Chronic lung disease after premature birth

[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.

Conditional hypoxia inducible factor-1α induction in embryonic pulmonary epithelium impairs maturation and augments lymphangiogenesis

Hypoxia inducible factor (HIF) 1a, EPAS1 and NEPAS are expressed in the embryonic mouse lung and each isoform exhibits distinct spatiotemporal expression patterns throughout morphogenesis. To further assess the role of the HIF1a isoform in lung epithelial cell differentiation and homeostasis, we created transgenic mice that express a constitutively active isoform of human HIF-1a (HIF-1a three point mutant (TPM)), in a doxycycline-dependent manner. Expression of HIF1a TPM in the developing pulmonary epithelium resulted in lung hypoplasia characterized by defective branching morphogenesis, altered cellular energetics and impaired epithelial maturation, culminating in neonatal lethality at birth from severe respiratory distress. Histological and biochemical analyses revealed expanded glycogen pools in the pulmonary epithelial cells at E18.5, concomitant with decreased pulmonary surfactant, suggesting a delay or an arrest in maturation. Importantly, these defects occurred in the absence of apoptosis or necrosis. In addition, sub-pleural hemorrhaging was evident as early as E14.5 in HIF1a TPM lungs, despite normal patterning of the blood vasculature, consistent with defects in endothelial barrier function. Epithelial expression of HIF1a TPM also resulted in increased VEGFA and VEGFC production, an increase in the number of lymphatic vessels and indirect activation of the multiple Notch pathway components in endothelial precursor cells. Collectively, these data indicate that HIF-1a protein levels in the pulmonary epithelium must be tightly controlled for proper development of the epithelial and mesenchymal compartments.

Alveolarization continues during childhood and adolescence: new evidence from helium-3 magnetic resonance

RATIONALE

The current hypothesis that human pulmonary alveolarization is complete by 3 years is contradicted by new evidence of alveolarization throughout adolescence in mammals.

OBJECTIVES

We reexamined the current hypothesis using helium-3 ((3)He) magnetic resonance (MR) to assess alveolar size noninvasively between 7 and 21 years, during which lung volume nearly quadruples. If new alveolarization does not occur, alveolar size should increase to the same extent.

METHODS

Lung volumes were measured by spirometry and plethysmography in 109 healthy subjects aged 7-21 years. Using (3)HeMR we determined two independent measures of peripheral airspace dimensions: apparent diffusion coefficient (ADC) of (3)He at FRC (n = 109), and average diffusion distance of helium (X(rms)) by q-space analysis (n = 46). We compared the change in these parameters with lung growth against a model of lung expansion with no new alveolarization.

MEASUREMENTS AND MAIN RESULTS

ADC increased by 0.19% for every 1% increment in FRC (95% confidence interval [CI], 0.13-0.25), whereas the expected change in the absence of neoalveolarization is 0.41% (95% CI, 0.31-0.52). Similarly, increase of (X(rms)) with FRC was significantly less than the predicted increase in the absence of neoalveolarization. The number of alveoli is estimated to increase 1.94-fold (95% CI, 1.64-2.30) across the age range studied.

CONCLUSIONS

Our observations are best explained by postulating that the lungs grow partly by neoalveolarization throughout childhood and adolescence. This has important implications: developing lungs have the potential to recover from early life insults and respond to emerging alveolar therapies. Conversely, drugs, diseases, or environmental exposures could adversely affect alveolarization throughout childhood.

Quantitative assessment of chronic lung disease of infancy using computed tomography

The aims of this study were to determine whether infants and toddlers with chronic lung disease of infancy (CLDI) have smaller airways and lower lung density compared with full-term healthy controls. Multi-slice computed tomography (CT) chest scans were obtained at elevated lung volumes during a brief respiratory pause in sedated infants and toddlers; 38 CLDI were compared with 39 full-term controls. For CLDI subjects, gestational age at birth ranged from 25 to 29 weeks. Airway size was measured for the trachea and the next three to four generations into the right lower lobe; lung volumes and tissue density were also measured. The relationship between airway size and airway generation differed between the CLDI and full-term groups; the sizes of the first and second airway generations were larger in the shorter CLDI than in the shorter full-term subjects. The increased size in the airways in the CLDI subjects was associated with increasing mechanical ventilation time in the neonatal period. CLDI subjects had a greater heterogeneity of lung density compared with full-term subjects. Our results indicate that quantitative analysis of multi-slice CT scans at elevated volumes provides important insights into the pulmonary pathology of infants and toddlers with CLDI.

Elastase inhibitory activity of airway α1-antitrypsin is protected by treatment with a catalytic antioxidant in a baboon model of severe bronchopulmonary dysplasia

Recent studies in animal models of bronchopulmonary dysplasia (BPD) suggest that antioxidant treatments may be beneficial for the disease. However, the mechanisms by which these drugs improve the course of BPD are not completely known. Alpha1-antitrypsin (α1-AT) is one of the major serine protease inhibitors in human plasma that has antielastase and antiapoptotic activities. Both activities of α1-AT are dependent on its reactive site loop (RSL), which is highly susceptible to oxidative inactivation. In this study, we investigated the elastase inhibitory activity of α1-AT in two different baboon models of BPD, the "new BPD" and the "severe BPD" models, and determined the effect of treatment with a catalytic antioxidant, Mn(III) meso-tetrakis(N-ethylpyridinium-2-yl)porphyrin (MnTE-2-PyP), on the elastase inhibitory activity of α1-AT in the severe BPD model. Our results demonstrate the presence of sufficient elastase inhibitory activity of the airway α1-AT in the new but not in the severe BPD model. Treatment of severe BPD group baboons with the catalytic antioxidant MnTE-2-PyP resulted in augmentation of the elastase inhibitory activity of α1-AT. These findings suggest that prevention of the oxidative inactivation of α1-AT may be one of the mechanisms by which antioxidant therapy improves the pulmonary outcomes in animal models of severe BPD.

Respiratory syncytial virus hospitalization trends in infants with chronic lung disease of infancy, 1998-2008

OBJECTIVE

Infants with chronic lung disease of infancy (CLDI) are at high risk for severe respiratory syncytial virus (RSV) illness requiring hospitalization. Palivizumab was first licensed in 1998 for the prevention of RSV disease in high-risk infants, including those with CLDI. We performed a retrospective cohort study of all hospitalized children with CLDI aged <2 years between 1998 and 2008 in the USA to determine trends in rates of hospitalizations due to RSV (RSVH) since the launch of palivizumab.

MATERIALS AND METHODS

Data from the United States National Hospital Discharge Survey, a multistage systematic survey sample of US hospitals, were assembled. We defined RSVH using International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes of 079.6 (RSV), 466.11 (acute bronchiolitis due to RSV), and 480.1 (pneumonia due to RSV). Quarterly rates of RSVH were assessed for children with CLDI (ICD-9-CM code 770.7) and calculated between 1998 and 2008. Because RSV may be miscoded, the analysis was repeated after expanding the definition of RSVH to include all acute bronchitis and acute bronchiolitis (ABH) (ICD-9-CM = 466). Trends were described using linear regression with seasonal indicators included in the model.

RESULTS

On average, about 966 RSVH (range 98-1373 RSVH) per year were found for children <2 years with CLDI in the USA between 1998 and 2008. Over the 11-year period, the predicted rate of RSVH statistically significantly decreased by 48% (from 93.78 to 49.06 RSVH per 1 million children) (P = 0.013). Addition of ABH resulted in a nonstatisically significant decrease of 32% over the 10-year period (P = 0.102).

