Airway function measurements and the long-term follow-up of survivors of preterm birth with and without chronic lung disease

Cardiopulmonary exercise testing in adolescence following extremely premature birth

BACKGROUND

Although extremely premature birth disrupts lung development, adolescent survivors of extreme prematurity show good clinical and physiologic outcomes. Cardiopulmonary limitations may not be clinically evident at rest. Data regarding exercise limitation in adolescents following preterm birth in the postsurfactant era are limited.

RESEARCH QUESTION

What are the long-term effects of bronchopulmonary dysplasia (BPD) and extreme prematurity (<29 weeks) on ventilatory response during exercise in adolescents in the postsurfactant era?

STUDY DESIGN AND METHODS

We followed a longitudinally recruited cohort of children aged 13-19 years who were born at a gestational age of <29 weeks (study group - SG). We compared the cardiopulmonary exercise testing (CPET) results of those with and without BPD, to their own CPET results from elementary school age (mean 9.09 ± 1.05 years).

RESULTS

Thirty-seven children aged 15.73 ± 1.31 years, mean gestational age 26 weeks ( ± 1.19), completed the study. CPET parameters in adolescence were within the normal range for age, including mean V̇O2 peak of 91% predicted. The BPD and non-BPD subgroups had similar results. In the longitudinal analysis of the SG, improvement was observed in adolescence, compared with elementary school age, in breathing reserve (36.37 ± 18.99 vs. 26.58 ± 17.92, p = 0.044), tidal volume as a fraction of vital capacity achieved at maximal load (0.51 ± 0.13 vs. 0.37 ± 0.08, p < 0.001), and respiratory exchange ratio at maximal load (1.18 ± 0.13 vs. 1.11 ± 0.10, p = 0.021).

INTERPRETATION

In the current cohort, adolescents born extremely premature have essentially normal ventilatory response during exercise, unrelated to BPD diagnosis. CPET results in this population improve over time.

Are Babies Born Preterm High-Risk Asthma Candidates?

Among preterm infants, the risk of developing asthma is a matter of debate. This review discusses the state of the art of poorly understood prematurity-associated asthma. Impaired pulmonary function is common in children born prematurely. Preterm infants are prone to developing viral respiratory tract infections, bronchiolitis in the first year of life, and recurrent viral wheezing in preschool age. All of these conditions may precede asthma development. We also discuss the role of both atopic sensitization and intestinal microbiome and, consequently, immune maturation. Diet and pollution have been considered to better understand how prematurity could be associated with asthma. Understanding the effect of factors involved in asthma onset may pave the way to improve the prediction of this asthma phenotype.

Preterm Birth, Developmental Smoke/Nicotine Exposure, and Life-Long Pulmonary Sequelae

This review delineates the main pulmonary issues related to preterm birth, perinatal tobacco/nicotine exposure, and its effects on offspring, focusing on respiratory health and its possible transmission to subsequent generations. We review the extent of the problem of preterm birth, prematurity-related pulmonary effects, and the associated increased risk of asthma later in life. We then review the impact of developmental tobacco/nicotine exposure on offspring asthma and the significance of transgenerational pulmonary effects following perinatal tobacco/nicotine exposure, possibly via its effects on germline epigenetics.

Lifelong Lung Sequelae of Prematurity

The clinical, functional, and structural pattern of chronic lung disease of prematurity has changed enormously in last years, mirroring a better perinatal management and an increasing lung immaturity with the survival of increasingly premature infants. Respiratory symptoms and lung function impairment related to prematurity seem to improve over time, but premature birth increases the likelihood of lung function impairment in late childhood, predisposing to chronic obstructive pulmonary disease (COPD). It is mandatory to identify those individuals born premature who are at risk for developing long-term lung disease through a better awareness of physicians, the use of standardized CT imaging scores, and a more comprehensive periodic lung function evaluation. The aim of this narrative review was to provide a systematic approach to lifelong respiratory symptoms, lung function impairment, and lung structural anomalies in order to better understand the specific role of prematurity on lung health.

Time-Specific Factors Influencing the Development of Asthma in Children

Susceptibility to asthma is complex and heterogeneous, as it involves both genetic and environmental insults (pre- and post-birth) acting in a critical window of development in early life. According to the Developmental Origins of Health and Disease, several factors, both harmful and protective, such as nutrition, diseases, drugs, microbiome, and stressors, interact with genotypic variation to change the capacity of the organism to successfully adapt and grow in later life. In this review, we aim to provide the latest evidence about predictive risk and protective factors for developing asthma in different stages of life, from the fetal period to adolescence, in order to develop strategic preventive and therapeutic interventions to predict and improve health later in life. Our study shows that for some risk factors, such as exposure to cigarette smoke, environmental pollutants, and family history of asthma, the evidence in favor of a strong association of those factors with the development of asthma is solid and widely shared. Similarly, the clear benefits of some protective factors were shown, providing new insights into primary prevention. On the contrary, further longitudinal studies are required, as some points in the literature remain controversial and a source of debate.

