Exogenous human surfactant for treatment of severe respiratory distress syndrome: a randomized prospective clinical trial

Reflections on the introduction of surfactant therapy for neonates with respiratory distress

When pulmonary surfactant was first detected in the 1950s by Pattle and Clements, many thousands of infants perished each year due to a respiratory illness termed hyaline membrane disease. Hyaline membranes are formed by plasma leaking through damaged endothelial barriers into the terminal bronchiolar: alveolar spaces. Since the leaking plasma lacks erythrocytes, these clots are opaque. Insightful research by Avery and Mead soon led to the suggestion that the neonatal respiratory distress syndrome (RDS) did not arise because of the presence of hyaline membranes, but rather was related to the lack of sufficient pulmonary surfactant, mainly as a result of immaturity. Unfortunately, initial attempts at treating RDS with aerosolized dipalmitoyl-phosphatidylcholine, the major single molecular component, proved unsuccessful. Almost 20 years later, it was demonstrated by Enhorning and Robertson that treating prematurely delivered rabbit pups with natural surfactant prevents respiratory failure. Initially, it appeared unlikely that animal surfactants could be used for therapy with human infants. However, in 1980, Fujiwara demonstrated that a modified bovine surfactant extract promoted gaseous exchange with infants suffering from RDS. Soon a number of bovine and porcine-modified surfactants and two wholly synthetic formulations were shown to alleviate RDS. The present review relates some of the key scientific findings and significant clinical contributions responsible for reducing the neonatal morbidity and mortality associated with RDS. It further describes some of the more recent findings on the biological, biophysical, and physiological significance of pulmonary surfactant in health and disease.

Heterogeneous Treatment Effects of High-Frequency Oscillatory Ventilation for Acute Respiratory Distress Syndrome: A Post Hoc Analysis of the Oscillation for Acute Respiratory Distress Syndrome Treated Early (OSCILLATE) Trial

OBJECTIVES

We sought to evaluate whether different subgroups of adults with acute respiratory distress syndrome (ARDS) respond differently to high-frequency oscillatory ventilation (HFOV).

DESIGN

The Oscillation for ARDS Treated Early (OSCILLATE) trial was a randomized controlled trial of HFOV vs. conventional ventilation that found an increased risk of in-hospital mortality (primary outcome) with HFOV. In a post hoc analysis, we applied three different approaches to evaluate heterogeneity of treatment effect for in-hospital mortality: 1) subgroup analyses based on baseline Pao2:Fio2 ratio and oxygenation index (OI); 2) a risk-based approach using a multivariable outcome prediction model; and 3) a clustering approach via multivariable latent class analysis. We used multivariable logistic regression models to assess for interaction.

SETTING

Thirty-nine ICUs, five countries.

SUBJECTS

Five hundred forty-eight adults with moderate to severe ARDS.

INTERVENTIONS

HFOV vs. conventional mechanical ventilation with low tidal volume and higher positive end-expiratory pressure.

MEASUREMENTS AND MAIN RESULTS

The effect of HFOV on in-hospital mortality was consistent across categories of Pao2:Fio2 ratio (adjusted odds ratio [aOR], 2.04; 95% CI, 1.32-3.17 and aOR, 1.16; 95% CI, 0.49-2.75 for groups with Pao2:Fio2 above or equal to 80, vs. below 80, respectively; interaction p = 0.23) and OI (aOR, 1.78; 95% CI, 0.67-4.70; aOR, 3.19; 95% CI, 1.44-7.09; aOR, 1.73; 95% CI, 0.82-3.65; and aOR, 1.33; 95% CI, 0.61-2.90 for quartiles of baseline OI, respectively; interaction p = 0.44). Point estimates for the effect of HFOV were consistent across risk categories (aOR, 2.44; 95% CI, 0.40-14.83; aOR, 1.69; 95% CI, 0.75-3.85; and aOR, 2.10; 95% CI, 0.59-7.54 for the lowest, moderate, and highest risk categories, respectively; interaction p = 0.32). Using a clustering approach, point estimates for HFOV were also consistent (cluster 1: aOR, 1.85; 95% CI, 1.15-3.00 and cluster 2: aOR, 1.75; 95% CI, 0.91-3.38; interaction p = 0.75).

CONCLUSIONS

We did not identify heterogeneity in the effect of HFOV across different subgroups of patients with ARDS.

Historical perspective on surfactant therapy: Transforming hyaline membrane disease to respiratory distress syndrome

Lung surfactant is the first drug so far designed for the special needs of the newborn. In 1929, Von Neergard described lung hysteresis and proposed the role of surface forces. In 1955-1956, Pattle and Clements found direct evidence of lung surfactant. In 1959, Avery discovered that the airway's lining material was not surface-active in hyaline membrane disease (HMD). Patrick Bouvier Kennedy's death, among half-million other HMD-victims in 1963, stimulated surfactant research. The first large surfactant treatment trial failed in 1967, but by 1973, prediction of respiratory distress syndrome using surfactant biomarkers and promising data on experimental surfactant treatment were reported. After experimental studies on surfactant treatment provided insight in lung surfactant biology and pharmacodynamics, the first trials of surfactant treatment conducted in the 1980s showed a striking amelioration of severe HMD and its related deaths. In the 1990s, the first synthetic and natural surfactants were accepted for treatment of infants. Meta-analyses and further discoveries confirmed and extended these results. Surfactant development continues as a success-story of neonatal research.

Outpatient Respiratory Management of Infants, Children, and Adolescents with Post-Prematurity Respiratory Disease: An Official American Thoracic Society Clinical Practice Guideline

Background: Premature birth affects millions of neonates each year, placing them at risk for respiratory disease due to prematurity. Bronchopulmonary dysplasia is the most common chronic lung disease of infancy, but recent data suggest that even premature infants who do not meet the strict definition of bronchopulmonary dysplasia can develop adverse pulmonary outcomes later in life. This post-prematurity respiratory disease (PPRD) manifests as chronic respiratory symptoms, including cough, recurrent wheezing, exercise limitation, and reduced pulmonary function. This document provides an evidence-based clinical practice guideline on the outpatient management of infants, children, and adolescents with PPRD. Methods: A multidisciplinary panel of experts posed questions regarding the outpatient management of PPRD. We conducted a systematic review of the relevant literature. The Grading of Recommendations, Assessment, Development, and Evaluation approach was used to rate the quality of evidence and the strength of the clinical recommendations. Results: The panel members considered the strength of each recommendation and evaluated the benefits and risks of applying the intervention. In formulating the recommendations, the panel considered patient and caregiver values, the cost of care, and feasibility. Recommendations were developed for or against three common medical therapies and four diagnostic evaluations in the context of the outpatient management of PPRD. Conclusions: The panel developed recommendations for the outpatient management of patients with PPRD on the basis of limited evidence and expert opinion. Important areas for future research were identified.

The highly packed and dehydrated structure of pre-formed unexposed human pulmonary surfactant isolated from amniotic fluid

By coating the alveolar air-liquid interface, lung surfactant overwhelms surface tension forces that, otherwise, would hinder the lifetime effort of breathing. Years of research have provided a picture of how highly hydrophobic and specialized proteins in surfactant promote rapid and efficient formation of phospholipid-based complex three-dimensional films at the respiratory surface, highly stable under the demanding breathing mechanics. However, recent evidence suggest that the structure and performance of surfactant typically isolated from bronchoalveolar lung lavages may be far from that of nascent, still unused, surfactant as freshly secreted by type II pneumocytes into the alveolar airspaces. In the present work, we report the isolation of lung surfactant from human amniotic fluid (amniotic fluid surfactant, AFS) and a detailed description of its composition, structure and surface activity in comparison to a natural surfactant (NS) purified from porcine bronchoalveolar lavages. We observe that the lipid/protein complexes in AFS exhibit a substantially higher lipid packing and dehydration than in NS. AFS shows melting transitions at higher temperatures than NS and a conspicuous presence of non-lamellar phases. The surface activity of AFS is not only comparable to that of NS under physiologically-meaningful conditions, but displays significantly higher resistance to inhibition by serum or meconium, agents that inactivate surfactant in the context of severe respiratory pathologies. We propose that AFS may be the optimal model to study the molecular mechanisms sustaining pulmonary surfactant performance in health and disease, and the reference material to develop improved therapeutic surfactant preparations to treat yet unresolved respiratory pathologies.