CONCLUSION

These results suggest that there has been a decrease in the rate of RSVH in infants with CLDI between 1998 and 2008. The reasons for this decrease may include improved neonatal intensive care unit and outpatient management of CLDI, and possibly increased use of palivizumab in this high-risk population.

Phosphodiesterase 4 inhibition attenuates persistent heart and lung injury by neonatal hyperoxia in rats

Phosphodiesterase (PDE) 4 inhibitors are potent anti-inflammatory drugs with antihypertensive properties, and their therapeutic role in bronchopulmonary dysplasia (BPD) is still controversial. We studied the role of PDE4 inhibition with piclamilast on normal lung development and its therapeutic value on pulmonary hypertension (PH) and right ventricular hypertrophy (RVH) in neonatal rats with hyperoxia-induced lung injury, a valuable model for premature infants with severe BPD. The cardiopulmonary effects of piclamilast treatment (5 mg·kg(-1)·day(-1)) were investigated in two models of experimental BPD: 1) daily treatment during continuous exposure to hyperoxia for 10 days; and 2) late treatment and injury-recovery in which pups were exposed to hyperoxia or room air for 9 days, followed by 9 or 42 days of recovery in room air combined with treatment started on day 6 of oxygen exposure until day 18. Prophylactic piclamilast treatment reduced pulmonary fibrin deposition, septum thickness, arteriolar wall thickness, arteriolar vascular smooth muscle cell proliferation and RVH, and prolonged survival. In the late treatment and injury-recovery model, hyperoxia caused persistent aberrant alveolar and vascular development, PH, and RVH. Treatment with piclamilast in both models reduced arteriolar wall thickness, attenuated RVH, and improved right ventricular function in the injury recovery model, but did not restore alveolarization or angiogenesis. Treatment with piclamilast did not show adverse cardiopulmonary effects in room air controls in both models. In conclusion, PDE4 inhibition attenuated and partially reversed PH and RVH, but did not advance alveolar development in neonatal rats with hyperoxic lung injury or affect normal lung and heart development.

BPD: old and new problems

Bronchopulmonary dysplasia (BPD) is still one of the main long term complication of preterm birth, and it is the most common chronic respiratory disease in infants. Due to advances in perinatal care and neonatal respiratory therapy the clinical characteristics and the natural history of infants affected by BPD have widely changed in the last decades. The sever presentation of the old form of BPD has been replaced by a milder clinical form, without or with mild respiratory distress syndrome in the first days of life, that responds rapidly to surfactant therapy and instead requires prolonged ventilator support because of poor respiratory effort. "Old" and "new" BPD, are also histologically different, being two morphologic outcomes of variable combinations of factors injuring lungs of differing maturity. New BPD is characterized by diffusely reduced alveolar development, with airway injury, inflammation and fibrosis that are usually milder than in old form. Such "new" form of BPD is interpreted as a developmental disorder. The development of BPD is a multifactorial process with pathogenesis being linked to immature lung tissue, barotrauma and volutrauma resulting from mechanical ventilation, oxidant injury, and proinflammatory mediators.and inflammatory regulation may also have a role in the development of the new form. There is growing evidence that BPD results from an imbalance between proinflammatory and anti-inflammatory mechanisms, with a persistent imbalance that favors proinflammatory mechanisms. Reduction of the incidence and severity of BPD may be possible through a reduction of the amount of injury induced by respiratory support interventions.

Capnography in spontaneously breathing preterm infants with bronchopulmonary dysplasia

BACKGROUND

In adult patients with chronic obstructive pulmonary disease, there is a gradient between end-tidal carbon dioxide (EtCO(2)) and arterial carbon dioxide pressure (PaCO(2)), and the slope of the ascending phase of the capnogram is decreased due to obstruction. Corresponding data are lacking in infants with bronchopulmonary dysplasia (BPD).

OBJECTIVES

To compare PCO(2) -EtCO(2) gradient and capnogram shape in two groups of spontaneously breathing preterm subjects: infants with BPD and infants without respiratory disease (controls).

MATERIAL AND METHODS

Capnography was performed at 36 weeks postmenstrual age in 20 infants (12 BPD with oxygen dependency, 8 controls). Respiratory rate and the components of the respiratory cycle were measured. The PCO(2) -EtCO(2) gradient was calculated using EtCO(2) values and simultaneously sampled capillary values (PcCO(2)). Capnograms were compared between groups.

RESULTS

In BPD subjects, respiratory rate was increased (60 ± 16 bpm vs 43 ± 16 bpm, P = 0.009); a widened PcCO(2) -EtCO(2) gradient was observed (13 ± 4 mmHg vs 0 ± 7 mmHg, P = 0.0013); the ascending phase of the capnogram was not decreased, whereas the initial inspiratory phase was prolonged (0.32 ± 0.05 vs 0.24 ± 0.04, P = 0.001).

CONCLUSIONS

Compared with healthy infants, a higher PcCO(2) -EtCO(2) gradient was observed in infants with BPD, suggesting that ventilation-perfusion mismatch may be present in these infants. The capnogram did not exhibit the characteristic shape of airway obstruction.

Respostas cardiopulmonares durante o esforço em crianças e adolescentes nascidas prematuras

OBJETIVO: Descrever as respostas cardiopulmonares durante o esforço em crianças e adolescentes nascidos prematuros. FONTES DE DADOS: Busca nas bases científicas em saúde SciELO, Lilacs e PubMed, utilizando-se os descritores: "pressão arterial", "capacidade física", "cardiovascular", "prematuro", "criança", adolescente", "função pulmonar", nos idiomas inglês e português. Foram selecionados artigos publicados nos últimos 20 anos. SÍNTESE DOS DADOS: Crianças e adolescentes com histórico de prematuridade apresentam sinais de obstrução das vias aéreas, menores valores de função pulmonar e de capacidade ao exercício, maior incidência de hipertensão arterial e/ou valores mais elevados da pressão arterial sistólica do que os nascidos a termo. Além disso, há indícios de que as alterações na resistência vascular sistêmica desde os primeiros dias de vida comprometam o desenvolvimento cardiovascular até a idade adulta, predispondo a maiores riscos cardiovasculares. CONCLUSÕES: O esforço físico nos indivíduos nascidos prematuros acarreta respostas cardiopulmonares diferentes dos nascidos a termo, atribuídas a particularidades no desenvolvimento desses sistemas inerentes ao prematuro.

Identification of SPOCK2 as a susceptibility gene for bronchopulmonary dysplasia

RATIONALE

Bronchopulmonary dysplasia is the most common chronic respiratory disease in premature infants. Genetic factors might contribute to bronchopulmonary dysplasia susceptibility.

OBJECTIVES

To identify genetic variants involved in bronchopulmonary dysplasia through a genome-wide association study.

METHODS

We prospectively evaluated 418 premature neonates (gestational age <28 wk), of whom 22% developed bronchopulmonary dysplasia. Two discovery series were created, using a DNA pooling strategy in neonates from white and African ancestry. Polymorphisms associated with the disease were confirmed in an independent replication population. Genes were then explored by fine mapping and associations were replicated in an external Finnish population of 213 neonates. Validated genes expression patterns were studied in rat lung, after air or hyperoxia exposure.

MEASUREMENTS AND MAIN RESULTS

SPOCK2 gene was identified by both discovery series. The most significant polymorphism (rs1245560; P = 1.66 × 10(-7)) was confirmed by individual genotyping, and in the replication population (P = 0.002). Fine mapping confirmed the association of rs1245560 with bronchopulmonary dysplasia in both white and African populations with adjusted odds ratios of 2.96 (95% confidence interval [CI], 1.37-6.40) and 4.87 (95% CI, 1.88-12.63), respectively. In white neonates, rs1049269 was also associated with the disease (odds ratio, 3.21; 95% CI, 1.51-6.82). These associations were replicated in the Finnish population. In newborn rat lungs, SPOCK2 mRNA levels markedly increased during the alveolar stage of lung development. After rat exposure to hyperoxia, SPOCK2 expression increased relative to air-exposed controls.

