The lungs in immature infants: how important is surfactant therapy in preventing chronic lung problems?

Improving early diagnosis of bronchopulmonary dysplasia

INTRODUCTION

Bronchopulmonary disease (BPD) is associated with long-term neurodevelopmental and cardiorespiratory complications, often requiring significant use of resources. To reduce this healthcare burden, it is essential that those at high risk of BPD are identified early so that strategies are introduced to prevent disease progression. Our aim was to discuss potential methods for improving early diagnosis in the first week after birth.

AREAS COVERED

A narrative review was undertaken. The search strategy involved searching PubMed, Embase and Cochrane databases from 1967 to 2024. The results of potential biomarkers and imaging modes are discussed. Furthermore, the value of scoring systems is explored.

EXPERT OPINION

BPD occurs as a result of disruption to pulmonary vascular and alveolar development, thus abnormal levels of factors regulating those processes are promising avenues to explore with regard to early detection of high-risk infants. Data from twin studies suggests genetic factors can be attributed to 82% of the observed difference in moderate to severe BPD, but large genome-wide studies have yielded conflicting results. Comparative studies are required to determine which biomarker or imaging mode may most accurately diagnose early BPD development. Models which include the most predictive factors should be evaluated going forward.

Bronchopulmonary dysplasia from chest radiographs to magnetic resonance imaging and computed tomography: adding value

Bronchopulmonary dysplasia (BPD) is a common long-term complication of preterm birth. The chest radiograph appearance and survivability have evolved since the first description of BPD in 1967 because of improved ventilation and clinical strategies and the introduction of surfactant in the early 1990s. Contemporary imaging care is evolving with the recognition that comorbidities of tracheobronchomalacia and pulmonary hypertension have a great influence on outcomes and can be noninvasively evaluated with CT and MRI techniques, which provide a detailed evaluation of the lungs, trachea and to a lesser degree the heart. However, echocardiography remains the primary modality to evaluate and screen for pulmonary hypertension. This review is intended to highlight the important findings that chest radiograph, CT and MRI can contribute to precision diagnosis, phenotyping and prognosis resulting in optimal management and therapeutics.

Characterization of lung ultrasound imaging in preterm infants with bronchopulmonary dysplasia

BACKGROUND

Lung ultrasound (LUS) is a bedside technique that can be used on diagnosis and follow-up of neonatal respiratory diseases. However, there are rare reports on the ultrasound features of bronchopulmonary dysplasia (BPD) which is one of the most common chronic lung diseases in preterm infants.

OBJECTIVE

To describe the ultrasound features of different BPD levels, and to investigate the value of ultrasound in evaluating moderate-to-severe BPD.

METHODS

In this prospective cohort study, newborns of less than 37 weeks' gestational age in neonatal intensive care unit (NICU) were included. The LUS characteristics including pleural line, alveolar-interstitial syndrome (AIS), retrodiaphragmatic hyperechogenicity and diaphragmatic morphology were observed and recorded. The reliability of LUS in evaluating moderate and severe BPD were compared and calculated.

RESULTS

A total of 108 infants were enrolled in our study: 39, 24, 29, 16 infants had non, mild, moderate and severe BPD. The median(IQR) pleura thickness in the moderate-to-severe BPD group was 1.7(1.6-1.85) mm, which was thicker than that in the none-to-mild BPD infants (P <  0.001), meanwhile the proportions of rough pleural lines, diffuse AIS, retrodiaphragmatic hyperechogenicity, small cysts above the diaphragm and rough diaphragm in the moderate-to-severe BPD group were also higher than those in none-to-mild BPD group (86.7% vs 36.5, 57.8% vs 7.9%, 37.8% vs 0, 33.3% vs 0, P <  0.001). In evaluating moderate-to-severe BPD, rough pleura had 91.1% (95% confidence interval [CI]: 0.793-0.965) in sensitivity, 91.3% (95% CI: 0.797-0.966) in negative predictive value (NPV), and 66.7% (95% CI: 0.544-0.771) in specificity. Small cysts had 100% (95% CI: 0.941-1) in specificity, 100% (95% CI: 0.816-1) in PPV, and 37.8% in sensitivity (95% CI: 0.251-0.524). Rough diaphragm had 100% (95% CI: 0.943-1) in sensitivity, 100% (95% CI: 0.796-1) in PPV and 33.3% (95% CI: 0.211-0.478) in specificity.

