Pulmonary function in technology-dependent children 2 years and older with bronchopulmonary dysplasia

Early Origins of Chronic Obstructive Pulmonary Disease: Prenatal and Early Life Risk Factors

The main risk factor for chronic obstructive pulmonary disease (COPD) is active smoking. However, a considerable amount of people with COPD never smoked, and increasing evidence suggests that adult lung disease can have its origins in prenatal and early life. This article reviews some of the factors that can potentially affect lung development and lung function trajectories throughout the lifespan from genetics and prematurity to respiratory tract infections and childhood asthma. Maternal smoking and air pollution exposure were also analyzed among the environmental factors. The adoption of preventive strategies to avoid these risk factors since the prenatal period may be crucial to prevent, delay the onset or modify the progression of COPD lung disease throughout life.

Lung growth and pulmonary function after prematurity and bronchopulmonary dysplasia

Bronchopulmonary dysplasia (BPD) still carries a heavy burden of morbidity and mortality in survivors of extreme prematurity. The disease is characterized by simplification of the alveolar structure, involving a smaller number of enlarged alveoli due to decreased septation and a dysmorphic pulmonary microvessel growth. These changes lead to persistent abnormalities mainly affecting the smaller airways, lung parenchyma, and pulmonary vasculature, which can be assessed with lung function tests and imaging techniques. Several longitudinal lung function studies have demonstrated that most preterm-born subjects with BPD embark on a low lung function trajectory, never achieving their full airway growth potential. They are consequently at higher risk of developing a chronic obstructive pulmonary disease-like phenotype later in life. Studies based on computer tomography and magnetic resonance imaging, have also shown that in these patients there is a persistence of lung abnormalities like emphysematous areas, bronchial wall thickening, interstitial opacities, and mosaic lung attenuation also in adult age. This review aims to outline the current knowledge of pulmonary and vascular growth in survivors of BPD and the evidence of their lung function and imaging up to adulthood.

Physiologic findings in children previously ventilator dependent at home due to bronchopulmonary dysplasia

INTRODUCTION

Bronchopulmonary dysplasia (BPD) is the primary respiratory complication of premature birth. Some preterm newborns develop chronic respiratory failure, requiring home ventilator support. While physiologic measures have been described for prematurely born children, little is known about spirometric indices in patients with severe BPD who were previously ventilator dependent at home.

METHODS

We retrospectively reviewed medical charts of patients with severe BPD who were ventilator dependent at home. We excluded patients with other comorbidities that could contribute to the severity of BPD. Spirometry was performed when the patient was able to follow commands.

RESULTS

Between 1984 and 2012, within our severe BPD cohort who previously required home ventilator support, 19 patients were able to perform reproducible spirometry meeting ATS/ERS acceptability criteria. Ten (52.6%) were females, 13 (68.4%) were Caucasians. Mean age at liberation from ventilation was 2.4 years (C.I. 2.0, 2.9) and at decannulation was 3.5 years (C.I. 2.9, 4.0); median age at first reproducible spirometry measurement was 6.6 years (IQR: 4.9, 8.3). Spirometry results revealed significant airway obstruction, as demonstrated by Z-scores values of -1.5 (C.I. -2.5, -0.4) for FVC, -2.7 (C.I. -3.3, -1.9) for FEV1 , and -3.6 (C.I. -4.3, -2.9) for FEF25-75 . More so, serial spirometric measurements' slopes revealed that the airway obstruction remained static over time (FEV1 slope: -0.07, P-value: 0.2624; FVC slope: -0.01, P-value: 0.9064; and FEF25-75 : 0.0, P-value: 0.8532).

CONCLUSIONS

Extreme prematurity associated with severe BPD requiring home ventilator support carries significant risks of morbidity. These patients had substantially diminished respiratory function reflecting airflow abnormalities that remained static over time.

Respiratory outcomes for the tiniest or most immature infants

Extremely low birth weight (<1000 g birth weight) or extremely preterm (<28 weeks of gestation) infants are surviving in greater numbers as neonatal care advances. Many of these survivors, especially those who develop bronchopulmonary dysplasia, have more respiratory ill health in the first years after discharge home, reduced respiratory function and impaired exercise capacity throughout childhood and into adulthood compared with term-born controls. It is important to establish the long-term respiratory outcomes for the tiniest or most immature survivors as they grow older, since they may contribute disproportionately to rates of chronic obstructive pulmonary disease and respiratory ill-health in adulthood.