CONCLUSIONS

We identified SPOCK2 as a new possible candidate susceptibility gene for bronchopulmonary dysplasia. Its lung expression pattern points toward a potential role in alveolarization.

Change in prevalence of chronic conditions between childhood and adolescence among extremely low-birth-weight children

CONTEXT

Extremely low-birth-weight (ELBW) children have high rates of chronic conditions during childhood. Information on their trajectory of health during adolescence is needed for health care planning.

OBJECTIVE

To examine changes in the rates of chronic conditions between the ages of 8 and 14 years among ELBW children compared with normal-birth-weight (NBW) controls.

DESIGN, SETTING, AND PARTICIPANTS

Cohort study conducted from 2004 through 2009 of 181 ELBW children (weight < 1 kg) and 115 NBW controls of similar sociodemographic status born from 1992 through 1995 in Cleveland, Ohio.

MAIN OUTCOME MEASURES

Rates of chronic conditions overall (measured with the revised Questionnaire for Identifying Children With Chronic Conditions) and rates of asthma and obesity.

RESULTS

The overall rates of chronic conditions did not change significantly between the ages of 8 and 14 years among ELBW children (75% at age 8 years vs 74% at age 14 years) or NBW controls (37% at age 8 years vs 47% at age 14 years). In generalized estimating equations logistic regression adjusting for sociodemographic status, sex, and race, ELBW children continued to have a higher rate of chronic conditions than NBW controls at age 14 years (74% vs 47%, respectively, adjusted odds ratio [AOR], 2.8 [95% confidence interval {CI}, 1.7 to 4.6]). Rates of asthma requiring medication did not change between the ages of 8 and 14 years among ELBW children (23% at both ages) but increased among NBW controls from 8% at age 8 years to 17% at age 14 years (P = .002). Differences in rates of asthma between ELBW and NBW children were no longer significant at the age of 14 years (23% vs 17%, respectively; AOR, 1.5 [95% CI, 0.8 to 2.8]). Mean z scores for body mass index increased in ELBW children from 0.06 at age 8 years to 0.38 at age 14 years (P <.001) and rates of obesity increased from 12% at age 8 years to 19% at age 14 years (P = .02). However, the scores and rates did not change among NBW controls such that at the age of 14 years the differences between ELBW and NBW children in mean z scores for body mass index (0.38 vs 0.56, respectively; adjusted mean difference -0.2 [95% CI, -0.5 to 0.1]) or rates of obesity (19% vs 20%, respectively; AOR, 1.1 [95% CI, 0.6 to 2.0]) were not significant.

CONCLUSIONS

Among ELBW children, rates of overall chronic conditions and asthma did not change between the ages of 8 and 14 years but the rate of obesity increased. Compared with NBW controls, the rates of chronic conditions were higher but there were no significant differences in the rates of asthma or obesity.

NF-κB signaling in fetal lung macrophages disrupts airway morphogenesis

Bronchopulmonary dysplasia is a common pulmonary complication of extreme prematurity. Arrested lung development leads to bronchopulmonary dysplasia, but the molecular pathways that cause this arrest are unclear. Lung injury and inflammation increase disease risk, but the cellular site of the inflammatory response and the potential role of localized inflammatory signaling in inhibiting lung morphogenesis are not known. In this study, we show that tissue macrophages present in the fetal mouse lung mediate the inflammatory response to LPS and that macrophage activation inhibits airway morphogenesis. Macrophage depletion or targeted inactivation of the NF-κB signaling pathway protected airway branching in cultured lung explants from the effects of LPS. Macrophages also appear to be the primary cellular site of IL-1β production following LPS exposure. Conversely, targeted NF-κB activation in transgenic macrophages was sufficient to inhibit airway morphogenesis. Macrophage activation in vivo inhibited expression of multiple genes critical for normal lung development, leading to thickened lung interstitium, reduced airway branching, and perinatal death. We propose that fetal lung macrophage activation contributes to bronchopulmonary dysplasia by generating a localized inflammatory response that disrupts developmental signals critical for lung formation.

Omeprazole attenuates hyperoxic lung injury in mice via aryl hydrocarbon receptor activation and is associated with increased expression of cytochrome P4501A enzymes

Hyperoxia contributes to lung injury in experimental animals and bronchopulmonary dysplasia (BPD) in preterm infants. Cytochrome P4501A (CYP1A) enzymes, which are regulated by the aryl hydrocarbon receptor (AhR), have been shown to attenuate hyperoxic lung injury in rodents. Omeprazole, a proton pump inhibitor, used in humans to treat gastric acid-related disorders, induces hepatic CYP1A in vitro. However, the mechanism by which omeprazole induces CYP1A and its impact on CYP1A expression in vivo and hyperoxic lung injury are unknown. Therefore, we tested the hypothesis that omeprazole attenuates hyperoxic lung injury in adult wild-type (WT) C57BL/6J mice by an AhR-mediated induction of pulmonary and hepatic CYP1A enzymes. Accordingly, we determined the effects of omeprazole on pulmonary and hepatic CYP1A expression and hyperoxic lung injury in adult WT and AhR dysfunctional (AhRd) mice. We found that omeprazole attenuated lung injury in WT mice. Attenuation of lung injury by omeprazole paralleled enhanced pulmonary CYP1A1 and hepatic CYP1A2 expression in the omeprazole-treated mice. On the other hand, omeprazole failed to enhance pulmonary CYP1A1 and hepatic CYP1A2 expression and protect against hyperoxic lung injury in AhRd mice. In conclusion, our results suggest that omeprazole attenuates hyperoxic lung injury in mice by AhR-mediated mechanisms, and this phenomenon is associated with induction of CYP1A enzymes. These studies have important implications for the prevention and/or treatment of hyperoxia-induced disorders such as BPD in infants and acute respiratory distress syndrome in older children and adults.

Endothelial progenitor cells, bronchopulmonary dysplasia and other short-term outcomes of extremely preterm birth

AIM

To evaluate the impact of endothelial progenitor cells (EPCs), a subset of committed circulatory stem cells, on the development of bronchopulmonary dysplasia (BPD) and other short term outcomes in a cohort of extremely premature newborns.

METHODS

Progenitor cells were quantified by flow cytometry at birth in 36 neonates born <=28 weeks of gestation and at 36 postmenstrual weeks in 18 of them. Cells expressing the stemness markers CD34, CD133, or both were defined as circulating progenitor cells (CPCs). EPCs were defined as CPCs co-expressing the endothelial marker KDR.

RESULTS

Mean (SD) gestational age and birth weight of the infants studied were 26.2(1.5) weeks and 761.6(171.8) grams, respectively. EPC levels at birth did not differ between infants who subsequently developed BPD (n=9) and those who did not (n=24) [CD34(+)KDR(+) EPCs: 81(34-41) vs 80(56-110), p=0.7] and were not correlated with the duration of mechanical ventilation or O2-dependence, nor with the need of surfactant replacement. Infants with a hemodynamically significant patent ductus arteriosus (PDA) (n=22) had significantly lower EPC levels at birth than those with no PDA (n=11) [CD34(+)KDR(+) cells: 47(34-92) vs 142(84.5-221), p=0.008]. Data from the 18 infants studied both at birth and at 36 postmenstrual weeks showed that, while CPCs sharply decline over time, levels of all EPCs phenotypes are preserved after delivery.