Study protocol for the POPART study-Prophylactic Oropharyngeal surfactant for Preterm infants: A Randomised Trial

INTRODUCTION

Many preterm infants develop respiratory distress syndrome (RDS), a condition characterised by a relative lack of surfactant. Endotracheal surfactant therapy revolutionised the care of preterm infants in the 1990s. However, supporting newborns with RDS with continuous positive airway pressure (CPAP) and reserving endotracheal surfactant for those who develop respiratory failure despite CPAP yield better results than intubating all infants for surfactant. Half of preterm infants born before 29 weeks gestation initially managed with CPAP are intubated for surfactant. Intubation is difficult to learn and associated with adverse effects. Surfactant administration into the oropharynx has been reported in preterm animals and humans and may be effective. We wished to determine whether giving oropharyngeal surfactant at birth reduces the rate of endotracheal intubation for respiratory failure in preterm infants within 120 hours of birth.

METHODS AND ANALYSIS

Prophylactic Oropharyngeal surfactant for Preterm infants: A Randomised Trial (POPART, Eudract No. 2016-004198-41) is an investigator-led, unblinded, multicentre, randomised, parallel group, controlled trial. Infants are eligible if born at a participating centre before 29 weeks gestational age (GA) and there is a plan to offer intensive care. Infants are excluded if they have major congenital anomalies. Infants are randomised at birth to treatment with oropharyngeal surfactant (120 mg vial <26 weeks GA stratum; 240 mg vial 26-28⁺⁶ weeks GA stratum) in addition to CPAP or CPAP alone. The primary outcome is intubation within 120 hours of birth, for bradycardia and/or apnoea despite respiratory support in the delivery room or respiratory failure in the intensive care unit. Secondary outcomes include incidence of mechanical ventilation, endotracheal surfactant use, chronic lung disease and death before hospital discharge.

ETHICS AND DISSEMINATION

Approval for the study has been granted by the Research Ethics Committees at the National Maternity Hospital, Dublin, Ireland (EC31.2016) and at each participating site. The trial is being conducted at nine centres in six European countries. The study results will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

2016-004198-41; Pre-results.

Alveolar lipids in pulmonary disease. A review

Lung lipid metabolism participates both in infant and adult pulmonary disease. The lung is composed by multiple cell types with specialized functions and coordinately acting to meet specific physiologic requirements. The alveoli are the niche of the most active lipid metabolic cell in the lung, the type 2 cell (T2C). T2C synthesize surfactant lipids that are an absolute requirement for respiration, including dipalmitoylphosphatidylcholine. After its synthesis and secretion into the alveoli, surfactant is recycled by the T2C or degraded by the alveolar macrophages (AM). Surfactant biosynthesis and recycling is tightly regulated, and dysregulation of this pathway occurs in many pulmonary disease processes. Alveolar lipids can participate in the development of pulmonary disease from their extracellular location in the lumen of the alveoli, and from their intracellular location in T2C or AM. External insults like smoke and pollution can disturb surfactant homeostasis and result in either surfactant insufficiency or accumulation. But disruption of surfactant homeostasis is also observed in many chronic adult diseases, including chronic obstructive pulmonary disease (COPD), and others. Sustained damage to the T2C is one of the postulated causes of idiopathic pulmonary fibrosis (IPF), and surfactant homeostasis is disrupted during fibrotic conditions. Similarly, surfactant homeostasis is impacted during acute respiratory distress syndrome (ARDS) and infections. Bioactive lipids like eicosanoids and sphingolipids also participate in chronic lung disease and in respiratory infections. We review the most recent knowledge on alveolar lipids and their essential metabolic and signaling functions during homeostasis and during some of the most commonly observed pulmonary diseases.

High-Frequency Oscillatory Ventilation and Nitric Oxide: Alternative or Complementary to ECMO

One hundred and seventy-seven term or near-term neonates were referred to an ECMO center for severe PPHN-associated diseases. In 2 time periods from 1987 to 1991 and from 1992 to April 1995 alternative treatment modes were tried in an attempt to obviate ECMO. During the first time period patients underwent trial high-frequency oscillatory ventilation before ECMO. In the second time period patients first received inhaled NO followed by HFOV in a non-responders. If this also failed HFOV was combined with I NO. In both time periods about 40% of the patients were spared ECMO treatment by these alternative treatment modalities. I NO only benefited 15% of the ECMO candidates who apparently had fared just as well on HFOV alone in the preceding time period. While patients who were improved by I NO were spared HFOV with its potential severe complications, i.e. air leaks and cardiocirculatory instability, more extended long-term studies will have to show which of these 2 treatment modalities (INO or HFOV) should be given first priority in an attempt to avoid ECMO in neonates with severe respiratory failure.

Clinical trials in acute respiratory distress syndrome: challenges and opportunities

This year is the 50th anniversary of the first description of acute respiratory distress syndrome (ARDS). Since then, much has been learned about the pathogenesis of lung injury in ARDS, with an emphasis on the mechanisms of injury to the lung endothelium and the alveolar epithelium. In terms of treatment, major progress has been made in reducing mortality from ARDS with lung-protective ventilation, using a tidal volume of 6 mL per kg of predicted bodyweight and a plateau airway pressure of less than 30 cm H₂O. In more severely hypoxaemic patients with ARDS, neuromuscular blockade and prone positioning have further reduced mortality, probably by extending the therapeutic effects of lung protective ventilation. Fluid-conservative therapy has also increased ventilator-free days in patients with ARDS. The lack of success of pharmacological therapies for ARDS, however, presents a continued challenge in the field. In addition to presenting a brief summary of previous experience with clinical trials in ARDS, we focus in this Review on future opportunities to improve clinical trial design to maximise the likelihood of identifying beneficial pharmacological therapies. In view of the heterogeneity in ARDS, both prognostic and predictive enrichment strategies are needed that target therapies toward specific subgroups of patients with ARDS on the basis of both severity and biology. Approaches to reducing heterogeneity in ARDS clinical trials include using physiological, radiographic, and biological criteria to select patients for both phase 2 and 3 trials. Additionally, interest is growing in the design of preventive clinical trials in ARDS and to initiate early treatment of patients with acute lung injury before the need for endotracheal intubation. We also present promising new approaches to treating ARDS, including combination therapies, cell-based therapies, and generic pharmacological compounds with low-risk profiles that are already in routine clinical use for other clinical indications.

Radiologic Observations in Severe Neonatal Respiratory Distress Syndrome Treated with the Isolated Phospholipid Fraction of Natural Surfactant

Ten newborn babies with severe respiratory distress syndrome, all dependent on artificial ventilation, were treated via the airways with the isolated phospholipid fraction of bovine or porcine surfactant. After treatment with surfactant at a median age of 10.5h, there was in all patients a striking improvement of lung aeration in chest films, with a decrease in parenchymal fluid retention and in distension of bronchioli. These radiologic findings were associated with a dramatic improvement of oxygenation and a significant reduction of the right-to-left shunt. In spite of the rapid therapeutic response, four patients died from cerebral hemorrhage. One of the surviving patients developed bronchopulmonary dysplasia. Our findings document efficacy of this new surfactant preparation in the neonatal respiratory distress syndrome, but the long-term effects need to be further tested in randomized clinical trials.

Effect of surfactant on regional lung function in an experimental model of respiratory distress syndrome in rabbit

We assessed the changes in regional lung function following instillation of surfactant in a model of respiratory distress syndrome (RDS) induced by whole lung lavage and mechanical ventilation in eight anaesthetized, paralyzed, and mechanically ventilated New Zealand White rabbits. Regional specific ventilation (sV̇) was measured by K-edge subtraction synchrotron computed tomography during xenon washin. Lung regions were classified as poorly aerated (PA), normally aerated (NA), or hyperinflated (HI) based on regional density. A functional category was defined within each class based on sV̇ distribution (High, Normal, and Low). Airway resistance (Raw), respiratory tissue damping (G), and elastance (H) were measured by forced oscillation technique at low frequencies before and after whole lung saline lavage-induced (100 ml/kg) RDS, and 5 and 45 min after intratracheal instillation of beractant (75 mg/kg). Surfactant instillation improved Raw, G, and H ( P < 0.05 each), and gas exchange and decreased atelectasis ( P < 0.001). It also significantly improved lung aeration and ventilation in atelectatic lung regions. However, in regions that had remained normally aerated after lavage, it decreased regional aeration and increased sV̇ ( P < 0.001) and sV̇ heterogeneity. Although surfactant treatment improved both central airway and tissue mechanics and improved regional lung function of initially poorly aerated and atelectatic lung, it deteriorated regional lung function when local aeration was normal prior to administration. Local mechanical and functional heterogeneity can potentially contribute to the worsening of RDS and gas exchange. These data underscore the need for reassessing the benefits of routine prophylactic vs. continuous positive airway pressure and early “rescue” surfactant therapy in very immature infants.

