Evaluation of criteria for chronic lung disease in surviving very low birth weight infants. Newborn Lung Project

Increased aortic stiffness and elevated blood pressure in response to exercise in adult survivors of prematurity

Objectives

Adults born prematurely have an increased risk of early heart failure. The impact of prematurity on left and right ventricular function has been well documented, but little is known about the impact on the systemic vasculature. The goals of this study were to measure aortic stiffness and the blood pressure response to physiological stressors; in particular, normoxic and hypoxic exercise.

Methods

Preterm participants (n = 10) were recruited from the Newborn Lung Project Cohort and matched with term‐born, age‐matched subjects (n = 12). Aortic pulse wave velocity was derived from the brachial arterial waveform and the heart rate and blood pressure responses to incremental exercise in normoxia (21% O₂) or hypoxia (12% O₂) were evaluated.

Results

Aortic pulse wave velocity was higher in the preterm groups. Additionally, heart rate, systolic blood pressure, and pulse pressure were higher throughout the normoxic exercise bout, consistent with higher conduit artery stiffness. Hypoxic exercise caused a decline in diastolic pressure in this group, but not in term‐born controls.

Conclusions

In this first report of the blood pressure response to exercise in adults born prematurely, we found exercise‐induced hypertension relative to a term‐born control group that is associated with increased large artery stiffness. These experiments performed in hypoxia reveal abnormalities in vascular function in adult survivors of prematurity that may further deteriorate as this population ages.

Revisiting the definition of bronchopulmonary dysplasia in premature infants at a single center quaternary neonatal intensive care unit

OBJECTIVE

To compare the incidence of bronchopulmonary dysplasia (BPD) based on the 1988 Vermont Oxford Network (VON) criteria, National Institutes of Health (NIH) 2001 definition, and NIH 2018 definition.

METHODS

BPD incidence by each definition was compared in premature infants born at a single center between 2016 and 2018. Comorbidities were compared between those with and without BPD according to the newest definition.

RESULTS

Among 352 survivors, BPD incidence was significantly different at 9%, 28% and 34% according to VON, NIH 2001 and NIH 2018 definitions, respectively (p < 0.05). According to the newest definition, any grade of BPD was associated with more co-morbidities than those without BPD (P < 0.001).

CONCLUSION

At a center that emphasizes use of early noninvasive respiratory support, the incidence of BPD was significantly higher according to the NIH 2018 definition compared to other two definitions. The relationship between BPD diagnosis and long-term clinical outcomes remains unclear.

Early Pulmonary Vascular Disease in Young Adults Born Preterm

Rationale: Premature birth affects 10% of live births in the United States and is associated with alveolar simplification and altered pulmonary microvascular development. However, little is known about the long-term impact prematurity has on the pulmonary vasculature.Objectives: Determine the long-term effects of prematurity on right ventricular and pulmonary vascular hemodynamics.Methods: Preterm subjects (n = 11) were recruited from the Newborn Lung Project, a prospectively followed cohort at the University of Wisconsin-Madison, born preterm with very low birth weight (≤1,500 g; average gestational age, 28 wk) between 1988 and 1991. Control subjects (n = 10) from the same birth years were recruited from the general population. All subjects had no known adult cardiopulmonary disease. Right heart catheterization was performed to assess right ventricular and pulmonary vascular hemodynamics at rest and during hypoxic and exercise stress.Measurements and Main Results: Preterm subjects had higher mean pulmonary arterial pressures (mPAPs), with 27% (3 of 11) meeting criteria for borderline pulmonary hypertension (mPAP, 19-24 mm Hg) and 18% (2 of 11) meeting criteria for overt pulmonary hypertension (mPAP ≥ 25 mm Hg). Pulmonary vascular resistance and elastance were higher at rest and during exercise, suggesting a stiffer vascular bed. Preterm subjects were significantly less able to augment cardiac index or right ventricular stroke work during exercise. Among neonatal characteristics, total ventilatory support days was the strongest predictor of adult pulmonary pressure.Conclusions: Young adults born preterm demonstrate early pulmonary vascular disease, characterized by elevated pulmonary pressures, a stiffer pulmonary vascular bed, and right ventricular dysfunction, consistent with an increased risk of developing pulmonary hypertension.

Heart rate recovery after maximal exercise is impaired in healthy young adults born preterm

PURPOSE

The long-term implications of premature birth on autonomic nervous system (ANS) function are unclear. Heart rate recovery (HRR) following maximal exercise is a simple tool to evaluate ANS function and is a strong predictor of cardiovascular disease. Our objective was to determine whether HRR is impaired in young adults born preterm (PYA).

METHODS

Individuals born between 1989 and 1991 were recruited from the Newborn Lung Project, a prospectively followed cohort of subjects born preterm weighing < 1500 g with an average gestational age of 28 weeks. Age-matched term-born controls were recruited from the local population. HRR was measured for 2 min following maximal exercise testing on an upright cycle ergometer in normoxia and hypoxia, and maximal aerobic capacity (VO_2max) was measured.

RESULTS

Preterms had lower VO_2max than controls (34.88 ± 5.24 v 46.15 ± 10.21 ml/kg/min, respectively, p < 0.05), and exhibited slower HRR compared to controls after 1 and 2 min of recovery in normoxia (absolute drop of 20 ± 4 v 31 ± 10 and 41 ± 7 v 54 ± 11 beats per minute (bpm), respectively, p < 0.01) and hypoxia (19 ± 5 v 26 ± 8 and 39 ± 7 v 49 ± 13 bpm, respectively, p < 0.05). After adjusting for VO_2max, HRR remained slower in preterms at 1 and 2 min of recovery in normoxia (21 ± 2 v 30 ± 2 and 42 ± 3 v 52 ± 3 bpm, respectively, p < 0.05), but not hypoxia (19 ± 3 v 25 ± 2 and 40 ± 4 v 47 ± 3 bpm, respectively, p > 0.05).

CONCLUSIONS

Autonomic dysfunction as seen in this study has been associated with increased rates of cardiovascular disease in non-preterm populations, suggesting further study of the mechanisms of autonomic dysfunction after preterm birth.

Scoping review shows wide variation in the definitions of bronchopulmonary dysplasia in preterm infants and calls for a consensus

The use of different definitions for bronchopulmonary dysplasia (BPD) has been an ongoing challenge. We searched papers published in English from 2010 and 2015 reporting BPD as an outcome, together with studies that compared BPD definitions between 1978 and 2015. We found that the incidence of BPD ranged from 6% to 57%, depending on the definition chosen, and that studies that investigated correlations with long-term pulmonary and/or neurosensory outcomes reported moderate-to-low predictive values regardless of the BPD criteria.

CONCLUSION

A comprehensive and evidence-based definition for BPD needs to be developed for benchmarking and prognostic use.

Pulmonary Gas Exchange and Exercise Capacity in Adults Born Preterm

RATIONALE

Preterm birth, and its often-required medical interventions, can result in respiratory and gas exchange deficits into childhood. However, the long-term sequelae into adulthood are not well understood.

OBJECTIVES

To determine exercise capacity and pulmonary gas exchange efficiency during exercise in adult survivors of preterm birth.

METHODS

Preterm (n = 14), very low birth weight (<1,500 g) adults (20-23 yr) and term-born, age-matched control subjects (n = 16) performed incremental exercise on a cycle ergometer to volitional exhaustion while breathing one of two oxygen concentrations: normoxia (fraction of inspired oxygen, 0.21) or hypoxia (fraction of inspired oxygen, 0.12).

MEASUREMENTS AND MAIN RESULTS

Ventilation, mixed expired gases, arterial blood gases, power output, and oxygen consumption were measured during rest and exercise. We calculated the alveolar-to-arterial oxygen difference to determine pulmonary gas exchange efficiency. Preterm subjects had lower power output at volitional exhaustion than did control subjects in normoxia (150 ± 10 vs. 180 ± 10 W; P = 0.01), despite similar normoxic oxygen consumption. However, during hypoxic exercise, there was no difference in power output at volitional exhaustion between the two groups (116 ± 10 vs. 135 ± 10 W; P = 0.11). Preterm subjects also exhibited a more acidotic, acid-base balance throughout exercise compared with control subjects. In contrast to other studies, adults born preterm, as a group developed a wider alveolar-to-arterial oxygen difference and lower PaO2 than did control subjects during normoxic but not hypoxic exercise.

