Prognostic determinants of acute respiratory distress syndrome in adults: impact on clinical trial design

Use of risk reclassification with multiple biomarkers improves mortality prediction in acute lung injury

OBJECTIVE

Multiple single biomarkers have been associated with poor outcomes in acute lung injury; however, no single biomarker has sufficient discriminating power to clearly indicate prognosis. Using both derivation and replication cohorts, we tested novel risk reclassification methods to determine whether measurement of multiple plasma biomarkers at the time of acute lung injury diagnosis would improve mortality prediction in acute lung injury.

DESIGN

Analysis of plasma biomarker levels and prospectively collected clinical data from patients enrolled in two randomized controlled trials of ventilator therapy for acute lung injury.

SETTING

Intensive care units of university hospitals participating in the National Institutes of Health Acute Respiratory Distress Syndrome Network.

PATIENTS

Subjects enrolled in a trial of lower tidal volume ventilation (derivation cohort) and subjects enrolled in a trial of higher vs. lower positive end-expiratory pressure (replication cohort).

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

The plasma biomarkers were intercellular adhesion molecule-1, von Willebrand factor, interleukin-8, soluble tumor necrosis factor receptor-1, and surfactant protein-D. In the derivation cohort (n = 547), adding data on these biomarkers to clinical predictors (Acute Physiology and Chronic Health Evaluation III score) at the time of study enrollment improved the accuracy of risk prediction, as reflected by a net reclassification improvement of 22% (95% confidence interval 13% to 32%; p < .001). In the replication cohort (n = 500), the net reclassification improvement was 17% (95% confidence interval 7% to 26%; p < .001). A reduced set of three biomarkers (interleukin-8, soluble tumor necrosis factor receptor-1, and surfactant protein-D) had nearly equivalent prognostic value in both cohorts.

CONCLUSIONS

When combined with clinical data, plasma biomarkers measured at the onset of acute lung injury can improve the accuracy of risk prediction. Combining three or more biomarkers may be useful for selecting a high-risk acute lung injury population for enrollment in clinical trials of novel therapies.

Definition of ALI/ARDS

Although acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are caused by different injuries and conditions, their similar clinical picture makes a compelling case for them to be studied as a single entity. An array of potential specific targets for pharmacologic intervention can be applied to ALI/ARDS as one disease. Although a working definition of ALI/ARDS that includes pulmonary and extrapulmonary causes can have benefit in standardizing supportive care, it can also complicate assessments of the efficacy of therapeutic interventions. In this article, definitions that have been recently used for ALI/ARDS in various clinical studies are discussed individually.

Acute respiratory distress syndrome and multiple organ failure

PURPOSE OF REVIEW

Despite improvements in outcome due to lung protective ventilation strategies using low tidal volumes, the mortality rate from acute respiratory distress syndrome (ARDS) remains unacceptably high, ranging from 34 to 64%. The predominant cause of death in ARDS is not severe hypoxemia, which is one of the defining criteria of ARDS, but multiple organ failure (MOF).

RECENT FINDINGS

In view of the relationship between ARDS and MOF, two different but complementary pathophysiological perspectives will be developed in this article: ARDS as a consequence of MOF, and ARDS as the cause of MOF. This framework may be useful in guiding the development of novel therapeutic strategies that ultimately improve the outcome of ARDS and sepsis patients.

SUMMARY

ARDS is a severe lung disease characterized by a very complex pathophysiology, involving not only the respiratory system but also nonpulmonary distal organs. Elucidation of the pathophysiological mechanisms bi-directionally linking MOF to ARDS appears to be a promising area of research that hopefully will lead to improved outcomes for these devastating conditions.

Prognostic impact of clinical course-specific mRNA expression profiles in the serum of perioperative patients with esophageal cancer in the ICU: a case control study

Background

We previously reported that measuring circulating serum mRNAs using quantitative one-step real-time RT-PCR was clinically useful for detecting malignancies and determining prognosis. The aim of our study was to find crucial serum mRNA biomarkers in esophageal cancer that would provide prognostic information for post-esophagectomy patients in the critical care setting.

Methods

We measured serum mRNA levels of 11 inflammatory-related genes in 27 post-esophagectomy patients admitted to the intensive care unit (ICU). We tracked these levels chronologically, perioperatively and postoperatively, until the two-week mark, investigating their clinical and prognostic significance as compared with clinical parameters. Furthermore, we investigated whether gene expression can accurately predict clinical outcome and prognosis.

Results

Circulating mRNAs in postoperative esophagectomy patients had gene-specific expression profiles that varied with the clinical phase of their treatment. Multivariate regression analysis showed that upregulation of IL-6, VWF and TGF-β1 mRNA in the intraoperative phase (p = 0.016, 0.0021 and 0.009) and NAMPT and MUC1 mRNA on postoperative day 3 (p < 0.01) were independent factors of mortality in the first year of follow-up. Duration of ventilator dependence (DVD) and ICU stay were independent factors of poor prognosis (p < 0.05). Therapeutic use of Sivelestat (Elaspol^®, Ono Pharmaceutical Co., Ltd.) significantly correlated with MUC1 and NAMPT mRNA expression (p = 0.048 and 0.045). IL-6 mRNA correlated with hypercytokinemia and recovery from hypercytokinemia (sensitivity 80.9%) and was a significant biomarker in predicting the onset of severe inflammatory diseases.

Conclusion

Chronological tracking of postoperative mRNA levels of inflammatory-related genes in esophageal cancer patients may facilitate early institution of pharamacologic therapy, prediction of treatment response, and prognostication during ICU management in the perioperative period.

Impaired phospholipases A₂production by stimulated macrophages from patients with acute respiratory distress syndrome

The aim of this study was to investigate whether early phase of acute respiratory distress syndrome (ARDS) is associated with changes in immune response, either systemic or localized to the lung. ARDS and control mechanically ventilated patients, as well as healthy volunteers were studied. Alveolar macrophages (AMΦ) and blood monocytes (BM) were treated ex vivo with lipopolysaccharide (LPS), interferon-γ (IFNγ), and surfactant. Phospholipase A₂ (PLA₂) activity and TLR4 expression were evaluated as markers of cell response. AMΦ from ARDS patients did not respond upon treatment with either LPS or IFN-γ by inducing PLA₂ production. On the contrary, upon stimulation, in control patients the intracellular PLA₂, (mainly cPLA₂) levels were increased, but secretion of PLA₂ (mainly sPLA₂-IIA) was observed only after treatment with LPS. Surfactant suppressed PLA₂ production in cells from both groups of patients. Increased relative changes of total PLA₂ activity and an upregulation of TLR4 expression upon stimulation was observed in BM from primary ARDS, control patients and healthy volunteers. In BM from secondary ARDS patients, however, no PLA₂ induction was observed, with a concomitant down-regulation of TLR4 expression. Cytosolic PLA₂, its activated form, p-cPLA₂, and sPLA₂-IIA were the predominant PLA₂ types within the cells, while extracellularly only sPLA₂-IIA was identified. These results support the concept of down-regulated innate immunity in early ARDS that is compartmentalized in primary and systemic in secondary ARDS. PLA₂ isoforms could serve as markers of the immunity status in ARDS. Finally, our data highlight the role of surfactant in controlling inflammation.