Glutathione reductase deficiency alters lung development and hyperoxic responses in neonatal mice

Cellular antioxidants protect against hyperoxic lung injury. The role of the glutathione (GSH) system in lung development and bronchopulmonary dysplasia (BPD) pathogenesis has not been systematically investigated. The current study utilized GSH reductase-deficient (Gsr-KO) neonatal mice to test the hypothesis that early disruption of the GSH system negatively impacts lung development and hyperoxic responses. Lungs from wild-type (Gsr-WT) and Gsr-KO mice were analyzed for histopathology, developmental markers, redox indices, and transcriptome profiling at different developmental stages following exposure to room air or hyperoxia (85% O2) for up to 14 d. Lungs from Gsr-KO mice exhibited alveolar epithelial dysplasia in the embryonic and neonatal periods with relatively normal lung architecture in adulthood. GSH and its oxidized form (GSSG) were 50-70% lower at E19-PND14 in Gsr-KO lungs than in age-matched Gsr-WT. Differential gene expression between Gsr-WT and Gsr-KO lungs was analyzed at discrete developmental stages. Gsr-KO lungs exhibited downregulated cell cycle and DNA damage checkpoint genes at E19, as well as lung lipid metabolism and surfactant genes at PND5. In addition to abnormal baseline lung morphometry, Gsr-KO mice displayed a blunted response to hyperoxia. Hyperoxia caused a more robust upregulation of the lung thioredoxin system in Gsr-KO compared to Gsr-WT. Gsr-dependent, hyperoxia-responsive genes were highly associated with abnormal cytoskeleton, skeletal-muscular function, and tissue morphology at PND5. Overall, our data in Gsr-KO mice implicate the GSH system as a key regulator of lung development, cellular differentiation, and hyperoxic responses in neonatal mice.

Palivizumab Following Extremely Premature Birth Does Not Affect Pulmonary Outcomes in Adolescence

BACKGROUND

Prematurity is a risk factor for impaired lung function. We sought to assess the long-term effect of palivizumab immunization and extreme prematurity (<29 weeks gestation) on respiratory symptoms and pulmonary function in adolescence.

RESEARCH QUESTION

What is the long-term effect of palivizumab immunization and extreme prematurity (<29 weeks) on respiratory symptoms and pulmonary function in adolescence?

STUDY DESIGN AND METHODS

We examined survivors of extreme prematurity (<29 weeks gestation) at 13 to 18 years of age (study group). Study group babies who were born immediately before palivizumab immunization (nonpalivizumab group [NPG]) were compared with those babies who were born just after implementation (PG) and with a control group. For study group patients, lung function in adolescence was further compared longitudinally with that at primary school age.

RESULTS

Sixty-four adolescents aged 15.76 ± 1.52 years were included: 46 in the study group (17 PG and 29 NPG) and 18 in the control group. For the study group, wheezing episodes, inhaler use, and hospitalizations were uncommon. For the study group compared with the control group, FEV₁ percent predicted was 82.60% ± 13.54% vs 105.83% ± 13.12% (P < .001), and the lung clearance index was 7.67 ± 1.02 vs 7.46 ± 0.70 (P = .48), respectively. Study group adolescents with bronchopulmonary dysplasia had a higher lung clearance index than did adolescents with no bronchopulmonary dysplasia (7.94 ± 1.11 vs 7.20 ± 0.60; P = .002). PG and NPG adolescents were not significantly different. Comparing the study group in adolescence with primary school age, we found improvement in mean FEV₁ percent predicted bronchodilator response (0.37% ± 9.98% vs 5.67% ± 9.87%; P = .036) and mean provocative concentration causing 20% decline in FEV₁ (12.16 ± 4.71 mg/mL vs 4.14 ± 4.51 mg/mL, respectively; P < .001).

INTERPRETATION

Palivizumab did not provide any discernable long-term protective effect. Nevertheless, adolescent survivors of extreme prematurity showed good clinical and physiologic outcomes, except for mildly raised lung clearance index in patients with bronchopulmonary dysplasia. Airway hyperreactivity detected at primary school age, decreased by adolescence.

Lung Function of Adults Born at Very Low Birth Weight

BACKGROUND

Much remains unknown about the consequences of very low birth weight (VLBW) and bronchopulmonary dysplasia (BPD) on adult lungs. We hypothesized that VLBW adults would have impaired lung function compared with controls, and those with a history of BPD would have worse lung function than those without.

METHODS

At age 26 to 30 years, 226 VLBW survivors of the New Zealand VLBW cohort and 100 term controls born in 1986 underwent lung function tests including spirometry, plethysmographic lung volumes, diffusing capacity of the lung for carbon monoxide, and single-breath nitrogen washout (SBN₂).

RESULTS

An obstructive spirometry pattern was identified in 35% VLBW subjects versus 14% controls, with the majority showing mild obstruction. Compared with controls, VLBW survivors demonstrated significantly lower forced expiratory volume in 1 second (FEV₁), FEV₁/forced vital capacity (FVC) ratio (FEV₁/FVC), forced expiratory flow at 25% to 75% of FVC and higher residual volume (RV), RV/total lung capacity (TLC) ratio (RV/TLC), decreased diffusing capacity of the lung for carbon monoxide, and increased phase III slope for SBN₂. The differences persisted after adjustment for sex and smoking status. Within the VLBW group, subjects with BPD showed significant reduction in FEV₁, FEV₁/FVC, and forced expiratory flow at 25% to 75% of FVC, and increase in RV, RV/TLC, and phase III slope for SBN₂, versus subjects without. The differences remained after adjustment for confounders.

CONCLUSIONS

Adult VLBW survivors showed a higher incidence of airflow obstruction, gas trapping, reduced gas exchange, and increased ventilatory inhomogeneity versus controls. The findings suggest pulmonary effects due to VLBW persist into adulthood, and BPD is a further insult on small airway function.

