Neonatal chronic lung disease, oxygen dependency, and a family history of asthma

Family history of asthma influences outpatient respiratory outcomes in children with BPD

INTRODUCTION

Preterm children with bronchopulmonary dysplasia (BPD) are at increased risk for intermittent and chronic respiratory symptoms during childhood and adult life. Identifying children at higher risk for respiratory morbidities in the outpatient setting could help improve long-term outcomes. In this study, we hypothesized that a family history of asthma (FHA) is a risk factor for higher acute care usage and respiratory symptoms in preterm infants/children with BPD, following initial discharge home.

METHODS

Subjects were recruited from the Johns Hopkins Bronchopulmonary Dysplasia outpatient clinic between January 2008 and February 2020 (n = 827). Surveys were administered to caregivers and demographics and clinical characteristics were obtained through chart review.

RESULTS

Demographic features associated with FHA included public health insurance, lower median household income, and nonwhite race. Children with FHA had higher odds of emergency department (ED) visits, systemic steroid use, nighttime respiratory symptoms, and activity limitations. There was no association between FHA and BPD severity.

CONCLUSION

This study found that children with BPD and FHA were more likely to have respiratory symptoms and acute care usage during the first 3 years of life and that FHA was associated with lower socioeconomic status. Although there was no association between FHA and BPD severity, FHA could predict an increased likelihood of both ED visits and need for systemic steroids in infants/children with BPD followed in the outpatient setting.

Smoking in the family is most predictive of the development of childhood asthma in preterm babies <30 weeks gestation: Results of the Respiratory Outcomes Study 2 (RESPOS2)

OBJECTIVES

The Respiratory Outcomes Study 2 (RESPOS2) investigated the relationship between neonatal outcomes (specifically, chronic lung disease [CLD]) and environmental factors on the development of asthma and atopic outcomes at primary school age for preterm babies (PBs) <30 weeks gestational age (GA).

METHODS

The study included all surviving PBs <30 weeks GA admitted to the Neonatal Intensive Care Unit at Canberra Hospital, Australian Capital Territory between 2007 and 2009. Parents were sent a questionnaire regarding asthma and atopy symptoms when the PBs were aged 5-7 years old. Data were compared based on CLD status.

RESULTS

There were 103 PBs included in the study with a 68.9% response rate to the respiratory questionnaire (71/103). Of these PBs, 15/71 (21.1%) received a diagnosis of CLD. There were no significant differences with regards to asthma, hay fever or eczema in PBs either with or without CLD. The most significant predictor for the development of asthma was smoking in the family (Odds Ratio [OR]: 11.66, 95% Confidence Interval [CI]: 2.01-67.56) with a trend toward significance for family history of asthma (OR: 3.83, 95% CI: 0.85-17.25).

CONCLUSION

The RESPOS2 has confirmed previous reports that CLD in PBs <30 weeks GA is not associated with the development of childhood asthma, hay fever or eczema. In our group of PBs, the strongest predictor of the development of asthma was smoking in the family.

Maternal Asthma, Preterm Birth, and Risk of Bronchopulmonary Dysplasia

OBJECTIVE

To study the relationship between maternal asthma and the development of bronchopulmonary dysplasia (BPD).

STUDY DESIGN

Using a large population-based California cohort, we investigated associations between maternal asthma and preterm birth subtype, as well as maternal asthma and BPD. We used data from 2007-2010 maternal delivery discharge records of 2 009 511 pregnancies and International Classification of Diseases, Ninth Revision codes. Preterm birth was defined as <37 weeks gestational age (GA), with subgroups of <28 weeks, 28-32 weeks, and 33-37 weeks GA, as well as preterm subtype, defined as spontaneous, medically indicated, or unknown. Linkage between the 2 California-wide datasets yielded 21 944 singleton preterm infants linked to their mother's records, allowing estimation of the risk of BPD in mothers with asthma and those without asthma.