CONCLUSIONS

Depending on its unique advantages such as convenient, no radiation and repeatable, LUS is a valuable imaging method in assessing the severity of BPD, especially in moderate and severe BPD.

Neonatal Lung Disorders: Pattern Recognition Approach to Diagnosis

OBJECTIVE

Lung disease is a common indication for neonates to require medical attention, and neonatal chest radiographs are among the most common studies interpreted by pediatric radiologists. Radiographic features of many neonatal lung disorders overlap, and it may be difficult to differentiate among conditions.

CONCLUSION

This review presents an up-to-date practical approach to the radiologic diagnosis of neonatal lung disorders, with a focus on pattern recognition and consideration of clinical history, patient age, and symptoms.

Interstitial pneumonia pattern on day 7 chest radiograph predicts bronchopulmonary dysplasia in preterm infants

Background

Early identification of infants at higher risk of developing bronchopulmonary dysplasia (BPD) may enable a targeted approach to reduce BPD. We aimed to evaluate the hypothesis that the interstitial pneumonia pattern on the day 7 chest radiograph predicts BPD or death before 36 weeks postmenstrual age (PMA).

Methods

A retrospective cohort study was performed on 336 preterm infants (birth weight < 1500 g and gestational age < 32 postmenstrual weeks) who were admitted to a single tertiary academic center between January 2008 and December 2014. Day 7 chest radiographs were independently reviewed by two pediatric radiologists who were unaware of the clinical information regarding each individual infant.

Results

Data from 304 infants who survived more than 7 days after birth were collected. The interstitial pneumonia pattern on the day 7 chest radiograph was independently associated with BPD or death before 36 weeks PMA (odds ratio [OR] 4.0, 95% confidence interval [CI] 1.1–14.4). The interstitial pneumonia pattern on the day 7 chest radiograph predicted BPD or death with a specificity of 98%. Histologic chorioamnionitis was a preceding factor that was independently associated with the interstitial pneumonia pattern on the day 7 chest radiograph (OR 3.7, 95% CI 1.3–10.3).

Conclusions

The interstitial pneumonia pattern on the day 7 chest radiograph has a high specificity for predicting BPD or death and can be utilized to select high-risk preterm infants who will benefit from potentially preventive interventions against BPD.

Electronic supplementary material

The online version of this article (doi:10.1186/s12887-017-0881-1) contains supplementary material, which is available to authorized users.

Effect of hydrocortisone therapy on severe leaky lung syndrome in ventilated preterm infants

BACKGROUND

The aim of this study was (i) to determine the incidence and risk factors of severe leaky lung syndrome (sLLS), persistent pulmonary edema characterized by massive tracheal secretions and resistance to surfactant therapy, in extremely low gestational age newborns requiring ventilatory support; and (ii) to evaluate the effects of hydrocortisone (HC) therapy for sLLS on tracheal aspirate fluid (TAF) volume and β2-microglobulin levels in TAF.

METHODS

Infants born at <28 weeks gestation requiring ventilation beyond day of life (DOL) 7 were included. Daily TAF volume changes were assessed using a TAF scoring system. Levels of TAF β2-microglobulin, an indicator of capillary leakage, were measured at DOL0, 7, before, and 4 days after starting HC therapy (started at 4 mg/kg/day; tapered for 1-3 weeks).

RESULTS

Of the 54 infants enrolled, 24 (44%) were diagnosed with sLLS. Lower gestational age, lower birthweight, and higher TAF β2-microglobulin levels at DOL7 were independent risk factors for sLLS. Seventeen infants with sLLS received HC therapy starting at DOL17 (median), with subsequent decreases in TAF volume and β2-microglobulin levels.

CONCLUSIONS

The incidence of sLLS, as defined in this study, was 44% in extremely low gestational age newborns requiring ventilator support beyond a week. HC therapy effectively reduced TAF volume and β2-microglobulin levels, suggesting suppression of increased permeability of pulmonary capillaries in infants with sLLS.