Exacerbated innate host response to SARS-CoV in aged non-human primates

The emergence of viral respiratory pathogens with pandemic potential, such as severe acute respiratory syndrome coronavirus (SARS-CoV) and influenza A H5N1, urges the need for deciphering their pathogenesis to develop new intervention strategies. SARS-CoV infection causes acute lung injury (ALI) that may develop into life-threatening acute respiratory distress syndrome (ARDS) with advanced age correlating positively with adverse disease outcome. The molecular pathways, however, that cause virus-induced ALI/ARDS in aged individuals are ill-defined. Here, we show that SARS-CoV-infected aged macaques develop more severe pathology than young adult animals, even though viral replication levels are similar. Comprehensive genomic analyses indicate that aged macaques have a stronger host response to virus infection than young adult macaques, with an increase in differential expression of genes associated with inflammation, with NF-κB as central player, whereas expression of type I interferon (IFN)-β is reduced. Therapeutic treatment of SARS-CoV-infected aged macaques with type I IFN reduces pathology and diminishes pro-inflammatory gene expression, including interleukin-8 (IL-8) levels, without affecting virus replication in the lungs. Thus, ALI in SARS-CoV-infected aged macaques developed as a result of an exacerbated innate host response. The anti-inflammatory action of type I IFN reveals a potential intervention strategy for virus-induced ALI.

Severe acute respiratory syndrome coronavirus (SARS-CoV) infection causes acute lung injury that may develop into the life-threatening acute respiratory distress syndrome (ARDS) in mostly elderly individuals. Although SARS-CoV infection can be fatal, most patients recover, suggesting that protective host responses are operational to combat the viral infection. Therefore, we used age as predisposing factor to obtain insight into the pathogenesis of SARS-CoV. In this study, we show that SARS-CoV-infected aged macaques developed significantly more pathology than young adult animals, which could not be contributed to differences in viral replication. Using comparative microarray analyses, it was shown that although the nature of the host response to SARS-CoV infection was similar in aged and young adult macaques, the severity was significantly different, with aged macaques displaying an increase in differential expression of genes associated with inflammation. Interestingly, type I IFN-β mRNA levels correlated negatively with gross pathology. Therapeutic treatment of aged macaques with type I IFN reduced pathology without affecting virus replication. However, pro-inflammatory gene expression was significantly diminished. Thus, modulation of the host response by type I IFNs provides a promising outlook for novel intervention strategies.

Regulation of inflammatory cytokine expression in pulmonary epithelial cells by pre-B-cell colony-enhancing factor via a nonenzymatic and AP-1-dependent mechanism

Although our previous studies found Pre-B-cell colony-enhancing factor (PBEF) as a highly up-regulated gene in acute lung injury that could stimulate expressions of other inflammatory cytokines, the underlying molecular mechanisms remain to be fully elucidated. Growing evidence indicates that PBEF is a nicotinamide phosphoribosyltransferase involved in the mammalian salvage pathway of NAD synthesis. This study was designed to determine whether the effect of PBEF to stimulate expressions of inflammatory cytokines depends on its enzymatic activity. We prepared two human PBEF mutant (H247E and H247A) recombinant proteins and overexpressing constructs for their overexpressions in A549 cells and confirmed that enzymatic activities of both mutants were nearly or completely abolished. Two mutants stimulated interleukin-8 (IL-8) expression at both the mRNA level and protein level just as equally effective as the wild-type PBEF did. These effects were due to the increased transcription, not the mRNA stability, of the IL-8 gene. Reporter gene assays and gel shift experiments indicated that AP-1 transcription factor is required to mediate these effects. SB203580, a p38 MAPK pathway inhibitor, and JNK inhibitor 1 can attenuate these effects. Both PBEF mutants similarly stimulated the expression of two other inflammatory cytokines: IL-16 and CCR3. These results indicate that PBEF stimulated expression of IL-8, IL-16, and CCR3 via its non-enzymatic activity. This effect is AP-1-dependent, in part via the p38 MAPK pathway and the JNK pathway. This finding reveals a new insight, which may manifest a novel role of PBEF in the pathogenesis of acute lung injury and other inflammatory disorders.

Is it possible to predict outcome in pulmonary ECMO? Analysis of pre-operative risk factors

Serious pulmonary failure may be treated with extracorporeal membrane oxygenation (ECMO) when other treatment has failed. The aim of this study was to analyze pre-operative risk factors of early mortality in patients who underwent either veno-arterial (VA) ECMO or veno-venous (VV) ECMO for pulmonary failure. We studied a total of 26 risk factors in 72 patients with severe pulmonary insufficiency treated with ECMO. All consecutive cases treated at our institution between Sept 1990 and Aug 2007 were included. Univariate analysis and multiple logistic regression analysis were performed on 26 risk factors. The end point was early mortality (any death within 30 days of ECMO treatment). Thirty-six (50%) of the patients died within 30 days of treatment. Age, gender, body mass index(BMI)(adults), cause of pulmonary failure, pre-ECMO treatment with nitric oxide(NO), intra-aortic balloon pump(IABP), and type of ventilation did not significantly influence early mortality. Neither pre-operative blood gas results, oxygenation index or pre-operative PaO(2)/FiO(2) ratio, nor mean ventilator days prior to ECMO gave any indications on early mortality. Liver function did not predict early mortality, but pre-ECMO serum creatinine levels were significantly lower in patients who survived. Treatment with ECMO in patients with severe pulmonary failure may save lives. It is, however, difficult to predict outcome when initiating ECMO. In this analysis, only pre-operative serum creatinine levels correlated with survival. None of the other parameters, including those which were used to select patients for ECMO treatment, could significantly predict the outcome.

A simple clinical predictive index for objective estimates of mortality in acute lung injury

OBJECTIVE

We sought to develop a simple point score that would accurately capture the risk of hospital death for patients with acute lung injury (ALI).

DESIGN

This is a secondary analysis of data from two randomized trials. Baseline clinical variables collected within 24 hours of enrollment were modeled as predictors of hospital mortality using logistic regression and bootstrap resampling to arrive at a parsimonious model. We constructed a point score based on regression coefficients.

SETTING

Medical centers participating in the Acute Respiratory Distress Syndrome Clinical Trials Network (ARDSnet).

PATIENTS

Model development: 414 patients with nontraumatic ALI participating in the low tidal volume arm of the ARDSnet Acute Respiratory Management in ARDS study. Model validation: 459 patients participating in the ARDSnet Assessment of Low tidal Volume and elevated End-expiratory volume to Obviate Lung Injury study. Model Validation: 459 patients participating in the ARDSnet Assessment of Low tidal Volume and elevated End-expiratory volume to Obviate Lung Injury trial.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Variables comprising the prognostic model were hematocrit <26% (1 point), bilirubin >or=2 mg/dL (1 point), fluid balance >2.5 L positive (1 point), and age (1 point for age 40-64 years, 2 points for age >or=65 years). Predicted mortality (95% confidence interval) for 0, 1, 2, 3, and 4+ point totals was 8% (5% to 14%), 17% (12% to 23%), 31% (26% to 37%), 51% (43% to 58%), and 70% (58% to 80%), respectively. There was an excellent agreement between predicted and observed mortality in the validation cohort. Observed mortality for 0, 1, 2, 3, and 4+ point totals in the validation cohort was 12%, 16%, 28%, 47%, and 67%, respectively. Compared with the Acute Physiology Assessment and Chronic Health Evaluation III score, areas under the receiver operating characteristic curve for the point score were greater in the development cohort (0.72 vs. 0.67, p = 0.09) and lower in the validation cohort (0.68 vs. 0.75, p = 0.03).

CONCLUSIONS

Mortality in patients with ALI can be predicted using an index of four readily available clinical variables with good calibration. This index may help inform prognostic discussions, but validation in nonclinical trial populations is necessary before widespread use.

Keratinocyte growth factor expression is suppressed in early acute lung injury/acute respiratory distress syndrome by smad and c-Abl pathways

OBJECTIVE

Keratinocyte growth factor (KGF) is expressed primarily by fibroblasts, is important for alveolar epithelial proliferation/function, and protects against lung injury in multiple animal models. We wished to determine whether acute lung injury/acute respiratory distress syndrome (ALI/ARDS) alveolar fluid induces KGF and fibroblast genes important for alveolar repair.

DESIGN

A single-center cohort study enrolling patients between 2004 and 2006.

SETTING

A medical intensive care unit of a tertiary care medical center.

