Measuring respiratory outcome

Respiratory symptoms in preterm infants: burden of disease in the first year of life

Objective

While respiratory symptoms in the first year of life are relatively well described for term infants, data for preterm infants are scarce. We aimed to describe the burden of respiratory disease in a group of preterm infants with and without bronchopulmonary dysplasia (BPD) and to assess the association of respiratory symptoms with perinatal, genetic and environmental risk factors.

Methods

Single centre birth cohort study: prospective recording of perinatal risk factors and retrospective assessment of respiratory symptoms during the first year of life by standardised questionnaires. Main outcome measures: Cough and wheeze (common symptoms), re-hospitalisation and need for inhalation therapy (severe outcomes). Patients: 126 preterms (median gestational age 28.7 weeks; 78 with, 48 without BPD) hospitalised at the University Children's Hospital of Bern, Switzerland 1999-2006.

Results

Cough occurred in 80%, wheeze in 44%, rehospitalisation in 25% and long term inhalation therapy in wheezers in 13% of the preterm infants. Using logistic regression, the main risk factor for common symptoms was frequent contact with other children. Severe outcomes were associated with maximal peak inspiratory pressure, arterial cord blood pH, APGAR and CRIB-Score.

Conclusions

Cough in preterm infants is as common as in term infants, whereas wheeze, inhalation therapy and re-hospitalisations occur more often. Severe outcomes are associated with perinatal risk factors. Preterm infants who did not qualify for BPD according to latest guidelines also showed a significant burden of respiratory disease in the first year of life.

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.

Pulmonary perfusion during lipopolysaccharide (LPS) induced fetal endotoxemia in the preterm fetal sheep

OBJECTIVE

To study endotoxin induced changes in pulmonary blood flow during normoxia and hypoxia and analyzed the role of nitric oxide (NO) and endothelin (ET) in this process.

STUDY DESIGN

Twenty-seven fetal sheep were chronically instrumented at 107+/-1 days (term is 147 days). Experiments were performed 3 days after surgery. Fetuses were randomized into four groups. Group 1: control group (n=5); Group 2: LPS group (n=6) with lipopolysaccharide (LPS) injection at t -60min; Group 3: L-NAME (n=6) with nitro-l-arginine methyl ester (l-NAME) treatment at t -75min; Group 4: l-NAME+LPS group (n=6) with nitro-l-arginine methyl ester (l-NAME) pre-treatment at t -75min and LPS administration at t -60min as described above; Group 5: BQ123+LPS group (n=4) with BQ123 pre-treatment at t -75min and LPS injection at t -60min as described above.

RESULTS

Unlike in control fetuses, there was a marked elevation in pulmonary perfusion in response to LPS induced endotoxemia during normoxia (+112%; p<0.01), which was even further increased during hypoxia (+434%; p<0.001). This increase was partially blocked by BQ123 (p<0.05) and completely abolished by pre-treatment with l-NAME (p<0.001).

CONCLUSION

During fetal endotoxemia, pulmonary perfusion is increased by LPS induced production of nitric oxide. This may have a significant impact in the fetal inflammatory response syndrome, particularly in the inflammation of the fetal lungs observed in response to intrauterine infection.

Post-natal corticosteroid use

Corticosteroids given systemically in the first 2 weeks after birth may reduce chronic lung disease (CLD) and mortality, but there are concerns regarding the long-term adverse effects which may have influenced prescribing habits. The aim of this study was to determine whether corticosteroids were still prescribed and, if so, was there a consensus regarding the most appropriate regimen to use. Consultant paediatricians at all 223 neonatal units in the United Kingdom were sent a questionnaire asking which route, timing, dosage and indications they used when administering corticosteroids. There was a 72% response rate to the survey. Of those who responded, 33% never prescribed steroids and 3.75% gave inhaled steroids only. Corticosteroids were not prescribed in the 1st week after birth, 21.1% of respondents commenced administration in the 2nd week and 33.3% only outside the neonatal period. A total of 48% prescribed a daily dose of 0.5 mg/kg per day, 33% gave lower doses, with 7.9% prescribing 0.1 mg/kg per day or less. The majority (77%) prescribed corticosteroids only to ventilator-dependent infants, others also gave corticosteroids to chronically continuous positive airway pressure- or oxygen-dependent infants.

CONCLUSION

There are wide variations in corticosteroid usage. This emphasises the need to identify if there is a corticosteroid dosage regimen with a positive risk/benefit ratio.

