The acute respiratory distress syndrome (ARDS), a process of nonhydrostatic pulmonary edema and hypoxemia associated with a variety of etiologies, carries a high morbidity, mortality (10 to 90%), and financial cost. The reported annual incidence in the United States is 150,000 cases, but this figure has been challenged, and it may be different in Europe. Part of the reason for these uncertainties are the heterogeneity of diseases underlying ARDS and the lack of uniform definitions for ARDS. Thus, those who wish to know the true incidence and outcome of this clinical syndrome are stymied. The American-European Consensus Committee on ARDS was formed to focus on these issues and on the pathophysiologic mechanisms of the process. It was felt that international coordination between North America and Europe in clinical studies of ARDS was becoming increasingly important in order to address the recent plethora of potential therapeutic agents for the prevention and treatment of ARDS.

Acute lung injury has a substantial impact on public health, with an incidence in the United States that is considerably higher than previous reports have suggested.

To further understanding of the epidemiology of acute respiratory distress syndrome (ARDS), we prospectively identified 695 patients admitted to our intensive care units from 1983 through 1985 meeting criteria for seven clinical risks, and followed them for development of ARDS and eventual outcome. ARDS occurred in 179 of the 695 patients (26%). The highest incidence of ARDS occurred in patients with sepsis syndrome (75 of 176; 43%) and those with multiple emergency transfusions (> or = 15 units in 24 h) (46 of 115; 40%). Of patients with multiple trauma, 69 of 271 (25%) developed ARDS. If any two clinical risks for trauma were present, the incidence of ARDS was 23 of 57, or 40%. During the study period, we identified 48 patients with ARDS who did not have one of the defined clinical risks, yielding a sensitivity of 79% (179 of 227). Secondary factors associated with increased risk for ARDS in clinical risk subgroups include an elevated Acute Physiologic and Chronic Health Evaluation II (APACHE II) score in patients with sepsis and increased APACHE II and Injury Severity Scores (ISS) in trauma victims. Mortality was threefold higher when ARDS was present (62%) than among patients with clinical risks who did not develop ARDS (19%; p < 0.05). The difference in mortality if ARDS developed was particularly striking in patients with trauma (56% versus 13%), but less in those with sepsis (69% versus 49%). The mortality data should be interpreted with caution, since the fatality rate in ARDS patients appears to have decreased in our institution from the time that these data were collected.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute respiratory distress syndrome (ARDS) involves an intense inflammatory response in the lungs, with accumulation of both pro- and antiinflammatory cytokines in bronchoalveolar lavage fluid (BALF). Our goal was to determine how the balance between pro- and antiinflammatory mediators in the lungs changes before and after the onset of ARDS. We identified 23 patients at risk for ARDS and 46 with established ARDS and performed serial bronchoalveolar lavage (BAL). We used immunoassays to measure tumor necrosis factor alpha (TNF-alpha) and soluble TNF-alpha receptors I and II; interleukin 1 beta (IL-1 beta), IL-1 beta receptor antagonist, and soluble IL-1 receptor II; IL-6 and soluble IL-6 receptor; and IL-10. We used sensitive bioassays to measure net TNF-alpha, IL-1 beta, and IL-6 activity. Although individual cytokines increased before and after onset of ARDS, greater increases occurred in cognate receptors and/or antagonists, so that molar ratios of agonists/antagonists declined dramatically at the onset of ARDS. The molar ratios remained low for 7 d or longer, limiting the activity of soluble IL-1 beta and TNF-alpha in the lungs at the onset of ARDS. This significant antiinflammatory response early in ARDS may provide a key mechanism for limiting the net inflammatory response in the lungs.

The acute respiratory distress syndrome (ARDS), a process of non-hydrostatic pulmonary edema and hypoxemia associated with a variety of etiologies carries a high morbidity, mortality (10-90%) and financial cost. The reported annual incidence in the United States is 150,000 cases, but this figure has been challenged and may be different in Europe. Part of the reason for these uncertainties is the heterogeneity of diseases underlying ARDS and the lack of uniform definitions for ARDS. Thus, those whose wish to know the true incidence and outcome on this clinical syndrome are stymied. The European American Consensus Committee on ARDS was formed to focus on these issues and on the pathophysiologic mechanisms of the process. It was felt that international coordination between North America and Europe in clinical studies of ARDS was becoming increasingly important in order to address the recent plethora of potential therapeutic agents for the prevention and treatment of ARDS.

Mmol/ml, respectively) compared to N (7.99±0.60 Amol/ml).Phosphatidylcholine was decreased in A (62.64±2.20% PL) compared to N (76.27±2.05% PL). Phosphatidylglycerol was 11.58±1.21% PL in N and was decreased to 6.48±1.43% PL in A. SP-A was 123.64±20.66 zg/ml in N and was decreased to 49.28±21.68 jg/ml in AR and to 29.88±8.49 jg/ml in A. SP-B was 1.28±0.33 jig/ml in N and was decreased to 0.57±0.24 ,ug/ml in A. ST,,. was increased in AR (15.1±2.53 dyn/cm) and A (29.04±2.05 dyn/cm) compared to N (7.44±1.61 dyn/cm).

These results do not support the routine use of methylprednisolone for persistent ARDS despite the improvement in cardiopulmonary physiology. In addition, starting methylprednisolone therapy more than two weeks after the onset of ARDS may increase the risk of death. (ClinicalTrials.gov number, NCT00295269.).

To determine the relationship between airspace cytokines and cellular inflammatory responses in patients with the acute respiratory distress syndrome (ARDS), we performed bronchoalveolar lavage (BAL) in 82 prospectively identified, mechanically ventilated patients on Days 3, 7, 14, and/or 21 after the onset of ARDS. We studied the relationships between bronchoalveolar lavage fluid (BALF) cell populations and the concentrations of two potent neutrophil (PMN) chemoattractants, interleukin-8 (IL-8) and epithelial cell-derived neutrophil activator-78 (ENA-78); two potent monocyte chemoattractants, monocyte chemotactic peptide-1 (MCP-1) and macrophage inflammatory peptide-1 alpha (MIP-1 alpha); and the early response cytokine interleukin-1 beta (IL-1 beta) and its naturally occurring antagonist, IL-1 receptor antagonist protein (IRAP). We found that all of these cytokines were significantly increased regardless of the duration of ARDS. IL-8 and ENA-78 were the cytokines most strongly and consistently correlated with PMN concentrations in the lung fluids of patients with ARDS, and the correlations were independent of the other cytokines or coexisting lung infection. None of the cytokines tested correlated with macrophage concentrations. MCP-1 was directly correlated with lung injury score on Days 7, 14, and 21. Although neither IL-8 nor ENA-78 was associated with outcome, levels of IL-1 beta measured on Day 7 were associated with an increased risk of death (odds ratio [OR] = 2.8; 95% confidence interval [CI] = 1.1 to 7.4). These data demonstrate potential molecular mechanisms of the persistent inflammatory process in the lungs of patients with ARDS.