CONCLUSIONS

This study demonstrates that pulmonary gas exchange efficiency is lower in some adult survivors of preterm birth during exercise compared with control subjects. The gas exchange inefficiency, when present, is accompanied by low arterial blood oxygen tension. Preterm subjects also exhibit reduced power output. Overall, our findings suggest potential long-term consequences of extreme preterm birth and very low birth weight on cardiopulmonary function.

Lung function at 6 and 18 months after preterm birth in relation to severity of bronchopulmonary dysplasia

Many preterm infants with bronchopulmonary dysplasia (BPD) demonstrate impaired lung function and respiratory symptoms during infancy. The relationships between initial BPD severity, lung function and respiratory morbidity are not fully understood. We aimed to investigate the association between BPD severity and subsequent lung function and whether lung function impairment is related to respiratory morbidity.

STUDY DESIGN AND METHODS

In this longitudinal cohort study, 55 infants born preterm (23-30 weeks of gestation) with mild or moderate/severe BPD, based on oxygen requirement at 36 gestational weeks, were followed up at 6 and 18 months postnatal age. Respiratory symptoms, such as recurrent or chronic chough and wheeze, were noted and patient records were scrutinized. Lung function was assessed by passive lung mechanics, whole body plethysmography, and tidal and raised volume rapid thoraco-abdominal compression techniques. Results were related to published normative values.

RESULTS

Besides residual functional capacity (FRC) and respiratory system compliance (Cso ) assessed at 18 months, all measures of lung function were significantly below normative values. Moderate/severe BPD differed significantly from mild BPD only with respect to reduced Cso . At follow-up at 6 and 18 months, participants with respiratory symptoms showed lower; maximal forced expiratory flow at FRC (V'maxFRC) (P = 0.006, P = 0.001), forced mid-expiratory flows (MEF50 ) (P = 0.006, P = 0.048), and Cso (P = 0.004, P = 0.015) as compared to participants without symptoms.

CONCLUSIONS

In the present study BPD severity did not predict lung function, but may be associated with impaired alveolarization, indicated by reduced Cso . Respiratory morbidity was associated with reduced airway function and respiratory compliance in infancy after preterm birth.

Perinatal factors associated with long-term respiratory sequelae in extremely low birthweight infants

OBJECTIVE

To assess lung function at 8 years old in extremely low birthweight (ELBW) survivors and to identify perinatal determinants associated with impaired lung function.

DESIGN

Retrospective cohort study.

SETTING

Level III neonatal intensive care unit.

PATIENTS

ELBW survivors born in 1990-2004 with available spirometry at 8 years old were studied. Children were excluded if they had a Wechsler Intelligence Scale for Children Third Edition full IQ <70.

MAIN OUTCOME MEASURES

Multivariate logistic regression analysis was used to identify perinatal determinants associated with airway obstruction (forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) ratio <80%) at school age and the predictive power of potential determinants. Potential risk factors and predictors assessed in this study were gestational age, birth weight, small for gestational age, sex, chorioamnionitis, premature rupture of membranes, antenatal steroids, surfactant administration, respiratory distress syndrome, postnatal steroids, severe bronchopulmonary dysplasia and bubbly/cystic appearances of the lungs by X-ray during the neonatal period.

RESULTS

Of 656 ELBW survivors, 301 (45.9%) had attended a school-age follow-up at 8 years old. A total of 201 eligible children completed the lung function test. Bubbly/cystic appearance of the lungs (OR 4.84, 95% CI 1.26 to 18.70) was associated with a low FEV1/FVC ratio. Children with bubbly/cystic appearance had characteristics of immaturity and intrauterine inflammation.

CONCLUSIONS

Within a cohort of ELBW infants, a bubbly/cystic appearance of the lungs in the neonatal period was the strongest determinant of a low FEV1/FVC ratio at school age.

Ventilatory control in infants, children, and adults with bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD), or chronic lung disease of prematurity, occurs in ~30% of preterm infants (15,000 per year) and is associated with a clinical history of mechanical ventilation and/or high inspired oxygen at birth. Here, we describe changes in ventilatory control that exist in patients with BPD, including alterations in chemoreceptor function, respiratory muscle function, and suprapontine control. Because dysfunction in ventilatory control frequently revealed when O2 supply and CO2 elimination are challenged, we provide this information in the context of four important metabolic stressors: stresses: exercise, sleep, hypoxia, and lung disease, with a primary focus on studies of human infants, children, and adults. As a secondary goal, we also identify three key areas of future research and describe the benefits and challenges of longitudinal human studies using well-defined patient cohorts.

Bronchopulmonary dysplasia: new high resolution computed tomography scoring system and correlation between the high resolution computed tomography score and clinical severity

Objective

To develop an high resolution computed tomography (HRCT) scoring system for the assessment of bronchopulmonary dysplasia (BPD) and determine its usefulness as compared with the chest radiographic score.

Materials and Methods

Forty-two very low-birth-weight preterm infants with BPD (25 male, 17 female) were prospectively evaluated with HRCT performed at the mean age of 39.1-week postmenstrual age. Clinical severity of BPD was categorized as mild, moderate or severe. The HRCT score (0-36) of each patient was the sum of the number of bronchopulmonary segments with 1) hyperaeration and 2) parenchymal lesions (linear lesions, segmental atelectasis, consolidation and architectural distortion), respectively. We compared the HRCT scores with the chest radiographic scores (the Toce system) in terms of correlation with clinical severity.

Results

The HRCT score had good interobserver (r = 0.969, p < 0.001) and intraobserver (r = 0.986, p < 0.001) reproducibility. The HRCT score showed better correlation (r = 0.646, p < 0.001) with the clinical severity of BPD than the chest radiographic score (r = 0.410, p = 0.007). The hyperaeration score showed better correlation (r = 0.738, p < 0.001) with the clinical severity of BPD than the parenchymal score (r = 0.523, p < 0.001).

Conclusion

We have developed a new HRCT scoring system for BPD based on the quantitative evaluation of pulmonary abnormalities of BPD consisting of the hyperaeration score and the parenchymal score. The HRCT score shows better correlation with the clinical severity of BPD than the radiographic score.

Frequency and clinical correlates of radiographic patterns of bronchopulmonary dysplasia in very low birth weight infants by term age

Our aim was to study the frequency and clinical correlates of two radiographic patterns of bronchopulmonary dysplasia (BPD), the cystic BPD (cBPD) and the leaky lung syndrome (LLS). Radiographic findings of BPD from sixth day of life until term in a cohort of 82 very low birth weight (VLBW) infants were evaluated and scored independently by a neonatologist and a paediatric radiologist. Data on prenatal factors and events during the first hospitalisation were collected prospectively. Forty-four (53.7%) infants showed radiographic evidence of BPD, 19 (23.2%) cBPD and 25 (30.5%) LLS. In multivariate analysis, the best predictors for radiographic BPD were oxygen dependency at 28 days (odds ratio (OR) 10.2 [95% confidence interval (CI) 2.49-41.4]), more than 2 days on ventilator (OR 10.4 [95% CI 1.8-61.5]) and volume expanders in the first 2 h (OR 7.36 [95% CI 1.32-41.2]). During the first week of life, infants with radiographic BPD received less energy per kilogram (p < 0.001) and more daily fluids per kilogram of body weight (p = 0.013). Sixty-two percent of the infants with radiographic BPD were not oxygen dependent at 36 weeks postmenstrual age (PMA). Seventeen (89.5%) of the 19 infants who needed oxygen supplementation at 36 weeks PMA also had abnormal chest X-rays.

CONCLUSIONS

Radiographic BPD findings appeared to be common in VLBW infants. In addition to the well-known respiratory risk factors (oxygen and ventilator therapy), poor nutrition and excessive fluid administration in early life seem to be significantly associated with radiological findings of lung injury in these patients.

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.

Intra and interobserver reliability of the interpretation of high-resolution computed tomography on the lungs of premature infants

CONTEXT AND OBJECTIVE

High-resolution computed tomography (HRCT) of the lungs is more sensitive than radiographs for evaluating pulmonary disease, but little has been described about HRCT interpretation during the neonatal period or shortly afterwards. The aim here was to evaluate the reliability of the interpretation of HRCT among very low birth weight premature infants (VLBWPI; < 1500 g).

DESIGN AND SETTING

Cross-sectional study on intra and interobserver reliability of HRCT on VLBWPI.