Lung protective ventilation in extremely preterm infants

The lungs of an extremely preterm infant ≤28 weeks gestation are structurally and biochemically immature and vulnerable to injury from positive pressure ventilation. A lung protective approach to respiratory support is vital, aiming to ventilate an open lung, using the lowest pressure settings that maintain recruitment and oxygenation and avoiding hyperinflation with each tidal breath. For infants with severe respiratory distress syndrome and persistent atelectasis, lung protective ventilation requires recruitment using stepwise pressure increments, followed by reduction in ventilator pressures in search of an optimal point at which to maintain ventilation. Several studies, including a single randomised controlled trial, have found this lung protective strategy to be more effectively administered using high-frequency oscillatory ventilation rather than conventional ventilation. Many extremely preterm infants have minimal atelectasis and low oxygen requirements in the first days of life, and the ventilatory approach in this case should be one of avoidance of factors including overdistension that are known to contribute to later pulmonary deterioration. From a practical perspective, this means setting positive end-expiratory pressure at the lowest value that maintains oxygenation and restricting tidal volume using a volume-targeted mode of ventilation.

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.

Diuretics for respiratory distress syndrome in preterm infants

BACKGROUND

Lung edema may complicate respiratory distress syndrome (RDS) in preterm infants.

OBJECTIVES

The aim of this review was to assess the risks and benefits of diuretic administration in preterm infants with RDS.

SEARCH METHODS

The standard search method of the Cochrane Neonatal Review Group was used. The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library), MEDLINE and EMBASE were searched. These searches were updated in April 2003, March 2007, January 2011. In addition, the abstract books of the American Thoracic Society and Society for Pediatric Research were searched. MEDLINE and CENTRAL search was conducted using the keyword "Respiratory Distress Syndrome" alone, to find studies of medications recently classified as diuretics, such as theophylline. In addition, EMBASE, controlled-trials.com and clinicaltrials.gov searches were completed in January 2011. MEDLINE search updated to August 2011.

SELECTION CRITERIA

Trials were included in which preterm infants with RDS and less than five days of age were randomly allocated to diuretic administration. Of those trials, studies were only included in which at least one of the following outcomes measures was evaluated: mortality, patent ductus arteriosus, hypovolemic shock, intraventricular hemorrhage, renal failure, duration of oxygen supplementation, duration of mechanical ventilation, need for oxygen supplementation at 28 days of life, oxygen supplementation at 36 weeks of postmenstrual age (gestational age + postnatal age), length of stay, number of rehospitalizations during the first year of life, and neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

The standard method for the Cochrane Collaboration, which is described in the Cochrane Collaboration Handbook, was used. Two investigators extracted, assessed and coded separately all data for each study. Any disagreement was resolved by discussion.

MAIN RESULTS

Seven studies met inclusion criteria. Six studies using furosemide were done before the current era of prenatal steroids, surfactant and fluid restriction. Furosemide administration had no long-term benefits. Furosemide-induced transient improvement in pulmonary function did not outweigh an increased risk for patent ductus arteriosus and for hemodynamic instability. In one recent study, theophylline had no long-term benefits. Theophylline significantly decreased the risk of oligoanuria and transiently increased renal function, but did not significantly affect renal function at discharge or other outcomes.

AUTHORS' CONCLUSIONS

There are no data to support routine administration of furosemide in preterm infants with RDS. Elective administration of furosemide to any patient with RDS should be carefully weighed against the risk of precipitating hypovolemia or developing a symptomatic patent ductus arteriosus. There are not enough data to support routine administration of low-dose theophylline in preterm infants with RDS.

Decreased free water clearance is associated with worse respiratory outcomes in premature infants

OBJECTIVE

The goal was to elucidate predictors of decreased free water clearance (DFWC) in very low birth weight (VLBW) infants. We hypothesized that DFWC and fluid retention are linked to the severity of pulmonary problems and prolonged respiratory support, especially to nCPAP treatment.

METHODS

The investigation was carried out at Tampere University Hospital between 2001 and 2006. The study population comprised 74 VLBW infants born at 29.21 (24.57-34.14) weeks of gestation. Median birth weight was 1175 (575-1490) grams. We measured plasma and urine osmolality and 24-hour urine volume to calculate free water clearance (FWC) for each infant. If FWC was less than 30 ml/kg/day the infant was classified as having DFWC.

RESULTS

There were 38 (51.4%) infants with DFWC in the study population. The median duration of the observed DFT period was 14 (4-44) days. The gestational age at birth was lower for DFWC infants compared to infants with normal FWC (NFWC), 28.29 (24.57-32.86) vs. 30.00 (25.57-34.14) weeks (p = 0.001). DFWC infants also needed longer ventilator treatment, 2 (0-23) vs. 0.50 (0-23) days (p = 0.046), nCPAP treatment 30 (0-100) vs. 3 (0-41) days (p<0.0001) and longer oxygen supplementation 47 (0-163) vs. 22 (0-74) days (p = 0.011) than NFWC infants. All values presented here are medians with ranges.