Lung function evolution in children with old and new type bronchopulmonary dysplasia: a retrospective cohort analysis

Bronchopulmonary dysplasia (BPD) is one of the most important sequelae of premature birth. There is concern that in some patients, lung injuries early in life may have lifelong consequences. In this retrospective observational cohort study, lung function evolution in children with BPD was investigated from childhood to young adulthood. Data from 355 pulmonary function tests (PFT) in 24 patients were analyzed, with a median age at first PFT of 7.6 years and at last PFT 18.2 years. FEV₁ and FEV₁/FVC were below the 5th percentile in respectively 18 and 13/24 patients. Comparing first and last measurement, there was significant worsening in FEV₁ from a mean of 71.3% pred (SD 18.3) to 66.7% pred (SD 21.7) (p < 0.05) and in FEV₁/FVC from 85.4% pred (SD 15.2) to 79.8% pred (SD 17.3) (p = 0.01). Evaluation of the individual lung function changes with linear regression showed deterioration in FEV₁, FVC, and FEV₁/FVC in respectively 17, 13, and 17/24 patients. Total group analysis showed significant deterioration in FEV₁ (- 0.7%/year, p = 0.002) and FEV₁/FVC (- 0.5%/year, p = 0.01). None of the 11 patients born up to 1990 improved in FEV₁ vs 7 of the 13 patients born after 1990 (p = 0.006).Conclusion: This points out to further deterioration of the lung function during childhood in this selected group of children with BPD.What is Known:• Data on longitudinal changes in lung function in children with BPD are scarce.What is New:• In children with BPD at the severe end of the disease spectrum, lung function does not improve over time. On the contrary, in two-thirds of the subjects studied FEV₁and FEV₁/FVC worsen over time.• Lung function evolution towards adulthood was somewhat more favorable in children born after 1990 compared with those born earlier, probably reflecting improvements in neonatal care in subjects with new type BPD.

Differences and similarities between bronchopulmonary dysplasia and asthma in schoolchildren

BACKGROUND

The long-term respiratory characteristics of ex-preterm children with bronchopulmonary dysplasia (BPD) are not established. The objective of this study was to describe hallmarks of BPD at school age in comparison to children with atopic asthma.

METHODS

This study was a cross-sectional descriptive comparative study in a hospital-based setting. Thirty schoolchildren diagnosed with BPD (10.4 years/born at 26.6 weeks' gestation) and 30 age- and sex-matched children with asthma and sensitized to airborne allergens (IgE >0.35 kU_A /L) were analyzed. Measurements included fraction of exhaled nitric oxide (FENO, ppb), dynamic and static lung function, and bronchial provocation with methacholine (PD:20) and mannitol (PD:15), as well as an evaluation of respiratory symptoms using the asthma control test (C-ACT).

RESULTS

Lung function measures (FEV1% 77 vs 84, FEV1/FVC% 85 vs 91, FEF50% 61 vs 80) and carbon monoxide diffusion capacity (DLCO%, 81 vs 88) were all reduced in children with BPD compared to asthma (P values <0.042). FENO values were also significantly lower in children with BPD (12 vs 23, P = 0.019). The proportion of positive methacholine tests (74% vs 93%, P = 0.14) was comparable between BPD and asthma. However, less responsiveness towards mannitol (19% vs 61%, P = 0.007) and fewer self-reported symptoms (C-ACT, median 26 vs 24, P = 0.003) were found in the BPD group.

CONCLUSION

Respiratory hallmarks of BPD at school-age were reduced lung function, limited responsiveness towards indirectly acting mannitol but hyper-responsiveness towards direct acting methacholine and impairment in diffusion capacity. Children with BPD displayed less evidence of airway inflammation compared with atopic asthma.

Health-related quality of life in adolescent survivors of bronchopulmonary dysplasia

BACKGROUND AND OBJECTIVE

Bronchopulmonary dysplasia (BPD) is the most common chronic lung disease of infancy in the developed countries. Outcomes for BPD patients have traditionally been assessed using physiological parameters such as lung function, and no data are available on the health-related quality of life (HRQOL) for adolescents with BPD. The aim of this study was to assess HRQOL in adolescents with BPD, in comparison with age-matched and sex-matched control groups of healthy volunteers and asthmatic subjects.

METHODS

We enrolled 27 BPD patients (age range 11-19 years), 27 asthmatic patients and 27 healthy controls. HRQOL was assessed by the Short Form 36 (SF-36) questionnaire. Lung function was assessed by spirometry.

RESULTS

The BPD group did not differ significantly from the healthy controls in any scale or dimension of the SF-36 (the BPD group's summary scores were as follows: physical component summary mean 55.6 + 4.98 and mental component summary 51.8 + 7.75 vs 55.8 + 6.25 and 49.2 + 9.45 for the healthy control group, P > 0.5 and P = 0.26, respectively). Asthmatic adolescents scored lower than those of both healthy controls and patients with BPD in several SF-36 dimensions despite adolescents with BPD having lower lung function. No correlation emerged between lung function and HRQOL in BPD subjects.

CONCLUSION

Despite their impaired lung function, BPD patients have an HRQOL comparable with healthy peers and better than asthmatic patients. We did not find any association between HRQOL and lung function parameters.