CONCLUSIONS

Levels of EPCs at birth did not affect the risk of developing BPD in our group of extremely premature neonates. However, the association between low EPC counts at birth and PDA may be clinically relevant, and deserves further studies.

Post-natal corticosteroids are associated with reduced expiratory flows in children born very preterm

AIM

Infants born very prematurely often received corticosteroids to minimise the risk of developing bronchopulmonary dysplasia (BPD) but their long term impact on lung function at school age is unclear.

METHODS

A cross-sectional study of 105 children [mean gestation of 27 weeks] was undertaken. Lung function assessments were conducted at a mean age of 10 years according to standard criteria. Corticosteroid dose was obtained from the medical record.

RESULTS

Spirometry in the BPD group was not significantly different to the non-BPD group, mean per-cent predicted (95% confidence interval) forced expiratory volume in 1 s (FEV1) 83% (79, 87) versus 86% (83, 90), FEF25%-75% 67% (60, 73) versus 75% (69, 81). Antenatal steroid treatment alone did not adversely affect airflow FEV1, 88% (84.92) versus 90% (82.97), and forced expiratory flow (FEF)25%-75%, 75% (69.81) versus 87% (70.104). Children who received post-natal corticosteroids had significantly lower flows than those who did not (FEV1 82% (78.85) vs. 88% (85.92), P = 0.006; FEF25%-75% 65% (59.71) vs. 78% (72.84), P = 0.003). Regression analysis revealed days on oxygen and days ventilated were statistically significant but weak predictors of airflow at 10 years of age.

CONCLUSIONS

A diagnosis of BPD did not predict reduced spirometry in middle childhood. Children who received post-natal corticosteroids as preterm infants had reduced expiratory flows compared with those who did not. While post-natal corticosteroids may be a marker of severity of lung disease, the potential of post-natal corticosteroids to influence lung development requires further investigation.

The pharmacology of acute lung injury in sepsis

Acute lung injury (ALI) secondary to sepsis is one of the leading causes of death in sepsis. As such, many pharmacologic and nonpharmacologic strategies have been employed to attenuate its course. Very few of these strategies have proven beneficial. In this paper, we discuss the epidemiology and pathophysiology of ALI, commonly employed pharmacologic and nonpharmacologic treatments, and innovative therapeutic modalities that will likely be the focus of future trials.

Early amplitude integrated electroencephalography and outcome of very low birth weight infants

OBJECTIVE

Amplitude integrated electroencephalography (aEEG) has been used in neonates in various clinical and research applications. We hypothesized that an abnormal aEEG score could be used as a predictor of short-term adverse outcome.

METHODS

Very low birth weight infants were enrolled in a prospective observational cohort study. Two channel 12-hour continuous aEEG recordings were performed within 48 h of life and at 1 week of age. Recordings were classified as abnormal if they correspond to a 2 point difference in score. Short-term adverse outcome was defined as either death or Bayley scales ≤ 70 at 4 months corrected age.

RESULTS

One hundred infants were enrolled. Their average gestational age was 27.9 ± 2.6 weeks and average birth weight was 997 ± 299 gram. Fifteen enrolled infants died, one was withdrawn, 29 lost to follow up, and 55 examined at 4 months. Those with adverse outcome had significantly increased percentages of abnormal EEG at 1 week of life (31% vs. 8%), severe intraventricular hemorrhage (IVH) (27% vs. 4.5%), intubation in the delivery room (45% vs. 16%), and increased average days of mechanical ventilation (16 days vs. 4 days). Combining abnormal aEEG at 1 week of life to severe IVH on early head ultrasound increased the sensitivity of ultrasound to detect short-term adverse outcome from 27% to 50%.

CONCLUSION

aEEG is feasible in premature infants and when its data at 1 week of life are combined with early head ultrasound, sensitivity for detecting short-term adverse outcomes was increased.

Effects of secondhand smoke exposure on the health and development of african american premature infants

Objective. To explore the effects of secondhand smoke exposure on growth, health-related illness, and child development in rural African American premature infants through 24 months corrected age. Method. 171 premature infants (72 boys, 99 girls) of African American mothers with a mean birthweight of 1114 grams. Mothers reported on household smoking and infant health at 2, 6, 12, 18, and 24 months corrected age. Infant growth was measured at 6, 12, 18, and 24 months, and developmental assessments were conducted at 12 and 24 months. Results. Thirty percent of infants were exposed to secondhand smoke within their first 2 years of life. Secondhand smoke exposure was associated with poorer growth of head circumference and the development of otitis media at 2 months corrected age. Height, weight, wheezing, and child development were not related to secondhand smoke exposure. Conclusion. Exposure to secondhand smoke may negatively impact health of rural African American premature infants. Interventions targeted at reducing exposure could potentially improve infant outcomes.

Low birth weight and respiratory hospitalizations in adolescence

OBJECTIVE

Some low birth weight survivors are at increased risk of respiratory disease. We studied whether low birth weight was associated with hospitalization for respiratory illness in adolescence and to what degree bronchopulmonary dysplasia, cerebral palsy, and other comorbidities accounted for this association.

METHODS

We performed a population-based retrospective cohort study using Washington State birth certificates from 1987 to 1994 to identify exposed (low birth weight) and unexposed (normal birth weight) subjects. Normal birth weight subjects were randomly selected from birth certificates, frequency matched to low birth weight subjects by birth year. Deaths prior to age 12 were excluded. The primary exposure was low birth weight: subcategorized as moderately-low-birth weight (1,500-2,499 g) and very-low-birth weight (<1,500 g). The primary outcome was the first respiratory related hospitalization between the ages of 12-20. Respiratory hospitalizations were defined by ICD-9 discharge diagnosis codes.

RESULTS

After adjustment, the hazard ratio for hospitalization was 1.39 for moderately-low-birth weight (95% CI 1.17-1.65, P < 0.001) and 2.52 for very-low-birth weight (1.80-3.53, P < 0.001). Controlling for bronchopulmonary dysplasia attenuated the risk for very-low-birth weight to 1.76 (1.17-2.64; P = 0.006). A similar attenuation was seen after controlling for cerebral palsy [HR 1.49 (1.02-2.18), P = 0.04], suggesting that some of the risk is mediated through these diagnoses. Among moderately-low-birth weight survivors, controlling for these diagnoses had less of an effect.

CONCLUSIONS

Low birth weight was associated with an increased risk of respiratory hospitalizations in adolescence. Comorbidities explained some of this risk. However, low birth weight remained independently associated with an increased risk of hospitalization.

Perioperative factors associated with prolonged mechanical ventilation after complex congenital heart surgery

OBJECTIVE

To evaluate perioperative factors associated with prolonged mechanical ventilation in children undergoing complex cardiac surgery for congenital heart disease.

DESIGN

Retrospective chart review.

SETTING

A tertiary care pediatric cardiac intensive care.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

This retrospective cohort study included all patients undergoing complex cardiac surgical procedures (Risk Adjustment in Congenital Heart Surgery-1 category ≥ 3) at our institution during 2003. We defined prolonged mechanical ventilation as need for mechanical ventilation for ≥ 7 days (90th percentile of duration of mechanical ventilation for the whole cohort). Multivariate logistic regression analyses were used to determine independent relationships between perioperative factors and prolonged mechanical ventilation. A total of 362 patients were admitted to the cardiac intensive care unit after a cardiac surgical procedure of Risk Adjustment in Congenital Heart Surgery-1 ≥ 3 level of complexity and survived to hospital discharge. Median age was 242 days (range, 4 days-14.4 yrs), the median duration of mechanical ventilation was 1.5 days (range, 0-7 days), and 41 patients (11%) were ventilated for ≥ 7 days. Age of <30 days at surgery, higher Pediatric Risk of Mortality III score at the time of cardiac intensive care unit admission, the presence of major noncardiac structural anomalies, healthcare-associated infections, noninfectious pulmonary complications (pleural effusions and pneumothorax), and the need for reintervention were all independently associated with prolonged mechanical ventilation.