CONCLUSIONS

DFWC appears to be frequently connected with exacerbation and prolongation of pulmonary problems in VLBW infants. Cautious fluid administration seems to be indicated in VLBW infants with prolonged respiratory problems and DFWC.

Diuretics for respiratory distress syndrome in preterm infants

BACKGROUND

Lung edema may complicate respiratory distress syndrome (RDS) in preterm infants.

OBJECTIVES

The aim of this review was to assess the risks and benefits of diuretic administration in preterm infants with RDS.

SEARCH STRATEGY

The standard search method of the Cochrane Neonatal Review Group was used. MEDLINE, EMBASE and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) were searched using the following keywords: <exp respiratory distress syndrome> and <exp diuretics>. These searches were updated in April 2003 and March 2007. In addition, the abstract books of the American Thoracic Society and Society for Pediatric Research were searched. A MEDLINE and CENTRAL search was conducted in March 2007 using the keyword "Respiratory Distress Syndrome" alone, to make sure to find studies medications recently classified as diuretics, such as theophylline.

SELECTION CRITERIA

Trials were included in which preterm infants with RDS and less than 5 days of age were randomly allocated to diuretic administration. Of those trials, studies were only included in which at least one of the following outcomes measures was evaluated: mortality, patent ductus arteriosus, hypovolemic shock, intraventricular hemorrhage, renal failure, duration of oxygen supplementation, duration of mechanical ventilation, need for oxygen supplementation at 28 days of life, oxygen supplementation at 36 weeks of postmenstrual age (gestational age + postnatal age), length of stay, number of rehospitalizations during the first year of life, and neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

The standard method for the Cochrane Collaboration, which is described in the Cochrane Collaboration Handbook, was used. Two investigators extracted, assessed and coded separately all data for each study. Any disagreement was resolved by discussion.

MAIN RESULTS

Seven studies met inclusion criteria. Six studies using furosemide were done before the current era of prenatal steroids, surfactant and fluid restriction. Furosemide administration had no long-term benefits. Furosemide-induced transient improvement in pulmonary function did not outweigh an increased risk for patent ductus arteriosus and for hemodynamic instability. In one recent study, theophylline had no long-term benefits. Theophylline significantly decreased the risk of oligoanuria and transiently increased renal function, but did not significantly affect renal function at discharge or other outcomes.

AUTHORS' CONCLUSIONS

There are no data to support routine administration of furosemide in preterm infants with RDS. Elective administration of furosemide to any patient with RDS should be carefully weighed against the risk of precipitating hypovolemia or developing a symptomatic patent ductus arteriosus. There are not enough data to support routine administration of low-dose theophylline in preterm infants with RDS.

From the archives of the AFIP: Lung disease in premature neonates: radiologic-pathologic correlation

Pulmonary disease is the most important cause of morbidity in preterm neonates, whose lungs are often physiologically and morphologically immature. Surfactant deficiency in immature lungs triggers a cascade of alveolar instability and collapse, capillary leak edema, and hyaline membrane formation. The term respiratory distress syndrome (RDS) has come to represent the clinical expression of surfactant deficiency and its nonspecific histologic counterpart, hyaline membrane disease. Historically, chest radiographs of infants with RDS predictably demonstrated decreased pulmonary expansion, symmetric generalized reticulogranular lung opacities, and air bronchograms. Refinements in perinatal medicine, including antenatal glucocorticoid administration, surfactant replacement therapy, and increasingly sophisticated ventilatory strategies have decreased the prevalence of RDS and air leak, altered familiar radiographic features, and lowered the threshold of potential viability to a gestational age of approximately 23 weeks. Alveolar paucity and pulmonary interstitial thickness in these profoundly premature neonates impair normal gas exchange and may necessitate prolonged mechanical ventilation, increasing the risk of lung injury. Bronchopulmonary dysplasia (BPD), alternatively termed chronic lung disease of infancy, is a disorder of lung injury and repair originally ascribed to positive-pressure mechanical ventilation and oxygen toxicity. Before the advent of surfactant replacement therapy, chest radiographs of infants with classic BPD demonstrated coarse reticular lung opacities, cystic lucencies, and markedly disordered lung aeration that reflected alternating regions of alveolar septal fibrosis and hyperinflated normal lung parenchyma. In the current era of surfactant replacement, BPD is increasingly a disorder of very low-birth-weight neonates with arrested alveolar and pulmonary vascular development, minimal alveolar septal fibrosis and inflammation, and more subtle radiographic abnormalities.