Preschool Wheezing Phenotypes

Wheezing in preschool children is very common, with a wide differential diagnosis. It is essential to be sure of the exact sound that parents are describing; the term ‘wheeze‘ is often applied to non-specific sounds. Structural airway disease such as vascular ring should be considered. Thereafter we propose that umbrella terms for preschool wheeze should be abandoned in favour of ‘Hargreave phenotyping’, in which the presence and extent of the components of infection, inflammation, variable airflow obstruction, and fixed airflow obstruction are determined as far as is possible, rather than using a general umbrella term such as ‘asthma’. The justification for this approach is that it leads to a logical approach to treatment in the disparate airway diseases presenting in the preschool years, and should hopefully prevent over-treatment with inhaled corticosteroids. If, despite this approach, doubt remains as to the nature of the airway disease, then a therapeutic trial of treatment is permissible, but it should be for a short defined period only. In any event, such children should be reviewed regularly to see if treatments need to be changed.

Short- and Long-term Pulmonary Outcome of Palivizumab in Children Born Extremely Prematurely

BACKGROUND

Palivizumab reduces the severity of respiratory syncytial virus infection in premature infants, but whether there is a protective effect beyond the preschool age is unknown. This study sought to assess the short- and long-term effects of palivizumab immunization on respiratory morbidity and pulmonary function at school age in children born extremely prematurely.

METHODS

Infants born before 29 weeks' gestation in 2000 to 2003 were assessed at school age by parental questionnaire, hospital chart review, and lung function tests. Children born immediately before the introduction of routine palivizumab prophylaxis were compared with age-matched children who received palivizumab prophylaxis during the first respiratory syncytial virus season.

RESULTS

Sixty-three children with a mean age 8.9 years were included: 30 had received palivizumab and 33 had not (control subjects). The groups were similar in terms of gestational age, birth weight, need for mechanical ventilation, and oxygen supplementation. Fifty-three percent of the palivizumab group, compared with 39% of the control group, had bronchopulmonary dysplasia (P = .14). Wheezing occurred in the first 2 years of life in 27% of the palivizumab group and in 70% of control subjects (P = .008); respective hospitalization rates were 33% and 70% (P = .001). At school age, rates of hyperresponsiveness (provocative concentration leading to a 20% fall in FEV1 < 1 mg/mL) were 33% and 48%, respectively (P = .38). Spirometry, lung volumes, diffusion, and exhaled nitric oxide were within normal limits, with no significant differences between groups.

CONCLUSION

Palivizumab prophylaxis was associated with reduced wheezing episodes and hospitalizations during the first 2 years of life in children born extremely prematurely. However, it did not affect pulmonary outcome at school age.

Respiratory morbidity, lung function and fitness assessment after bronchopulmonary dysplasia

OBJECTIVE

To examine respiratory morbidity and exercise capacity at school age in children after bronchopulmonary dysplasia (BPD).

STUDY DESIGN

Former preterm children after BPD (n=23), without BPD (n=33) and term controls (n=33) were compared using respiratory health questionnaire, spirometry and six-minute walk test (6MWT).

RESULT

Wheezing was more frequent in BPD group (61%) vs non-BPD group (24%; P<0.001) and controls (15%; P<0.001) in the first year of life and until a year before inclusion. The children after BPD had lower mean value (P<0.001) for forced expiratory volume in 1 s (75.3%) vs non-BPD (89.8%) and controls (91.1%). Six-minute walking distance was lower after BPD by 58.3 m compared with non-BPD group (P=0.002) and by 53.7 m compared with controls (P=0.005). After adjusting for confounding factors the difference was not significant anymore.

CONCLUSION

More frequent wheezing and reduced lung function persist into school age after BPD.

Prematurity and prescription asthma medication from childhood to young adulthood: a Danish national cohort study

INTRODUCTION

Preterm birth is associated with increased risk of asthma-like symptoms and purchase of prescription asthma medication in childhood. We investigated whether this association persists into adulthood and whether it is affected by accounting for neonatal respiratory morbidity (acute respiratory disease and bronchopulmonary dysplasia).

METHODS

A national cohort of all infants born in Denmark in the period 1980-2009 was included in this register study. Data on purchase of asthma medication (combination of inhaled β-2 agonists and other drugs for obstructive airway disease) in 2010-2011 were obtained from the Danish National Prescription Registry. Associations between gestational age (GA), neonatal respiratory morbidity and a cross-sectional evaluation of asthma medication purchase were explored by multivariate logistic regressions.

RESULTS

A full dataset was obtained on 1,790,241 individuals, 84.6% of all infants born in the period. Odds-ratios (95% CI) for the association between GA and purchase of asthma medication during infancy were: 3.86 (2.46-6.04) in GA 23-27 weeks, 2.37 (1.84-3.04) in GA 28-31 weeks and 1.59 (1.43-1.77) in GA 32-36 weeks compared to term infants with GA 37-42 weeks. Associations weakened in older age groups and became insignificant in young adults born extremely and very preterm with odds-ratios: 1.41 (0.63-3.19) and 1.15 (0.83-1.60) in GA 23-27 and 28-31 respectively. When adjusting for neonatal respiratory morbidity, the associations weakened but persisted both in childhood and adolescence.

CONCLUSION

There was a strong dose-response association between gestational age and the purchase of prescription asthma medication in infancy and childhood. This association weakened during adolescence and was mostly non-significant in young adulthood. The increased risk of prescription asthma medication purchase in ex-preterm children could only partly be explained by neonatal respiratory morbidity.