RESULTS

Maternal asthma was associated with increased odds (OR, 1.42; 95% CI, 1.38-1.46) of preterm birth at <37 weeks GA, with the greatest risk for 28-32 GA (aOR, 1.60; 95% CI, 1.47-1.74). Among 21 944 preterm infants, we did not observe an elevated risk for BPD in infants born to mothers with asthma (aOR, 1.03; 95% CI, 0.9-1.2). Stratification by maternal treatment with antenatal steroids revealed increased odds of BPD in infants whose mothers had asthma but did not receive antenatal steroids (aOR, 1.54; 95% CI, 1.15-2.06), but not in infants whose mothers had asthma and were treated with antenatal steroids (aOR, 0.85; 95% CI, 0.67-1.07).

CONCLUSION

Asthma in mothers who did not receive antenatal steroid treatment is associated with an increased risk of BPD in their preterm infants.

Neonatal epithelial hypoxia inducible factor-1α expression regulates the response of the lung to experimental asthma

Allergic airway disease is characterized by a T helper type 2 cell-mediated airway inflammation and airway hyperresponsiveness. Little is known about the role of hypoxia-mediated signaling in the progression of the disease. To address this knowledge gap, a mouse model was created in which doxycycline exposure induces the functional deletion of hypoxia inducible factor-1α from alveolar type II and Clara cells of the lung. When hypoxia inducible factor-1α deletion was induced during the early postnatal development period of the lung, the mice displayed an enhanced response to the ovalbumin model of allergic airway disease. These hypoxia inducible factor-1α-deficient mice exhibit increased cellular infiltrates, eosinophilia in the lavage fluid and parenchyma, and T helper type 2 cytokines, as compared with ovalbumin-treated control mice. Moreover, these hypoxia inducible factor-1α-deficient mice display increased airway resistance when compared with their control counterparts. Interestingly, if the loss of hypoxia inducible factor-1α was induced in early adulthood, the exacerbated phenotype was not observed. Taken together, these results suggest that epithelial hypoxia inducible factor-1α plays an important role in establishing the innate immunity of the lung and epithelial-specific deficiency in the transcription factor, during early postnatal development, increases the severity of inflammation and functional airway resistance, following ovalbumin challenge. Finally, these results might explain some of the chronic respiratory pathology observed in premature infants, especially those that receive supplemental oxygen. This early hyperoxic exposure, from normal ambient and supplemental oxygen, would presumably inhibit normal hypoxia inducible factor-1α signaling, mimicking the functional deletion described.

Aerobic and lung performance in premature children with and without chronic lung disease of prematurity

OBJECTIVE

This study intended to identify pulmonary and exercise-related effects of chronic lung disease of infancy (CLD) versus prematurity (PRE) without CLD in children 5 to 7 years old who were born prematurely (24-30 weeks of gestation) with very low and extremely low birthweight of 500 to 1500 g (VLBW, ELBW).

SUBJECTS

Seventeen CLD and 14 PRE were compared with 24 term controls (CON). The premature children had no overt manifestations of a neuromuscular disease.

METHODS

Pulmonary function at rest and following exercise, and aerobic exercise performance were measured.

RESULTS

Peak [latin capital V with dot above]O2 and maximal aerobic power were not different among the groups, but O2 uptake at a given mechanical power was higher in the CLD than in PRE and in CON (P < 0.05). At rest, forced vital capacity was significantly lower in CLD than in PRE (P < 0.05) and CON (P < 0.0005), and FEV1 and FEF25-75 were lower in CLD than CON (P < 0.0005 and P < 0.005, respectively). Exercise-induced bronchoconstriction (EIB) was more prevalent among the 2 premature groups (P < 0.05).

CONCLUSIONS

Our children 5 to 7 years old born at VLBW or ELBW, with or without CLD, have some degree of pulmonary dysfunction at rest and following exercise and a higher prevalence of EIB with no reduction in maximal aerobic exercise performance. The findings suggest that the pulmonary limitations are associated with low birthweight even in the absence of CLD. The higher O2 uptake at a given mechanical power in the CLD group may cause early fatigability during prolonged exercise, even when aerobic performance is normal.