PATIENTS

Adult patients meeting the American-European Consensus Conference definition of ALI/ARDS.

INTERVENTIONS

Patients with ALI/ARDS were enrolled, and lavage fluid was collected within 48 hours of intubation. Lavage fluid was also collected from two control cohorts. The patients with ALI/ARDS were followed for 28 days or until death.

MEASUREMENT AND MAIN RESULTS

Fifteen patients with ALI/ARDS, five patients with cardiogenic edema, and five normal lung parenchyma controls were enrolled from 2004 to 2006. Primary normal human lung fibroblasts were incubated with bronchoalveolar lavage fluid and assessed for KGF, connective tissue growth factor, alpha-smooth muscle actin, and collagen 1 expression by real-time reverse transcriptase-polymerase chain reaction. Fibroblasts incubated with ALI/ARDS lavage fluid expressed 50% less KGF messenger RNA than those incubated with lavage fluid from CE patients (p < 0.01) and 33% than normal parenchymal controls (p < 0.03). Lavage fluid from patients with ALI/ARDS induced more connective tissue growth factor (p < 0.05), collagen 1 (p < 0.03), and alpha-smooth muscle actin (p < 0.04) than from CE patients. Preincubation of normal human lung fibroblasts with the transforming growth factor (TGF)-beta1 receptor/smad phosphorylation inhibitor SB431542 increased ALI/ARDS-induced KGF expression by 40% (p < 0.04). In cultured human lung fibroblasts, TGF-beta1 suppressed KGF messenger RNA and protein expression, which were reversed by SB431542 and by the c-Abl inhibitor, imatinib mesylate, but not by the p38 map kinase inhibitor, SB203580.

CONCLUSIONS

ALI/ARDS alveolar fluid suppresses KGF expression, in part, due to TGF-beta1. TGF-beta1 suppression of KGF requires both smad phosphorylation and c-Abl activation.

Plasma granulocyte colony-stimulating factor levels correlate with clinical outcomes in patients with acute lung injury

OBJECTIVES

To evaluate the association between plasma granulocyte colony-stimulating factor (G-CSF) levels and clinical outcomes including mortality in patients with acute lung injury (ALI), and to determine whether lower tidal volume ventilation was associated with a more rapid decrease in plasma G-CSF over time in patients with ALI.

DESIGN

Retrospective measurement of G-CSF levels in plasma samples that were collected prospectively as part of a large multicenter clinical trial.

SETTING

Intensive care units in ten university centers.

PATIENTS

The study included 645 patients enrolled in the National Heart, Lung, and Blood Institute Acute Respiratory Distress Syndrome Clinical Network trial of lower tidal volumes compared with traditional tidal volumes for ALI.

MEASUREMENTS AND MAIN RESULTS

Baseline plasma levels of G-CSF were associated with an increased risk of death and a decrease in ventilator-free days and organ failure-free days in multivariate analyses controlling for ventilation strategy, age, and sex (Odds ratio death 1.2/log10 increment G-CSF, 95% confidence interval 1.01 to 1.4). Stratification of G-CSF levels into quartiles revealed a strong association between the highest levels of G-CSF and an increased risk of death and decreased ventilator-free days and organ failure-free days in multivariate analyses controlling for ventilation strategy, Acute Physiology and Chronic Health Evaluation III score, Pao2/Fio2 ratio, creatinine, and platelet count (p < 0.05). Subgroup multivariate analysis of patients with sepsis as their risk factor for ALI revealed a U-shaped association between mortality and G-CSF levels such that risk increased linearly from the second through fourth (highest) quartiles, yet also increased in the first (lowest) quartile. G-CSF levels decreased over time in both tidal volume groups, and there was no statistical difference in the extent of decrease between ventilator strategies.

CONCLUSIONS

In patients with ALI, plasma G-CSF levels are associated with morbidity and mortality, but these levels are not influenced by tidal volume strategy. In patients with sepsis-related ALI, a bimodal association between baseline plasma G-CSF levels and subsequent morbidity and mortality from this disease was found.

Ceramide-dependent PP2A regulation of TNFalpha-induced IL-8 production in respiratory epithelial cells

IL-8 is a key mediator in the pathophysiology of acute lung injury. TNFalpha stimulates IL-8 production in respiratory epithelial cells by activating both the NF-kappaB and MAP kinase pathways. The precise mechanism by which these pathways are downregulated to terminate IL-8 production remains unclear. We studied the regulatory role of the serine/threonine phosphatase, PP2A, on the signaling pathways involved in IL-8 production from respiratory epithelial cells. Inhibition of PP2A using okadaic acid or gene knockdown using siRNA resulted in an augmentation of TNFalpha-induced IL-8 production. We also found that PP2A inhibition resulted in prolonged activation of JNK, p38, and ERK resulting in both increased transcriptional activation of the IL-8 promoter and posttranscriptional stabilization of IL-8 mRNA. Because TNFalpha had been shown to activate ceramide accumulation, and separate studies had linked ceramide with activation of PP2A, we hypothesized the pathway of TNFalpha-inducing ceramide to activate PP2A comprised an endogenous regulatory pathway. Inhibition of the immediate sphingomyelinase-dependent pathway as well as the de novo synthesis pathway of ceramide production reduced serine/threonine phosphatase activity and augmented IL-8 production. These data suggest that ceramide plays a role in activating PP2A to terminate ongoing IL-8 production. In summary, our data suggest that in respiratory epithelium, TNFalpha induces ceramide accumulation, resulting in subsequent activation of PP2A, which targets those kinases responsible for transcriptional activation of IL-8.

Interleukin-6 may predict survival in extracorporeal membrane oxygenation treatment

The cytokine network and its association with complement activation during cardiac surgery with cardiopulmonary bypass (CPB) is complex. Extracorporeal membrane oxygenation (ECMO) differs from CPB in duration of days to weeks rather than hours. However, few studies have analyzed the levels of inflammatory mediators during ECMO treatment. Plasma samples from 22 patients [nine neonates, one infant, four children and eight adults (14 males and eight female)] who underwent ECMO treatment were collected prior to, during and after treatment, and analyzed for concentrations of inflammatory and anti-inflammatory cytokines and parameters of complement activation. Seven children were treated for cardiac and seven for pulmonary failure and, in the adult group, four were treated for cardiac and four for pulmonary failure. ECMO was performed with veno-arterial (VA) bypass in all children and five adults, and with veno-venous (VV) bypass in three adults. Fourteen patients survived (64%) and eight (36%) patients died during follow-up. A marked (approximately 99%) and rapid (i.e., within two days) decrease in IL-6 was seen in survivors. The non-survivors were characterized by persistently high IL-6 levels throughout the observation period (i.e., until death). C-reactive protein (CRP) levels showed a similar pattern as the IL-6, with higher levels in non-survivors throughout the observation period. However, in contrast to IL-6, the differences between survivors and non-survivors reached statistical significance, but only at the end of the observation period. It is possible that early measurements of IL-6 in ECMO patients could give prognostic information beyond that of CRP.

Discovery of the gene signature for acute lung injury in patients with sepsis

The acute respiratory distress syndrome (ARDS)/acute lung injury (ALI) was described 30 yr ago, yet making a definitive diagnosis remains difficult. The identification of biomarkers obtained from peripheral blood could provide additional noninvasive means for diagnosis. To identify gene expression profiles that may be used to classify patients with ALI, 13 patients with ALI + sepsis and 20 patients with sepsis alone were recruited from the Medical Intensive Care Unit of the University of Pittsburgh Medical Center, and microarrays were performed on peripheral blood samples. Several classification algorithms were used to develop a gene signature for ALI from gene expression profiles. This signature was validated in an independently obtained set of patients with ALI + sepsis (n = 8) and sepsis alone (n = 1). An eight-gene expression profile was found to be associated with ALI. Internal validation found that the gene signature was able to distinguish patients with ALI + sepsis from patients with sepsis alone with 100% accuracy, corresponding to a sensitivity of 100%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 100%. In the independently obtained external validation set, the gene signature was able to distinguish patients with ALI + sepsis from patients with sepsis alone with 88.9% accuracy. The use of classification models to develop a gene signature from gene expression profiles provides a novel and accurate approach for classifying patients with ALI.