Gas exchange in the respiratory distress syndromes

This article describes the gas exchange abnormalities occurring in the acute respiratory distress syndrome seen in adults and children and in the respiratory distress syndrome that occurs in neonates. Evidence is presented indicating that the major gas exchange abnormality accounting for the hypoxemia in both conditions is shunt, and that approximately 50% of patients also have lungs regions in which low ventilation-to-perfusion ratios contribute to the venous admixture. The various mechanisms by which hypercarbia may develop and by which positive end-expiratory pressure improves gas exchange are reviewed, as are the effects of vascular tone and airway narrowing. The mechanisms by which surfactant abnormalities occur in the two conditions are described, as are the histological findings that have been associated with shunt and low ventilation-to-perfusion.

Delivery and performance of surfactant replacement therapies to treat pulmonary disorders

Lung surfactant is crucial for optimal pulmonary function throughout life. An absence or deficiency of surfactant can affect the surfactant pool leading to respiratory distress. Even if the coupling between surfactant dysfunction and the underlying disease is not always well understood, using exogenous surfactants as replacement is usually a standard therapeutic option in respiratory distress. Exogenous surfactants have been extensively studied in animal models and clinical trials. The present article provides an update on the evolution of surfactant therapy, types of surfactant treatment, and development of newer-generation surfactants. The differences in the performance between various surfactants are highlighted and advanced research that has been conducted so far in developing the optimal delivery of surfactant is discussed.

Methyl-beta-cyclodextrin restores the structure and function of pulmonary surfactant films impaired by cholesterol

Pulmonary surfactant, a defined mixture of lipids and proteins, imparts very low surface tension to the lung-air interface by forming an incompressible film. In acute respiratory distress syndrome and other respiratory conditions, this function is impaired by a number of factors, among which is an increase of cholesterol in surfactant. The current study shows in vitro that cholesterol can be extracted from surfactant and function subsequently restored to dysfunctional surfactant films in a dose-dependent manner by methyl-beta-cyclodextrin (MbetaCD). Bovine lipid extract surfactant was supplemented with cholesterol to serve as a model of dysfunctional surfactant. Likewise, when cholesterol in a complex with MbetaCD ("water-soluble cholesterol") was added in aqueous solution, surfactant films were rendered dysfunctional. Atomic force microscopy showed recovery of function by MbetaCD is accompanied by the re-establishment of the native film structure of a lipid monolayer with scattered areas of lipid bilayer stacks, whereas dysfunctional films lacked bilayers. The current study expands upon a recent perspective of surfactant inactivation in disease and suggests a potential treatment.

Animal derived surfactant extract for treatment of respiratory distress syndrome

BACKGROUND

Respiratory distress syndrome (RDS) is caused by a deficiency or dysfunction of pulmonary surfactant. A wide variety of surfactant products have been formulated and studied in clinical trials. These include synthetic surfactants and animal derived surfactant extracts. Trials of surfactant replacement have either tried to prevent the development of respiratory distress in high-risk premature infants or treat established respiratory distress in premature infants.

OBJECTIVES

To assess the effect of administration of animal derived surfactant extract on mortality, chronic lung disease and other morbidities associated with prematurity in preterm infants with established respiratory distress syndrome. Subgroup analysis were planned according to the specific surfactant product, the degree of prematurity, and the severity of disease.

SEARCH STRATEGY

Searches were made of the Oxford Database of Perinatal Trials, MEDLINE, EMBASE, and CINAHL from 1975 through December 2008. In addition, searches were made of previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants and journal hand searching in the English language.

SELECTION CRITERIA

Randomized or quazi-randomized controlled trials that compared the effect of animal derived surfactant extract treatment administered to infants with established respiratory distress syndrome in order to prevent complications of prematurity and mortality.

DATA COLLECTION AND ANALYSIS

Data regarding clinical outcomes were excerpted from the reports of the clinical trials by the review authors. Data analysis was done in accordance with the standards of the Cochrane Neonatal Review Group.

MAIN RESULTS

Thirteen randomized controlled trials were included in the analysis. The studies demonstrated an initial improvement in respiratory status (improved oxygenation and decreased need for ventilator support). The meta-analysis supports a significant decrease in the risk of any air leak (typical relative risk 0.47, 95% CI 0.39, 0.58; typical risk difference -0.16, 95% CI -0.21, -0.12), pneumothorax (typical relative risk 0.42, 95% CI 0.34, 0.52; typical risk difference -0.17, 95% CI -0.21, -0.13), and a significant decrease in the risk of pulmonary interstitial emphysema (typical relative risk 0.45, 95% CI 0.37, 0.55; typical risk difference -0.20, 95% CI -0.25, -0.15). There is a significant decrease in the risk of neonatal mortality (typical relative risk 0.68, 95% CI 0.57, 0.82; typical risk difference -0.09, 95% CI -0.13, -0.05), a significant decrease in the risk of mortality prior to hospital discharge (typical relative risk 0.63, 95% CI 0.44, 0.90; typical risk difference -0.10, 95% CI -0.18, -0.03) and a significant decrease in the risk of bronchopulmonary dysplasia (BPD) or death at 28 days of age (typical relative risk 0.83, 95% CI 0.77, 0.90; typical risk difference -0.11, 95 CI -0.16, -0.06). No differences are reported in the risk of patent ductus arteriosus, necrotizing enterocolitis, intraventricular hemorrhage, BPD or retinopathy of prematurity.

AUTHORS' CONCLUSIONS

Infants with established respiratory distress syndrome who receive animal derived surfactant extract treatment have a decreased risk of pneumothorax, a decreased risk of pulmonary interstitial emphysema, a decreased risk of mortality, and a decreased risk of bronchopulmonary dysplasia or death.

High-frequency oscillatory ventilation reduces lung inflammation: a large-animal 24-h model of respiratory distress

OBJECTIVE

High-frequency oscillatory ventilation (HFOV) may reduce ventilator-induced lung injury in experimental neonatal respiratory distress. However, these data permit no conclusions for large animals or adult patients with acute respiratory distress syndrome (ARDS), because in neonates higher frequencies and lower amplitudes can be used, resulting in lower tidal volumes (VT) and airway pressures. The aim of this study was to compare gas exchange, lung histopathology and inflammatory cytokine expression during lung-protective pressure-controlled ventilation (PCV) and HFOV in a long-term large-animal model of ARDS.

DESIGN

Prospective, randomized, controlled pilot study.

SETTING

University animal laboratory.

SUBJECTS

Sixteen female pigs (55.3 +/- 3.9 kg).

INTERVENTIONS

After induction of ARDS by repeated lavage, the animals were randomly assigned to PCV (VT = 6 ml/kg) and HFOV (6 Hz). After lung injury, a standardised lung recruitment was performed in both groups, and ventilation was continued for 24 h.

MEASUREMENTS AND RESULTS

After lung recruitment sustained improvements in the oxygenation index were observed in both groups. The mean airway pressure (mPaw) was significantly lower in the HFOV group during the experiment (p < 0.01). Histologically, lung inflammation was significantly ameliorated in the HFOV group (p < 0.05). The messenger RNA expression of IL-1-beta in lung tissue was significantly lower in the HFOV-treated animals (p < 0.01).

CONCLUSIONS

These data suggest that HFOV compared with conventional lung-protective ventilation can reduce lung inflammation in a large-animal 24-h model of ARDS. Furthermore, it was shown that lung recruitment leads to sustained improvements in gas exchange with a significantly lower mPaw when HFOV is used.

Amiloride-sensitive nasal potential difference is not changed by estradiol and progesterone replacement but relates to BPD or death in a randomized trial on preterm infants

Postnatal replacement of placental estradiol (E2) and progesterone (P) in preterm infants may improve lung function, possibly mediated through enhanced epithelial Na(+) transport and alveolar fluid clearance. Preterm infants of <29 wk gestational age and <1000 g birth weight requiring mechanical ventilation within 12 h of birth were randomized to receive either 2.5 mg/kg E2 and 22.5 mg/kg P per day (E2/P), or vehicle placebo. Epithelial Na(+) transport was assessed in 29 infants by measuring total nasal potential difference (NPD) and amiloride-sensitive NPD (ASNPD) on postnatal days of life 1, 3, 5, and 7, and mean values of all four measurements were calculated. Bronchopulmonary dysplasia (BPD) was defined as need for supplemental oxygen (goal Sa(O2) 90%) or mechanical ventilation at 36 wk corrected postmenstrual age. Mean ASNPD was -6.5 +/- 2.8 mV in infants receiving E2/P and -6.1 +/- 2.6 mV in infants receiving placebo (not significant). NPD was -10.6 +/- 3.8 mV and -10.7 +/- 3.6 mV, respectively. The ASNPD was significantly higher in infants surviving without BPD (-7.1 +/- 2.5 mV) than in infants developing BPD or not surviving (-5.2 +/- 2.4 mV). In conclusion, ASNPD is not changed by postnatal replacement of E2 and P. Infants at high risk of developing BPD had lower ASNPD values in the immediate postnatal period.