Nonassociation of Interleukin 4 Intron 3 and 590 Promoter Polymorphisms with Bronchopulmonary Dysplasia for Ventilated Preterm Infants

Interleukin 4 (IL-4) stimulates and amplifies the inflammatory response, stimulates collagen synthesis in fibroblasts, promotes the progression to fibrosis and has been shown to inhibit the production of several inflammatory cytokines in the development of bronchopulmonary dysplasia (BPD) and airway hyperreactivity. We aimed to investigate whether IL-4 polymorphisms in ventilated preterm infants were associated with BPD. BPD was defined as infants who remained dependent on active respiratory support or oxygen supplementation at 36 weeks postconceptional age. A case-control study of 224 preterm infants (<30 weeks) who had respiratory distress syndrome and needed intermittent mandatory ventilation (IMV) were undertaken between January 1999 and December 2003. The typing of each genetic polymorphism was performed by polymerase-chain-reaction-based restriction analysis. Genotype distribution and allelic frequencies were compared between ventilated preterm infants who developed BPD and those who did not and the duration of IMV. The demography of these ventilated BPD and non-BPD preterm infants was not different. We observed no significant differences in genotype distribution or allelic frequency of the IL-4 intron 3 or IL-4 promoter polymorphisms between ventilated preterm infants who developed BPD and who did not. There was no significant association of the genotype or allelic frequency of IL-4 polymorphism with duration of IMV. We conclude that neither IL-4 intron 3 nor the 590 promoter polymorphism is a useful marker for predicting the susceptibility to BPD in ventilated Taiwanese preterm infants.

Bronchopulmonary dysplasia in preterm infants: pathophysiology and management strategies

Bronchopulmonary dysplasia (BPD) has classically been described as including inflammation, architectural disruption, fibrosis, and disordered/delayed development of the infant lung. As infants born at progressively earlier gestations have begun to survive the neonatal period, a 'new' BPD, consisting primarily of disordered/delayed development, has emerged. BPD causes not only significant complications in the newborn period, but is associated with continuing mortality, cardiopulmonary dysfunction, re-hospitalization, growth failure, and poor neurodevelopmental outcome after hospital discharge. Four major risk factors for BPD include premature birth, respiratory failure, oxygen supplementation, and mechanical ventilation, although it is unclear whether any of these factors is absolutely necessary for development of the condition. Genetic susceptibility, infection, and patent ductus arteriosus have also been implicated in the pathogenesis of the disease. The strategies with the strongest evidence for effectiveness in preventing or lessening the severity of BPD include prevention of prematurity and closure of a clinically significant patent ductus arteriosus. Some evidence of effectiveness also exists for single-course therapy with antenatal glucocorticoids in women at risk for delivering premature infants, surfactant replacement therapy in intubated infants with respiratory distress syndrome, retinol (vitamin A) therapy, and modes of respiratory support designed to minimize 'volutrauma' and oxygen toxicity. The most effective treatments for ameliorating symptoms or preventing exacerbation in established BPD include oxygen therapy, inhaled glucocorticoid therapy, and vaccination against respiratory pathogens.Many other strategies for the prevention or treatment of BPD have been proposed, but have weaker or conflicting evidence of effectiveness. In addition, many therapies have significant side effects, including the possibility of worsening the disease despite symptom improvement. For instance, supraphysiologic systemic doses of glucocorticoids lessen the incidence of BPD in infants at risk for the disease, and promote weaning of oxygen and mechanical ventilation in infants with established BPD. However, the side effects of systemic glucocorticoid therapy, most notably the recently recognized adverse effects on neurodevelopment, preclude their routine use for the prevention or treatment of BPD. Future research in BPD will most probably focus on continued incremental improvements in outcome, which are likely to be achieved through the combined effects of many therapeutic modalities.

Intrauterine smoke exposure: a new risk factor for bronchopulmonary dysplasia?

OBJECTIVE

To evaluate the role of intrauterine smoke exposure and other variables on the development of bronchopulmonary dysplasia (BPD) in infants with birth weight < 1500 g (VLBW).