Chronic lung disease of prematurity: long-term respiratory outcome

Chronic respiratory morbidity is a common adverse outcome of preterm birth, especially in infants who develop bronchopulmonary dysplasia (BPD), which is still a major cause of long-term lung dysfunction with a heavy burden on health care services and medical resources throughout childhood. The most severely affected patients remain symptomatic even in adulthood, and this may be influenced also by environmental variables (e.g. smoking), which can contribute to persistent obstruction of airflow. Of all obstructive lung diseases in humans, BPD has the earliest onset and probably lasts the longest. Since the prevention of BPD is an elusive goal, minimizing neonatal lung injury and closely monitoring survivors remain the best courses of action. This review describes the clinical and functional changes characteristic of the long-term pulmonary sequelae of preterm birth, focusing particularly on BPD.

Moderately preterm children have more respiratory problems during their first 5 years of life than children born full term

RATIONALE

Pulmonary outcomes of moderate-preterm children (MP) are unknown.

OBJECTIVES

To investigate the prevalence of respiratory symptoms during infancy and at preschool age of MP compared with full-term (FT) and early preterm children (EP) and to determine factors associated with respiratory symptoms of MP at school age.

METHODS

Prospective cohort study.

OUTCOME VARIABLES

number of rehospitalizations caused by respiratory problems, prevalence of respiratory symptoms determined by ISAAC Questionnaires, and factors associated with respiratory symptoms determined by univariate and multivariate analyzes.

MEASUREMENTS AND MAIN RESULTS

A total of 988 MP, 551 EP, and 573 FT children were included. The number of hospitalizations caused by respiratory problems during the first year of life was doubled in MP compared with FT (6% vs. 3%; P < 0.001). At preschool age, compared with FT, MP reported more cough or wheeze during a cold (63% vs. 50%; P < 0.001); cough or wheeze without a cold (23% vs. 15%; P = 0.001); nocturnal cough (33% vs. 26%; P = 0.005); dyspnea (8% vs. 4%; P = 0.011); and use of medication (inhaled steroids, 9% vs. 6%; P = 0.042) (antibiotics, 12% vs. 7%; P = 0.002). Factors associated with respiratory symptoms at 5 years among MP were respiratory problems, eczema, rehospitalization in infancy, passive smoking in infancy, family history of asthma, and higher social class. Multivariate analyzes showed the same results except for rehospitalization in infancy.

CONCLUSIONS

MP have more respiratory symptoms than FT during early childhood. Factors associated with respiratory symptoms at school age are early respiratory problems, family history of asthma, higher social class, and passive smoking.

Pulmonary outcome and its correlates in school-aged children born with a gestational age ≤ 32 weeks

BACKGROUND

There is limited data regarding factors influencing the respiratory outcome at school age of ex-preterms born since the introduction of antenatal steroids, surfactant replacement together with less aggressive ventilation.

OBJECTIVES

To establish the main antenatal, neonatal and early childhood respiratory correlates of respiratory status in school-aged children born at ≤ 32 weeks of gestation.

METHODS

Ex-preterm children born at ≤ 32 weeks of gestation between 1997 and 2001 at Bordeaux University Hospital were evaluated at school age, using a respiratory questionnaire and lung function tests (spirometry, plethysmography, exercise challenge test and CO lung diffusing capacity DLCO measurements). Factors associated with lung function were investigated using polynomial regression analyses.

RESULTS

Of the 151 included children [mean age: 8.6 ± 0.8 years; mean gestational age, 30.1 ± 1.7 weeks; mean birth weight = 1310 ± 380 g; 68.2% ventilated at birth; 46.4% treated with surfactant; 36.4% with prior bronchopulmonary dysplasia (BPD)], 47% presented obstructive lung abnormalities, 11% restrictive or mixed lung abnormalities, 41% exercise-induced bronchoconstriction, and 15.5% reduced DLCO. Surfactant therapy was independently associated with a lower risk of lung abnormalities (p < 0.05). The association between BPD and lung abnormalities at school age was not significant, but prior BPD increased the risk of restrictive or mixed abnormalities (odds ratio: 6.11, confidence interval [1.1; 33.99]). Early childhood respiratory events were not associated with the occurrence of lung abnormalities.

CONCLUSION

Children born at ≤ 32 weeks of gestation remain at risk for impaired lung function at school age in particular when they did not receive surfactant. Restrictive or mixed lung defects are mainly associated with prior BPD.

Catch-up alveolarization in ex-preterm children: evidence from (3)He magnetic resonance

RATIONALE

Histologic data from fatal cases suggest that extreme prematurity results in persisting alveolar damage. However, there is new evidence that human alveolarization might continue throughout childhood and could contribute to alveolar repair.

OBJECTIVES

To examine whether alveolar damage in extreme-preterm survivors persists into late childhood, we compared alveolar dimensions between schoolchildren born term and preterm, using hyperpolarized helium-3 magnetic resonance.

METHODS

We recruited schoolchildren aged 10-14 years stratified by gestational age at birth (weeks) to four groups: (1) term-born (37-42 wk; n = 61); (2) mild preterm (32-36 wk; n = 21); (3) extreme preterm (<32 wk, not oxygen dependent at 4 wk; n = 19); and (4) extreme preterm with chronic lung disease (<32 wk and oxygen dependent beyond 4 wk; n = 18). We measured lung function using spirometry and plethysmography. Apparent diffusion coefficient, a surrogate for average alveolar dimensions, was measured by helium-3 magnetic resonance.