Cardio-respiratory response to moderate chloral hydrate sedation in young lambs

AIM

Chloral hydrate (CH) is the most commonly used sedative for medical procedures and lung function tests in infancy. The aim was to determine whether moderate CH sedation affects airway function, lung volume and ventilation.

METHODS

Thirteen chronically instrumented 7- to 8-week-old lambs were studied both before and after CH sedation (50 mg/kg as intravenous bolus followed by 25 mg/kg/hour as continuous infusion). Nitrogen washout technique and lung mechanics analysis were used to assess functional residual capacity (FRC) and airway function. Moment analysis and lung clearance index were calculated as measures of gas mixing efficiency in distal airways. Respiratory rate, tidal volume, minute ventilation and indices of inspiratory drive were determined together with heart rate, blood pressure and oxygenation.

RESULTS

No significant CH-induced changes were found for gas mixing efficiency, FRC or lung mechanics. Minute ventilation decreased slightly, but significantly, while indices of inspiratory drive remained unchanged. Heart rate increased significantly, but mean arterial blood pressure was unaffected.

CONCLUSION

Moderate CH sedation did not significantly affect airway function or FRC. Although indices of inspiratory drive were not affected, minute ventilation decreased slightly. These findings indicate that reliable results can be obtained from lung function testing when CH is used for sedation.

Lung function among infants born preterm, with or without bronchopulmonary dysplasia

OBJECTIVE

Both healthy preterm infants and those with bronchopulmonary dysplasia (BPD) have poor lung function during childhood and adolescence, although there is no evidence whether prematurity alone explains the reduction in lung function found in BPD infants. Our study seeks to know if lung function, measured in infancy by means of rapid thoracic compression with raised volume technique, is different between preterm infants with and without BPD.

METHODS

Lung function was measured in 43 preterm infants with BPD and in 32 preterm infants without BPD at a chronological age range of 2-28 months. Forced vital capacity (FVC), forced expiratory volume at 0.5 sec, and forced expiratory flows at 50, 75, 85%, and 25-75% of FVC were obtained from maximal expiratory volume curves by means of rapid thoracic compression with raised volume technique. Maximal flow at functional residual capacity was measured using rapid thoracic compression at tidal volume. Multiple regression analysis and generalized least squares (GLS) random-effects regression model were used to control for variables such as gender, weeks of gestation, age, birth weight, and tobacco smoke exposure. A sub-analysis was performed in infants born at 28+ weeks of gestation.

RESULTS

BPD was associated to significantly lower flows (regression coefficients: -0.51, -0.54, -57, -0.53, and -0.82, respectively for FEF(50), FEF(75), FEF(85), FEF(25-75)). This association was driven by males and maintained in the subgroup of infants born at 28+ weeks of gestation.

CONCLUSION

BPD is associated with an additional decrease of lung function during the first 2 years of life in infants born preterm.

Respostas cardiopulmonares durante o esforço em crianças e adolescentes nascidas prematuras

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

Effects of gender on the health and development of medically at-risk infants

OBJECTIVES

To examine gender-differentiated health and cognitive/motor/language developmental outcomes among medically at-risk infants.

DESIGN

Longitudinal descriptive and comparative secondary analysis.

SETTING

Neonatal Intensive Care Unit, intermediate care unit, and infectious disease clinic of tertiary medical centers in the southeast and east United States.

PARTICIPANTS

One hundred eight (108) premature infants, 67 medically fragile infants, and 83 infants seropositive for HIV.

METHODS

Neonatal and later health variables were obtained from the medical record to determine the technology dependence scores and frequency of common health problems. Data for physical growth and cognitive/motor/language development were obtained through the physical measurement, including the Bayley Scales of Infant Development-Second Edition, the Vineland Adaptive Behavior Scale, the Toll Control Developmental Checklist, and the Preschool Language Scale-3 during home visits between 6 and 27 months corrected ages.