CONCLUSIONS

Younger age, greater severity of illness at postoperative admission, healthcare-associated infections, noninfectious pulmonary complications, and the need for reintervention are associated with prolonged mechanical ventilation after complex cardiac surgery. Future studies and quality improvement initiatives should focus on those risk factors that are modifiable to promote early extubation in children recovering from complex congenital heart surgery.

In utero exposure to Ureaplasma spp. is associated with increased rate of bronchopulmonary dysplasia and intraventricular hemorrhage in preterm infants

AIMS

We determined the association between short-term neonatal morbidities, such as bronchopulmonary dysplasia (BPD) and intraventricular hemorrhage (IVH), and Ureaplasma spp. in amniotic fluid, placental and amniotic membrane of preterm infants.

METHODS

This study enrolled 257 patients who were born by cesarean section at <34 weeks' gestation. Patients were divided into two groups according to detection of Ureaplasma spp. by culture-based and/or polymerase chain reaction (PCR) techniques.

RESULTS

Significant differences were observed between both groups for all IVH (P=0.032) and IVH grades III or IV (P=0.013), as wells as for BPD [odds ratio (OR) 5.46, 95% confidence interval (CI) 2.02-14.77], oxygen requirement at 28 days postnatal age (OR 1.93, 95% CI 1.00-3.70), and for death between 28 days and 36 postmenstrual weeks or BPD (OR 4.20, 95% CI 1.77-9.96). Ureaplasma spp. was a significant predictor (P<0.001) of BPD after correcting for birth weight (P=0.003) and positive pressure ventilation (P=0.001).

CONCLUSIONS

In our study population Ureaplasma spp. was associated with BPD and IVH in preterm infants even after adjustment for multiple risk factors.

A consensus approach to the classification of pediatric pulmonary hypertensive vascular disease: Report from the PVRI Pediatric Taskforce, Panama 2011

Current classifications of pulmonary hypertension have contributed a great deal to our understanding of pulmonary vascular disease, facilitated drug trials, and improved our understanding of congenital heart disease in adult survivors. However, these classifications are not applicable readily to pediatric disease. The classification system that we propose is based firmly in clinical practice. The specific aims of this new system are to improve diagnostic strategies, to promote appropriate clinical investigation, to improve our understanding of disease pathogenesis, physiology and epidemiology, and to guide the development of human disease models in laboratory and animal studies. It should be also an educational resource. We emphasize the concepts of perinatal maladaptation, maldevelopment and pulmonary hypoplasia as causative factors in pediatric pulmonary hypertension. We highlight the importance of genetic, chromosomal and multiple congenital malformation syndromes in the presentation of pediatric pulmonary hypertension. We divide pediatric pulmonary hypertensive vascular disease into 10 broad categories.

Risk of asthma in young adults who were born preterm: a Swedish national cohort study

OBJECTIVE

Preterm birth is associated with asthma-like symptoms in childhood and possibly in adolescence, but the longer-term risk of asthma is unknown and increasingly relevant as larger numbers of these individuals enter adulthood. Our objective was to evaluate whether those who were born preterm are more likely to be prescribed asthma medications in young adulthood than those who were born term.

PATIENTS AND METHODS

We conducted a national cohort study of all singleton infants born in Sweden from 1973 through 1979 (n = 622 616), followed to ages 25.5 to 35.0 years to determine whether asthma medications were prescribed in 2005-2007. Asthma medication data were obtained from all outpatient and inpatient pharmacies throughout Sweden. To improve the positive predictive value for asthma, the outcome was defined as prescription of (1) both a β-2 agonist inhalant and a glucocorticoid inhalant or (2) a combination inhalant containing a β-2 agonist and other drugs for obstructive airway diseases.

RESULTS

Young adults who were born extremely preterm (23-27 weeks' gestation) were 2.4 times more likely (adjusted 95% CI: 1.41-4.06) to be prescribed asthma medications than those who were born term. No association was found between later preterm birth (28-32 or 33-36 weeks' gestation) and asthma medications in young adulthood.

CONCLUSIONS

This is the first study with sufficient statistical power to evaluate the risk of asthma beyond adolescence in individuals who were born extremely preterm. The results suggest that extreme preterm birth (23-27 weeks' gestation), but not later preterm birth, is associated with an increased risk of asthma at least into young adulthood.

Augmented oxygen-mediated transcriptional activation of cytochrome P450 (CYP)1A expression and increased susceptibilities to hyperoxic lung injury in transgenic mice carrying the human CYP1A1 or mouse 1A2 promoter in vivo

Supplemental oxygen administration is frequently administered to pre-term and term infants having pulmonary insufficiency. However, hyperoxia contributes to the development of bronchopulmonary dysplasia (BPD) in premature infants. Cytochrome P450 (CYP)A enzymes have been implicated in hyperoxic lung injury. In this study, we tested the hypothesis that hyperoxia induces CYP1A1 and 1A2 enzymes by transcriptional activation of the corresponding promoters in vivo, and transgenic mice expressing the human CYP1A1 or the mouse 1A2 promoter would be more susceptible to hyperoxic lung injury than wild type (WT) mice. Adult WT (CD-1) (12week-old) mice, transgenic mice carrying a 10kb human CYP1A1 promoter and the luciferase (luc) reporter gene (CYP1A1-luc), or mice expressing the mouse CYP1A2 promoter (CYP1A2-luc) were maintained in room air or exposed to hyperoxia for 24-72h. Hyperoxia exposure of CYP1A1-luc mice for 24 and 48h resulted in 2.5- and 1.25-fold increases, respectively, in signal intensities, compared to room air controls. By 72h, the induction had declined to control levels. CYP1A2-luc mice also showed enhanced luc expression after 24-48h, albeit to a lesser extent than those expressing the CYP1A1 promoter. Also, these mice showed decreased levels of endogenous CYP1A1 and 1A2 expression after prolonged hyperoxia, and were also more susceptible to lung injury than similarly exposed WT mice, with CYP1A2-luc mice showing the greatest injury. Our results support the hypothesis that hyperoxia induces CYP1A enzymes by transcriptional activation of its corresponding promoters, and that decreased endogenous expression of these enzymes contribute to the increased susceptibilities to hyperoxic lung injury in the transgenic animals. In summary, this is the first report providing direct evidence of hyperoxia-mediated induction of CYP1A1 and CYP1A2 expression in vivo by mechanisms entailing transcriptional activation of the corresponding promoters, a phenomenon that has implications for hyperoxic lung injury, as well as other pathologies caused by oxidative stress.

The Transition from Bronchopulmonary Dysplasia to Childhood Chronic Lung Disease

The impact of a preterm birth on lung function in later life is not always predictable and the variability of lung phenotype in these children can be striking even among children of the same gestational age. Although many children with a history of bronchopulmonary dysplasia (BPD) improve with age, others continue to manifest significant pulmonary abnormalities. Several different lung phenotypes have been described in older children with a history of BPD. These descriptions have been based in part on chronic respiratory symptoms, pulmonary function abnormalities, and response to respiratory illnesses. These lung phenotypes include large and/or small airway dysfunction, impaired alveolar growth characterized by decreased pulmonary reserve, and pulmonary hypertension found primarily in children with severe chronic lung disease. Children with a history of BPD can manifest 1 or more of these lung phenotypes with varying degrees of severity. Currently, treatment of respiratory symptoms is primarily supportive and symptom based. Although many children improve with age, others continue to have chronic respiratory symptoms into adult life. The development of standardized guidelines for the care of children after discharge from the neonatal intensive care unit may help direct appropriate therapy, limit lung injury, and maximize lung growth potential in this vulnerable group of children.