METHODS

86 VLBWPI underwent HRCT. Two pediatric radiologists analyzed the HRCT images. The reliability was measured by the proportion of agreement, kappa coefficient (KC) and positive and negative agreement indices.

RESULTS

For radiologist A, the intraobserver reliability KC was 0.79 (confidence interval, CI: 0.54-1.00) for normal/abnormal examinations; for each abnormality on CT, KC ranged from 0.05 to 1.00. For radiologist B, the intraobserver reliability KC was 0.79 (CI: 0.54-1.00) for normal/abnormal examinations; for each abnormality on CT, KC ranged from 0.37 to 0.83. The interobserver agreement was 88% for normal/abnormal examinations and KC was 0.71 (CI: 0.5- 0.93); for most abnormal findings, KC ranged from 0.51-0.67.

CONCLUSION

For normal/abnormal examinations, the intra and interobserver agreements were substantial. For most of the imaging findings, the intraobserver agreement ranged from moderate to substantial. Our data demonstrate that in clinical practice, there is no reason for more than one tomographic image evaluator, provided that this person is well trained in VLBWPI HRCT interpretation. Analysis by different observers should be reserved for research and for difficult cases in clinical contexts.

Pathogenesis and prevention of chronic lung disease in the neonate

Often used interchangeably, chronic lung disease (CLD) or bronchopulmonary dysplasia (BPD) develops primarily in extremely low birth weight infants weighing <1000 g who receive prolonged oxygen therapy and or positive pressure ventilation. CLD, which occurs in as many as 30 percent of infants born weighing <1000 g, contributes significantly to the morbidity and mortality seen in very low birth weight infants. Despite extensive research aimed at identifying risk factors and devising preventative therapies, many questions about the etiology and pathogenesis of BPD remain. This article reviews the embryologic development of the lung and the pathogenesis of CLD or BPD. The authors discuss some of the measures that have been used in an attempt to both prevent and treat BPD.

PedsQL relates to function and behavior in very low and normal birth weight 2- and 3-year-olds from a regional cohort

STUDY OBJECTIVE

To compare PedsQL scores in young children who were very low (< or =1,500 g) or normal birth weight (>2,500 g) and to examine the relationship of the PedsQL score to behavioral and functional scores.

METHODS

The PedsQL, Achenbach Child Behavior Checklist and the PEDI functional scales were telephone administered to parents of a regional cohort of 672 very low birth weight and 455 normal birth weight children, 2- and 3-years old. PedsQL scales were regressed on behavior, function and health conditions.

RESULTS

Mean (SD) overall PedsQL score was 91 (8.4) for normal birth weight and 87 (12) for very low birth weight children, and changed little when standardized to the race/ethnicity and maternal education of corresponding Wisconsin births. Mobility function and the CBCL explained 58% of the variance in PedsQL, but the relationship was curvilinear.

CONCLUSION

The PedsQL is sensitive to health problems of very low birth weight in young children. The PedsQL is quite strongly related to mobility and behavior problems, but scales these differently than do standard instruments. Parents either do not think of subtle issues with child function and behavior without specific prompting or do not perceive them as problems affecting quality of life.

Outcome and hospital cost for infants weighing less than 500 grams: a tertiary centre experience in Taiwan

AIM

To determine the outcome and hospital cost for infants weighing < or =500 g at a tertiary centre in Taiwan.

METHODS

We retrospectively reviewed the medical records of infants who were born alive with birthweight < or =500 g at the National Taiwan University Hospital from 1997 to 2004. Their outcome and hospital cost were analysed.

RESULTS

A total of 168 infants were included for analysis that 146 of them died after compassionate care in the delivery room and 22 received postnatal resuscitation. The infants who received resuscitation were more likely to have higher birthweights, older gestational ages and multiple births compared with those who received compassionate care. After resuscitation, five of the infants died and 17 were admitted to neonatal intensive care unit (NICU) for further management. Subsequently, 12 infants died and five infants survived to discharge. Two infants were discharged against advice and died within days. After exclusion of those receiving compassionate care, the NICU survival rate was 22.7% and the long-term survival rate was 13.6%. The most common early morbidities were respiratory distress syndrome, intraventricular haemorrhage and patent ductus arteriosus, whereas the late morbidities included cholestatic jaundice, retinopathy of prematurity and chronic lung disease. The average total hospital costs for the NICU survivors with birthweight < or =500 g was US $42,411 and the average hospital cost per day was US $350.

CONCLUSION

Exclusive compassionate care was given to the majority of the infants weighing < or =500 g in Taiwan. The survival rate remained low in these marginally viable infants.

Pulmonary testing using peak flow meters of very low birth weight children born in the perisurfactant era and school controls at age 10 years

We determined lung function at age 10 years in very low birthweight (VLBW, <or=1,500 g) children and controls, and compared the sensitivity to detect subgroup differences by peak expiratory flow (PEF), forced expiratory volume in one second (FEV(1)), forced vital capacity (FVC) and their diurnal variation. VLBW children were recruited across the perisurfactant era at admission to six NICUs in Wisconsin and Iowa, and controls from area classrooms. Two hundred sixty five VLBW children and 360 controls were tested by the Jaeger AM1 peak flow meter at age 10 years. Two hundred six VLBW and 79 controls had additional home monitoring. Abnormality was defined as observed/predicted ratio <0.8 for PEF, FEV(1), and FVC, and by criteria of Pelkonen for diurnal PEF variation. VLBW children were compared to controls, VLBW children with bronchopulmonary dysplasia (BPD) to those without, and those with respiratory conditions to those without. PEF and FEV(1) showed high reproducibility (intraclass correlations, ICC 0.75-0.83). Controls and VLBW children with and without BPD differed significantly on all measures. Baseline test results did not differ across birth years, but PEF variation was less after surfactant availability (P = 0.04). Observed over predicted FEV(1) was the most sensitive in detecting differences between groups (P < 0.001), with mean (s.d.) 0.97 (0.12) for controls, 0.88 (0.14) for VLBW children without BPD, and 0.78 (0.13) for those with BPD. Odds ratios for abnormality were especially high with respiratory medication use during the first 5 years of life, 4.4 (95% CI: 2.0-9.8) for FEV(1) and 5.1 (95% CI: 2.0-13.2) for diurnal PEF variation. Our results show that respiratory abnormalities persist to at least age 10 years for VLBW children born in the surfactant era.

Follow-up study of a randomized controlled trial of postnatal dexamethasone therapy in very low birth weight infants: effects on pulmonary outcomes at age 8 to 11 years

OBJECTIVE

To determine whether postnatal dexamethasone (DEX) exposure affects pulmonary outcomes at school age in children born with very low birth weight (VLBW).

STUDY DESIGN

Follow-up study of 68 VLBW children who participated in a randomized controlled trial of postnatal DEX. Pulmonary function was assessed by spirometry. Current asthma status was obtained from a parent.

RESULTS

Sixty-eight percent of the placebo group had below-normal forced expiratory volume in 1 second (FEV1), compared with 40% of the DEX group (chi2 = 4.84; P = .03), with trends for lower forced vital capacity (FVC) and FEV1 values in the placebo group. Fifty percent of the placebo group and 34% of DEX group had below normal FEV1/FVC (chi2 =1.59; P =.21). Parent-reported prevalence of asthma did not differ between groups. Logistic regression analysis suggested that the positive effects of DEX on pulmonary function at follow-up were mediated in part by shortened exposure to mechanical ventilation.

CONCLUSIONS

Postnatal DEX exposure was associated with higher expiratory flow with no adverse effects on pulmonary outcomes at school age. The prevalences of asthma and impaired pulmonary function underscore the influence of neonatal illness on health at school age, and stress the importance of repeated follow-up examinations of these children.

A scoring system to predict chronic oxygen dependency

INTRODUCTION

Chronic oxygen dependency (COD) is a common adverse outcome of very premature birth. It is, therefore, important to develop an accurate and simple predictive test to facilitate targeting of interventions to prevent COD. Our aim was to determine if a simple score based on respiratory support requirements predicted COD development.

METHODS

A retrospective study of 136 infants, median gestation age (GA) 28 weeks (range: 23-33 weeks) and a prospective study of 75 infants, median GA 30 weeks (range: 23-32 weeks), were performed. The score was calculated by multiplying the inspired oxygen concentration by the level of respiratory support (mechanical ventilation: 2.5; continuous positive airway pressure: 1.5; nasal cannula or head box oxygen or air: 1.0). Scores were calculated on data from days 2 and 7, and their predictive ability compared to that of the maximum inspired oxygen concentration at those ages and (retrospective study) the results of lung volume measurement.