Follow-up data their use in evidence-based decision-making

Experience with certain perinatal interventions, such as supplemental oxygen and dexamethasone, leads to the conclusion that follow-up data are needed to be well informed about the safety of certain perinatal interventions. Experience with indomethacin suggests that follow-up data also are regarded by some clinicians as a necessary aspect of evidence about effectiveness. Ideally, clinical trials of perinatal interventions might involve collection of data about neonatal predictors of outcome (such as a neuroimaging study and a standardized neurologic assessment); several developmental and neurologic assessments before school entry; a comprehensive evaluation of the child's cognitive function, behavioral competencies, and academic performance at 7 to 8 years of age; serial detailed assessments of the family psychosocial functioning; and an inventory of resources available for the child. Many clinical trials have not included follow-up after the neonatal period, and in such cases information about the effect of the intervention on participants' HRQL is incomplete. The approach taken in several recent trials, in which the outcome of interest is neurodevelopmental outcome at 18 months, attempts to strike a balance between a theoretical ideal (a comprehensive, longitudinal follow-up through school age) and a follow-up regimen that is not prohibitively expensive. Such trials include follow-up during the first 1 to 3 years of life, when major disabilities can be identified reliably, thereby providing moderately informative data about participants' eventual quality of life, related to the presence or absence of major disability. If, however, there is reason to suspect that the intervention has effects on the developing brain, follow-up after school entry may provide additional evidence pertinent to the risks and benefits of the intervention.

Populations at risk for developing respiratory syncytial virus and risk factors for respiratory syncytial virus severity: infants with predisposing conditions

According to National Vital Statistics Reports, premature infants (< 36 weeks gestation) account for approximately 7.4% of all births. During the 8 years from 1989 to 1997, multiple births steadily increased across all categories from twin to quintuplet and higher orders. During that same period low birth weight (< 2500 g) births increased almost 12%, and very low birth weight (< 1500 g) births increased approximately 20%.Attendant to these national trends in multiple and preterm births, overall gestation-specific survival rates have improved substantially. This improved outcome can be attributed in large measure to advances in neonatal care and technology. Despite the encouraging statistics on survival, infants born prematurely, at low or very low birth weights and/or with chronic conditions that predispose to lower respiratory tract illness, continue to incur serious risk of long term morbidity and the consumption of inpatient hospital services. In a recent 2-year study of US children, low and very low birth weights were found to be independent risk factors for bronchiolitis-associated mortality. In the past 14 years what defines bronchopulmonary dysplasia (BPD)/chronic lung disease (CLD) has shifted away from clinical, radiographic and pathologic findings in the preterm infant toward the pathophysiology of arrested lung development and the need for supportive care beyond 36 weeks corrected gestational age. The incidence of BPD/CLD ranges from 14 to 43%, with higher rates observed among infants of lower gestational age and birth weight. The health care team approach to the management of BPD directs its efforts toward minimizing pulmonary vascular resistance, alleviating airway obstruction and improving short term lung mechanics. Measures to prevent BPD/CLD attempt to forestall both acute and chronic lung function abnormalities. To that end researchers have investigated the early use of continuous positive airway pressure, vitamin supplementation and recombinant human copper/zinc superoxide dismutase. Despite significant gains in the survival of infants born at lower gestational ages, prematurity, low birth weight and/or underlying chronic pulmonary disease put the pediatric patient at risk for increased frequency and severity of respiratory syncytial virus lower respiratory tract illness and the potential for its long term sequelae.

Novel technique to average breathing loops for infant respiratory function testing

Breathing loops can be obtained by plotting two respiratory signals on an x-y diagram: the resulting loops represent a non-parametric description of the respiratory system. In infancy, loops are commonly measured during tidal breathing and their interpretation is hampered by high within-subject variability. Therefore a two-dimensional averaging technique for loops has been developed. The algorithm is based on segmentation of the loops and required two steps. First, the total length of the loop of every breathing cycle was divided into a specified number of equidistant intervals and the co-ordinates calculated by stepwise linear approximation of the curve. Second, averaged loops were calculated using the arithmetical mean (or the median if there were artifacts) of the x and y co-ordinates of the loops for all calculated points. To compare the new technique with averaging in the time domain a simulation study was performed using respiratory signals with a coefficient of variation (CV) of 5%, 10%, 15% and 20%. In contrast to the new technique, with increasing CV, averaging in the time domain led to increasing contortions in the averaged flow-volume loops. Mean errors of peak tidal expiratory flow were -3.3%, -13.9%, -21.3% and -34.2%, whereas errors with the new technique were considerably lower (0.5%, 0.4%, 0.5% and -0.1%) and independent of the level of CV.

Factors adversely affecting lung growth

Antenatal lung growth is adversely affected in conditions where there is intra-or extrathoracic compression, impaired fetal breathing movements and/or reduction in amniotic fluid volume. Postnatally, factors in infancy most commonly associated with abnormal lung function are passive smoking and premature delivery, its associated complications and management. Many conditions affecting lung growth are readily diagnosed by antenatal ultrasonography. Postnatally, pulmonary hypoplasia should be suspected if an infant requires high airway pressures during resuscitation and subsequent ventilatory support, in the absence of severe parenchymal disease on the chest radiograph. Antenatal therapy has been directed at relieving lung compression, but the efficacy of such interventions has not been proven in randomized trials. Certain disorders associated with impaired lung growth have a high perinatal mortality. Infants who are less severely affected suffer respiratory symptoms with lung function abnormalities or may only be distinguished by chronic tachypnoea during infancy.