Surfactant era (1990-2002) 2-year outcomes of infants less than 1500 g from a Community Level 3 Neonatal Intensive Care Unit

OBJECTIVE

To report Bayley scores of 572 twenty-four-month corrected age infants whose birth weights (BWs) were less than 1500 g cared for in a Community Level 3 Neonatal Intensive Care Unit (NICU) between 1990 and 2002 when surfactant was routinely used.

STUDY DESIGN

Survival, "normal" defined as both Mental Developmental Index (MDI) and Psychomotor Developmental Index (PDI)>84, MDI>69 and MDI>84 were analyzed by gestational age (GA) and BW. Comparisons were made between infants born pre- and post-1996 when high-frequency oscillatory ventilation came into frequent use, Medicaid and non-Medicaid infants, multiples and singletons, outborn and inborn infants, boys and girls and infants with intrauterine growth retardation (IUGR) and those appropriate for gestational age (AGA).

RESULTS

There was a correlation between GA and BW and improving outcomes. Scores do not approach those of normal standardization sample populations (60% for "normal", 68% for MDI>84 and 95% for MDI>69) until 1400 g and 30 weeks. Medicaid, outborn and IUGR infants, and boys did worse in some aspects.

CONCLUSION

There was a correlation between both GA and BW and improving outcomes. Availability of these developmental data on a laminated pocket card can facilitate presentation of outcome experience to families by pediatric and obstetric caregivers.

Evolution of pulmonary surfactants for the treatment of neonatal respiratory distress syndrome and paediatric lung diseases

This review documents the evolution of surfactant therapy, beginning with observations of surfactant deficiency in respiratory distress syndrome, the basis of exogenous surfactant treatment and the development of surfactant-containing novel peptides patterned after SP-B. We critically analyse the molecular interactions of surfactant proteins and phospholipids contributing to surfactant function.

CONCLUSION

Peptide-containing surfactant provides clinical efficacy in the treatment of respiratory distress syndrome and offers promise for treating other lung diseases in infancy.

Sustained inflation and incremental mean airway pressure trial during conventional and high-frequency oscillatory ventilation in a large porcine model of acute respiratory distress syndrome

Background

To compare the effect of a sustained inflation followed by an incremental mean airway pressure trial during conventional and high-frequency oscillatory ventilation on oxygenation and hemodynamics in a large porcine model of early acute respiratory distress syndrome.

Methods

Severe lung injury (Ali) was induced in 18 healthy pigs (55.3 ± 3.9 kg, mean ± SD) by repeated saline lung lavage until PaO₂ decreased to less than 60 mmHg. After a stabilisation period of 60 minutes, the animals were randomly assigned to two groups: Group 1 (Pressure controlled ventilation; PCV): FIO₂ = 1.0, PEEP = 5 cmH₂O, V_T = 6 ml/kg, respiratory rate = 30/min, I:E = 1:1; group 2 (High-frequency oscillatory ventilation; HFOV): FIO₂ = 1.0, Bias flow = 30 l/min, Amplitude = 60 cmH₂O, Frequency = 6 Hz, I:E = 1:1. A sustained inflation (SI; 50 cmH₂O for 60s) followed by an incremental mean airway pressure (mPaw) trial (steps of 3 cmH₂O every 15 minutes) were performed in both groups until PaO₂ no longer increased. This was regarded as full lung inflation. The mPaw was decreased by 3 cmH₂O and the animals reached the end of the study protocol. Gas exchange and hemodynamic data were collected at each step.

Results

The SI led to a significant improvement of the PaO₂/FiO₂-Index (HFOV: 200 ± 100 vs. PCV: 58 ± 15 and T_Ali: 57 ± 12; p < 0.001) and PaCO₂-reduction (HFOV: 42 ± 5 vs. PCV: 62 ± 13 and T_Ali: 55 ± 9; p < 0.001) during HFOV compared to lung injury and PCV. Augmentation of mPaw improved gas exchange and pulmonary shunt fraction in both groups, but at a significant lower mPaw in the HFOV treated animals. Cardiac output was continuously deteriorating during the recruitment manoeuvre in both study groups (HFOV: T_Ali: 6.1 ± 1 vs. T₇₅: 3.4 ± 0.4; PCV: T_Ali: 6.7 ± 2.4 vs. T₇₅: 4 ± 0.5; p < 0.001).

Conclusion

A sustained inflation followed by an incremental mean airway pressure trial in HFOV improved oxygenation at a lower mPaw than during conventional lung protective ventilation. HFOV but not PCV resulted in normocapnia, suggesting that during HFOV there are alternatives to tidal ventilation to achieve CO₂-elimination in an "open lung" approach.

Cost-effectiveness of neonatal extracorporeal membrane oxygenation based on 7-year results from the United Kingdom Collaborative ECMO Trial

OBJECTIVE

To assess the long-term cost-effectiveness of extracorporeal membrane oxygenation (ECMO) for mature newborn infants with severe respiratory failure.

METHODS

A prospective economic evaluation was conducted alongside a pragmatic randomized, controlled trial in which 185 infants were randomly allocated to ECMO (n = 93) or conventional management (n = 92) and then followed up to 7 years of age. Information about their use of health services during the follow-up period was combined with unit costs (pound sterling, 2002-2003 prices) to obtain a net cost per child. The cost-effectiveness of neonatal ECMO was expressed in terms of incremental cost per additional life year gained and incremental cost per additional disability-free life year gained. The nonparametric bootstrap method was used to present cost-effectiveness acceptability curves and net benefit statistics at alternative willingness-to-pay thresholds held by decision-makers for an additional life year and for an additional disability-free life year.

RESULTS

Over 7 years, neonatal ECMO was effective at reducing known death or severe disability. Mean health service costs during the first 7 years of life were 30,270 pound sterling in the ECMO group and 10,229 pound sterling in the conventional management group, generating a mean cost difference of 20,041 pound sterling that was statistically significant. The incremental cost per life year gained was estimated at 13,385 pound sterling. The incremental cost per disability-free life year gained was estimated at 23,566 pound sterling. At the notional willingness-to-pay threshold of 30,000 pound sterling for an additional life year, the probability that neonatal ECMO is cost-effective at 7 years was estimated at 0.98. This translated into a mean net benefit of 24,362 pound sterling for each adoption of neonatal ECMO rather than conventional management.

CONCLUSIONS

This study provides rigorous evidence of the cost-effectiveness of neonatal ECMO during childhood.

High frequency oscillatory ventilation and prone positioning in a porcine model of lavage-induced acute lung injury

Background

This animal study was conducted to assess the combined effects of high frequency oscillatory ventilation (HFOV) and prone positioning on pulmonary gas exchange and hemodynamics.

Methods

Saline lung lavage was performed in 14 healthy pigs (54 ± 3.1 kg, mean ± SD) until the arterial oxygen partial pressure (PaO₂) decreased to 55 ± 7 mmHg. The animals were ventilated in the pressure controlled mode (PCV) with a positive endexpiratory pressure (PEEP) of 5 cmH₂O and a tidal volume (V_T) of 6 ml/kg body weight. After a stabilisation period of 60 minutes, the animals were randomly assigned to 2 groups. Group 1: HFOV in supine position; group 2: HFOV in prone position. After evaluation of prone positioning in group 2, the mean airway pressure (P_mean) was increased by 3 cmH₂O from 16 to 34 cmH₂O every 20 minutes in both groups accompanied by measurements of respiratory and hemodynamic variables. Finally all animals were ventilated supine with PCV, PEEP = 5 cm H₂O, V_T = 6 ml/kg.

Results

Combination of HFOV with prone positioning improves oxygenation and results in normalisation of cardiac output and considerable reduction of pulmonary shunt fraction at a significant (p < 0.05) lower P_mean than HFOV and supine positioning.

Conclusion

If ventilator induced lung injury is ameliorated by a lower P_mean, a combined treatment approach using HFOV and prone positioning might result in further lung protection.