RESULTS

Infants that were oxygen dependent at 28 days and 36 weeks post-menstrual age (PMA) had higher scores on days 2 (p<0.0001, p<0.0001, respectively) and 7 (p<0.0001, p<0.0001, respectively) than the non-oxygen dependent infants in both the retrospective and prospective cohorts. Construction of receiver operator characteristic curves demonstrated the score performed better than the inspired oxygen level and lung volume measurement results. A score on day 7 >0.323 had 95% specificity and 78% sensitivity in predicting COD at 28 days, and 80% specificity and 73% sensitivity in predicting COD at 36 weeks PMA.

CONCLUSION

Chronic oxygen dependency can be predicted using a simple scoring system.

Bronchopulmonary dysplasia--long term follow up

Fifty percent of BPD infants require readmission to hospital during infancy, particularly if they suffer an RSV infection. Many BPD infants require supplementary oxygen at home, early discharge can be achieved if those still requiring nasogastric feeding are given appropriate community support. Troublesome respiratory symptoms are common in children who had BPD, as are lung function abnormalities even in adolescents and young adults.

Neonatal risk factors for respiratory morbidity during the first year of life among premature infants

CONTEXT AND OBJECTIVE

There have been dramatic increases in very low birth weight infant survival. However, respiratory morbidity remains problematic. The aim here was to verify associations between pulmonary mechanics, pulmonary structural abnormalities and respiratory morbidity during the first year of life.

DESIGN AND SETTING

Prospective cohort study at Instituto Fernandes Figueira, Fundação Oswaldo Cruz, Rio de Janeiro.

METHODS

Premature infants with birth weight < 1500 g were studied. Lung function tests and high-resolution chest tomography were performed before discharge. During the first year, infants were assessed for respiratory morbidity (obstructive airways, pneumonia or hospitalization). Neonatal lung tests and chest tomography and covariables potentially associated with respiratory morbidity were independently assessed using relative risk (RR). RR was subsequently adjusted via logistic regression.

RESULTS

Ninety-seven newborn infants (mean birth weight: 1113 g; mean gestational age: 28 weeks) were assessed. Lung compliance and lung resistance were abnormal in 40% and 59%. Tomography abnormalities were found in 72%; respiratory morbidity in 53%. Bivariate analysis showed respiratory morbidity associated with: mechanical ventilation, prolonged oxygen use (beyond 28 days), oxygen use at 36 weeks, respiratory distress syndrome, neonatal pneumonia and patent ductus arteriosus. Multivariate analysis gave RR 2.7 (confidence interval: 0.7-10.0) for simultaneous lung compliance and chest tomography abnormalities. Adjusted RR for neonatal pneumonia and mechanical ventilation were greater.

CONCLUSIONS

Upon discharge, there were high rates of lung mechanism and tomography abnormalities. More than 50% presented respiratory morbidity during the first year. Neonatal pneumonia and mechanical ventilation use were statistically significant risk factors.

Elevated Carbon Dioxide Tension as a Predictor of Subsequent Adverse Events in Infants with Bronchopulmonary Dysplasia

Infants with bronchopulmonary dysplasia (BPD) are at risk for numerous complications following discharge from the Neonatal Intensive Care Unit (NICU). Few studies have evaluated risk factors for adverse events (AE). This retrospective study provided an initial evaluation of the use of capillary carbon dioxide (PCO2) tension as a predictor of infants with BPD at increased risk for AE. PCO2 was compared in patients who suffered, or avoided, severe AE, defined as pulmonary hypertension, death, or subsequent reintubation or tracheostomy for respiratory illness. One hundred twelve consecutive patients followed at the BPD clinic were evaluated, and data from 104 subjects were suitable for analysis. Mean PCO2, obtained shortly before or after discharge from NICU, was 47.2 mmHg (range, 31-83). PCO2 was significantly higher in patients who required reintubation and ventilation (54.7 vs. 46.7, p < 0.04). No cutoff value of PCO2 clearly distinguished patients with subsequent AE. PCO2 was not significantly higher in the group of patients who had a severe AE than in the group of patients who did not have a severe AE, but logistic regression showed a significant association between PCO2 and risk of both severe AE (p = 0.018), and readmission to hospital (p = 0.038). An elevated PCO2 is associated with an increased risk of AE, including reintubation, and readmission to hospital, in infants with BPD. Patients with an elevated discharge PCO2 may require closer monitoring during followup. Prospective studies will be needed to confirm these observations.

Validation of the National Institutes of Health consensus definition of bronchopulmonary dysplasia

OBJECTIVE

A number of definitions of bronchopulmonary dysplasia (BPD), or chronic lung disease, have been used. A June 2000 National Institute of Child Health and Human Development/National Heart, Lung, and Blood Institute Workshop proposed a severity-based definition of BPD for infants <32 weeks' gestational age (GA). Mild BPD was defined as a need for supplemental oxygen (O2) for > or =28 days but not at 36 weeks' postmenstrual age (PMA) or discharge, moderate BPD as O2 for > or =28 days plus treatment with <30% O2 at 36 weeks' PMA, and severe BPD as O2 for > or =28 days plus > or =30% O2 and/or positive pressure at 36 weeks' PMA. The objective of this study was to determine the predictive validity of the severity-based, consensus definition of BPD.

METHODS

Data from 4866 infants (birth weight < or =1000 g, GA <32 weeks, alive at 36 weeks' PMA) who were entered into the National Institute of Child Health and Human Development Neonatal Research Network Very Low Birth weight (VLBW) Infant Registry between January 1, 1995 and December 31, 1999, were linked to data from the Network Extremely Low Birth Weight (ELBW) Follow-up Program, in which surviving ELBW infants have a neurodevelopmental and health assessment at 18 to 22 months' corrected age. Linked VLBW Registry and Follow-up data were available for 3848 (79%) infants. Selected follow-up outcomes (use of pulmonary medications, rehospitalization for pulmonary causes, receipt of respiratory syncytial virus prophylaxis, and neurodevelopmental abnormalities) were compared among infants who were identified with BPD defined as O2 for 28 days (28 days definition), as O2 at 36 weeks' PMA (36 weeks' definition), and with the consensus definition of BPD.

RESULTS

A total of 77% of the neonates met the 28-days definition, and 44% met the 36-weeks definition. Using the consensus BPD definition, 77% of the infants had BPD, similar to the cohort identified by the 28-days definition. A total of 46% of the infants met the moderate (30%) or severe (16%) consensus definition criteria, identifying a similar cohort of infants as the 36-weeks definition. Of infants who met the 28-days definition and 36-weeks definition and were seen at follow-up at 18 to 22 months' corrected age, 40% had been treated with pulmonary medications and 35% had been rehospitalized for pulmonary causes. In contrast, as the severity of BPD identified by the consensus definition worsened, the incidence of those outcomes and of selected adverse neurodevelopmental outcomes increased in the infants who were seen at follow-up.

CONCLUSION

The consensus BPD definition identifies a spectrum of risk for adverse pulmonary and neurodevelopmental outcomes in early infancy more accurately than other definitions.

A pulmonary score for assessing the severity of neonatal chronic lung disease

BACKGROUND

Limited data are available to describe the spectrum of severity of neonatal chronic lung disease. In the multicenter Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity trial, all infants had some degree of pulmonary dysfunction, because eligibility required a median oxygen saturation of < or =94% with room air. Infants randomized to the supplemental oxygen group (oxygen saturation target of 96-99%) had more pulmonary morbidity than did those in the conventional group (oxygen saturation target of 88-94%). This prompted the retrospective development of a pulmonary severity score to compare the baseline status of the 2 groups.

OBJECTIVES

To describe a pulmonary score that reflects the severity of neonatal lung disease and to evaluate the association of the score and its components with subsequent pulmonary morbidity through 3 months of corrected age.