METHODS

This case-control study investigated 277 VLBW infants (141 cases, 136 controls) admitted at birth to neonatal intensive care unit and survived to discharge. A retrospective telephone interview provided detailed parental information supplementing clinical data. Logistic regression assessed the effects of birth weight < 1000 g, gestational age < 30 weeks (GA<30), respiratory distress syndrome (RDS), neonatal mechanical ventilation > 7 days (MV>7), patent ductus arteriosus (PDA), intrauterine smoke exposure > or = 3 months (ISE), and of parental history of asthma on BPD (oxygen dependency at 28 days with characteristic radiographic abnormalities) occurrence.

RESULTS

Including all variables, only GA<30, RDS and MV>7 were significantly associated with BPD. ISE did not contribute significantly to this model (odds ratio [OR] 1.94; 95% confidence interval 0.88-4.26). Excluding iatrogenic variable MV>7, GA<30, RDS, PDA and ISE (OR 2.21; 95% confidence interval 1.03-4.76) were significantly associated with BPD. Analyzing GA as a continuous variable, the OR was 0.63 for each additional week.

CONCLUSIONS

Prolonged mechanical ventilation, RDS and low gestational age were the major BPD determinants. Intrauterine smoke exposure seems to influence independently BPD development.

An update on bronchopulmonary dysplasia: is there a relationship to the development of childhood asthma?

There appears to be some interesting commonalities between asthma and BPD. The prevalence of both conditions is on the rise, both conditions tend to cluster in families, and they share wheezing phenotypes, i.e., mild-moderate reversible airway obstruction and a similar degree of response to pharmacological provocation. Furthermore, significant overlap exists with regard to the presence of elevated concentrations of airway inflammatory mediators concurrent with reduced levels of anti-inflammatory activity, in serum and BAL fluid, as well as histological evidence for airway 'remodelling'. Both BPD and asthma are characterized by increased smooth muscle contraction, and in asthma, the smooth muscle may be involved in the primary development of the asthmatic phenotype. Since wheezing is a common finding among children with BPD, an interesting question is whether BPD is a phenotypic variant of asthma?

Urinary leukotriene E(4) excretion during the first month of life and subsequent bronchopulmonary dysplasia in premature infants

BACKGROUND

Inflammation plays an important role in the pathogenesis of bronchopulmonary dysplasia (BPD), but the exact nature of this inflammatory process is incompletely understood. Older infants with established BPD have higher levels of urinary leukotriene E(4) (LTE(4)) compared to healthy infants of the same age. This suggests that cysteinyl leukotrienes may play a role in the abnormalities seen in BPD.

OBJECTIVES

To measure urinary LTE(4) levels during the first month of life in premature infants, and to determine whether there are significant differences in premature infants who develop BPD, as compared to those who do not develop BPD.

DESIGN

Prospective, blinded, controlled study.

SETTING

Neonatal ICUs of a tertiary-care university hospital.

METHODS

Thirty-seven premature infants (< 33 weeks of gestational age) were enrolled prospectively at birth. Urinary LTE(4) levels were measured blinded, using a standard radioimmunoassay technique at 2 days, 7 days, and 28 days of life. At 1 month of age, infants were classified as with or without BPD, based on need for supplemental oxygen, and characteristic chest radiographs. Clinical features and urinary LTE(4) were compared between the two groups.

RESULTS

Mean +/- SD gestational age was 29 +/- 2.6 weeks. None of the infants had a family history of asthma. Thirteen of 37 infants were classified as having BPD at 28 days after birth. Mean gestational age in infants who developed BPD was 27 +/- 2.4 weeks, compared to 30 +/- 2 weeks in infants who did not develop BPD (p < 0.05). In infants with BPD, mean urinary LTE(4) levels of urinary creatinine were 1,762 +/- 2,003 pg/mg, 1,236 +/- 992 pg/mg, and 5,541 +/- 5,146 pg/mg at days 2, 7, and 28, respectively, compared to 1,304 +/- 1,195 pg/mg, 1,158 +/- 1,133 pg/mg, and 2,800 +/- 2,080 pg/mg in infants without BPD. LTE(4) levels at 2 days, 7 days, and 28 days did not correlate with the subsequent development of BPD. LTE(4) levels at day 28 were significantly higher than LTE(4) levels at day 2 and day 7 in both groups, even after correcting for gestational age or birth weight (p < 0.05). There was significant inverse correlation between LTE(4) levels at day 2 with gestational age and birth weight (p < 0.05). All 13 infants with BPD received steroid pulses, compared to 3 of 26 infants without BPD. Gestational age and use of postnatal steroid pulses, diuretics, and theophylline (for apnea of prematurity) were significantly associated with each other and with the subsequent development of BPD.