MEASUREMENTS AND MAIN RESULTS

The two extreme preterm groups had a lower FEV1 (P = 0.017) compared with term-born and mild preterm children. Apparent diffusion coefficient was 0.092 cm(2)/second (95% confidence interval, 0.089-0.095) in the term group. Corresponding values were 0.096 (0.091-0.101), 0.090 (0085-0.095), and 0.089 (0.083-0.094) in the mild preterm and two extreme preterm groups, respectively, implying comparable alveolar dimensions across all groups. Results did not change after controlling for anthropometric variables and potential confounders.

CONCLUSIONS

Alveolar size at school age was similar in survivors of extreme prematurity and term-born children. Because extreme preterm birth is associated with deranged alveolar structure in infancy, the most likely explanation for our finding is catch-up alveolarization.

Exercise-induced bronchoconstriction in school-age children born extremely preterm

BACKGROUND

School children born preterm often show airway hyperresponsiveness to methacholine or histamine. Less attention has been paid to their airway response to exercise, an important point because of the role of exercise in the child's daily life. The aim of this study was to describe the characteristics of, and potential determinants to, the airway response to exercise in children born extremely preterm.

METHODS

Forty-two nonasthmatic nonatopic children born before 32 wk gestation were compared with 27 healthy nonasthmatic nonatopic term children at age 7. Spirometry and respiratory impedance were measured at baseline and repeated after a single-step 6-min treadmill exercise in a climate-controlled room.

RESULTS

The preterm group showed significant broncho-constriction induced by exercise. Prematurity, but not low baseline lung function, neonatal oxygen supplementation, mechanical ventilation, chronic lung disease, or maternal smoking, was a determinant of exercise-induced bronchoconstriction.

CONCLUSION

Children born extremely preterm present significant exercise-induced airway obstruction at age 7. The response has different characteristics from that occurring in asthmatics and is likely to express airway noneosinophilic inflammation.

Perinatal factors in non-disabled ELBW school children and later performance

AIM

To determine the association between perinatal events and subsequent motor performance, cardiorespiratory endurance and respiratory function in non-disabled extremely low birthweight (ELBW) school children at 12 years of age.

METHODS

Forty-eight ELBW infants were included in this study. The Movement Assessment Battery for Children (MABC), VO(2) max score as a measure of cardiorespiratory endurance and respiratory function testing were performed and perinatal variables were extracted from the children's hospital files. Children with MABC score ≤ 15th centile were described as having suspect motor performance. Children were classified as being unfit with a VO(2) max > 1 standard deviation below the mean according to gender and age. Perinatal risk factors were explored as risk factors for motor outcome, cardiorespiratory endurance and respiratory function.

RESULTS

MABC category was significantly related with gender (P = 0.005) and chronic neonatal lung disease (P = 0.013). Multiple regression analysis showed motor outcome at 12 years to be independently related to male gender (P = 0.03) and chronic neonatal lung disease (P = 0.045). Sixty-five percent of all the children were identified as unfit. Chronic neonatal lung disease was significantly related to cardiorespiratory endurance (P = 0.03) and predicted VO(2) max at 12 years (P = 0.05). No perinatal factors were significantly related to respiratory function variables.

CONCLUSION

Male gender and chronic neonatal lung disease were associated with later motor outcome of ELBW school children. It is suggested that objective and consistent follow-up from childhood through preadolescence are important to address motor and fitness issues especially for male children born with ELBW.

Inflammatory markers in induced sputum of school children born before 32 completed weeks of gestation

OBJECTIVE

To test whether chronic bronchial inflammation may be a contributing risk factor for persistent airflow limitation in children born before 32 weeks of gestation in later life.

STUDY DESIGN

Thirty-six of 160 children born before 32 completed weeks of gestation who were born between 1988 and 1992 were recruited at a median age of 11 years. Eighteen age-matched children born at term were controls; 47% of the premature infants and 61% of the term born children produced sputum of sufficient quality for interleukin (IL)-8, cell numbers, and differential counts.

RESULTS

Compared with term born children, sputum from the premature group had a higher proportion of neutrophils (62% vs 3.8%; P < .001) and higher IL-8/protein values (1.93 μg/g vs 0.64 μg/g; P = .008). Forced expiratory flow 25%-75% and forced expiratory volume in 1 second/vital capacity were significantly lower (73.4 % vs 116% predicted, P = .002 and 97% vs 101%, P = .012, respectively). Lung function values and sputum indices did not correlate. IL-8/protein and neutrophil percentages correlated significantly with decreasing gestational age (Spearman rank coefficient = -0.58, P = .020 and -.70, P =.03 respectively).

CONCLUSION

A significant proportion of school children born very preterm demonstrate persistent peripheral airway obstruction that is accompanied by neutrophilic lower airway inflammation.

Lung function among infants born preterm, with or without bronchopulmonary dysplasia

OBJECTIVE

Both healthy preterm infants and those with bronchopulmonary dysplasia (BPD) have poor lung function during childhood and adolescence, although there is no evidence whether prematurity alone explains the reduction in lung function found in BPD infants. Our study seeks to know if lung function, measured in infancy by means of rapid thoracic compression with raised volume technique, is different between preterm infants with and without BPD.

METHODS

Lung function was measured in 43 preterm infants with BPD and in 32 preterm infants without BPD at a chronological age range of 2-28 months. Forced vital capacity (FVC), forced expiratory volume at 0.5 sec, and forced expiratory flows at 50, 75, 85%, and 25-75% of FVC were obtained from maximal expiratory volume curves by means of rapid thoracic compression with raised volume technique. Maximal flow at functional residual capacity was measured using rapid thoracic compression at tidal volume. Multiple regression analysis and generalized least squares (GLS) random-effects regression model were used to control for variables such as gender, weeks of gestation, age, birth weight, and tobacco smoke exposure. A sub-analysis was performed in infants born at 28+ weeks of gestation.