Racial and ethnic disparities in mortality from acute lung injury

OBJECTIVE

Little is known about the influence of race and ethnicity on mortality from acute lung injury (ALI). We sought to determine whether black race or Hispanic ethnicity is independently associated with mortality among patients with ALI.

DESIGN

Retrospective cohort study of patients enrolled in the Acute Respiratory Distress Syndrome Network randomized controlled trials.

SETTING

Adult intensive care units participating in the Acute Respiratory Distress Syndrome Network trials.

PATIENTS

A total of 2362 mechanically ventilated patients (1715 white, 449 black, and 198 Hispanic) with ALI.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was 60-day mortality. A secondary outcome was number of ventilator-free days. Crude mortality was 33% for both blacks and Hispanics compared with 27% for whites (p = 0.02). After adjusting for demographic and clinical covariates, the association between race/ethnicity and mortality persisted (odds ratio [OR] = 1.42; 95% confidence interval [CI] 1.10-1.84 for blacks; OR = 1.94; 95% CI, 1.36-2.77 for Hispanics; OR = 1.00 for whites). After adjustment for severity of illness (Acute Physiology Score), black race was no longer significantly associated with mortality (OR = 1.25; 95% CI, 0.95-1.66), whereas the association with Hispanic ethnicity persisted (OR = 2.00; 95% CI, 1.37-2.90). Hispanics had significantly fewer ventilator-free days compared with whites after adjustment for demographic and clinical covariates (mean difference in days = -2.3; 95% CI -3.90 to -0.70).

CONCLUSIONS

Black and Hispanic patients with ALI have a significantly higher risk of death compared with white patients. This increased risk seemed to be mediated by increased severity of illness at presentation for blacks, but was unexplained among Hispanics.

Critical role of PBEF expression in pulmonary cell inflammation and permeability

Previous studies in our lab have identified pre-B-cell colony enhancing factor (PBEF) as a novel biomarker in acute lung injury. This study continues to elucidate the underlying molecular mechanism of PBEF in the pathogenesis of acute lung injury in pulmonary cell culture models. Our results revealed that IL-1beta induced PBEF expression in pulmonary vascular endothelial cells at the transcriptional level and a -1535 T-variant in the human PBEF gene promoter significantly attenuated its binding to an IL-1beta-induced unknown transcription factor. This may underlie the reduced expression of PBEF and thus the lower susceptibility to acute lung injury in -1535T carriers. Furthermore, overexpression of PBEF significantly augmented IL-8 secretion and mRNA expression by more than 6-fold and 2-fold in A549 cells and HPAEC, respectively. It also significantly augmented IL-1beta-mediated cell permeability by 44% in A549 cells and 65% in endothelial cells. The knockdown of PBEF expression significantly inhibited IL-1beta-stimulated IL-8 secretion and mRNA level by 60% and 70%, respectively, and the knockdown of PBEF expression also significantly attenuated IL-1beta-induced cell permeability by 29% in epithelial cells and 24% in endothelial cells. PBEF expression also affected the expression of two other inflammatory cytokines (IL-16 and CCR3 genes). These results suggest that PBEF is critically involved in pulmonary vascular and epithelial inflammation and permeability, which are hallmark features in the pathogenesis of acute lung injury. This study lends further support to our finding that PBEF is a potential new target in acute lung injury.

Augmentation of Pulmonary Epithelial Cell IL-8 Expression and Permeability by Pre-B-cell Colony Enhancing Factor

Background

Previous studies in our lab have identified Pre-B-cell colony enhancing factor (PBEF) as a novel biomarker in acute lung injury (ALI). The molecular mechanism of PBEF involvement in the pathogenesis of ALI is still incompletely understood. This study examined the role of PBEF in regulating pulmonary alveolar epithelial cell IL-8 expression and permeability.

Methods

Human pulmonary alveolar epithelial cells (cell line and primary cells) were transfected with human PBEF cDNA or PBEF siRNA and then cultured in the presence or absence of TNFα. PBEF and IL-8 expression were analyzed by RT-PCR and Western blotting. In addition, changes in pulmonary alveolar epithelial and artery endothelial cell barrier regulation with altered PBEF expression was evaluated by an in vitro cell permeability assay.

Results

Our results demonstrated that, in human pulmonary alveolar epithelial cells, the overexpression of PBEF significantly augmented basal and TNFα-stimulated IL-8 secretion by more than 5 to 10-fold and increased cell permeability by >30%; the knockdown of PBEF expression with siRNA significantly inhibited basal and TNFα-stimulated IL-8 secretion by 70% and IL-8 mRNA levels by 74%. Further, the knockdown of PBEF expression also significantly attenuated TNFα-induced cell permeability by 43%. Similar result was observed in human pulmonary artery endothelial cells.

Conclusion

These results suggest that PBEF may play a vital role in basal and TNFα-mediated pulmonary inflammation and pulmonary epithelial barrier dysfunction via its regulation of other inflammatory cytokines such as IL-8, which could in part explain the role of PBEF in the susceptibility and pathogenesis of ALI. These results lend further support to the potential of PBEF to serve as a diagnostic and therapeutic target to ALI.

Circulating angiopoietin 2 correlates with mortality in a surgical population with acute lung injury/adult respiratory distress syndrome

There are few blood biomarkers predictive of mortality in adult respiratory distress syndrome (ARDS), and none that currently serve as therapeutic targets. Here, we ask whether a circulating protein angiopoietin 2 (Ang2) correlates with severity of lung injury and mortality in a surgical intensive care unit cohort with acute lung injury (ALI)/ARDS. Tie 2 is a tyrosine kinase receptor expressed on endothelial cells. One ligand, angiopoietin 1, phosphorylates Tie 2 and stabilizes adult vasculature. An alternate ligand, Ang2, serves as a context-dependent antagonist and disrupts barrier function. Previously, our laboratory detected high circulating Ang2 levels in septic patients and a correlation with low Pa(O2)/F(IO2). In this study, daily plasma was collected in 63 surgical intensive care unit patients. Eighteen patients met clinical criteria for ALI or ARDS. The median Ang2 at admission in patients who never developed ALI/ARDS was 3.7 ng/mL (interquartile range [IQR], 5.6; n = 45). The Ang2 on the day a patient met criteria for ALI/ARDS was 5.3 ng/mL (IQR, 6.7) for survivors (n = 11) and 19.8 ng/mL (IQR, 19.2) for nonsurvivors (n = 7; P= 0.004). To explore the mechanism of high Ang 2 leading to increased permeability, plasma from patients with ALI was applied to cultured lung endothelial cells and found to disrupt normal junctional architecture. This effect can be rescued with the Tie 2 agonist angiopoietin 1. A patient's convalescent (low Ang2) plasma did not disrupt junctional architecture. Although further studies with larger sample sizes will be needed to confirm these results, high Ang2 in critically ill patients with ALI/ARDS is associated with a poor outcome. These data, coupled with our cell culture experiments, suggest that antagonism of Ang2 may provide a future novel therapeutic target for ARDS.

Recruitment maneuvers for acute lung injury: a systematic review

RATIONALE

There are conflicting data regarding the safety and efficacy of recruitment maneuvers (RMs) in patients with acute lung injury (ALI).

OBJECTIVES

To summarize the physiologic effects and adverse events in adult patients with ALI receiving RMs.

METHODS

Systematic review of case series, observational studies, and randomized clinical trials with pooling of study-level data.