CONCLUSION

Urinary LTE(4) levels measured on the second day of life in very-low-birth-weight infants inversely correlate with gestational age and birth weight. Urinary LTE(4) levels may reflect lung injury and/or inflammation in premature infants, not necessarily related to BPD as it is presently defined.

Very low birthweight and asthma by age seven years in a national cohort

Several studies have suggested that very low birthweight (VLBW < 1500 g) is associated with increased rates of respiratory problems in childhood and that the presence of chronic lung disease further increases the risk. We aimed to assess rates of asthma at 7-8 years of age in a national cohort of VLBW infants born in 1986 and for whom perinatal data were available. Two hundred ninety-nine former VLBW children (96% of surviving children living in New Zealand) were assessed at a home visit. Parents were asked a comprehensive questionnaire, including three questions aimed at assessing morbidity from asthma: 1) was the child diagnosed as having asthma before age 7 years; 2) was the child still experiencing asthma at the age of 7 years; and 3) was the child prescribed daily medication for asthma at the age of 7 years. Overall, 50% of the cohort had been diagnosed with asthma before age 7, compared with 27% of a sample of New Zealand children assessed contemporaneously in an international study; 32% had asthma at age 7, and 11% were taking daily medication. All three categories of asthma were associated with a family history of asthma, but there was no association with any perinatal factors. A diagnosis of asthma before age 7 was more likely when the mother smoked in pregnancy (P < 0.005) and currently smoked (P < 0.01), and trended so when parents lacked high school qualifications and in Maori or Pacific Island families (P < 0.10). In contrast, daily medication was more frequent when parents had educational qualifications and in non-Maori or Pacific Island families (P < 0.05). On multiple logistic regression, a family history of asthma was a significant predictor for any and current asthma (P < 0.001) and daily medication (P < 0.05); maternal smoking in pregnancy was a significant predictor for any asthma (P < 0.05); and non-Maori or Pacific Island ethnicity was a significant predictor for asthma treatment (P < 0.05). We conclude that rates of childhood asthma are high in this VLBW cohort, but the high prevalence appears to be unrelated to perinatal factors, including respiratory morbidity. There are suggestions that social factors contribute to both asthma risk and treatment.

Effects of birthweight and oxygen supplementation on lung function in late childhood in children of very low birth weight

Impaired respiratory function has been found frequently in ex-premature children, but it is unclear which specific factors influence this impairment the most. The aim of this study was to determine the importance of the contributions of birth weight, gestational age, neonatal respiratory disease, and its treatment on subsequent childhood lung function at age 11 years in a cohort of children of very low birth weight (VLBW; </=1,500 g). Detailed clinical histories were recorded, and lung function was measured in 60% (102 children) of surviving VLBW infants born 1981/1982, and compared with 82 matched control children (birth weight >2,000 g) of similar age. VLBW children were shorter and lighter than controls (P < 0.0001) at 11 years of age, and had reduced expiratory flows (P < 0.00001) and forced vital capacities (P < 0.001). The residual volume to total lung capacity ratio (RV/TLC ratio) was increased (P < 0.00001), while total lung capacity (TLC) remained unchanged. Those with bronchopulmonary dysplasia (BPD) had the lowest mean expiratory flows. Males had lower expiratory flows than females. On univariate analysis, gestational age by itself accounted for 8.8% of the explained variance in FEV(1) at 11 years of age, but birth weight accounted for 16% on its own; both together accounted for a further 0.2% (16.2%), suggesting that the latter was the dominant factor. On multivariate analysis, the contribution of birth weight and gestational age was small, and the best predictors at 11 years of age, which together explained 43.4% of the total variance in FEV(1), were log days of supplemental oxygen (9.6%) and a reported history of asthma (10.8%). For FEF(25-75), these predictors explained 7.2% and 13.4%, respectively, of the total explained variance of 40.6%. The relation between neonatal oxygen supplementation and childhood FEV(1) was such that up to 20 days of supplemental oxygen had little effect on subsequent FEV(1) at 11 years of age, but each additional week of supplemental oxygen after that time was associated with a progressive reduction in FEV(1) of 3%. These data confirm the significant role of supplemental oxygen in the neonatal period and a history of asthma on the subsequent reduction of expiratory flows in VLBW children. Birth weight was a more important prenatal factor than gestational age, but both were of lesser predictive significance than either supplemental oxygen or a reported history of asthma.