Comparison of clinical efficacy of Newfactan versus Surfacten for the treatment of respiratory distress syndrome in the newborn infants

Newfactan is a domestically developed, bovine lung-derived, semi-synthetic surfactant. The aim of this study was to compare the clinical efficacy of Newfactan with that of Surfacten in the treatment of respiratory distress syndrome (RDS). Newfactan or Surfacten was randomly allocated to 492 newborn infants who were diagnosed as RDS and required surfactant instillation in four participating hospitals. The comparisons were made individually in two subsets of infants by birth weight (<1,500 g group [n=253] and > or =1,500 g group [n=239]). Short-term responses to surfactant and acute complications, such as the total doses of surfactant instilled, response type, extubation rate, ventilator settings, changes in respiratory parameters, air leak, patent ductus arteriosus, pulmonary hemorrhage, and intraventricular hemorrhage, and mortality during the 96 hr after surfactant instillation were measured. Long-term outcome and complications, such as total duration of intubation, bronchopulmonary dysplasia and periventricular leukomalacia, and ultimate mortality were measured. There were no significant differences in demographic and perinatal variables, shortterm responses to surfactant and acute complications, and long-term outcome and complications between Newfactan and Surfacten in both birth weight groups. We concluded that Newfactan was comparable to Surfacten in the clinical efficacy in the treatment of RDS in both birth weight groups.

History of Surfactant up to 1980

Remarkable insight into disturbed lung mechanics of preterm infants was gained in the 18th and 19th century by the founders of obstetrics and neonatology who not only observed respiratory failure but also designed devices to treat it. Surfactant research followed a splendid and largely logical growth curve. Pathological changes in the immature lung were characterized in Germany by Virchow in 1854 and by Hochheim in 1903. The Swiss physiologist von Neergard fully understood surfactant function in 1929, but his paper was ignored for 25 years. The physical properties of surfactant were recognized in the early 1950s from research on warfare chemicals by Pattle in Britain and by Radford and Clements in the United States. The causal relationship of respiratory distress syndrome (RDS) and surfactant deficiency was established in the USA by Avery and Mead in 1959. The Australian obstetrician Liggins induced lung maturity with glucocorticoids in 1972, but his discovery was not fully believed for another 20 years. A century of basic research was rewarded when Fujiwara introduced surfactant substitution in Japan in 1980 for treatment and prevention of RDS.

Respiratory characteristics of infants with pulmonary hypoplasia syndrome following preterm rupture of membranes: a preliminary study for establishing clinical diagnostic criteria

BACKGROUND

At present, the diagnosis of pulmonary hypoplasia is based on postmortem findings, and there are no clear clinical diagnostic criteria to facilitate its identification and management.

AIM

To characterise the respiratory status of pulmonary hypoplasia syndrome (PHS) following preterm rupture of membranes so as to establish its clinical diagnostic criteria.

STUDY DESIGN

Retrospective comparison of respiratory characteristics of six typical PHS infants with six wet lung syndrome (WLS) infants who served as controls.

SUBJECTS

The PHS and WLS infants were selected from 1094 patients admitted to a tertiary care neonatal unit over a 6-year period, with criteria based on perinatal history, respiratory signs, X-ray and laboratory findings, and ventilator settings.

OUTCOME MEASURES

The compared variables were lung volume index (LVI) calculated from lung dimensions on chest X-ray, ventilatory index (VI), ventilatory efficiency index (VEI), response to artificial surfactant treatment, and ventilation days.

RESULTS

In PHS compared to WLS infants, LVI was lower (4.5 +/- 0.5 vs. 9.5 +/- 1.5; p < 0.01), VI was higher (0.108 +/- 0.030 vs. 0.022 +/- 0.005; p < 0.05), and VEI was lower (0.083 +/- 0.012 vs. 0.258 +/- 0.052; p < 0.01) (mean +/- S.E.). Artificial surfactant was given to four PHS infants, but none of them showed respiratory improvement. Ventilation days were 11-79 in three surviving PHS infants and 2-14 in WLS infants.

CONCLUSIONS

In this preliminary study, low LVI (< 6.5) and VEI (< 0.15) were the most useful indicators of PHS.

Cost effectiveness analysis of neonatal extracorporeal membrane oxygenation based on four year results from the UK Collaborative ECMO Trial

OBJECTIVE

To assess the cost effectiveness of extracorporeal membrane oxygenation (ECMO) for mature newborn infants with severe respiratory failure over a four year time span.

DESIGN

Cost effectiveness analysis based on a randomised controlled trial in which infants were individually allocated to ECMO (intervention) or conventional management (control) and then followed up to 4 years of age.

SETTING

Infants were recruited from 55 approved recruiting hospitals throughout the United Kingdom. Infants allocated to ECMO were transferred to one of five specialist regional centres. Follow up of surviving infants was performed in the community.

SUBJECTS

A total of 185 mature (gestational age at birth >or= 35 weeks, birth weight >or= 2000 g) newborn infants with severe respiratory failure (oxygenation index >or= 40).

MAIN OUTCOME MEASURES

Incremental cost per additional life year gained; incremental cost per additional disability-free life year gained.

RESULTS

Over four years, the policy of neonatal ECMO was effective at reducing known death or severe disability (relative risk = 0.64; 95% confidence interval 0.47 to 0.86; p = 0.004). After adjustment for censoring and discounting at 6%, the mean additional health service cost of neonatal ECMO was pound 17367 (95% confidence interval pound 12072 to pound 22224) per infant ( pound UK, 2001 prices). Over four years, the incremental cost of neonatal ECMO was pound 16707 ( pound 9828 to pound 37924) per life year gained and pound 24775 ( pound 13106 to pound 69690) per disability-free life year gained. These results remained robust after variations in the values of key variables performed as part of a sensitivity analysis.

CONCLUSIONS

The study provides rigorous evidence of the cost effectiveness of ECMO at four years for mature infants with severe respiratory failure.

Surfactant therapy for respiratory distress syndrome in premature neonates: a comparative review

Exogenous surfactant therapy has been part of the routine care of preterm neonates with respiratory distress syndrome (RDS) since the beginning of the 1990s. Discoveries that led to its development as a therapeutic agent span the whole of the 20th century but it was not until 1980 that the first successful use of exogenous surfactant therapy in a human population was reported. Since then, randomized controlled studies demonstrated that surfactant therapy was not only well tolerated but that it significantly reduced both neonatal mortality and pulmonary air leaks; importantly, those surviving neonates were not at greater risk of subsequent neurological impairment. Surfactants may be of animal or synthetic origin. Both types of surfactants have been extensively studied in animal models and in clinical trials to determine the optimum timing, dose size and frequency, route and method of administration. The advantages of one type of surfactant over another are discussed in relation to biophysical properties, animal studies and results of randomized trials in neonatal populations. Animal-derived exogenous surfactants are the treatment of choice at the present time with relatively few adverse effects related largely to changes in oxygenation and heart rate during surfactant administration. The optimum dose of surfactant is usually 100 mg/kg. The use of surfactant with high frequency oscillation and continuous positive pressure modes of respiratory support presents different problems compared with its use with conventional ventilation. The different components of surfactant have important functions that influence its effectiveness both in the primary function of the reduction of surface tension and also in secondary, but nonetheless just as important, role of lung defense. With greater understanding of the individual surfactant components, particularly the surfactant-associated proteins, development of newer synthetic surfactants has been made possible. Despite being an effective therapy for RDS, surfactant has failed to have a significant impact on the incidence of chronic lung disease in survivors. Paradoxically the cost of care has increased as surviving neonates are more immature and consume a greater proportion of neonatal intensive care resources. Despite this, surfactant is considered a cost-effective therapy for RDS compared with other therapeutic interventions in premature infants.

Surfactant therapy in neonates with respiratory failure due to haemorrhagic pulmonary oedema

We studied the clinical and biochemical factors associated with surfactant dysfunction and factors affecting the responsiveness to exogenous surfactant among 27 neonates with haemorrhagic pulmonary oedema (HPE). HPE was defined as the presence of a large amount of blood-stained lung effluent and respiratory failure which was difficult to differentiate from respiratory distress syndrome. Among the neonates, 33% had very low birth weight, 96% were preterm, 70% were delivered by caesarean section, and 44% had delivery room intubation. The onset of HPE was at 1.5+/-0.1 h (mean +/- SEM) after birth. In 26 cases, surfactant was administered at 3.0+/-1.3 h after the onset of HPE. The concentrations of surfactant protein A (SP-A), disaturated phosphatidylcholine (DSPC), and albumin in the epithelial lining fluid were determined using the first lung effluent from the patients. The level of inhibitory activity against pulmonary surfactant in the effluent was determined in vitro. Surfactant inhibitory activity was associated with lower birth weight, earlier gestational age, delivery room intubation, earlier onset of HPE, and lower SP-A or DSPC concentration. A good response to exogenous surfactant, which was defined as ventilatory index <0.047 at 1 h after surfactant administration, was seen in 82% of cases, and was associated with lower serum albumin, lower birth weight, and earlier gestational age. Cases with higher DSPC concentration prior to surfactant administration and shorter interval between the onset of HPE and surfactant administration showed an immediate response to surfactant, followed by no increase in ventilatory index for 24 h after surfactant administration.