DESIGN AND METHODS

A pulmonary score was developed empirically by a consensus panel of 3 neonatologists and was defined as the fraction of inspired oxygen (Fio2) x (support) + (medications), where Fio2 is the actual or "effective" (for nasal cannula) Fio2; support is 2.5 for a ventilator, 1.5 for nasal continuous positive airway pressure, or 1.0 for nasal cannula or hood oxygen; and medications is 0.20 for systemic steroids for bronchopulmonary dysplasia, 0.10 each for regular diuretics or inhaled steroids, and 0.05 each for methylxanthines or intermittent diuretics. The scores could range from 0.21 to 2.95. Pulmonary morbidity was defined as any of the following occurring from randomization at a mean of 35.4 weeks' postmenstrual age through 3 months of corrected age: death or rehospitalization with a pulmonary cause; an episode of pneumonia/sepsis/exacerbation of chronic lung disease; or continued hospitalization, supplemental oxygen therapy, diuretic treatment, or systemic steroid therapy at 3 months. Between-group differences were tested with the Kruskal-Wallis or chi2 test.

RESULTS

Data through death or the 3-month corrected age examination were available for 588 infants. Enrolled infants represented a wide spectrum of severity of chronic lung disease, with baseline pulmonary scores at randomization ranging from 0.21 to 2.6. The median pulmonary score at enrollment did not differ between the conventional and supplemental groups (0.42 and 0.45, respectively). However, higher baseline pulmonary scores were observed for infants who did versus did not develop subsequent pulmonary morbidity (0.48 vs 0.38). The pulmonary score was associated with subsequent pulmonary morbidity. Regression analyses adjusting for Supplemental Therapeutic Oxygen for Prethreshold Retinopathy of Prematurity group assignment, gestational age at birth, race, gender, and postmenstrual age at randomization revealed that the score was a significant independent predictor of subsequent pulmonary morbidity (odds ratio: 7.2; 95% confidence interval: 3.6-14.4).

CONCLUSIONS

The pulmonary score, calculated near term, reflects a wide spectrum of bronchopulmonary dysplasia severity and is associated with subsequent pulmonary morbidity through corrected age of 3 months. This simple score could prove useful in clinical and research settings. Validation of the score requires additional study.

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.

Sevrage de l’oxygène

Oxygen weaning is a controversial problem which can be summarized in three questions: what do we expect from oxygen supplementation? what are the optimal targets? with what sort of monitoring? We shall try to evaluate these different questions assuming the uncertainty of the proposed answers and the short-lived character of them.

Is the new definition of bronchopulmonary dysplasia more useful?

OBJECTIVE

To determine the incidence of bronchopulmonary dysplasia (BPD) in low birth weight (LBW) infants <1251 g managed with early bubble nasal continuous positive airway pressure (NCPAP) and a gentle ventilation strategy using the newly proposed definition for BPD and the previous definitions.

METHODS

Needs for supplemental oxygen and positive pressure (positive pressure ventilation or NCPAP) during initial hospitalization were evaluated in 266 inborn LBW infants (birth weight <1251 g). The data were categorized in three weight groups, <751, 751 to 1000 and 1001 to 1250 g and the incidence of BPD was computed in survivors based on oxygen need at 28 days, 36 weeks postmenstrual age (PMA) and the new severity of BPD criteria, that is, mild BPD: need for supplemental oxygen > or =28 days, but not at 36 weeks PMA; moderate BPD: need for supplemental oxygen > or =28 days and <30% at 36 weeks PMA and severe BPD: need for supplemental oxygen > or =28 days, and >30% at 36 weeks PMA and/or positive pressure at 36 weeks PMA. Further, BPD-associated comorbidities and short-term outcome data during hospitalization were compared among the groups, defined by severity of BPD.

RESULTS

Among LBW infants <1251 g, the incidences of BPD at 28 days and 36 weeks PMA were 21.1 and 7.4% respectively. Using the newly defined criteria, the incidences of mild, moderate and severe BPD were 13.5, 4.8 and 2.6%, respectively. In total, 64.6% of these infants had mild BPD and 70.8% weighed <751 g at birth. Associated comorbidities correlated significantly with grades of underlying pulmonary disease. Also, significantly longer hospital stay, discharge at a higher PMA and lower growth velocity was observed with increasing grades of BPD.

CONCLUSIONS

The new system for grading the severity of BPD offers a better description of underlying pulmonary disease and correlates with the infant's maturity, growth and overall severity of illness. Whether it will have a role in predicting long-term outcome remains to be determined.

Elevated platelet-derived growth factor-BB concentrations in premature neonates who develop chronic lung disease

BACKGROUND

Chronic lung disease (CLD) in the preterm newborn is associated with inflammation and fibrosis. Platelet-derived growth factor-BB (PDGF-BB), a potent chemotactic growth factor, may mediate the fibrotic component of CLD. The objectives of this study were to determine if tracheal aspirate (TA) concentrations of PDGF-BB increase the first 2 weeks of life in premature neonates undergoing mechanical ventilation for respiratory distress syndrome (RDS), its relationship to the development of CLD, pulmonary hemorrhage (PH) and its relationship to airway colonization with Ureaplasma urealyticum (Uu).

METHODS

Infants with a birth weight less than 1500 grams who required mechanical ventilation for RDS were enrolled into this study with parental consent. Tracheal aspirates were collected daily during clinically indicated suctioning. Uu cultures were performed on TA collected in the first week of life. TA supernatants were assayed for PDGF-BB and secretory component of IgA concentrations using ELISA techniques.

RESULTS

Fifty premature neonates were enrolled into the study. Twenty-eight infants were oxygen dependent at 28 days of life and 16 infants were oxygen dependent at 36 weeks postconceptual age. PDGF-BB concentrations peaked between 4 and 6 days of life. Maximum PDGF-BB concentrations were significantly higher in infants who developed CLD or died from respiratory failure. PH was associated with increased risk of CLD and was associated with higher PDGF-BB concentrations. There was no correlation between maximum PDGF-BB concentrations and Uu isolation from the airway.

CONCLUSIONS

PDGF-BB concentrations increase in TAs of infants who undergo mechanical ventilation for RDS during the first 2 weeks of life and maximal concentrations are greater in those infants who subsequently develop CLD. Elevation in lung PDGF-BB may play a role in the development of CLD.

Rehospitalization in the first year of life among infants with bronchopulmonary dysplasia

OBJECTIVE

To describe rates and identify risk factors for rehospitalization during the first year of life among infants with bronchopulmonary dysplasia (BPD).

STUDY DESIGN

This was a retrospective cohort study of infants born at a gestational age (GA) <33 weeks, between 1995 and 1999. BPD was defined as requirement of supplemental oxygen and/or mechanical ventilation at 36 weeks' corrected GA. The outcome was rehospitalization for any reason before first birthday.

RESULTS

In the first year of life, 118 of 238 (49%) infants with BPD were rehospitalized, more than twice the rate of rehospitalization of the non-BPD population, which was 309 of 1359 (23%) (P=<.0001). No measured factor discriminated between those infants with BPD who were and were not rehospitalized, even when only rehospitalizations for respiratory diagnoses were considered.

CONCLUSIONS

Among premature infants, BPD substantially increases the risk of rehospitalization during the first year of life. Neither demographic nor physiologic factors predicted rehospitalization among the infants with BPD. Other factors, such as air quality of home environment, passive smoking exposure, respiratory syncytial virus prophylaxis, breast-feeding status, and/or parenting and primary care management styles, should be examined in future studies.

CC chemokine concentrations increase in respiratory distress syndrome and correlate with development of bronchopulmonary dysplasia

Inflammation is one of the primary processes underlying respiratory distress syndrome (RDS) and its evolution into bronchopulmonary dysplasia (BPD). Recruitment and subsequent activation of macrophages in the lung are mediated by CC chemokines. The role of CC chemokines has not been extensively studied in the course of RDS. Serial tracheal aspirates (TA) were obtained from 56 mechanically ventilated infants with birth weights less than 1,500 g during intervals in the first 21 days of life. Tracheal aspirate concentrations of monocyte chemoattractant proteins-1,2,3 (MCP-1,2,3) and macrophage inflammatory proteins-1alpha and -1beta (MIP-1alpha, MIP-1beta) were determined by enzyme-linked immunosorbent assay (ELISA). Tracheal aspirate concentrations of MCP-1, MCP-2, MCP-3, and MIP-1beta increased during the first week of life in infants with RDS, whereas MIP-1alpha concentrations did not increase appreciably. Increased TA cytokine concentrations were associated with the development of BPD. Maximal TA concentrations of MCP-1, MCP-2, MCP-3, MIP-1alpha, and MIP-1beta were significantly higher in infants who were oxygen-dependent at 28 postnatal days compared to infant who were not. Similarly, maximal TA MCP-1, MCP-2, and MCP-3 but not MIP-1alpha and MIP-1beta concentrations were significantly higher in infants who were oxygen-dependent at 36 weeks of postconceptional age (PCA) than those who were not oxygen-dependent at 36 weeks PCA. Histologic chorioamnionitis and isolation of Ureaplasma urealyticum from the airways were associated with higher maximal TA concentrations of MIP-1alpha and MIP-1beta. Pulmonary hemorrhage was associated with increased maximal concentrations of MCP-1, MCP-2, and MCP-3. These data suggest a role for CC chemokines in the development of BPD in the newborn infant.