Prolonged mechanical ventilation induces cell cycle arrest in newborn rat lung

RATIONALE

The molecular mechanism(s) by which mechanical ventilation disrupts alveolar development, a hallmark of bronchopulmonary dysplasia, is unknown.

OBJECTIVE

To determine the effect of 24 h of mechanical ventilation on lung cell cycle regulators, cell proliferation and alveolar formation in newborn rats.

METHODS

Seven-day old rats were ventilated with room air for 8, 12 and 24 h using relatively moderate tidal volumes (8.5 mL.kg⁻¹).

MEASUREMENT AND MAIN RESULTS

Ventilation for 24 h (h) decreased the number of elastin-positive secondary crests and increased the mean linear intercept, indicating arrest of alveolar development. Proliferation (assessed by BrdU incorporation) was halved after 12 h of ventilation and completely arrested after 24 h. Cyclin D1 and E1 mRNA and protein levels were decreased after 8-24 h of ventilation, while that of p27(Kip1) was significantly increased. Mechanical ventilation for 24 h also increased levels of p57(Kip2), decreased that of p16(INK4a), while the levels of p21(Waf/Cip1) and p15(INK4b) were unchanged. Increased p27(Kip1) expression coincided with reduced phosphorylation of p27(Kip1) at Thr¹⁵⁷, Thr¹⁸⁷ and Thr¹⁹⁸ (p<0.05), thereby promoting its nuclear localization. Similar -but more rapid- changes in cell cycle regulators were noted when 7-day rats were ventilated with high tidal volume (40 mL.kg⁻¹) and when fetal lung epithelial cells were subjected to a continuous (17% elongation) cyclic stretch.

CONCLUSION

This is the first demonstration that prolonged (24 h) of mechanical ventilation causes cell cycle arrest in newborn rat lungs; the arrest occurs in G₁ and is caused by increased expression and nuclear localization of Cdk inhibitor proteins (p27(Kip1), p57(Kip2)) from the Kip family.

Oxygen use for preterm infants: factors that may influence clinical decisions surrounding oxygen titration

Preterm infants in neonatal intensive care units frequently require oxygen therapy. Clinicians are responsible for titrating oxygen to maximize the benefits and minimize the risks of this therapy. Studies have identified various toxic effects of oxygen on the developing tissues of the preterm infant; however, optimal target SpO(2) ranges have not been identified. Current trends in neonatology are focusing on defining optimal oxygen saturation ranges to improve infant outcomes and to decrease complications associated with the oxygen use. Consequently, research-based guidelines are being developed in neonatal intensive care units to guide oxygen administration. As target oxygen saturation ranges are developed, issues regarding health care professional compliance with these ranges have been identified. The specific reasons for this noncompliance have not been widely explored. However, factors such as nursing shortages, staffing issues, and a de-emphasis on staff education surrounding oxygen use have been offered as possible reasons. Understanding factors shaping clinical decision-making about oxygen titration is critical when designing policies and educational programs to change oxygen titration practice and ultimately improve patient outcomes. In this article, the literature outlining the importance of oxygen titration for preterm infants is reviewed. Discussion then focuses on factors that influence clinical decision-making and how these factors may influence decisions surrounding the use of oxygen for preterm infants.

Use of azithromycin for the prevention of bronchopulmonary dysplasia in preterm infants: a randomized, double-blind, placebo controlled trial

OBJECTIVE

Since preventive therapies for bronchopulmonary dysplasia (BPD) are limited we treated preterm infants with azithromycin to decrease the incidence of BPD.

METHODS

Infants less than 1,250 g birth weight were randomized to azithromycin or placebo within 12 hr of beginning mechanical ventilation and within 72 hr of birth. The treatment group received azithromycin 10 mg/kg/day for 7 days followed by 5 mg/kg/day for a maximum of 6 weeks. Aspirates were collected during the study to assay for Ureaplasma. The primary endpoints were incidence of BPD or mortality. (Clinical Trials Identifier: NCT00319956.)

RESULTS

A total of 220 infants were enrolled (n=111 azithromycin, and 109 placebo). Mortality was 18% for the azithromycin group versus 22% for the placebo group (P = 0.45). Incidence of BPD was 76% for the azithromycin group versus 84% for the placebo group (P=0.2). The multiple logistic regression analysis demonstrated an odds ratio of 0.46 decrease in the chance of developing BPD or death for the azithromycin group, but was not statistically significant. The incidence of BPD in the Ureaplasma subgroup was 73% in the azithromycin group versus 94% in the placebo group (P=0.03). Analysis of patients in the Ureaplasma subgroup only, using the exact logistic model demonstrated a decrease in BPD or death in the azithromycin group with an estimated odds ratio of 0.026 (0.001-0.618, 95% confidence interval).

CONCLUSIONS

Routine use of azithromycin therapy for the prevention of BPD cannot be recommended. The early treatment of Ureaplasma colonized/infected patients might be beneficial, but a larger multi-centered trial is required to assess this more definitively.

Preterm birth and respiratory disease in later life

Chronic respiratory diseases are a common complication of preterm birth, particularly among very immature infants or those suffering from bronchopulmonary dysplasia. Major progress in the treatment of preterm newborns has changed the pattern of late respiratory complications. The major respiratory problem in infancy and early childhood is respiratory exacerbations caused by infections (particularly viral ones), which need hospitalization. The symptoms become mild in school-age children; however, a group of children still present with chronic airway obstruction defined by recurrent episodes of wheezing and decreased lung function tests (decreased forced expiratory volume). For some preterm infants, particularly those with bronchopulmonary dysplasia, obstructive lung disease persists into adulthood. They are very likely to develop chronic obstructive pulmonary disease or similar disease later in life. In these patients, a program of lung function monitoring and pulmonary prophylaxis by means of elimination of specific risk factors in adulthood is advisable.

Effect of repeated treatment of pregnant women with sulfadoxine-pyrimethamine and azithromycin on preterm delivery in Malawi: a randomized controlled trial

Preterm delivery, which is associated with infections during pregnancy, is common in sub-Saharan Africa. We enrolled 1,320 pregnant women into a randomized, controlled trial in Malawi to study whether preterm delivery and low birth weight (LBW) incidence can be reduced by intermittent preventive treatment of maternal malaria and reproductive tract infections. The participants received either sulfadoxine-pyrimethamine (SP) twice (controls), monthly SP, or monthly SP and two doses of azithromycin (AZI-SP). The incidence of preterm delivery was 17.9% in controls, 15.4% in the monthly SP group (P = 0.32), and 11.8% in AZI-SP group (risk ratio = 0.66, P = 0.01). Compared with controls, those in AZI-SP group had a risk ratio of 0.61 (P = 0.02) for LBW. Incidence of serious adverse events was low in all groups. In conclusion, the incidence of preterm delivery and LBW can in some conditions be reduced by treating pregnant women with monthly SP and two azithromycin doses.

Bronchopulmonary dysplasia - prevalence, severity and predictive factors in a national cohort of extremely premature infants

AIM

To study prevalence and predictive factors of bronchopulmonary dysplasia (BPD) in a cohort of preterm infants with a high incidence of prenatal steroid and surfactant treatment.