MEASUREMENTS AND MAIN RESULTS

Forty studies (1,185 patients) met inclusion criteria. Oxygenation (31 studies; 636 patients) was significantly increased after an RM (PaO2): 106 versus 193 mm Hg, P = 0.001; and PaO2/FiO2 ratio: 139 versus 251 mm Hg, P < 0.001). There were no persistent, clinically significant changes in hemodynamic parameters after an RM. Ventilatory parameters (32 studies; 548 patients) were not significantly altered by an RM, except for higher PEEP post-RM (11 versus 16 cm H2O; P = 0.02). Hypotension (12%) and desaturation (9%) were the most common adverse events (31 studies; 985 patients). Serious adverse events (e.g., barotrauma [1%] and arrhythmias [1%]) were infrequent. Only 10 (1%) patients had their RMs terminated prematurely due to adverse events.

CONCLUSIONS

Adult patients with ALI receiving RMs experienced a significant increase in oxygenation, with few serious adverse events. Transient hypotension and desaturation during RMs is common but is self-limited without serious short-term sequelae. Given the uncertain benefit of transient oxygenation improvements in patients with ALI and the lack of information on their influence on clinical outcomes, the routine use of RMs cannot be recommended or discouraged at this time. RMs should be considered for use on an individualized basis in patients with ALI who have life-threatening hypoxemia.

Organizing pneumonia and pulmonary lymphatic architecture in diffuse alveolar damage

Diffuse alveolar damage represents the pathologic basis of most cases of the acute respiratory distress syndrome. Diffuse alveolar damage reflects injury to the pulmonary alveolar wall and microvasculature, leading to the exudation of water and plasma proteins that can overwhelm the local lymphatic drainage. Organizing pneumonia is a prominent histopathologic feature in some cases of diffuse alveolar damage. We examined whether diffuse alveolar damage-organizing pneumonia and changes in lymphatic architecture might be indicators of clinical outcome in acute respiratory distress syndrome. Formalin-fixed lung sections (n = 26) from thoracoscopic lung biopsies of patients with diffuse alveolar damage in the fibroproliferative phase, with or without organizing pneumonia, were immunostained with anti-CD31 and anti-D240, markers of vascular and lymphatic endothelium, respectively, and examined by morphometric analysis. Positively staining vessels were enumerated and maximal luminal diameters recorded in randomly selected low-power fields. Patients with diffuse alveolar damage-organizing pneumonia showed greater survival than those with diffuse alveolar damage (67% versus 33%, P = .03). The maximal luminal diameter of D240+ lymphatic vessels was larger for diffuse alveolar damage-organizing pneumonia than diffuse alveolar damage (28 +/- 4 versus 59 +/- 16 microm, P = .02). In addition, larger lymphatic luminal diameters (28 +/- 4 versus 47 +/- 11 microm) were associated with increased survival (P = .12). We conclude that lung biopsy histopathology and pulmonary lymphatic morphology may predict survival in acute respiratory distress syndrome.

IL6 gene-wide haplotype is associated with susceptibility to acute lung injury

Experimental and clinical studies support the key role of interleukin 6 (IL-6), a potent proinflammatory cytokine, in the development of acute lung injury (ALI). Plasma IL-6 levels are influenced mainly by genetic determinants, and a -174G/C polymorphism of the gene has been recently associated with susceptibility to ALI. Here we aimed to validate the association of the IL6 gene with ALI in a case-control sample from Spain. DNA was isolated from 67 consecutive patients who fulfilled international criteria for severe sepsis and for ALI and 96 population-based controls drawn from the general population. Genotypes of the -174G/C polymorphism along with other 14 tagging variants of the IL6 gene were evaluated. Twenty polymorphisms unlinked to IL6 gene were additionally compared between cases and controls to rule out population stratification. None of the individual single-nucleotide polymorphisms was significantly associated with susceptibility to ALI. However, we found that a common haplotype from -1363 to +4835 from the transcription start site, and spanning the gene, conferred risk for susceptibility to ALI (odds ratio, 2.73; 95% confidence interval, 1.39-5.37; P = 0.003). Adjustment for relevant covariates did not modify this result. These data support the association of the IL6 gene with ALI susceptibility and illustrate the value of haplotype analysis as a robust approach for evaluating IL6 gene effects in association studies.

Predictors of mortality in acute lung injury during the era of lung protective ventilation

BACKGROUND

Lung protective ventilation has been widely adopted for the management of acute lung injury (ALI) and acute respiratory distress syndrome (ARDS). Consequently, ventilator associated lung injury and mortality have decreased. It is not known if this ventilation strategy changes the prognostic value of previously identified demographic and pulmonary predictors of mortality, such as respiratory compliance and the arterial oxygen tension to inspired oxygen fraction ratio (Pao(2)/Fio(2)).

METHODS

Demographic, clinical, laboratory and pulmonary variables were recorded in 149 patients with ALI/ARDS. Significant predictors of mortality were identified in bivariate analysis and these were entered into multivariate analysis to identify independent predictors of mortality.

RESULTS

Hospital mortality was 41%. In the bivariate analysis, 17 variables were significantly correlated with mortality, including age, APACHE II score and the presence of cirrhosis. Pulmonary parameters associated with death included Pao(2)/Fio(2) and oxygenation index ((mean airway pressurexFio(2)x100)/Pao(2)). In unadjusted analysis, the odds ratio (OR) of death for Pao(2)/Fio(2) was 1.57 (CI 1.12 to 3.04) per standard deviation decrease. However, in adjusted analysis, Pao(2)/Fio(2) was not a statistically significant predictor of death, with an OR of 1.29 (CI 0.82 to 2.02). In contrast, oxygenation index (OI) was a statistically significant predictor of death in both unadjusted analysis (OR 1.89 (CI 1.28 to 2.78)) and in adjusted analysis (OR 1.84 (CI 1.13 to 2.99)).

CONCLUSIONS

In this cohort of patients with ALI/ARDS, OI was an independent predictor of mortality, whereas Pao(2)/Fio(2) was not. OI may be a superior predictor because it integrates both airway pressure and oxygenation into a single variable.

Predictors of hospital mortality in a population-based cohort of patients with acute lung injury

OBJECTIVE

Studies describing predictors of mortality in patients with acute lung injury were primarily derived from selected academic centers. We sought to determine the predictors of mortality in a population-based cohort of patients with acute lung injury and to characterize the performance of current severity of illness scores in this population.

DESIGN

Secondary analysis of a prospective, multicenter, population-based cohort.

SETTING

Twenty-one hospitals in Washington State.

PATIENTS

The cohort included 1,113 patients with acute lung injury identified during the year 1999-2000.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We evaluated physiology, comorbidities, risk factors for acute lung injury, and other variables for their association with death at hospital discharge. Bivariate predictors of death were entered into a multiple logistic regression model. We compared Acute Physiology and Chronic Health Evaluation (APACHE) II, APACHE III, and Simplified Acute Physiology Score II to the multivariable model using area under the receiver operating characteristic curve. The model was validated in an independent cohort of 886 patients with acute lung injury. Modified acute physiology score, age, comorbidities, arterial pH, minute ventilation, PaCO2, PaO2/FiO2 ratio, intensive care unit admission source, and intensive care unit days before onset of acute lung injury were independently predictive of in-hospital death (p < .05). The area under the receiver operating characteristic curve for the multivariable model was superior to that of APACHE III (.81 vs. .77, p < .001) but was no different after external validation (.71 vs. .70, p = .64).

CONCLUSIONS

The predictors of mortality in patients with acute lung injury are similar to those predictive of mortality in the general intensive care unit population, indicating disease heterogeneity within this cohort. Accordingly, APACHE III predicts mortality in acute lung injury as well as a model using variables selected specifically for patients with acute lung injury.