The TNF-alpha -308, MCP-1 -2518 and TGF-beta1 +915 polymorphisms are not associated with the development of chronic lung disease in very low birth weight infants

Chronic lung disease (CLD) in premature newborns is associated with increased concentrations of inflammatory cytokines in tracheal aspirates (TA). We determined if polymorphisms of cytokine genes influence the risk of developing CLD by genotyping 178 mechanically ventilated very low birth weight (VLBW) infants for the tumor necrosis factor-alpha (TNF-alpha) -308 G/A, transforming growth factor-beta(1) (TGF-beta(1)) +915 G/C and monocyte chemoattractant protein-1 (MCP-1) -2518 A/G polymorphisms. Genomic DNA was isolated from TA and genotypes determined by restriction length polymorphism. There was no effect of any of these polymorphisms on the development of CLD (29 vs 23%, P=0.371, TNF-alpha -308 AA/AG vs TNF-alpha -308 GG; 23 vs 26%, P=0.681, MCP-1 -2518 GG/AG vs MCP-1 -215-8 AA; 24 vs 24%, P=0.978, TGF-beta(1) +915 CG vs TGF-beta(1) +915 GG). TA IL-8 and MCP-1 concentrations were not different between genotype groups. Infants with the TNF-alpha -308 A allele had increased risk of IVH (RR 2.07; 95% CI 1.02-4.18, P=0.041) and infants with the TGF-beta(1) +915 C allele were at greater risk of death (32 vs 9%, P=0.016). These data suggest that these polymorphisms do not play a significant role in determining risk for CLD in preterm infants, but may play a role in other complications in the neonatal period.

Interleukin-4 and 13 concentrations in infants at risk to develop Bronchopulmonary Dysplasia

BACKGROUND

An exaggerated inflammatory response occurs in the first few days of life in infants who subsequently develop bronchopulmonary dysplasia (BPD). The increase of inflammatory cytokines in many disease processes is generally balanced by a rise in anti-inflammatory cytokines. Interleukin-4 (IL-4) and interleukin-13 (IL-13) have been shown to inhibit production of several inflammatory cytokines important in the development of BPD.

METHODS

We sought to determine if a correlation exists between the presence or absence of IL-4 and IL-13 in tracheal aspirates (TA) during the first 3 weeks of life and the development of BPD in premature infants. Serial TAs were prospectively obtained from 36 very low birth weight infants and IL-4 and IL-13 concentrations were determined by ELISA.

RESULTS

Infants who developed BPD (n = 19) were less mature (25.3 +/- 0.02 wks vs. 27.8 +/- 0.05 wks; p < 0.001), and had lower birth weights (739 +/- 27 g vs.1052 +/- 41 g; p < 0.001). IL-4 and IL-13 were detectable in only 27 of 132 and 9 of 132 samples assayed respectively. Furthermore, the levels detected for IL-4 and IL-13 were very low and did not correlate with the development of BPD.

CONCLUSIONS

TA concentrations of IL-4 and IL-13 do not increase significantly during acute lung injury in premature infants.

A theoretical study of chemical delivery within the lung using exogenous surfactant

A mathematical model is developed for lung injury treatments involving the delivery of therapeutic chemicals, such as drugs and gene vectors, into the lung using simultaneous tracheal instillation of exogenous pulmonary surfactant. The influence of exogenous surfactant dose, flow rate, bulk liquid viscosity, pulmonary absorption rate and chemical molecular diffusivity on the chemical delivery to the lung is investigated. Our results reveal that different pulmonary absorption rates lead to significantly different distribution patterns and change the time taken for the total amount of chemical to be absorbed along the airways. The various factors can also influence where the majority of the chemical is placed within the lung and this is relevant to the targeting of drugs to particular lung generations.

Pulmonary outcome at 1 year corrected age in premature infants treated at birth with recombinant human CuZn superoxide dismutase

OBJECTIVE

To examine whether treatment of premature infants with intratracheal recombinant human CuZn superoxide dismutase (r-h CuZnSOD) reduces bronchopulmonary dysplasia and improves pulmonary outcome at 1 year corrected age.

DESIGN

Three hundred two premature infants (600-1200 g birth weight) treated with exogenous surfactant at birth for respiratory distress syndrome were randomized to receive either intratracheal r-h CuZnSOD (5 mg/kg in 2 mL/kg saline) or placebo every 48 hours (as long as intubation was required) for up to 1 month of age. Short-term, as well as longer-term pulmonary outcome was assessed.

RESULTS

There were no differences between groups in the incidence of death or the development of bronchopulmonary dysplasia (oxygen requirement with an Edwards chest radiograph score of >or=3) at 28 days of life or 36 weeks' postmenstrual age. r-h CuZnSOD was well-tolerated and not associated with significant increases in any adverse event. At a median of 1 year corrected age, health assessments and physical examinations were performed on 209 (80%) surviving infants, with complete data available on 189 infants. Thirty-seven percent of placebo-treated infants had repeated episodes of wheezing or other respiratory illness severe enough to require treatment with asthma medications such as bronchodilators and/or corticosteroids compared with 24% of r-h CuZnSOD-treated infants, a 36% reduction. In infants <27 weeks' gestation, 42% treated with placebo received asthma medications compared with 19% of r-h CuZnSOD-treated infants, a 55% decrease. Infants <27 weeks' gestation who received r-h CuZnSOD also had a 55% decrease in emergency department visits and a 44% decrease in subsequent hospitalizations. Growth measurements and the results of physical examinations were comparable between groups.

CONCLUSIONS

These data indicate that treatment at birth with r-h CuZnSOD may reduce early pulmonary injury, resulting in improved clinical status when measured at 1 year corrected age. r-h CuZnSOD appears to be a safe and effective therapy that improves pulmonary outcome in high-risk premature infants.

Placental and other perinatal risk factors for chronic lung disease in very low birth weight infants

To clarify the relationship between chorioamnionitis and chronic lung disease (CLD) in very low birth weight (VLBW) infants, we performed a retrospective cohort study of all inborn patients between 1995-1997 with gestational age (GA) less than 32 wk, birth weight less than 1.5 kg, survival to 36 wk adjusted GA, and placentas submitted to pathology (n = 371). Racial distribution as defined by the mother was 40% white/60% nonwhite. Prevalence of CLD, defined as O(2) dependence at 36 wk adjusted GA, was 30%. In a preliminary analysis GA and birth weight for GA (standard deviations from the mean, Z-score), considered together, were inversely related to CLD. After adjustment for GA and Z-score, other risk factors for CLD were white race, acute respiratory distress, pulmonary air leak, patent ductus arteriosus, and septicemia. Two placental lesions were inversely related to CLD: histologic chorioamnionitis and acute atherosis (a placental indicator of preeclampsia). Following multivariate analysis, independent risk factors for CLD were GA (OR, 0.6; 95% CI = 0.5, 0.7), birthweight for GA (OR, 0.4; 95% CI = 0.3, 0.6), white race (OR, 1.9; 95% CI = 1.0, 3.3), patent ductus arteriosus (OR, 2.0; 95% CI = 1.0, 3.5), and pulmonary air leak (OR, 3.0; 95% CI = 1.3, 7.1). Acute atherosis was inversely related to CLD (OR, 0.2; 95% CI = 0.1, 0.8). Chorioamnionitis was stratified by subtype and again no association with CLD was seen in the population as a whole. Finally, chorioamnionitis of all subtypes tended to be increased in white infants and decreased in black infants with CLD. This dichotomy was not explained by differences in death rates, acute respiratory distress, intubation on d 2 of life, or total duration of assisted ventilation. We conclude that while chorioamnionitis was not a risk factor for CLD in our total population, racial differences in its relationship to CLD are worthy of further study.