RESULTS

Fewer effects on health and developmental outcomes related to gender were observed with medically fragile infants than the other two groups of infants. The cognitive/motor/language scores were decreased with increasing age of the infants in all groups.

CONCLUSION

Male gender can be considered a significant biological risk factor for infants' cognitive and motor development, especially for premature infants. Because of their increased risk, it is recommended that male infants who are born prematurely or seropositive for HIV have early and advanced developmental screening tests by trained personnel through periodic pediatric clinic.

Stenotrophomonas maltophilia flagellin induces a compartmentalized innate immune response in mouse lung

Intranasal (i.n.) instillation of different amounts of purified Stenotrophomonas maltophilia flagellin preparation (1, 5 and 15 microg) in BALB/c mice stimulated a transient innate immune response in the lungs. This was characterized by infiltration of different kinds of leukocytes (neutrophils, monocytes and lymphocytes), production of various inflammatory mediators (tumour necrosis factor alpha, interleukin 1 beta, interleukin 10, nitric oxide, myeloperoxidase and malondialdehyde) and activated alveolar macrophages (AMs). The proinflammatory cytokine production resulted in accumulation of activated neutrophils and macrophages and their products following immunostimulation with flagellin. The activation of AMs by flagellin was non-specific as AMs obtained from flagellin-treated animals, even after 4 h of exposure, were found to engulf and kill S. maltophilia and Staphylococcus aureus efficiently compared to macrophages obtained from control animals. i.n. instillation of 5 microg flagellin resulted in the generation of an effective innate immunity compared to other flagellin doses. Our data provide strong evidence that S. maltophilia flagellin stimulates innate immunity in mouse lung.

[Bronchopulmonary dysplasia and prematurity. Short-and long-term respiratory changes]

Bronchopulmonary dysplasia (BPD) is the most frequent chronic lung disease in premature children. With the inclusion of antenatal steroid therapy, surfactant use and novel mechanical ventilation strategies, survival of premature newborns has increased, whereupon the incidence of BPD has not only decreased but has also risen in extremely premature newborns. This has led to a high respiratory morbidity in the first 2-3 years of life, with numerous admissions to hospital and respiratory exacerbations mostly due to viral infections. Although there is a trend towards improvement, during school age and adolescence, respiratory symptoms may persist, due to changes in pulmonary function often showing a lower exercise capacity. Although BPD symptoms are similar to those of asthma, as there is limitation in airflow and bronchial hyperresponsiveness (BHR), pathophysiological mechanisms could be different in both diseases. On the other hand, isolated prematurity plays an important role in the child's respiratory pathology, proving that pulmonary function alterations in preterm children are present since the first months of life. A higher respiratory morbidity has also been observed in these children when compared to full-term newborns, not only during the first years of life but also subsequently. In this study, different aspects of chronic respiratory disease associated with prematurity will be analysed, drawing special attention to clinical symptoms, respiratory function changes, BHR and exercise capacity. All these aspects will be reviewed from early childhood until adolescence and young adult age. Similarities and differences between BPD and asthma will also be discussed.

Pulmonary outcomes in bronchopulmonary dysplasia

The incidence of bronchopulmonary dysplasia (BPD), defined as oxygen need at 36 weeks of postmenstrual age, is about 30% for infants with birth weights <1000 g. BPD is associated with persistent structural changes in the lung that result in significant effects on lung mechanics, gas exchange, and pulmonary vasculature. Up to 50% of infants with BPD require readmission to the hospital for lower respiratory tract illness in the first year of life. Long-term measurements of lung function in BPD include normalization of pulmonary mechanics and some lung volumes over time as somatic and lung growth occur, whereas abnormality of small airway function persists. The majority of data reveals no long-term decrease in exercise capacity. Mild to moderate radiological abnormalities persist. BPD is a result of dynamic processes involving inflammation, injury, repair, and maturation. Infants with BPD have significant pulmonary sequelae during childhood and adolescence, and continued surveillance of young adults with BPD is critical.