CONCLUSION

exogenous surfactant appeared to be a useful adjunctive therapy for overcoming surfactant inhibition and normalising the respiratory status of infants with haemorraghic pulmonary oedema. Surfactant treatment for this indication awaits further investigations including a randomised controlled study.

Cardiocirculatory effects of patent ductus arteriosus in extremely low-birth-weight infants with respiratory distress syndrome

BACKGROUND

Cardiocirculatory effects of hemodynamically significant patent ductus arteriosus (hsPDA) have not been systematically studied in extremely low-birth-weight (ELBW) infants with respiratory distress syndrome (RDS). The objective of the present study was to evaluate the effects of hsPDA on the left ventricular output (LVO) and organ blood flows in ELBW infants with RDS.

METHODS

Extremely low-birth-weight infants (birth-weight <1000 g) treated with surfactant for RDS were studied by serial Doppler flow examinations. Doppler flow variables in 19 infants in whom hsPDA developed (hsPDA group) were compared with those in 19 infants without hsPDA matched for gestational age, birth-weight, and postnatal age (non-hsPDA group). All infants in the hsPDA group had pharmacologic closure of ductus arteriosus when hsPDA developed.

RESULTS

Before pharmacological closure of PDA, the hsPDA group had significantly higher LVO, lower blood flow volume of the abdominal aorta, and lower mean blood flow velocities in the celiac artery, superior mesenteric artery, and renal artery than the non-hsPDA group. These alterations in the hsPDA group reverted to the levels in the non-hsPDA group after the closure of PDA and had no deleterious effects on the cardiorespiratory status. No significant differences between the groups were found in mean blood flow velocities of the anterior cerebral artery throughout the study period.

CONCLUSION

These results indicate that although LVO is increased, the splanchnic and renal blood flows are decreased when hsPDA develops in ELBW infants with RDS. The effects of these alterations of LVO and organ blood flows on the cardiorespiratory course seem to be minor when early pharmacologic closure of PDA is done.

Innovative practices of ventilatory support with pediatric patients

OBJECTIVES

The recognition that alveolar overdistension rather than peak inspiratory airway pressure is the primary determinant of lung injury has shifted our understanding of the pathogenesis of ventilator-induced side effects. In this review, contemporary ventilatory methods, supportive treatments, and future developments relevant to pediatric critical care are reviewed.

DATA SYNTHESIS

A strategy combining recruitment maneuvers, low-tidal volume, and higher positive end-expiratory pressure (PEEP) decreases barotrauma and volutrauma. Given that appropriate tidal volumes are critical in determining adequate alveolar ventilation and avoiding lung injury, volume-control ventilation with high PEEP levels has been proposed as the preferable protective ventilatory mode. Pressure-related volume control ventilation and high-frequency oscillatory ventilation (HFOV) have taken on an important role as protective lung strategies. Further data are required in the treatment of children, confirming the preliminary results in specific lung pathologies. Spontaneous breathing supported artificially during inspiration (pressure support ventilation) is widely used to maintain or reactivate spontaneous breathing and to avoid hemodynamic variation. Volume support ventilation reduces the need for manual adaptation to maintain stable tidal and minute volume and can be useful in weaning. Prone positioning and permissive hypercapnia have taken on an important role in the treatment of patients undergoing artificial ventilation. Surfactant and nitric oxide have been proposed in specific lung pathologies to facilitate ventilation and gas exchange and to reduce inspired oxygen concentration. Investigation of lung ventilation using a liquid instead of gas has opened new vistas on several lung pathologies with high mortality rates.

RESULTS

The conviction emerges that the best ventilatory treatment may be obtained by applying a combination of types of ventilation and supportive treatments as outlined above. Early treatment is important for the overall positive final result. Lung recruitment maneuvers followed by maintaining an open lung favor rapid resolution of pathology and reduce side effects.

CONCLUSIONS

The methods proposed require confirmation through large controlled clinical trials that can assess the efficacy reported in pilot studies and case reports and define the optimal method(s) to treat individual pathologies in the various pediatric age groups.

Lung surfactants for neonatal respiratory distress syndrome: animal-derived or synthetic agents?

Exogenous surfactant therapy is widely used in the management of neonatal respiratory distress syndrome. Two types of surfactants are available: synthetic surfactants, and those derived from animal sources ("natural" surfactants). Both of these surfactants have been shown to be effective. In this article, we review the evidence to compare the two types of surfactants in terms of their physical properties, physiologic effects, and clinical outcomes. Natural surfactants have been shown to have advantages over synthetic surfactants in their physical properties and physiologic effects in animals, as well as in humans. A systematic review of 11 randomized clinical trials comparing natural and synthetic surfactants demonstrated that the use of natural surfactant preparations results in greater clinical benefits compared with synthetic surfactants. These benefits include a more rapid improvement in oxygenation and lung compliance after surfactant therapy, a decrease in the risk of mortality (typical relative risk 0.87; typical risk difference -0.02), and a decrease in the risk of pneumothorax (typical relative risk 0.63; typical risk difference -0.04). Although the use of natural surfactants results in a slightly increased risk of intraventricular hemorrhage (typical relative risk 1.09; typical risk difference 0.03), there is no increase in the risk of grade 3 or 4 intraventricular hemorrhage. There are theoretical but unproven risks of natural surfactants, such as transmission of infectious agents, immunogenicity and impurities in composition. The use of natural surfactants is preferred in most situations. In addition, clinicians should determine the costs of different types of surfactants in their individual practice settings and use this information in decision-making.

Current surfactant use in premature infants

Exogenous surfactant therapy has been a significant advance in the management of preterm infants with RDS. It has become established as a standard part of the management of such infants. Both natural and synthetic surfactants lead to clinical improvement and decreased mortality, with natural surfactants having additional advantages over currently available synthetic surfactants. The use of prophylactic surfactant administered after initial stabilization at birth to infants at risk for RDS has benefits compared with rescue surfactant given to treat infants with established RDS. In infants who do not receive prophylaxis, earlier treatment (before 2 hours) has benefits over later treatment. The use of multiple doses of surfactant is a superior strategy to the use of a single dose, whereas the use of a higher threshold for retreatment seems to be as effective as a low threshold. Adverse effects of surfactant therapy are infrequent and usually not serious. Long-term follow-up of infants treated with surfactant in the neonatal period is reassuring. In the future we are likely to see the development of new types of surfactants. Further research is required to determine the optimal use of surfactant in conjunction with other respiratory interventions.

Surfactant replacement therapy--economic impact

Surfactant replacement is an effective treatment for neonatal respiratory distress syndrome. (RDS). As widespread use of surfactant is becoming a reality, it is important to assess the economic implications of this new form of therapy. A comparison study was carried out at the Neonatal Intensive Care Unit (NICU) of Northwest Armed Forces Hospital, Saudi Arabia. Among 75 infants who received surfactant for RDS and similar number who were managed during time period just before the surfactant was available, but by set criteria would have made them eligible for surfactant. All other management modalities except surfactant were the same for all these babies. Based on the intensity of monitoring and nursing care required by the baby, the level of care was divided as: Level IIIA, IIIB, Level II, Level I. The cost per day per bed for each level was calculated, taking into account the use of hospital immovable equipment, personal salaries of nursing, medical, ancillary staff, overheads and maintenance, depreciation and replacement costs. Medications used, procedures done, TPN, oxygen, were all added to individual patient's total expenditure. 75 infants in the Surfactant group had 62 survivors. They spent a total of 4300 days in hospital. (av 69.35) Out of which 970 d (av 15.65 per patient) were ventilated days. There were 56 survivors in the non-surfactant group of 75. They had spent a total of 5023 days in the hospital (av 89.69/patient) out of which 1490 were ventilated days (av 26.60 d). Including the cost of surfactant (two doses), cost of hospital stay for each infant taking the average figures of stay would be SR 118, 009.75 per surfactant treated baby and SR 164, 070.70 per non-surfactant treated baby. The difference of 46,061 SR is 39.03% more in non-surfactant group. One Saudi rial = 8 Rs (approx at the time study was carried out.) Medical care cost varies from place to place. However, it is definitely cost-effective where surfactant is concerned. Quality adjusted life years (QALY) for NICU care compares favourably with cost per QALY of several forms of adult health interventions. Audit, both medical and financial, of these services, at regular intervals is essential.

Evaluating the validity of responsiveness to inhaled nitric oxide in pediatric patients with ARDS: an analytic tool

OBJECTIVES

To determine whether improved oxygenation indicates a valid response to inhaled nitric oxide (iNO) therapy in patients with pediatric ARDS, and to establish an analytic tool to differentiate the iNO effects from those of other interactive factors in pediatric patients with ARDS.