Behavioural models of population growth rates: implications for conservation and prediction

Conservation biologists often wish to predict how vertebrate populations will respond to local or global changes in conditions such as those resulting from sea-level rise, deforestation, exploitation, genetically modified crops, global warming, human disturbance or from conservation activities. Predicting the consequences of such changes almost always requires understanding the population growth rate and the density dependence. Traditional means of directly measuring density dependence are often extremely difficult and have the problem that if the environment changes then it is necessary to remeasure the density dependence. We describe an alternative approach that does not require such long datasets and can be used to predict the density dependence under novel conditions. Game theory can be used to describe behavioural decisions that individuals make in response to interference, prey depletion, territorial behaviour or social dominance, and the resultant fitness consequences. It is then possible to predict how survival or reproductive output changes with population size. From this we can then make predictions about the responses of populations to environmental changes. We will illustrate how this can be applied to a range of species and a range of applied problems.

Home oxygen status and rehospitalisation and primary care requirements of infants with chronic lung disease

OBJECTIVES

To determine whether the rehospitalisation and primary care requirements of infants with chronic lung disease (CLD) during the first two years after birth were influenced by a requirement for supplementary oxygen after discharge from the neonatal intensive care unit.

METHODS

Review of records from both the hospital and general practitioner.

PATIENTS

235 infants, median gestational age 27 (range 22-31) weeks, 88 of whom were receiving supplementary oxygen when discharged home.

RESULTS

Overall, the infants required a median of 2 (range 0-20) admissions per patient, 8 (0-41) outpatient attendances, 13 (0-76) contacts with the general practitioner, and 17 (0-169) consultations with other primary healthcare professionals. The home oxygen patients required significantly more and longer admissions (p < 0.01) and more outpatient attendances (p < 0.05). The total cost of care per infant of the home oxygen group was greater (p < 0.001); this reflected higher costs for hospital stay (p < 0.01), total inpatient care (p < 0.01), and primary care drugs (p < 0.01).

CONCLUSION

Despite routine use of antenatal steroids and postnatal surfactant, certain patients with CLD, particularly those who receive home oxygen treatment, show high rates of utilisation of health service resources after discharge from the neonatal care unit.

Health care utilisation of infants with chronic lung disease, related to hospitalisation for RSV infection

AIMS

To compare the use of health care resources and associated costs between infants with chronic lung disease (CLD) who had or had not an admission with a proven respiratory syncytial virus (RSV) infection.

METHODS

Review of community care, outpatient attendances, and readmissions in the first two years after birth.

PATIENTS

235 infants (median gestational age 27 weeks) evaluated in four groups: 45 infants with a proven RSV admission (RSV proven); 24 with a probable bronchiolitis admission; 60 with other respiratory admissions; and 106 with non-respiratory or no admissions.

RESULTS

The RSV proven compared to the other groups required more frequent and longer admissions to general paediatric wards and intensive care units, more outpatient attendances and GP consultations for respiratory related disorders, and had a higher total cost of care.

CONCLUSION

RSV hospitalisation in patients with CLD is associated with increased health service utilisation and costs in the first two years after birth.

Monocyte chemoattractant protein-1 and interleukin-8 are increased in bronchopulmonary dysplasia: relation to isolation of Ureaplasma urealyticum

BACKGROUND

An exaggerated inflammatory response occurs in infants who subsequently develop bronchopulmonary dysplasia (BPD). Ureaplasma urealyticum (Uu) is frequently isolated from cultures of tracheal secretions obtained from very low birth weight infants and is associated with an increased risk of BPD.

METHODS

We examined the relationships between isolation of genital mycoplasmas, tracheal aspirate (TA) interleukin-8 (IL-8), and monocyte chemoattractant protein-1 (MCP-1) concentrations and the development of BPD. Serial TAs were obtained prospectively from 35 very low birth weight infants, and IL-8 and MCP-1 concentrations were determined by enzyme-linked immunoadsorbent assay. Tracheal cultures for bacteria and genital mycoplasmas were performed on aspirates obtained during the first 2 days of life.

RESULTS

Infants who developed BPD (n=18) were less mature (25.2+/-0.2 vs 27.8+/-0.5 weeks; P<0.001), of lower birth weight (746+/-28 vs 1052+/-41 g; P<0.001), and more likely to have a positive tracheal culture for Uu (39% vs 6%; P=0.026) than those who did not develop BPD (n=17). Tracheal concentrations of IL-8 and MCP-1 were significantly increased in infants who developed BPD (IL-8: P=0.0001; MCP-1: P<0.001, analysis of variance) and correlated with duration of mechanical ventilation and oxygen treatment. Uu-positive infants had an increased incidence of BPD (88% in infants with Uu vs 42% in infants without Uu; P=0.020) and had TA concentrations of IL-8 and MCP-1 that were significantly increased compared with those of Uu-negative infants.

CONCLUSIONS

Increased TA concentrations of IL-8 and MCP-1 during the first 2 weeks of life are associated with the development of BPD. Recovery of Uu from TAs is associated with a more robust inflammatory reaction and an increased risk of BPD.

Neonatal Chronic Lung Disease

Chronic lung disease (CLD), formerly known as bronchopulmonary dysplasia, is presently defined as the need for oxygen therapy either at 28 days of age or greater than 36 weeks postmenstrual age. Clinical signs and symptoms include tachypnea, retractions, apnea, and radiographic findings of poorly inflated lungs with reticulogranular opacities. The disease develops as a result of chronic pulmonary inflammation and continuous lung injury induced by oxygen, positive pressure ventilation, and other causes. Fifty to sixty-five percent of neonates with CLD are rehospitalized with respiratory problems, and 21% of very low birth weight neonates are diagnosed with asthma or other respiratory disorders by the age of five. These infants are at risk of adverse neurodevelopmental sequelae as they have a more complicated neonatal course. Many studies have explored various preventive therapies including α1-proteinase inhibitors, superoxide dismutase, antioxidants, and ventilatory management. Although the results from these trials are promising, further studies are needed to define which patients are most likely to benefit from preventive therapy. Two preventive treatment approaches that have shown a decrease in morbidity and an improvement in mortality are antenatal steroids and surfactant therapy. Postnatal corticosteroid therapy continues to be the mainstay of treatment for CLD, however, there are a number of detrimental side effects associated with this treatment. Due to the increased incidence in periventricular leukomalacia, early treatment of steroid therapy cannot be recommended. The optimal time to start steroid therapy appears to be after the first week of life. In addition, the lowest dose and shortest duration of treatment needs to be implemented in order to minimize potential complications. Although bronchodilators and diuretics continue to be used extensively in infants with CLD, there are surprisingly few well-controlled studies that have evaluated the clinical impact of this therapy. Further trials are needed in order to support the routine use of these therapies in CLD. Unfortunately, inhaled steroids have not shown an improvement in long-term outcomes of CLD, however, they have shown a decrease in systemic steroid usage. CLD is a complex disease with many unanswered questions. Further studies are needed to evaluate the effects of various treatment modalities with particular focus on the long-term outcomes such as oxygen and ventilator dependency as well as the incidence of CLD.

Developmental outcomes of infants with bronchopulmonary dysplasia: comparison with other medically fragile infants

The purpose of this study was to compare the developmental outcomes and mother-infant interactions of infants with bronchopulmonary dysplasia (BPD) and those of other medically fragile infants. One-hour behavioral observations were made of the interactions of mothers with two groups of infants (23 with BPD, 39 medically fragile without BPD or neurological problems) at enrollment, every 2 months during hospitalization, 1 month after discharge, and at 6 months' and 12 months' corrected age. Assessment of the home environment also was done at 6 and 12 months. Multiple regressions were calculated separately for child mental, adaptive, language, and motor outcomes. Predictors were: home environment assessment, measures of maternal interactive behaviors (positive attention, expression of negative affect, medicalized caregiving), infant group membership, and presence of intraventricular hemorrhage (IVH) in the infant. There were no significant differences between the two groups in any of the developmental outcomes or interactive variables, and the presence of IVH had no effect on these variables. Maternal positive attention and the home environment were correlated with mental development, and mother negative affect was related to adaptive behavior for both groups. Differences in developmental and interactive behaviors between infants with BPD and other prematurely born infants found in other studies appear to be a result of chronic health problems and, thus, are not unique to infants with BPD.