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.

Diuretics for respiratory distress syndrome in preterm infants

BACKGROUND

Lung edema may complicate respiratory distress syndrome (RDS) in preterm infants.

OBJECTIVES

The aim of this review was to assess the risks and benefits of diuretic administration in preterm infants with RDS.

SEARCH STRATEGY

We used the standard search method of the Cochrane Neonatal Review Group. We searched Medline, Embase and the Cochrane Controlled Trials Register from the Cochrane Library, using the following keywords: <exp respiratory distress syndrome> and <exp diuretics>. In addition, we searched the abstract books of the American Thoracic Society and Pediatric Research Societies.

SELECTION CRITERIA

We only included trials in which preterm infants with RDS and less than 5 days of age were randomly allocated to diuretic administration. Of those trials, we only included studies in which at least one of the following outcomes measures was evaluated: mortality, patent ductus arteriosus, hypovolemic shock, intraventricular hemorrhage, renal failure, duration of oxygen supplementation, duration of mechanical ventilation, need for oxygen supplementation at 28 days of life, oxygen supplementation at 36 weeks of postconceptional age (gestational age + postnatal age), length of stay, number of rehospitalizations during the first year of life, and neurodevelopmental outcome.

DATA COLLECTION AND ANALYSIS

We used the standard method for the Cochrane Collaboration which is described in the Cochrane Collaboration Handbook. Two investigators extracted, assessed and coded separately all data for each study. Any disagreement was resolved by discussion.

MAIN RESULTS

Six studies met inclusion criteria. Studies available for this systematic review were all done before the current era of prenatal steroids, surfactant, indomethacin and fluid restriction. Furosemide administration had no long-term benefits. Furosemide-induced transient improvement in pulmonary function did not outweigh an increased risk for patent ductus arteriosus and for hemodynamic instability.

REVIEWER'S CONCLUSIONS

There are no current data to support routine diuretic administration in preterm infants with RDS. Elective administration of furosemide or any diuretic to any patient with RDS should be carefully weighed against the risk of precipitating hypovolemia. In addition, elective administration of furosemide should be weighed against the risk of developing a symptomatic patent ductus arteriosus.

Imaging of medical disease of the newborn lung

Surfactant deficiency remains the most common and serious pulmonary affliction of premature infants. Exogenous surfactant and corticosteroid administration have had a major impact in improving survival and morbidity in this disease with consequent alterations in the clinical and radiographic course. Chronic lung disease, although still common, is usually less severe than previously, especially in larger infants. Significant therapeutic strides in treating persistent pulmonary hypertension with or without meconium aspiration have been the use of high-frequency ventilators, inhaled nitric oxide, and ECMO. Prompt recognition and treatment of infection, atelectasis, and air leak whether primary or secondary are important to overall outcome. Less common pulmonary conditions, such as lymphangiectasia, pulmonary hypoplasia, and alveolar proteinosis, may initially masquerade as more common lesions. Persistent pulmonary hypertension is often the initial diagnosis and part of the clinical problem. Attention must be paid to the clinical and radiographic appearance and excursion of the thoracic cage because deformities and malformations may be the cause of respiratory problems.

Bronchopulmonary dysplasia. Impact of surfactant replacement therapy

Bronchopulmonary dysplasia is a major contributor to the morbidity and mortality of infants born prematurely. Surfactant replacement therapy has had a significant impact on the death rate from respiratory distress syndrome, yet the impact on bronchopulmonary dysplasia is minimal. Despite these findings, the overall incidence and severity of bronchopulmonary dysplasia are likely to decline over time as neonatal care continues to advance.

Lung disease in premature neonates: impact of new treatments and technologies

Advances in perinatal medicine and neonatology have dramatically changed clinical outcomes for premature neonates and have ushered in a new era of radiological complexity. "Portable" chest radiographs continue to be the mainstay in diagnostic imaging of fragile newborns, but radiologists may be confronted with new and unexpected radiological expressions of once-familiar disease processes. Familiarity with the radiological impact of emerging treatments in premature neonates is essential for accurate film interpretation.