The strongest risk factors for BPD are prematurity and low birth weight 19-25. Almost 80% of infants who are born at 22-24 weeks of gestation are diagnosed with BPD 26 , whereas only 20% of infants born at 28 weeks of gestation develop BPD. Among infants with BPD, 95% are VLBW 27. Other perinatal risk factors include intrauterine growth restriction (IUGR) 13 , male sex 13,20,23 and, inconsistently, chorioamnionitis 28 , race or ethnicity 13,20,23 , and smoking 29,30. Genetic risk factors may also contribute to the development of BPD, as indicated by twin studies 31,32 , and there is an ongoing search for genetic markers for BPD 33-37. Early respiratory patterns of premature infants provide insight into risk factors for BPD. An early study suggested that peak inspiratory ventilator pressure and requirement for assisted ventilation on day 4 of life are early predictors of BPD 38. Subsequent studies found that three patterns of lung disease generally emerge in the first 2 weeks of life 39-45 (FIG. 2). In the first pattern, infants have fairly minimal lung disease and progressively recover. In the second pattern, early persistent pulmonary deterioration (EPPD), substantial and prolonged respiratory support is required from birth. In the third pattern, an initial improvement in lung disease in the first week of life is followed by a respiratory decompensation termed pulmonary deterioration, which often requires mechanical ventilation and an increase in supplemental oxygen. Risk factors that may be associated with pulmonary deterioration include late surfactant deficiency 46 , sepsis, increased levels of inflammatory proteins (such as RANTES) 47 and patent ductus arteriosus 40,43. Almost 50% of infants with pulmonary deterioration and almost 70% of infants with EPPD develop BPD 48. The National Institute of Child Health and Human Development (NICHD) Neonatal Research Network developed an online, publicly available risk estimator (https:// neonatal.rti.org/index.cfm) that accurately estimates the risk of developing BPD by postnatal day 49. Investigators identified risk factors for BPD, and the competing outcome of death, among gestational age, birth weight, ethnicity and sex, ventilatory support (ranging from no support (breathing room air without positive airway pressure) to high frequency ventilation) and fraction of inspired oxygen (FiO 2), on postnatal days 1, 3, 7, 14, 21 and 28 in 3,636 infants born at 23-30 weeks of gestation. The BPD prediction tool is internally and externally validated. The models predict the correct level of BPD or the occurrence of death in >80% of cases and have the highest area under the curve (AUC) among current BPD risk predictors 50. This tool is used to provide counselling to families and to quantify risk for determining patient inclusion in early phase therapeutic trials. Interestingly, systemic inflammation occurs early in the neonatal period and precedes clinical symptoms in infants with BPD 51. This finding suggests that a therapeutic window of opportunity exists during the early p...
Paediatric pulmonary arterial hypertension (PAH) shares common features of adult disease, but is associated with several additional disorders and challenges that require unique approaches. This article discusses recent advances, ongoing challenges and distinct approaches for the care of children with PAH, as presented by the Paediatric Task Force of the 6th World Symposium on Pulmonary Hypertension. We provide updates of the current definition, epidemiology, classification, diagnostics and treatment of paediatric PAH, and identify critical knowledge gaps. Several features of paediatric PAH including the prominence of neonatal PAH, especially in pre-term infants with developmental lung diseases, and novel genetic causes of paediatric PAH are highlighted. The use of cardiac catheterisation as a diagnostic modality and haemodynamic definitions of PAH, including acute vasoreactivity, are addressed. Updates are provided on issues related to utility of the previous classification system to reflect paediatric-specific aetiologies and approaches to medical and interventional management of PAH, including the Potts shunt. Although a lack of clinical trial data for the use of PAH-targeted therapy persists, emerging data are improving the identification of appropriate targets for goal-oriented therapy in children. Such data will likely improve future clinical trial design to enhance outcomes in paediatric PAH.
To determine whether angiogenesis is necessary for normal alveolarization, we studied the effects of two antiangiogenic agents, thalidomide and fumagillin, on alveolarization during a critical period of lung growth in infant rats. Newborn rats were treated with daily injections of fumagillin, thalidomide, or vehicle during the first 2 wk of life. Compared with control treatment, fumagillin and thalidomide treatment reduced lung weight-to-body weight ratio and pulmonary arterial density by 20 and 36%, respectively, and reduced alveolarization by 22%. Because these drugs potentially have nonspecific effects on lung growth, we also studied the effects of Su-5416, an inhibitor of the vascular endothelial growth factor receptor known as kinase insert domain-containing receptor/fetal liver kinase (KDR/flk)-1. As observed with the other antiangiogenic agents, Su-5416 treatment decreased alveolarization and arterial density. We conclude that treatment with three different antiangiogenic agents attenuated lung vascular growth and reduced alveolarization in the infant rat. We speculate that angiogenesis is necessary for alveolarization during normal lung development and that injury to the developing pulmonary circulation during a critical period of lung growth can contribute to lung hypoplasia.
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