more impaired LV-GLS. These findings could indicate an elevated lifetime risk of developing heart failure in preterm born individuals. Measures of diastolic function and myocardial work were similar compared to controls.

Use of impulse oscillometry to assess lung function in prematurely born children and young people: Comparisons with spirometry

Premature birth is a risk factor for bronchopulmonary dysplasia (BPD); both of which are associated with obstructive airway disease throughout childhood. Impulse oscillometry (IOS) is an effort-independent, passive measure of tidal breathing, which could have benefits in assessing lung function amongst younger patients unable to perform valid spirometry. A literature search was conducted to investigate the use of IOS in prematurely born children and young people. IOS results correlate with those of spirometry. Reversibility of airway obstruction in children with BPD is variable. IOS could have benefits in assessing individual patient response and suitability for bronchodilator therapy. More work, however, is required to establish multi-ethnic reference ranges and standardise commercially available devices prior to its routine incorporation into clinical practice.

The prevention and management strategies for neonatal chronic lung disease

INTRODUCTION

Survival from even very premature birth is improving, but long-term respiratory morbidity following neonatal chronic lung disease (bronchopulmonary dysplasia (BPD)) has not reduced. Affected infants may require supplementary oxygen at home, because they have more hospital admissions particularly due to viral infections and frequent, troublesome respiratory symptoms requiring treatment. Furthermore, adolescents and adults who had BPD have poorer lung function and exercise capacity.

AREAS COVERED

Antenatal and postnatal preventative strategies and management of infants with BPD. A literature review was undertaken using PubMed and Web of Science.

EXPERT OPINION

There are effective preventative strategies which include caffeine, postnatal corticosteroids, vitamin A, and volume guarantee ventilation. Side-effects, however, have appropriately caused clinicians to reduce use of systemically administered corticosteroids to infants only at risk of severe BPD. Promising preventative strategies which need further research are surfactant with budesonide, less invasive surfactant administration (LISA), neurally adjusted ventilatory assist (NAVA) and stem cells. The management of infants with established BPD is under-researched and should include identifying the optimum form of respiratory support on the neonatal unit and at home and which infants will most benefit in the long term from pulmonary vasodilators, diuretics, and bronchodilators.