DESIGN

Consecutive case series evaluated by post hoc analysis tool.

PATIENTS AND METHODS

Nineteen patients treated with iNO for ARDS or pulmonary hypertension were enrolled in our study. We evaluated the PaO(2)/fraction of inspired oxygen ratio (PF ratio), oxygenation index (OI), patient position (prone vs supine), PaCO(2), pH, and vasoactive drug support, and classified patients' responsiveness to iNO into three categories: (1) possible response, an increase in PF ratio, with no alteration of the aforementioned variables in a direction known to improve oxygenation; (2) nonspecific response, an increase in PF ratio with no increase in OI, and alteration of one or more of the other four criteria in a direction known to improve oxygenation; and (3) undetermined response, an increase in both the PF ratio and OI, indicating a deliberate augmentation in ventilator support.

RESULTS

A total of 119 data points were evaluated. Fifty data points (42%) exhibited no response to iNO. Thirty-two data points (27%) were classified as having possible responses, 35 data points (29%) as nonspecific, and 2 data points (2%) as undetermined responses to the iNO treatment.

CONCLUSIONS

In ARDS, improved oxygenation amid iNO treatment is multifactorial. In only 27% of our evaluated data points could the increase in PF ratio be attributed to iNO. We suggest that when clinically utilizing iNO, the interactive factors described by us should be taken into account for data analysis.

Necrotizing enterocolitis in infants with very low birth weight

Necrotizing enterocolitis (NEC) is a disease in which the primary risk factor is prematurity. Despite, and partially as a result of, the tremendous strides neonatal care has taken, it is a major cause of morbidity and mortality of the newborn. The infant with very low birth weight is particularly susceptible, and the management of the condition in this group differs somewhat from other neonates. The outcomes continue to improve, but there are significant sequelae. Prevention, which would be the best "cure," is elusive, in no small part because of the multifactorial nature of the etiology of NEC.

International randomised controlled trial of patient triggered ventilation in neonatal respiratory distress syndrome

AIM

To compare the effects of patient triggered ventilation (PTV) with conventional ventilation (IMV) in preterm infants ventilated for respiratory distress syndrome (RDS).

METHODS

Nine hundred and twenty four babies from 22 neonatal intensive care units were assessed. They were under 32 weeks of gestation and had been ventilated for respiratory distress syndrome (RDS) for less than 6 hours within 72 hours of birth. The infants were randomly allocated to receive either PTV or IMV. Analysis was on an "intention to treat" basis. Death before discharge home or oxygen therapy at 36 weeks of gestation; pneumothorax while ventilated; cerebral ultrasound abnormality nearest to 6 weeks; and duration of ventilation in survivors were the main outcome measures.

RESULTS

There was no significant difference in outcome between the two groups. Unadjusted rates for death or oxygen dependency at 36 weeks of gestation were 47.4% and 48.7%, for PTV and IMV, respectively; for pneumothorax these were 13.4% and 10.3%; and for cerebral ultrasound abnormality nearest to 6 weeks these were 35.4% and 36.9%. Median duration of ventilation for survivors in both groups was 6 days. Overall, 79% of babies received only their assigned ventilation. PTV babies were more likely to depart from their intended ventilation (27% vs 15%). The trend towards higher pneumothorax rates with PTV occurred only in infants below 28 weeks of gestation (18.8% vs 11.8%).

CONCLUSIONS

There was no observed benefit from the use of PTV, with a trend towards a higher rate of pneumothorax under 28 weeks of gestation. Although PTV has a similar outcome to IMV for treatment of RDS in infants of 28 weeks or more gestation, within 72 hours of birth, it was abandoned more often. It cannot be recommended for infants of less than 28 weeks' gestation with the ventilators used in this study.

Respiratory failure: current status of experimental therapies

A number of advances in the treatment of infants and children with respiratory failure have been investigated in the laboratory with translation to clinical practice. Investigators have recognized that application of high ventilating pressures and failure to apply adequate levels of positive end-expiratory pressure (PEEP) can inflict injury to the already failing lung. Other interventions such as prone positioning and application of new ventilating strategies such as proportional assist ventilation (PAV), inverse ratio ventilation (IRV), high frequency ventilation, liquid ventilation, and intratracheal pulmonary ventilation (ITPV), continue to be developed and explored. Administration of inhaled nitric oxide (iNO) may improve pulmonary physiology and gas exchange in patients with respiratory insufficiency. Finally, the technique of extracorporeal life support (ECLS) is being simplified and refined. This report summarizes the status of these advances and describes the basic science and clinical research that brought them to clinical application.

Randomized comparison of high-frequency ventilation with high-rate intermittent positive pressure ventilation in preterm infants with respiratory failure

OBJECTIVE

In a randomized, controlled, multicenter trial, we tested the hypothesis that high-frequency ventilation (HFV) with a high lung volume strategy results in fewer treatment failures than intermittent positive pressure ventilation (IPPV) with high rates and low peak inspiratory pressures.

STUDY DESIGN

Infants with a gestational age between >/=24 weeks and <30 weeks, requiring mechanical ventilation within 6 hours of birth, were randomly assigned to receive either IPPV or HFV until 240 hours after randomization, extubation, or meeting treatment failure criteria. Treatment failure, the primary end point, was determined when air leaks, an oxygenation index >35 to 45 (depending on gestational age), death, or chronic lung disease occurred. Chronic lung disease was defined as persistent requirement of mechanical ventilation, continuous positive airway pressure, or supplemental oxygen at a postmenstrual age of 36 weeks. Secondary end points included the incidence of intracranial hemorrhage.

RESULTS

The third scheduled interim analysis led to termination of the trial after recruitment of 284 infants. Treatment failure criteria were met by 46% of infants receiving IPPV and 54% of infants receiving HFV (1-tailed primary hypothesis, P =.92; 2-tailed chi2 test, P =.15). Air leaks occurred in 31% and 42% (P =.042), CLD in 23% and 25%, and grade 3-4 intracranial hemorrhage in 13% and 14% of IPPV-treated and HFV-treated patients, respectively. The mortality rate before discharge was 10% in both groups.

CONCLUSION

HFV with a high lung volume strategy did not cause less lung injury in preterm infants than IPPV with a high rate and low peak inspiratory pressures.

Phagocyte-induced lipid peroxidation of lung surfactant

Surfactant therapy is given routinely to premature newborns with respiratory failure. However, alterations in surfactants have been shown to be a significant factor in some forms of respiratory failure in newborns in animal models of lung injury. To investigate whether antioxidant supplementation might help to protect exogenous surfactant from damage by oxygen free radicals, we examined the influence of vitamin E in combination with surfactant on superoxide production as estimated by the nitroblue tetrazolium reduction test, and measured surfactant peroxidation with a new colorimetric method with or without addition of superoxide dismutase (SOD) or vitamin E. Our results showed that surfactant interacts with free radicals; surfactant reduced superoxide production by neutrophils and was peroxidized when incubated with resting and with stimulated cells. Vitamin E supplementation decreased superoxide radical production and in a dose-dependent manner decreased surfactant peroxidation. The decrease in lipid peroxidation by SOD was not significant. These findings suggest that phagocytes induce lipid peroxidation of lung surfactant, a reaction that might be prevented by antioxidants.

Utility of deadspace and capnometry measurements in determination of surfactant efficacy in surfactant-depleted lungs

OBJECTIVE

To investigate if bronchoalveolar lavage leads to increased alveolar and physiologic deadspace or a deadspace/ tidal volume ratio and if surfactant replacement restores the lung to its prelavage condition.

DESIGN

Prospective, animal cohort study.

SETTING

An animal laboratory in a university medical center.

SUBJECTS

Seven adult rabbits receiving artificial ventilation.

METHODS

Our single-breath CO2 analysis station contained the following equipment: pneumotachometer Ventrak 1550, a mainstream capnometer Capnogard 1265, a signal processor, and computer software. Repeated bronchoalveolar lavage was performed in seven adult rabbits to simulate acute respiratory distress syndrome. Surfactant therapy was administered after bronchoalveolar lavage induced a 20% reduction in baseline arterial PO2. The calculated parameters of alveolar and physiologic deadspace and the deadspace/tidal volume ratio were derived from the single-breath CO2 plot by Ventrak 1550 in combination with the Capnogard 1265. The arterial end-tidal Pco2 difference, the alveolar-arterial PO2 difference, and the arterial/alveolar PO2 ratio were obtained by capnography and arterial blood gas analysis. Measurements of these parameters were performed before bronchoalveolar lavage, during bronchoalveolar lavage, and after surfactant application.