RESULTS

BPD was associated to significantly lower flows (regression coefficients: -0.51, -0.54, -57, -0.53, and -0.82, respectively for FEF(50), FEF(75), FEF(85), FEF(25-75)). This association was driven by males and maintained in the subgroup of infants born at 28+ weeks of gestation.

CONCLUSION

BPD is associated with an additional decrease of lung function during the first 2 years of life in infants born preterm.

Maternal smoking during pregnancy, prematurity and recurrent wheezing in early childhood

BACKGROUND

Prenatal maternal smoking and prematurity independently affect wheezing and asthma in childhood.

OBJECTIVE

We sought to evaluate the interactive effects of maternal smoking and prematurity upon the development of early childhood wheezing.

METHODS

We evaluated 1,448 children with smoke exposure data from a prospective urban birth cohort in Boston. Maternal antenatal and postnatal exposure was determined from standardized questionnaires. Gestational age was assessed by the first day of the last menstrual period and early prenatal ultrasound (preterm < 37 weeks gestation). Wheezing episodes were determined from medical record extraction of well and ill/unscheduled visits. The primary outcome was recurrent wheezing, defined as ≥ 4 episodes of physician documented wheezing. Logistic regression models and zero inflated negative binomial regression (for number of episodes of wheeze) assessed the independent and joint association of prematurity and maternal antenatal smoking on recurrent wheeze, controlling for relevant covariates.

RESULTS

In the cohort, 90 (6%) children had recurrent wheezing, 147 (10%) were exposed to in utero maternal smoke and 419 (29%) were premature. Prematurity (odds ratio [OR] 2.0; 95% confidence interval [CI], 1.3-3.1) was associated with an increased risk of recurrent wheezing, but in utero maternal smoking was not (OR 1.1, 95% CI 0.5-2.4). Jointly, maternal smoke exposure and prematurity caused an increased risk of recurrent wheezing (OR 3.8, 95% CI 1.8-8.0). There was an interaction between prematurity and maternal smoking upon episodes of wheezing (P = 0.049).

CONCLUSIONS

We demonstrated an interaction between maternal smoking during pregnancy and prematurity on childhood wheezing in this urban, multiethnic birth cohort.

[Adult respiratory sequelae of premature birth]

INTRODUCTION

Between 5 and 7% of babies are born prematurely. In the paediatric age group, the respiratory morbidity of these patients is well known, particularly in cases of bronchopulmonary dysplasia (BPD). On the other hand, very few data are available concerning their adult respiratory status.

BACKGROUND

There are currently three different groups of ex-premature babies: (1) those with no BPD who are usually not considered as respiratory high-risk adults but have not been well studied; (2) ex-premature babies with BPD who have an increased risk of asthma, respiratory infections, bronchial obstruction aggravated by smoking, and non-atopic bronchial hyperreactivity; this group has been well studied but not beyond 30 years of age; (3) the babies born very prematurely and affected with a new form of BPD due to neonatal intensive care at a very immature stage of pulmonary development, and for whom the future in adult life is unknown but worrying because of reduced lung volumes since birth.

VIEWPOINTS AND CONCLUSIONS

The respiratory physician must be aware of these groups of adults who he may encounter and who may develop, sooner or later, a certain type of chronic obstructive pulmonary disease.

Exhaled air temperature in children with bronchopulmonary dysplasia

BACKGROUND

Because they have similar functional and clinical profiles, bronchopulmonary dysplasia (BPD) survivors are often treated as asthmatic patients. In truth, very little is known about the possible biochemical and inflammatory mechanisms playing a part in BPD survivors' lungs. The aim of this study was to measure exhaled breath temperature in BPD survivors by comparison with asthmatic cases and healthy controls.

METHODS

Three groups of age-matched adolescents (n = 17 each), that is, BPD survivors (gestational ages <31 weeks, birth weights <1,500 g), asthmatic subjects and healthy controls, underwent exhaled breath temperature and exhaled nitric oxide measurements, and spirometry.

RESULTS

Exhaled breath temperature was significantly lower in the BPD survivors (26.72°C [25.11-27.57]) than in the asthmatic patients (29.60°C [29.20-30.02], P < 0.001), while no significant difference emerged by comparison with healthy controls (26.97°C [26.58-27.38]). Considering the whole study population, a significant correlation was found between exhaled breath temperatures and exhaled nitric oxide concentrations (R = 0.42, P = 0.004). Spirometry revealed an obstructive lung function pattern in both the asthmatic cases and the BPD survivors, with lower parameters in the latter.

CONCLUSIONS

Exhaled breath temperatures and exhaled nitric oxide concentrations are significantly lower in BPD survivors than in asthmatic cases, suggesting that different pathogenetic mechanisms characterize these two chronic obstructive lung diseases.

Obstructive lung disease in children with mild to severe BPD

BACKGROUND

Bronchopulmonary dysplasia (BPD) is a common cause of respiratory insufficiency in children born very premature.

OBJECTIVES

The purpose of this study was to examine the impact of the severity of BPD on pulmonary morbidity at school age, as measured by conventional spirometry and impulse oscillometry. We also studied the association between changes in lung function and structural changes in the lungs of children with BPD via High-Resolution Computed Tomography (HRCT). Finally we studied the prevalence of atopy associated with BPD.