METHODS

BPD was analysed in a national cohort of infants with gestational age (GA) of 22-27 completed weeks (wks) or birth weight (BW) of 500-999 g. Of 464 infants who were transferred to a NICU, 377 infants with GA ≤ 30 wks and survived beyond 28 days were included in the study.

RESULTS

Moderate or severe BPD was strongly related to GA. Of infants with GA 22-25 wks, 67.3% developed BPD compared to 36.6% at GA 26-30 wks. Overall, moderate and severe BPD was significantly more common in boys (63.3%) than in girls (36.6%) (p = 0.0004), but female gender was not a protective factor in infants with GA 22-25 wks. In multivariate analyses, BPD was significantly associated with gender, surfactant treatment and treatment for PDA.

CONCLUSIONS

BPD remains a severe complication of extreme prematurity in spite of prenatal steroids and surfactant treatment. Whether associations with surfactant and PDA treatment simply reflect severity of early lung disease or have causal relationships should probably be studied in randomized controlled trials.

Nebulized Furosemide in the Treatment of Bronchopulmonary Dysplasia in Preterm Infants

Bronchopulmonary dysplasia (BPD) is a chronic pulmonary disease commonly seen in preterm infants who require supplemental oxygen and/or assisted mechanical ventilation. BPD, a major cause of morbidity and mortality among premature infants, occurs in 5,000 to 10,000 premature infants in the United States each year. Despite numerous medical advances, no single intervention will prevent or treat BPD; hence, premature infants have an increased risk for developing significant sequelae that affect both cognitive and motor function. This article provides a brief overview of BPD and reviews the available literature regarding the safe and effective use of nebulized furosemide in the treatment of this disorder.

Respiratory outcomes and atopy in school-age children who were preterm at birth, with and without bronchopulmonary dysplasia

OBJECTIVE

To assess pulmonary function and the prevalence of atopy in school-age children who were very low birth weight as infants and to compare those who had bronchopulmonary dysplasia to those who did not.

METHOD

We studied 85 (39 male and 46 female) at a mean age of 84 (range, 62 to 107) months who were very low birth weight infants. Bronchopulmonary dysplasia was defined as oxygen dependency at 36 weeks gestational age. We excluded 8 patients (4 for cerebral palsy and 4 for no collaboration). Detailed perinatal and clinical data were collected. Lung function was evaluated using conventional spirometry. Atopy (assessed by the allergy skin-prick test) was considered when at least one positive skin test occurred in a panel of the most common environmental allergens in the local region. Comparisons between the bronchopulmonary dysplasia and no bronchopulmonary dysplasia groups were performed using the Mann-Whitney, x2 and Fisher's exact tests.

RESULTS

We compared the bronchopulmonary dysplasia (n = 13) and no bronchopulmonary dysplasia (n = 64) groups. Atopy was observed in 4 (30.8%) of the bronchopulmonary dysplasia patients and in 17 (26.6%) of the no bronchopulmonary dysplasia patients (p = 0.742). Two (15.4%) patients with bronchopulmonary dysplasia had a family history of atopy vs. 17 (26.6%) in the no bronchopulmonary dysplasia group (p = 0.5). Lung function tests showed airway obstruction in 2 (15.4%) of the bronchopulmonary dysplasia patients and in 10 (15.6%) of the no bronchopulmonary dysplasia patients (p = 1.0). Four (33.3%) of the bronchopulmonary dysplasia patients had small airway obstruction vs. 14 (22.2%) of the no bronchopulmonary dysplasia patients (p = 0.466).

CONCLUSION

Our data showed no significant differences in lung function between bronchopulmonary dysplasia and no bronchopulmonary dysplasia patients at school age and no evidence of an association between atopy and bronchopulmonary dysplasia.

Lung interstitial cells during alveolarization

Recent progress in neonatal medicine has enabled survival of many extremely low-birth-weight infants. Prenatal steroids, surfactants, and non-invasive ventilation have helped reduce the incidence of the classical form of bronchopulmonary dysplasia characterized by marked fibrosis and emphysema. However, a new form of bronchopulmonary dysplasia marked by arrest of alveolarization remains a complication in the postnatal course of extremely low-birth-weight infants. To better understand this challenging complication, detailed alveolarization mechanisms should be delineated. Proper alveolarization involves the temporal and spatial coordination of a number of cells, mediators, and genes. Cross-talk between the mesenchyme and the epithelium through soluble and diffusible factors are key processes of alveolarization. Lung interstitial cells derived from the mesenchyme play a crucial role in alveolarization. Peak alveolar formation coincides with intense lung interstitial cell proliferation. Myofibroblasts are essential for secondary septation, a critical process of alveolarization, and localize to the front lines of alveologenesis. The differentiation and migration of myofibroblasts are strictly controlled by various mediators and genes. Disruption of this finely controlled mechanism leads to abnormal alveolarization. Since arrest in alveolarization is a hallmark of a new form of bronchopulmonary dysplasia, knowledge regarding the role of lung interstitial cells during alveolarization and their control mechanism will enable us to find more specific therapeutic strategies for bronchopulmonary dysplasia. In this review, the role of lung interstitial cells during alveolarization and control mechanisms of their differentiation and migration will be discussed.

Fatty acid-binding proteins and peribronchial angiogenesis in bronchopulmonary dysplasia

Inflammation plays a key role in the pathogenesis of bronchopulmonary dysplasia (BPD). Fatty acid-binding proteins (FABPs) 4 and 5 regulate the inflammatory activity of macrophages. Whether FABPs 4 and 5 could play a role in the pathogenesis of BPD via the promotion of macrophage inflammatory activity is unknown. This study sought to examine whether the expression levels of FABP4 and FABP5 were altered in bronchoalveolar lavage fluid and lung tissue in a baboon model of BPD. This study also sought to characterize the cell types that express these proteins. Real-time PCR, immunoblotting, immunohistochemistry, and double immunofluorescence were used to examine the expression of FABPs in samples of BPD. Morphometric analysis was used to quantify FABP4-positive peribronchial blood vessels in lung sections. FABP4 was primarily expressed in macrophages in samples of BPD. In addition, FABP4 was expressed in the endothelial cells of blood vessels in peribronchial areas and the vasa vasorum, but not in the alveolar vasculature in samples of BPD. FABP4 concentrations were significantly increased in lungs and bronchoalveolar lavage fluid samples with BPD. An increased density of FABP4-positive peribronchial blood vessels was evident in both baboon and human BPD sections. FABP5 was expressed in several cell types, including alveolar epithelial cells and macrophages. FABP5 concentrations did not show any significant alterations in BPD. In conclusion, FABP4 but not FABP5 levels are increased in BPD. FABP4 is differentially expressed in endothelial cells of the bronchial microvasculature, which demonstrates a previously unrecognized expansion in BPD.

NO inhibits hyperoxia-induced NF-κB activation in neonatal pulmonary microvascular endothelial cells

Inhaled NO (iNO) may be protective against hyperoxic injury in the premature lung, but the mechanism is unknown. We hypothesized that NO would prevent hyperoxia-induced nuclear factor kappa B (NF-κB) activation in neonatal pulmonary microvascular endothelial cells [human pulmonary microvascular endothelial cell (HPMEC)] and prevent the up-regulation of target genes. After hyperoxic exposure (O2 >95%), nuclear NF-κB consensus sequence binding increased and was associated with IκBα degradation. Both of these findings were prevented by exposure to NO. Furthermore, intracellular adhesion molecule (ICAM)-1 mRNA and protein levels increased in cells exposed to hyperoxia, an effect abrogated by NO. To evaluate the potentially toxic effect of NO plus hyperoxia, cell viability and proliferation were assessed. Cells exposed to NO plus hyperoxia demonstrated improved survival as measured by trypan blue exclusion when compared with cells exposed to hyperoxia alone. These differences in cell death could not be attributed to apoptosis measured by caspase-3 activity. Finally, cellular proliferation inhibited by hyperoxia was rescued by concurrent exposure to NO. These data demonstrate that NO prevents hyperoxia-induced NF-κB activation in HPMEC and results in decreased expression of adhesion molecules and decreased cellular toxicity. This may help to explain the protective effects of NO on hyperoxic injury in the developing lung vasculature.