Relation between serum insulinlike growth factor-1, insulinlike growth factor binding protein-2, and insulinlike growth factor binding protein-3 and nutritional intake in premature infants with bronchopulmonary dysplasia

BACKGROUND

The usefulness of serum insulinlike growth factor (IGF)-system-peptide measurement to assess the adequacy of nutritional intake in premature infants with chronic lung disease bronchopulmonary dysplasia (BPD) was assessed.

METHODS

Twenty-nine premature infants had serial measurements taken of their serum IGF-1, insulinlike growth factor binding protein (IGFBP)-2, and IGFBP-3 concentrations between 2 and 6 weeks of age. Regression analyses were used to examine the relation between nutritional parameters and IGF-1, IGFBP-2, and IGFBP-3 concentrations in premature infants with and without BPD.

RESULTS

The group of infants with BPD (n = 12) did not differ from infants without BPD (n = 17) in gestational age or weight at entry, but gained less weight during the study period. In infants without BPD, IGF-1 correlated positively with protein intake (r = 0.50) and caloric intake (r = 0.41) over the 3 days before sample collection and with weight change over the previous week (r = 0.46). In contrast, infants with BPD showed a significant correlation between IGF-1 and weight change (r = 0.54) only. There was a significant negative correlation between IGFBP-2 and protein intake in infants without BPD (r = -0.50) and in infants with BPD (r = -0.41). Negative correlations between IGFBP-2 and both weight change (r = -0.64) and caloric intake (r = -0.43) over the previous week were found only in the group of infants without BPD. IGFBP-3 correlated positively with weight changes and protein intake in both groups but correlated with caloric intake only in the group without BPD. Multiple regression analyses were used to determine significant independent variables associated with IGF-1, IGFBP-2, and IGFBP-3. In infants without BPD, significant independent predictors of IGFBP-2 were 7-day weight change and 2-day protein intake; 3-day caloric intake was the only significant independent predictor for IGFBP-3. For infants with BPD, 3-day weight gain was the only independent variable associated with serum IGF-1. Protein intake in the week before sample collection was an independent predictor of IGFBP-2 and 3-day weight change and 2-day protein intake were independent predictors of IGFBP-3.

CONCLUSIONS

These results confirm that changes in serum IGF-1, IGFBP-2, and IGFBP-3 reflect the nutritional status of premature infants and demonstrate that the relation between these proteins and nutritional intake differs in premature infants with and without BPD. Refinement of these observations by future studies may permit a more accurate determination of the protein and caloric intake sufficient for growth and repair after injury in premature infants with lung disease.

Depletion models can predict shorebird distribution at different spatial scales

Predicting the impact of habitat change on populations requires an understanding of the number of animals that a given area can support. Depletion models enable predictions of the numbers of individuals an area can support from prey density and predator searching efficiency and handling time. Depletion models have been successfully employed to predict patterns of abundance over small spatial scales, but most environmental change occurs over large spatial scales. We test the ability of depletion models to predict abundance at a range of scales with black-tailed godwits, Limosa limosa islandica. From the type II functional response of godwits to their prey, we calculated the handling time and searching efficiency associated with these prey. These were incorporated in a depletion model, together with the density of available prey determined from surveys, in order to predict godwit abundance. Tests of these predictions with Wetland Bird Survey data from the British Trust for Ornithology showed significant correlations between predicted and observed densities at three scales: within mudflats, within estuaries and between estuaries. Depletion models can thus be powerful tools for predicting the population size that can be supported on sites at a range of scales. This greatly enhances our confidence in predictions of the consequences of environmental change.

Randomised trial of fluid restriction in ventilated very low birthweight infants

BACKGROUND

Fluid restriction has been reported to improve survival of infants without chronic lung disease (CLD), but it remains unknown whether it reduces CLD in a population at high risk of CLD routinely exposed to antenatal steroids and postnatal surfactant without increasing other adverse outcomes.

AIM

To investigate the impact of fluid restriction on the outcome of ventilated, very low birthweight infants.

STUDY DESIGN

A randomised trial of two fluid input levels in the perinatal period was performed. A total of 168 ventilated infants (median gestational age 27 weeks (range 23-33)) were randomly assigned to receive standard volumes of fluid (60 ml/kg on day 1 progressing to 150 ml/kg on day 7) or be restricted to about 80% of standard input.

RESULTS

Similar proportions of infants on the two regimens had CLD beyond 28 days (56% v 51%) and 36 weeks post conceptional age (26% v 25%), survived without oxygen dependency at 28 days (31% v 27%) and 36 weeks post conceptional age (58% v 52%), and developed acute renal failure. There were no statistically significant differences between other outcomes, except that fewer of the restricted group (19% v 43%) required postnatal steroids (p < 0.01). In the trial population overall, duration of oxygen dependency related significantly to the colloid (p < 0.01), but not crystalloid, input level; after adjustment for specified covariates, the hazard ratio was 1.07 (95% confidence interval 1.02 to 1.13).

CONCLUSIONS

In ventilated, very low birthweight infants, fluid restriction in the perinatal period neither reduces CLD nor increases other adverse outcomes. Colloid infusion, however, is associated with increased duration of oxygen dependency.

First intention high-frequency oscillation with early lung volume optimization improves pulmonary outcome in very low birth weight infants with respiratory distress syndrome

OBJECTIVES

The lack of decline in chronic lung disease of prematurity despite the generalized use of surfactant and alternative modes of ventilation such as high-frequency oscillation (HFO) has been attributed to some misunderstanding of how HFO has to be used. We used a new ventilatory strategy in very low birth weight (VLBW) infants, by initiating HFO immediately after intubation and attempting early lung volume optimization before surfactant was administered.

STUDY DESIGN

The outcome of 32 VLBW infants, managed with first intention HFO over a period of 24 months (September 1, 1996 and August 31, 1998) was compared by chart review with 39 historical controls, consecutively managed with conventional mechanical ventilation (CMV) over a period of 24 months (January 1, 1994 and December 31, 1995).

SETTING

An 11-bed tertiary care pediatric and neonatal intensive care unit of a university teaching hospital.

RESULTS

The 2 groups of patients were similar in demographic distribution of birth weight, gestational age, race, and gender. Patients on first intention HFO were ventilator-dependent (median [95% confidence interval]: 5 [3-6] vs 14 [6-23] days) and oxygen-dependent (12 [4-17] vs 51 [20-60] days) for a shorter time than patients on CMV. The incidence of chronic lung disease at 36 weeks of gestational age was significantly lower in the HFO group compared with the CMV group (0% vs 34%).

CONCLUSIONS

First intention HFO with early lung volume optimization shortened the need for respiratory support and improved pulmonary outcome of VLBW infants with respiratory distress syndrome significantly.

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.

The chest radiograph appearances of very premature infants at 36 weeks post-conceptional age

The chest radiograph of very premature infants at 36 weeks post-conceptional age (PCA) was evaluated with regard to the degree of hyperinflation and cardiomegaly, and the presence of fibrosis/interstitial shadowing, cystic elements, air bronchograms and opacification. The evolution of abnormalities was assessed by comparing the radiograph appearance at 36 weeks PCA with that at 28 days post-natal age (PNA). Three scoring systems were used to determine how any abnormalities present could be best quantified to reflect disease severity as determined by chronic dependency upon supplementary oxygen status. Chest radiographs at 36 weeks PCA from 60 infants (median gestational age 26 weeks (range 24-28)) were studied. 47 infants also had radiographs at 28 days PNA. Only three infants had no chest radiograph abnormalities at 36 weeks PCA, although 24 infants were not dependent upon supplementary oxygen. The most common abnormalities were interstitial shadowing and hyperinflation, while cystic elements and cardiomegaly were rare. The radiographic appearance had deteriorated from 28 days PNA to 36 weeks PCA (p < 0.05); more infants at 36 weeks PCA were hyperinflated (p < 0.01). The chest radiograph appearances of infants who were dependent upon supplementary oxygen scored higher than those who were not (p < 0.01) using all three scoring systems. The system that assessed only the presence of interstitial shadowing, cystic elements and hyperinflation had the highest specificity in identifying oxygen dependency beyond 36 weeks PCA and had the highest area under the respective receiver operator characteristic curve. In conclusion, the majority of very immature infants have an abnormal chest radiograph appearance at 36 weeks PCA. The appearance can, however, be meaningfully scored by evaluating only three abnormalities.