METHODS

We studied 60 very low birth weight (VLBW) children, 28 with respiratory distress syndrome (RDS) who did not develop BPD ("preterm non-BPD") and 32 with RDS who developed BPD. The severity of BPD was graded as mild, moderate or severe. Follow-up at age 6-8 years consisted of spirometry, oscillometry, thoracic HRCT, allergy skin-prick test, blood samples and a questionnaire.

RESULTS

All children with BPD showed some evidence of impaired lung function (more negative reactance, FEV1<80% predicted, greater reversibility), although less than half of these children were symptomatic. The majority of children with BPD (19/26) showed abnormalities on HRCT. There was no evidence that atopy was associated with BPD.

CONCLUSIONS

Children with mild BPD exhibited similar impairments in respiratory mechanics and lung structure to those diagnosed with moderate BPD. The widespread involvement of the peripheral airways suggests that all children diagnosed with BPD are potentially at risk of developing chronic obstructive pulmonary disease later in life.

The EPICure study: comparison of pediatric spirometry in community and laboratory settings

RATIONALE

Accuracy of spirometry testing is a prerequisite for its use as an objective outcome measure in large epidemiological studies. We compared spirometry measurements obtained by trained pediatricians in a variety of school settings with those obtained in the laboratory by respiratory physiologists.

METHODS

Following a 3-day training course, three pediatricians carried out spirometry in children born extremely preterm (EP) and age matched controls in schools across the UK and Ireland (The EPICure study). A subgroup had repeated measurements in the laboratory. Spirometric flows and volumes were expressed as Z-scores. Bland-Altman analysis was used to calculate within-subject differences.

RESULTS

Fifty children (40% boys), 37 (74%) of whom were born EP, with a mean age 10.8 years had paired spirometry results (average interval between tests: 20.3 weeks). There was no statistically significant difference between any of the outcome variables: mean (95% CI of difference) in Z-scores [school-laboratory]) being 0.0 (-0.1; 0.1) for FEV(1), 0.1 (-0.1; 0.3) for FVC, -0.1 (-0.3; 0.1) for FEF(25-75), and 0.0 (-0.3; 0.1) for FEV(1)/FVC. Within individuals, the 95% limits of agreement for repeated measures were within +/- 1 Z-score for FEV(1) and FVC, and within +/- 1.5 Z-score for FEF(25-75) and FEV(1)/FVC.

CONCLUSION

With appropriate training, quality control, and support, pediatric spirometry can reliably be performed outside the lung function laboratory.

Respiratory health in prematurely born preschool children with and without bronchopulmonary dysplasia

OBJECTIVE

To investigate the respiratory health of preterm infants with bronchopulmonary dysplasia (BPD) at preschool age and to determine whether lung function (measured by forced oscillation technique (FOT) and interruption technique (Rint) is affected by BPD in preterm infants compared with preterm infants without BPD.

PARTICIPANTS

3 to 5 years of age born preterm with BPD (N = 40, mean gestational age 28 weeks, mean birth weight 1051 g), and without BPD (N = 36, mean gestational age 29 weeks, mean birth weight 1179 g).

OUTCOME VARIABLES

prevalence of symptoms determined by European Community Respiratory Health Survey and lung function measured by FOT and Rint.

RESULTS

A large percentage of infants in both preterm groups reported respiratory symptoms during the last 12 months. Lung function measurements showed higher resonant frequency (Hz) in BPD compared with non-BPD (mean 26.8 vs 22.7, P < .001) and lower mean reactance X(4-24) (hPa.s/l)(-3.0 vs -1.9, P = .005). No differences were found in respiratory resistance between the groups, although the mean values of both groups were increased compared with reference values.

CONCLUSION

Preterm birth affects respiratory health at 3 to 5 years of age. Children with BPD could be distinguished from children without BPD based on a higher resonant frequency and a lower mean reactance.

Lung function in infants and young children with chronic lung disease of infancy: the next steps?

Over the past year, a series of papers have reviewed the literature concerning assessment and interpretation of lung function in infants and young children with chronic lung disease of infancy. This manuscript, which represents the final paper in that series, summarizes the findings to date and highlights key areas for future research. Despite the huge literature in this field, interpretation of results and their use in guiding clinical management are still limited by difficulties in 'normalizing data' according to body size and maturation and selection of appropriate control groups. Furthermore, sensitive tests that more closely reflect the underlying pathophysiology of 'new' bronchopulmonary dysplasia, together with simple and reliable methods of assessing lung maturity at birth and true oxygen requirements at specified time points are urgently required. Research in this field is also challenged by the need to separate the independent effects of genetic predisposition, gene-environment interactions, preterm delivery, neonatal respiratory disorders and various treatment strategies on the growing lung. The extent to which disruption of lung growth following premature exposure to the extra-uterine environment leads to an earlier or more aggravated decline in respiratory function in later adult life remains to be elucidated. Whatever its origin, given the increasing survival of smaller and more immature infants, the long term sequelae of neonatal lung disease, are likely to continue to change, requiring ongoing, carefully designed longitudinal studies. Future research strategies need to encompass a multicenter, multi-disciplinary, collaborative approach with closer links between clinicians and basic scientists, to ensure that the most relevant research questions are addressed using appropriate methodology and that findings are implemented into clinical practice in a more timely fashion.