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.

The building blocks of mammalian lung development

Progress has recently been made in identifying progenitor cell populations in the embryonic lung. Some progenitor cell types have been definitively identified by lineage-tracing studies. However, others are not as well characterized and their existence is inferred on the basis of lung morphology, or mutant phenotypes. Here, I focus on lung development after the specification of the initial lung primordium. The evidence for various lung embryonic progenitor cell types is discussed and future experiments are suggested. The regulation of progenitor proliferation in the embryonic lung, and its coordinate control with morphogenesis, is also discussed. In addition, the relationship between embryonic and adult lung progenitors is considered.

5-Lipoxygenase-activating protein (FLAP) inhibitor MK-0591 prevents aberrant alveolarization in newborn mice exposed to 85% oxygen in a dose- and time-dependent manner

Bronchopulmonary dysplasia is characterized by prolonged oxygen dependency due to compromised gas-exchange capability. This is attributable mainly to inadequate and aberrant alveolarization resulting from insults like hyperoxia. Leukotrienes are associated with hyperoxia-induced inhibition of alveolarization. We hypothesized that a 5-lipoxygenase-activating protein (FLAP) inhibitor given while newborn mice were exposed to 85% oxygen would prevent aberrant alveolarization in a dose- and time-dependent manner. Newborn mice were exposed to either room air or hyperoxia for 14 days. Pups were treated with either vehicle or MK-0591 10, 20, or 40 mg/kg subcutaneously daily for days 1-4, 5-9, or 10-14. On day 14, the lungs were inflated, fixed, and stained for histopathological and morphometric analyses. Hyperoxia groups treated with MK-0591 20 or 40 mg/kg during days P1-P4 or P10-P14 showed alveolarization that resembled that of room air controls while untreated hyperoxia groups showed definite evidence of aberrant alveolarization but no inflammation. In a hyperoxia-exposed newborn mice model, a FLAP inhibitor given during critical window periods may prevent aberration of alveolarization in a dose- and time-dependent manner.

Respiratory muscle activity related to flow and lung volume in preterm infants compared with term infants

Infants with chronic lung disease (CLD) have a capacity to maintain functional lung volume despite alterations to their lung mechanics. We hypothesize that they achieve this by altering breathing patterns and dynamic elevation of lung volume, leading to differences in the relationship between respiratory muscle activity, flow and lung volume. Lung function and transcutaneous electromyography of the respiratory muscles (rEMG) were measured in 20 infants with CLD and in 39 healthy age-matched controls during quiet sleep. We compared coefficient of variations (CVs) of rEMG and the temporal relationship of rEMG variables, to flow and lung volume [functional residual capacity (FRC)] between these groups. The time between the start of inspiratory muscle activity and the resulting flow (tria)--in relation to respiratory cycle time--was significantly longer in infants with CLD. Although FRC had similar associations with tria and postinspiratory activity (corrected for respiratory cycle time), the CV of the diaphragmatic rEMG was lower in CLD infants (22.6 versus 31.0%, p = 0.030). The temporal relationship of rEMG to flow and FRC and the loss of adaptive variability provide additional information on coping mechanisms in infants with CLD. This technique could be used for noninvasive bedside monitoring of CLD.

Techniques of early respiratory management of very low and extremely low birth weight infants

The generalized anatomic and physiologic immaturity of preterm infants of very low birth weight (VLBW) (<or=1,500 g) and extremely low birth weight (ELBW) (<or=1,000 g) places them at high risk for death or associated negative sequelae, including chronic lung disease of infancy (CLDI). The standard treatment for pulmonary immaturity, mechanical ventilation (MV) at birth, can lead to barotrauma, volutrauma, pulmonary edema, infection, and inflammation. To minimize these negative outcomes, multiple treatment strategies have been proposed and evaluated as to their subsequent clinical course. This article compares, contrasts, and integrates the use of MV, nasal continuous positive airway pressure (NCPAP), and surfactant administration to encourage and support consideration of their use in the VLBW and ELBW population. Supporting a reduction of the use of MV in favor of NCPAP is safe and recommended because this practice is likely to decrease the probable sequelae of CLDI while permitting an individualized approach.

Motor trajectories from 4 to 18 months corrected age in infants born at less than 30 weeks of gestation

BACKGROUND

Preterm infants are recognised as developing at a significantly slower rate than their full-term peers and with different movement quality.

AIM

This study aimed to describe the longitudinal gross motor trajectories of these infants in the first 18 months of (corrected) age and investigate factors associated with gross motor development.

STUDY DESIGN

A longitudinal study was conducted with convenience samples of 58 preterm infants born < or = 29 weeks of gestation and 52 control full-term infants in Australia.

OUTCOME MEASURES

The infants were assessed at 4, 8, 12 and 18 months of (corrected) age using the Alberta Infant Motor Scale (AIMS).

RESULTS

Forty-six preterm and 48 control infants completed all four assessments. The preterm group scored significantly lower on various sub-scores at all age levels. Almost half of the preterm infants demonstrated less progression in the sit sub-scale from 4 to 8 months (corrected) age, possibly due to an imbalance between flexor and extensor strength in the trunk. At 12 and 18 months of (corrected) age, lack of rotation and fluency in their movements were evident in some preterm infants. Presence of intra-ventricular haemorrhage and chronic lung disease were associated with poor motor performance at 4 months and use of postnatal steroids was associated with poor motor performance at 4, 8 and 18 months of corrected age.

CONCLUSION

The imbalance between flexor and extensor muscle strength in preterm infants had a stronger impact on motor development than usually expected. The AIMS appears to be a sensitive assessment tool to demonstrate the unique movement characteristics in this preterm cohort.

Highly conserved transcriptional responses to mechanical ventilation of the lung

Cross-species analysis of microarray data has shown improved discriminating power between healthy and diseased states. Computational approaches have proven effective in deciphering the complexity of human disease by identifying upstream regulatory elements and the transcription factors that interact with them. Here we used both methods to identify highly conserved transcriptional responses during mechanical ventilation, an important therapeutic treatment that has injurious side effects. We generated control and ventilated whole lung samples from the premature baboon model of bronchopulmonary dysplasia (BPD), processed them for microarray, and combined them with existing whole lung oligonucleotide microarray data from 85 additional control samples from mouse, rat, and human and 19 additional ventilated samples from mouse and rat. Of the 2,531 orthologs shared by all 114 samples, 60 were modulated by mechanical ventilation [false discovery rate (FDR)-adjusted q value (q(FDR)) = 0.005, ANOVA]. These included transcripts encoding the transcription factors ATF3 and FOS. Because of compelling known roles for these transcription factors, we used computational methods to predict their targets in the premature baboon model of BPD, which included elastin (ELN), gastrin-releasing polypeptide (GRP), and connective tissue growth factor (CTGF). This approach identified highly conserved transcriptional responses to mechanical ventilation and may facilitate identification of therapeutic targets to reduce the side effects of this valuable treatment.