Biomarkers of inflammation, coagulation and fibrinolysis predict mortality in acute lung injury

Background

Acute lung injury (ALI) is a major cause of acute respiratory failure with high mortality despite lung-protective ventilation. Prior work has shown disordered inflammation and coagulation in ALI, with strong correlations between biomarker abnormalities and worse clinical outcomes. We measured plasma markers of inflammation, coagulation and fibrinolysis simultaneously to assess whether these markers remain predictive in the era of lung-protective ventilation.

Methods

Plasma samples and ventilator data were prospectively collected from 50 patients with early ALI. Plasma biomarkers of inflammation (IL-6, IL-8, intercellular adhesion molecule 1), of coagulation (thrombomodulin, protein C) and of fibrinolysis (plasminogen activator inhibitor 1) were measured by ELISA. Biomarker levels were compared between survivors (n = 29) and non-survivors (n = 21) using Mann–Whitney analysis.

Results

The tidal volume for the study group was 6.6 ± 1.1 ml/kg predicted body weight and the plateau pressure was 25 ± 7 cmH₂O (mean ± standard deviation), consistent with lung-protective ventilation. All markers except IL-6 were significantly different between survivors and nonsurvivors. Nonsurvivors had more abnormal values. Three biomarkers – IL-8, intercellular adhesion molecule 1 and protein C – remained significantly different by multivariate analysis that included age, gender, Simplified Acute Physiology Score II and all biomarkers that were significant on bivariate analysis. Higher levels of IL-8 and intercellular adhesion molecule 1 were independently predictive of worse outcomes (odds ratio = 2.0 and 5.8, respectively; P = 0.04 for both). Lower levels of protein C were independently associated with an increased risk of death (odds ratio = 0.5), a result that nearly reached statistical significance (P = 0.06).

Conclusion

Despite lung-protective ventilation, abnormalities in plasma levels of markers of inflammation, coagulation and fibrinolysis predict mortality in ALI patients, indicating more severe activation of these biologic pathways in nonsurvivors.

Prediction of death and prolonged mechanical ventilation in acute lung injury

Introduction

Prediction of death and prolonged mechanical ventilation is important in terms of projecting resource utilization and in establishing protocols for clinical studies of acute lung injury (ALI). We aimed to identify risk factors for a combined end-point of death and/or prolonged ventilator dependence and developed an ALI-specific prediction model.

Methods

In this retrospective analysis of three multicenter clinical studies, we identified predictors of death or ventilator dependence from variables prospectively recorded during the first three days of mechanical ventilation. After the prediction model was derived in an international cohort of patients with ALI, it was validated in two independent samples of patients enrolled in a clinical trial involving 17 academic centers and a North American population-based cohort.

Results

A combined end-point of death and/or ventilator dependence at 14 days or later occurred in 68% of patients in the international cohort, 60% of patients in the clinical trial, and 59% of patients in the population-based cohort. In the derivation cohort, a model based on age, oxygenation index on day 3, and cardiovascular failure on day 3 predicted death and/or ventilator dependence. The prediction model performed better in the clinical trial validation cohort (area under the receiver operating curve 0.81, 95% confidence interval 0.77 to 0.84) than in the population-based validation cohort (0.71, 95% confidence interval 0.65 to 0.76).

Conclusion

A model based on age and cardiopulmonary function three days after the intubation is able to predict, moderately well, a combined end-point of death and/or prolonged mechanical ventilation in patients with ALI.

Mortality rates for patients with acute lung injury/ARDS have decreased over time

BACKGROUND

Over the last decade, several studies have suggested that survival rates for patients with acute lung injury (ALI) or ARDS may have improved. We performed a systematic analysis of the ALI/ARDS literature to document possible trends in mortality between 1994 and 2006.

METHODS

We used the Medline database to select studies with the key words "acute lung injury," "ARDS," "acute respiratory failure," and "mechanical ventilation." All studies that reported mortality rates for patients with ALI/ARDS defined according to the criteria of the American European Consensus Conference were selected. We excluded studies with < 30 patients and studies limited to specific subgroups of ARDS patients such as sepsis, trauma, burns, or transfusion-related ARDS.

RESULTS

Seventy-two studies were included in the analysis. There was a wide variation in mortality rates among the studies (15 to 72%). The overall pooled mortality rate for all studies was 43% (95% confidence interval, 40 to 46%). Metaregression analysis suggested a significant decrease in overall mortality rates of approximately 1.1%/yr over the period analyzed (1994 to 2006). The mortality reduction was also observed for hospital but not for ICU or 28-day mortality rates.

CONCLUSIONS

In this literature review, the data are consistent with a reduction in mortality rates in general populations of patients with ALI/ARDS over the last 10 years.

Pediatric acute lung injury

Among ventilated children, the incidence of acute lung injury (ALI) was 9%; of that latter group 80% developed the acute respiratory distress syndrome (ARDS). The population-based prevalence of pediatric ARDS was 5.5 cases/100.000 inhabitants. Underlying diseases in children were septic shock (34%), respiratory syncytial virus infections (16%), bacterial pneumonia (15%), near-drowning 9%, and others. Mortality ranged from 18% to 27% for ALI (including ALI-non ARDS and ARDS) and from 29% to 50% for ARDS. Mortality was only 3%-11% in children with ALI-non ARDS. As risk factors, oxygenation indices and multi-organ failure have been identified. New insights into the pathophysiology (for example the interplay between intraalveolar coagulation/fibrinolysis and inflammation and the genetic polymorphism for the angiotensin-converting enzyme) offer new therapeutic options. Lung protective mechanical ventilation with optimal lung recruitment is the mainstay of supportive therapy. New therapeutic modalities refer to corticosteroid and surfactant treatment. Well-designed follow up studies are needed.

Trauma-associated lung injury differs clinically and biologically from acute lung injury due to other clinical disorders

OBJECTIVE

Patients with trauma-associated acute lung injury have better outcomes than patients with other clinical risks for lung injury, but the mechanisms behind these improved outcomes are unclear. We sought to compare the clinical and biological features of patients with trauma-associated lung injury with those of patients with other risks for lung injury and to determine whether the improved outcomes of trauma patients reflect their baseline health status or less severe lung injury, or both.

DESIGN, SETTING, AND PATIENTS

Analysis of clinical and biological data from 1,451 patients enrolled in two large randomized, controlled trials of ventilator management in acute lung injury.

MEASUREMENTS AND MAIN RESULTS

Compared with patients with other clinical risks for lung injury, trauma patients were younger and generally less acutely and chronically ill. Even after adjusting for these baseline differences, trauma patients had significantly lower plasma levels of intercellular adhesion molecule-1, von Willebrand factor antigen, surfactant protein-D, and soluble tumor necrosis factor receptor-1, which are biomarkers of lung epithelial and endothelial injury previously found to be prognostic in acute lung injury. In contrast, markers of acute inflammation, except for interleukin-6, and disordered coagulation were similar in trauma and nontrauma patients. Trauma-associated lung injury patients had a significantly lower odds of death at 90 days, even after adjusting for baseline clinical factors including age, gender, ethnicity, comorbidities, and severity of illness (odds ratio, 0.44; 95% confidence interval, 0.24-0.82; p = .01).

CONCLUSIONS

Patients with trauma-associated lung injury are less acutely and chronically ill than other lung injury patients; however, these baseline clinical differences do not adequately explain their improved outcomes. Instead, the better outcomes of the trauma population may be explained, in part, by less severe lung epithelial and endothelial injury.