Measuring respiratory outcome

Chronic respiratory morbidity is a common outcome of very premature birth. Infants who are chronically oxygen dependent with an abnormal chest radiograph are described as suffering from chronic lung disease (CLD), and those with the worst abnormalities diagnosed as having bronchopulmonary dysplasia. CLD infants are very likely to be readmitted to hospital during infancy, particularly during a respiratory syncytial virus (RSV) epidemic. Very low birthweight, prematurity and CLD are associated with recurrent respiratory symptoms and lung function abnormalities during the preschool years. These problems are detected even in adolescents who were chronically oxygen dependent after premature birth. Further research to identify effective preventative strategies is urgently required.

Lung function outcome in children of premature birth

Since the 1960s there has been a continual improvement in the survival of premature infants of birthweight less than 1500 g. This has resulted in an increase in the prevalence of bronchopulmonary dysplasia (BPD), or its milder form, chronic lung disease (CLD) of prematurity. In children with BPD; the initial air trapping improves in the first 3-4 years of life, but small airway obstruction is often slow to improve, suggesting dysanaptic lung growth. Despite this, the majority of older children and adolescents with BPD/CLD do not have significant respiratory symptoms. Children born prematurely with or without hyaline membrane disease may also have a reduction in expiratory flows during childhood, albeit less severe. The clinical significance of this in the longer term is unclear. Although significant associations between decrements in expiratory flows, neonatal oxygen therapy and assisted ventilation have been demonstrated. Airway function has also been reported to be largely unrelated with perinatal events but strongly associated with birthweight. The latter suggests that intra-uterine factors such as under-nutrition may be more important than hitherto recognized. Because of a lack of longitudinal studies, it is unclear how lung function will track during adolescence and adult life. Bronchial hyper-responsiveness is significantly increased in children with BPD and to a lesser extent in those born prematurely with or without hyaline membrane disease. It is unclear whether this is due to a genetic predisposition, neonatal lung injury or anatomically smaller airways. Given the morbidity and fiscal cost of a premature birth, effective strategies to reduce the premature birth rate are needed.

Recurrent wheezing in very preterm infants

AIMS

To document the prevalence of, and identify risk factors for, recurrent wheezing treated with bronchodilators in the first year of life.

METHODS

Parental history and neonatal data were collected prospectively in a regional cohort of very preterm infants (< 33 weeks). Data on maternal smoking, siblings at home, breast feeding, respiratory symptoms, and hospital re-admissions were documented at 12 months.

RESULTS

Outcome data were available for 525/560 (95%) of survivors. The incidence of recurrent wheeze was 76/525 (14.5%) in very preterm infants and 20/657 (3%) in a cohort of term newborns. Significant risk factors for recurrent wheeze in very preterm infants were parental history of asthma, maternal smoking, siblings at home, neonatal oxygen supplementation at 28 days, 36, and 40 weeks of gestation.

CONCLUSIONS

Wheezing respiratory illnesses are common in very preterm infants. The factors involved are similar to those in more mature infants, with the addition of immaturity and neonatal lung injury.