MEASUREMENTS AND MAIN RESULTS

The alveolar and physiologic deadspace and the deadspace/tidal volume ratio were significantly higher in lavaged animals. After application of natural surfactant, these parameters were significantly reduced but the baseline values could not be reached. Bronchoalveolar lavage led to a significant fall in the arterial/alveolar PO2 ratio, which increased after surfactant therapy. There was a negative correlation between the arterial/alveolar PO2 ratio and the deadspace/tidal volume ratio. The alveolar and physiologic deadspace and the deadspace/tidal volume ratio correlated with the arterial end-tidal Pco2 difference. The best correlation was obtained between the arterial end-tidal Pco2 difference and the alveolar deadspace/tidal volume ratio (r = 0.98).

CONCLUSIONS

Bronchoalveolar lavage elevates the alveolar and physiologic deadspace and the deadspace/tidal volume ratios and is combined with a fall in the arterial/alveolar PO2 ratio. Surfactant treatment improves the gas exchange but does not restore the lung to its prebronchoalveolar lavage condition, which indicates that the exogenous surfactant affects only partly the recruitment of the atelectatic areas.

Comparison of pulmonary inflammatory mediators in preterm infants treated with intermittent positive pressure ventilation or high frequency oscillatory ventilation

Ventilated preterm infants prone to the development of bronchopulmonary dysplasia have been shown to have increased inflammatory mediators in their tracheal aspirates. High frequency oscillatory ventilation (HFOV) is thought to be less traumatic than intermittent positive pressure ventilation (IPPV) in premature infants with surfactant deficiency, and therefore may reduce the inflammatory response in tracheobronchial aspirates. We randomized 76 premature infants requiring mechanical ventilation (birth weight 420-1830 g, median 840 g, gestational age 23 3/7 to 29 2/7 wk, median 26 4/7 to receive either an IPPV with a high rate (60-80/min) and low peak pressures, or an HFOV aiming at an optimization of lung volume, within 1 h of intubation. Tracheal aspirates were systematically collected during the first 10 d of life and analyzed for albumin, IL-8, leukotriene B4 (LTB4), and the secretory component (SC) for IgA as a reference protein. Bacterially colonized samples were excluded. On the treatment d 1, 3, 5, 7, and 10, the resulting median values of albumin (milligrams/mg of SC) were 28, 23, 24, 18, and 10, in IPPV-ventilated infants, and 33, 28, 18, 25, and 39 in HFOV-ventilated infants, respectively. Median IL-8 values (nanograms/mg of SC) were 671, 736, 705, 1362, and 1879 (IPPV) and 874, 1713, 1029, 1426, and 1823 (HFOV), respectively, and median LTB4 values (nanograms/mg of SC) were 26, 13, 27, 22, and 11 (IPPV) and 15, 12, 7, 12, and 16 (HFOV), respectively. Values were similar in IPPV- and HFOV-ventilated infants, and no significant differences were noted. We conclude that HFOV, when compared with a high rate low pressure IPPV, does not reduce concentrations of albumin, IL-8, and LTB4 in tracheal aspirates of preterm infants requiring mechanical ventilation.

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.

Developmental outcome in very low birthweight infants. Current status and future trends

Surfactant therapy has significantly reduced mortality, but not morbidity, in the very low birthweight (VLBW) infant. Questions persist as to the edge of viability, the allocation of health care resources for the VLBW infant, and whether or not we are improving survival at the cost of contributing more handicapped individuals to society. Since surfactant alone has not reduced morbidity, other medical and behavioral treatments are being studied that may help to optimize neurodevelopmental outcome in the VLBW infant.

Cytological changes in endotracheal aspirates associated with chronic lung disease

Endotracheal aspirates taken serially from mechanically ventilated premature infants born at < 28 weeks gestation between March 1992 and August 1993 were studied to determine whether early cytological changes would be a good predictor of lung damage in infants who develop chronic lung disease (CLD). CLD was diagnosed if the infant required supplemental oxygen at 36 weeks corrected gestational age. Fifty-five infants were enrolled in the study, five died and of the 50 infants remaining, 17 (34%) developed CLD. The infants with CLD had a significantly lower gestation (25.5 +/- 1.8 (mean +/- 1 SD) versus 26.2 +/- 0.9 weeks, p < 0.05), significantly more required surfactant (14/17 vs. 16/33, p < 0.05) and were ventilated for a significantly longer period (43.3 +/- 26.6 vs. 19.3 +/- 12.8 days, p < 0.0001). Endotracheal aspirate cytology showed that infants with CLD had significantly more degenerated columnar epithelial cells on day 3 (p = 0.001), and more neutrophils on day 10 (p = 0.007). Though not predictive of CLD, cytological changes consistent with bronchial epithelial and pulmonary damage followed by an inflammatory response were found in the tracheal aspirates of a group of infants clinically diagnosed with CLD.

Recent declines in New York City infant mortality rates

BACKGROUND

Although infant mortality rates have declined gradually in New York City for many years, the rate of that decline began to accelerate dramatically at the end of the 1980s.

OBJECTIVE

To analyze the recent accelerated decline in infant mortality for three race/ethnicity designations in New York City and to investigate whether shifts in birth weight distribution or changes in birth weight-specific death rates were more important in determining these declines between 1988 to 1989 and 1992 to 1993.

METHODS

Two complete cohorts of linked birth-death certificate files consisting of all live births in New York City in 1988 to 1989 and 1992 to 1993 were examined. For each cohort, separate multinomial logistic regressions were estimated by race/ethnicity to analyze the probability of a neonatal or postneonatal death relative to survival as a function of a spectrum of covariates. The coefficients from these regressions were used to construct direct and indirect standardization exercises to predict changes in infant mortality holding characteristics of the cohort, including birth weight distribution, constant over time, or holding the influence of determinants, including birth weight-specific death rates, constant over time.

RESULTS

For whites, Hispanics, and blacks, infant mortality rates declined by 27.4%, 24.8%, and 22.7%, respectively, between 1988 to 1989 and 1992 to 1993. For whites and blacks, the largest decreases occurred for neonatal mortality rates, whereas for Hispanics, postneonatal rates fell the greatest. Although infant mortality rates among very low birth weight infants (<1500 g) fell by 27.8%, 19.3%, and 16.6% for whites, Hispanics, and blacks, the greatest decreases in rates were seen among normal birth weight infants (>2500 g). Infant mortality rate declines for this category of infants reached 31%, 31.7%, and 31.3%, respectively, for whites, Hispanics, and blacks. Direct and indirect standardization exercises indicated that the most important factor in determining these declines were decreases in birth weight-specific death rates, not improvements in the birth weight distribution over time.

CONCLUSIONS

We conclude that the large decreases in infant mortality rates witnessed in New York City between 1988 to 1989 and 1992 to 1993 were attributable not to improvements in birth weight distribution of the population but to declines in birth weight-specific death rates and that normal birth weight infants showed the greatest improvement.

Effect of neonatal surfactant therapy on lung function at school age in children born very preterm

Our aim was to evaluate long-term effects of exogenous surfactant therapy on pulmonary functional outcome in children born very preterm. We examined 40 children aged 7-12 years who were born before 30 weeks of gestation with an immature surfactant system, and were randomized to one of three treatment groups: human surfactant given at birth (prophylactic), human surfactant given after development of neonatal respiratory distress syndrome (rescue), and placebo (air) treatment. Spirometric parameters of preterm born children were compared with those of 20 children born at term. In addition, spirometric parameters were monitored twice daily for 4 weeks using a home spirometer. All spirometric parameters were significantly lower in the preterm groups than in the controls, except for the forced vital capacity (FVC) in the prophylactically treated group. Bronchial obstruction was found in 53% of the prophylactically treated group, in 36% of the rescue group, in 67% of the placebo group, and in 0% of the control group. Peak expiratory flow (PEF) and FVC values were higher in those children who received surfactant compared with the placebo group (P < 0.05). In 16 children (40%) born preterm, a beta2-agonist induced an increase in PEF > or = 15% at least three times during 2 weeks of home monitoring; eight children (20%) had abnormal diurnal PEF variation. Multiple regression analysis indicated that the independent variables associated with favorable outcomes in spirometric parameters were surfactant therapy (P = 0.012-0.045) and short intubation time after birth (P = 0.0009-0.0044). Bronchial obstruction, responsiveness to a beta2-agonist, and high diurnal PEF variation are common in children born before 30 gestational weeks. Surfactant supplementation reducing the need for mechanical ventilation or supplementary oxygen after birth may decrease the severity of immaturity related bronchial obstruction in childhood.