Vitamin E inhibits endotoxin-mediated transport of phosphatases to lipid rafts

The production and release of inflammatory mediators is regulated by the coordinated activity of kinases and phosphatases. These proteins are known to regulate one another through an unknown mechanism. Previously, we have demonstrated that autocrine release of oxidants regulates macrophage activation in a similar fashion. The purpose of this study is to determine if attenuated oxidant activity by antioxidant exposure can regulate endotoxin-mediated kinase and phosphatase activity. Human promonocytic THP-1 cells were stimulated with lipopolysaccharide. Selected cells were pretreated with alpha-tocopherol succinate, LY294002, or an AKT inhibitor (1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate). Lipid raft and cellular protein were analyzed for lipid raft toll-like receptor 4 (TLR4) receptor formation and mitogen-activated protein kinase (MAPK) activation. Harvested supernatants were analyzed for tumor necrosis factor (TNF)-alpha production. Lipopolysaccharide stimulation led to the lipid raft mobilization of TLR4 and heat shock protein 70. This was followed by lipid raft mobilization of SH related complex homology 2 domain-containing inositol-5-phosphate (SHIP), activation of the MAPK, and production of TNF-alpha. Pretreatment with alpha-tocopherol succinate did not affect mobilization of TLR4 or heat shock protein 70, but did result in attenuated mobilization of SHIP, activation of the MAPK, and production of TNF-alpha. In addition, alpha-tocopherol succinate was associated with increased activation of the counter-regulatory kinase protein kinase B. Pretreatment with LY294002 or 1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate reversed the effects of alpha-tocopherol succinate. Thus, it seems that endotoxin-mediated activation requires the coordinated activity of kinases and phosphatases. Antioxidant exposure in the form of vitamin E seems to attenuate endotoxin-mediated SHIP activation resulting in increased AKT activity, and attenuated MAPK activation and TNF-alpha production.

Megakaryocytes and platelet homeostasis in diffuse alveolar damage

Platelet homeostasis reflects a balance between the production of platelets via cytoplasmic fragmentation of megakaryocytes in the pulmonary microvasculature and their catabolism. Increased numbers of megakaryocytes are entrapped in the injured lung, potentially affecting circulating platelet counts. We enumerated pulmonary megakaryocytes and blood platelets in patients with diffuse alveolar damage (DAD) in order to determine their association with clinical outcome. Lung biopsies were examined from 21 patients with histologically documented DAD in its proliferative phase and secondary to a variety of causes. Blood platelet counts were determined within 24 h prior to lung biopsy, and CD61+ pulmonary megakaryocytes were localized in in situ immunohistochemical stains. The overall mortality in this series was 67%. Patients with DAD attributable to drug toxicity (DAD-D) had higher mortality (80%) and greater number of intrapulmonary CD61+ megakaryocytes than those with DAD due to other causes (23+/-7, 10+/-2, p<0.05). Patients with blood platelet counts =350 th/cm(3) showed increased survival (p<0.05). The findings support the hypothesis that abnormal platelet homeostasis is associated with increased mortality in acute lung injury and indicate that thrombocytosis in ARDS is associated with improved survival. The mechanisms of altered platelet homeostasis in DAD merit further investigation.

Bronchoalveolar lavage fluid from patients with acute lung injury/acute respiratory distress syndrome induces myofibroblast differentiation

OBJECTIVE

Myofibroblasts express alpha-smooth muscle actin (alphaSMA), are important in tissue repair, and are present in the early phase of acute lung injury/acute respiratory distress syndrome (ALI/ARDS). We wished to determine whether bronchoalveolar lavage fluid (BALF) from ALI/ARDS patients can induce myofibroblast differentiation and if this induction is associated with outcome.

DESIGN

A single-center cohort study enrolling patients between 2002 and 2005.

SETTING

Medical intensive care unit of a tertiary care medical center.

PATIENTS

Adult patients meeting the American-European Consensus Conference definition of ALI/ARDS.

INTERVENTIONS

BALF was collected from ALI/ARDS patients within 48 hrs of intubation and incubated with normal human lung fibroblasts in vitro, and alphaSMA expression was assessed by reverse transcription polymerase chain reaction. BALF was also collected and tested from negative control patients. ALI/ARDS patients were followed for 28 days or death.

MEASUREMENTS AND MAIN RESULTS

Thirty-one lung injury and 11 negative control patients were enrolled from 2002 to 2005. ALI/ ARDS BALF demonstrated potent alphaSMA induction with a mean value 92% greater than negative controls (34.5% +/- 7.6% vs. 18% +/- 2.4% of maximal transforming growth factor [TGF]-beta1 [5 ng/mL], p < .02). The specific TGF-beta1 receptor inhibitor SB431542 reduced ALI/ARDS BALF-stimulated alphaSMA induction by 52% (p < .005). There was no correlation between ALI/ARDS BALF-induced alphaSMA and procollagen 3 induction (r = -.08, p = .66). The odds ratio for survival was 6.75 (1.15-39.80) times higher for ALI/ARDS patients with alphaSMA induction between 15% and 75% of maximal TGF-beta1 induction (5 ng/mL) than outside this range.

CONCLUSIONS

ALI/ARDS BALF-induced myofibroblast differentiation is partially attributable to TGF-beta1. Procollagen 3 and alphaSMA are regulated by distinct mechanisms in ALI/ARDS and there may be an optimal level of myofibroblast induction that is associated with better outcome.

Surfactant protein A and surfactant protein D variation in pulmonary disease

Surfactant proteins A (SP-A) and D (SP-D) have been implicated in pulmonary innate immunity. The proteins are host defense lectins, belonging to the collectin family which also includes mannan-binding lectin (MBL). SP-A and SP-D are pattern-recognition molecules with the lectin domains binding preferentially to sugars on a broad spectrum of pathogen surfaces and thereby facilitating immune functions including viral neutralization, clearance of bacteria, fungi and apoptotic and necrotic cells, modulation of allergic reactions, and resolution of inflammation. SP-A and SP-D can interact with receptor molecules present on immune cells leading to enhanced microbial clearance and modulation of inflammation. SP-A and SP-D also modulate the functions of cells of the adaptive immune system including dendritic cells and T cells. Studies on SP-A and SP-D polymorphisms and protein levels in bronchoalveolar lavage and blood have indicated associations with a multitude of pulmonary inflammatory diseases. In addition, accumulating evidence in mouse models of infection and inflammation indicates that recombinant forms of the surfactant proteins are biologically active in vivo and may have therapeutic potential in controlling pulmonary inflammatory disease. The presence of the surfactant collectins, especially SP-D, in non-pulmonary tissues, such as the gastrointestinal tract and genital organs, suggest additional actions located to other mucosal surfaces. The aim of this review is to summarize studies on genetic polymorphisms, structural variants, and serum levels of human SP-A and SP-D and their associations with human pulmonary disease.

Keratinocyte Growth Factor Gene Transduction Ameliorates Acute Lung Injury And Mortality in Mice

At present there is no known effective pharmacological therapy for acute lung injury (ALI). Because keratinocyte growth factor (KGF) promotes epithelial cell growth, intratracheal administration of KGF has the possibility of restoring lung tissue integrity in injured lungs and improving patient outcomes. However, treatment using recombinant KGF protein is limited by its short effective duration. Thus, we investigated the effectiveness of intratracheal KGF gene transduction using adenoviral vector in ALI. We constructed an adenoviral vector expressing mouse KGF (mKGF), and 1.0 x 10(9 ) plaque-forming units of mKGF cDNA-expressing (Ad-KGF) and control (Ad-1w1) adenoviral vector was intratracheally instilled, using a MicroSprayer, into anesthetized BALB/c mice. Three days later, the mice were exposed to >90% oxygen for 72 hr, and the effect of KGF on hyperoxia-induced lung injury was examined. In the Ad-KGF group, KGF was strongly expressed in the airway epithelial cells, while peribronchiolar and alveolar inflammation caused by adenoviral vector instillation was minimal. The KGF overexpression not only induced proliferation of surfactant protein C-positive cuboidal cells, especially in the terminal bronchiolar and alveolar walls, but also prevented lung injury including intraalveolar exudation/hemorrhage, albumin permeability increase, and pulmonary edema. The arterial oxygen tension and the survival rate were significantly higher in the KGF-transfected group. These findings suggest that KGF gene transduction into the airway epithelium is a promising potential treatment for ALI.