Lung function tests in neonates and infants with chronic lung disease: forced expiratory maneuvers

This fourth paper in a review series on the role of lung function testing in infants and young children with acute neonatal disorders and chronic lung disease of infancy (CLDI) addresses measurements of forced expiration using rapid thoraco-abdominal compression (RTC) techniques and the forced deflation technique. Following orientation of the reader to the subject area, we focus our comments on the areas of inquiry proposed in the introductory paper to this series. The quality of the published literature is reviewed critically, and recommendations are provided to guide future investigation in this field. All studies on infants and young children with CLDI using forced expiratory or deflation maneuvers demonstrated that forced flows at low lung volume remain persistently low through the first 3 years of life. Measurement of maximal flow at functional residual capacity (V'maxFRC) is the most commonly used method for assessing airway function in infants, but is highly dependent on lung volume and airway tone. Recent studies suggested that the raised volume RTC technique, which assesses lung function over an extended volume range as in older children, may be a more sensitive means of discriminating changes in airway function in infants with respiratory disease. The forced deflation technique allows investigation of pulmonary function during the early development of CLDI in intubated subjects, but its invasive nature precludes its use in the routine setting. For all techniques, there is an urgent need to establish suitable reference data and evaluate within- and between-occasion repeatability, prior to establishing the clinical usefulness of these techniques in assessing baseline airway function and/or response to interventions in subjects with CLDI.

Lung function tests in neonates and infants with chronic lung disease of infancy: functional residual capacity

This is the second paper in a review series that will summarize available data and discuss the potential role of lung function testing in infants and young children with acute neonatal respiratory disorders and chronic lung disease of infancy. The current paper addresses the expansive subject of measurements of lung volume using plethysmography and gas dilution/washout techniques. Following orientation of the reader to the subject area, we focus our comments on areas of inquiry proposed in the introductory paper to this series. The quality of the published literature is reviewed critically, and recommendations are provided to guide future investigation in this field. Measurements of lung volume are important both for assessing growth and development of lungs in health and disease, and for interpreting volume-dependent lung function parameters such as respiratory compliance, resistance, forced expiratory flows, and indices of gas-mixing efficiency. Acute neonatal lung disease is characterized by severely reduced functional residual capacity (FRC), with treatments aimed at securing optimal lung recruitment. While FRC may remain reduced in established chronic lung disease of infancy, more commonly it becomes normalized or even elevated due to hyperinflation, with or without gas-trapping, secondary to airway obstruction. Ideally, accurate and reliable bedside measurements of FRC would be feasible from birth, throughout all phases of postnatal care (including assisted ventilation), and during subsequent long-term follow-up. Although lung volume measurements in extremely preterm infants were described in a research environment, resolution of several issues is required before such investigations can be translated into routine clinical monitoring.

Viral respiratory infections in children with technology dependence and neuromuscular disorders

BACKGROUND

Viral acute respiratory infections represent a significant cause of morbidity and mortality across all ages, especially in patients with chronic underlying conditions. Although recognized anecdotally, the risks of viral infection to those children with chronic underlying conditions rendering them technology dependent, or to those children with neuromuscular disorders, have not been well studied.

METHODS

Studies of children with underlying conditions that result in technology dependence and those with neuromuscular disorders who required hospitalization for respiratory syncytial virus infection are reviewed. Additionally surveys of physician perceptions toward risk factors for severe viral illness and prevention in this population of patients are reported. Possible mechanisms to explain the increased risk of disease severity with viral respiratory infections are explored as well.

RESULTS

Current or recent use of supplemental oxygen is associated with more severe disease in children with chronic underlying conditions, especially bronchopulmonary dysplasia. Supplemental oxygen use may be a marker for several factors known to increase the severity of viral respiratory illnesses. Children with neuromuscular weakness are also likely to experience more severe disease, most likely resulting from compromised airway clearance.

CONCLUSIONS

Although the number of children who are technology-dependent or have severe neuromuscular weakness is small, their risk of severe disease after viral respiratory infection may be similar to that of premature infants or other high risk groups. A better understanding of the factors responsible for severe viral disease in these children would help create better strategies for treatment and prevention.

Infant pulmonary function testing

Pulmonary function tests in infants have been used for many years, but they have been largely relegated to specialized centers and research purposes. More recently, development of commercial equipment and newer techniques has allowed for more broad use and application of these tests. This review describes different techniques that have been used to study infants and toddlers, and their clinical applications.