Systematic review of determinants of mortality in high frequency oscillatory ventilation in acute respiratory distress syndrome

INTRODUCTION

Mechanical ventilation has been shown to cause lung injury and to have a significant impact on mortality in acute respiratory distress syndrome. Theoretically, high frequency oscillatory ventilation seems an ideal lung protective ventilation mode. This review evaluates determinants of mortality during use of high frequency oscillatory ventilation.

METHODS

PubMed was searched for literature reporting randomized trials and cohort studies of high frequency ventilation in adult patients with acute respiratory distress syndrome. Data on mortality and determinants were extracted for patients treated with high frequency oscillatory ventilation. Linear regression analyses were conducted to produce graphical representations of adjusted effects of determinants of mortality.

RESULTS

Cohorts of patients treated with high frequency oscillatory ventilation from two randomized trials and seven observational studies were included. Data from cohorts comparing survivors with non-survivors showed differences in age (42.3 versus 51.2 years), prior time on conventional mechanical ventilation (4.0 versus 6.2 days), APACHE II score (22.4 versus 26.1), pH (7.33 versus 7.26) and oxygenation index (26 versus 34). Each extra day on conventional ventilation was associated with a 20% higher mortality adjusted for age and APACHE II score (relative risk (RR) 1.20, 95% confidence interval (CI) 1.15-1.25). However, this association was confounded by differences in pH (pH adjusted RR 1.03, 95% CI 0.73-1.46). Oxygenation index seemed to have an independent effect on mortality (RR 1.10, 95% CI 0.95-1.28).

CONCLUSION

Prolonged ventilation on conventional mechanical ventilation prior to high frequency oscillatory ventilation was not related to mortality. Oxygenation index was a determinant of mortality independent of other disease severity markers.

Health care disparities in critical illness

Disparities in critical illness are evident in a variety of racial and ethnic groups. Most data available in the literature reflect variations in the incidence, presentation, diagnosis,treatment, and outcomes between African Americans and whites. Most research in critical care concerning disparities relates to cardiovascular illnesses. Significantly less in-formation is available regarding disparities in common ICU diagnoses. Data are significantly lacking delineating the reasons for disparities in the critically ill. Further re-search is required to elucidate the root causes for racial or ethnic differences, provide adequate education for health care providers, and develop and implement evidence-based interventions targeted for specific patient groups.

Severe respiratory failure: advanced treatment options

BACKGROUND

Severe respiratory failure (including acute lung injury and acute respiratory distress syndrome) continues to be associated with significant mortality and morbidity in patients of all ages.

OBJECTIVE

To review the laboratory and clinical data in support of and future directions for the advanced treatment of severe respiratory failure.

DATA SOURCES

MEDLINE/PubMed search of all relevant primary and review articles.

DATA SYNTHESIS

Our understanding of lung pathophysiology and the role of ventilator-induced lung injury through basic science investigation has led to advances in lung protective strategies for the mechanical ventilation support of patients with severe respiratory failure. Specific modalities reviewed include low-tidal volume ventilation, permissive hypercapnia, the open lung approach, recruitment maneuvers, airway pressure release ventilation, high-frequency oscillatory ventilation, prone positioning, and extracorporeal life support. The pharmacologic strategies (including corticosteroids, surfactant, and nitric oxide) investigated for the treatment of severe respiratory failure are also reviewed.

CONCLUSION

In patients with severe respiratory failure, an incremental approach to the management of severe hypoxemia requires implementation of the strategies reviewed, with knowledge of the evidence base to support these strategies.

Urinary desmosine as a biomarker in acute lung injury

Acute lung injury (ALI) is a complex disorder associated with an acute inflammatory response thought to contribute to tissue injury. Desmosine, a cross-linking amino acid present in elastin, is released during matrix degradation and cleared by the kidney. Results from animal models and human disease studies have suggested that ALI is associated with the release of desmosine, resulting in increased urinary desmosine. A radioimmunoassay was used to monitor urinary desmosine levels over 10 days in ten patients with ALI. The concentration of desmosine was measured with and without acid hydrolysis. Baseline urinary desmosine was increased in two of ten patients. The concentration of desmosine at baseline did not appear to be related to age, gender, neutrophil elastase (NE)/alpha(1)-antiprotease complex concentration or P(a)O(2)/F(i)O(2) ratio. No meaningful changes in desmosine levels were noted after removal from mechanical ventilation. Baseline desmosine concentrations did not appear to correlate with the risk of death. The limited sensitivity, predictive correlations and dynamic modulation would suggest that urine desmosine has a limited role as a biomarker for ALI. Hydrolysis of urine samples appears necessary for optimal measurement of urine desmosine.

Designing clinical trials in acute lung injury/acute respiratory distress syndrome

PURPOSE OF REVIEW

To review the implications of recent literature for clinical trial design in acute lung injury/acute respiratory distress syndrome (ARDS).

RECENT FINDINGS

Refinement of acute lung injury/acute respiratory distress syndrome diagnostic criteria and study enrollment criteria, greater efforts to define usual care appropriately, and balancing of efficacy and effectiveness design principles will be key components of future trials.

SUMMARY

Clinical trial design in acute lung injury/acute respiratory distress syndrome faces many challenges. Although we have learned much from past trials, persistent design dilemmas must be addressed for future trials.

Postoperative acute respiratory distress syndrome development in the thoracic surgery patient

Acute respiratory distress syndrome (ARDS) in the thoracic surgery patient is a dreaded complication that occurs in 4% to 5% of pneumonectomies. This peculiar syndrome is indistinct from other forms of ARDS yet is associated with an exceedingly higher mortality rate. Current management parallels ARDS treatment of other etiologies.

The pulmonary and hepatic immune microenvironment and its contribution to the early systemic inflammation following blunt chest trauma

OBJECTIVE

Blunt chest trauma is accompanied by an early increase in plasma cytokine concentrations. However, the local sources of these mediators are poorly defined. We investigated the impact of blunt chest trauma on the inflammatory mediator milieu in different compartments (lung tissue, bronchoalveolar lavage, liver tissue, Kupffer cells, plasma) along with the time course of trauma-induced pulmonary endothelial barrier dysfunction to elucidate potential relationships. In addition, the correlation between intratracheally instilled interleukin-6 and its systemic release were studied.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Basic science laboratory of a university affiliated level 1 trauma center.

SUBJECTS

Male C3H/HeN mice, 8-9 wks old, n = 141.

INTERVENTIONS

Blunt chest trauma induced by a focused blast wave, intravenous injection of Evans blue, and intratracheal instillation of recombinant human interleukin-6.

MEASUREMENTS AND MAIN RESULTS

Two hours after blunt chest trauma, plasma interleukin-6 was markedly increased. Simultaneously, interleukin-6, tumor necrosis factor-alpha, macrophage inflammatory protein-2, monocyte chemotactic polypeptide-1 and neutrophil/monocyte accumulation in bronchoalveolar lavage and interleukin-6, monocyte chemotactic polypeptide-1, and myeloperoxidase activity in lung tissue were significantly increased. This was accompanied by a coinciding elevation in the Evans blue lung-plasma ratio. Recombinant human interleukin-6, instilled intratracheally before blunt chest trauma, was detected in a dose-dependent manner in the plasma of the mice. Additionally, Kupffer cell interleukin-6, tumor necrosis factor-alpha, and interleukin-10 production was significantly augmented as early as 30 mins after the insult.

CONCLUSIONS

These results indicate that early increased cytokine concentrations in the lung, particularly interleukin-6, are important mediator sources as their local peak coincides with the systemic inflammatory response and is accompanied by a simultaneous impaired function of the pulmonary endothelial barrier. A direct relationship between their local and systemic concentrations can be established. Furthermore, this is the first study to show that Kupffer cells are activated early after blunt chest trauma.