Cytokine balance in the lungs of patients with acute respiratory distress syndrome

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.

Anti-interleukin 8 autoantibody: interleukin 8 complexes in the acute respiratory distress syndrome. Relationship between the complexes and clinical disease activity

Increased levels of interleukin 8 (IL-8) are found in bronchoalveolar lavage (BAL) fluids from patients with the acute respiratory distress syndrome (ARDS). However, IL-8 is not an efficient predictor of the course of ARDS. Our prior studies demonstrated that IL-8 present in lung fluids from patients with ARDS is associated with anti-IL-8 autoantibodies (anti-IL-8:IL-8 complexes). These data led us to hypothesize that the complexes might better predict the development of acute lung injury. Accordingly, we measured concentrations of free and complexed IL-8 in BAL fluids from 19 patients at risk and 45 with established ARDS on Days 1, 3, 7, 14, and 21 after the onset of ARDS. The concentrations of anti-IL-8:IL-8 complexes in patients with ARDS on Day 1 were significantly higher than in patients at risk (p < 0.05). There was a significant association between anti-IL-8:IL-8 complex concentrations and the onset of ARDS (p = 0.03). Similarly, anti-IL-8:IL-8 complex concentrations were significantly higher in patients on Day 1 of ARDS who later died (p < 0.05), and the association between high anti-IL-8: IL-8 complex concentrations and the probability of dying was significant (p = 0.03). The presence of anti-IL-8:IL-8 complexes in BAL fluids of patients with ARDS is an important prognostic indicator for the development and outcome of ARDS.

Nitric oxide and nitrotyrosine in the lungs of patients with acute respiratory distress syndrome

Nitric oxide (NO) end-products (nitrate and nitrite) are present in bronchoalveolar lavage (BAL) fluid of patients with inflammatory lung diseases. Reactive oxygen-nitrogen intermediates damage macromolecules by oxidation or nitration of critical residues in proteins. The goal of this study was to measure NO end-products (nitrate+ nitrite), in BAL fluid before and after the onset of acute respiratory distress syndrome (ARDS) and to determine if these products are associated with expression of inducible nitric oxide synthase enzyme (iNOS) in BAL cells and nitration of BAL proteins. We performed bronchoalveolar lavage (BAL) in patients at risk for ARDS (n = 19), or with ARDS (n = 41) on Days 1, 3, 7, 14, and 21 after onset, and measured total nitrite (after reducing nitrate to nitrite) and protein-associated nitrotyrosine concentration in each BAL fluid sample. Cytospin preparations of BAL cells were analyzed by immunocytochemistry for iNOS and nitrotyrosine. Nitrate+nitrite were detected in BAL fluid from patients at risk for ARDS, and for as long as 21 d after the onset of ARDS. Nitrotyrosine was detectable in all BAL fluid samples for as long as 14 d after the onset of ARDS (range, 38.8 to 278.5 pmol/mg of protein), but not in BAL of normal volunteers. Alveolar macrophages of patients with ARDS were positive for iNOS and nitrotyrosine, and remained positive for as long as 14 d after onset of ARDS. The BAL nitrate+nitrite did not predict the onset of ARDS, but the concentration was significantly higher on Days 3 and 7 of ARDS in patients who died. Thus, NO end products accumulate in the lungs before and after onset of ARDS; iNOS is expressed at high levels in AM during ARDS; and nitration of intracellular and extracellular proteins occurs in the lungs in ARDS. The data support the concept that NO-dependent pathways are important in the lungs of patients before and after the onset of ARDS.

Acute lung injury and acute respiratory distress syndrome. The clinical syndrome

Acute lung injury (ALI) is a syndrome of severe acute respiratory failure defined by a constellation of clinical criteria. The exact incidence of ALI is not known, but it generally occurs in the setting of acute severe illness. The course of ALI after onset is quite variable, but outcome is associated with risk factor, age, and comorbidity. Survival from this syndrome has improved over time. Survivors often are impaired after hospital discharge but tend to improve over time; however, ALI does confer a significant additional burden on survivors with regard to pulmonary function and health-related quality of life.

Diabetic patients have a decreased incidence of acute respiratory distress syndrome

OBJECTIVE

Our ability to predict which critically ill patients will develop acute respiratory distress syndrome (ARDS) is imprecise. Based on the effects of diabetes mellitus on the inflammatory cascade, we hypothesized that a history of diabetes might alter the incidence of ARDS.

DESIGN

A prospective multicenter study.

SETTING

Intensive care units at four university medical centers.

PATIENTS

One hundred thirteen consecutive patients with septic shock.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

All patients were prospectively followed during their intensive care course for the development of ARDS. A history of diabetes was identified in 28% (32/113) of the patients. In this study, nondiabetics were more likely to develop septic shock from a pulmonary source (48%, 39/81) compared with diabetics (25%, 8/32) (p = .02). Forty-one percent (46/113) of the patients with septic shock developed ARDS. Forty-seven percent of the nondiabetic patients developed ARDS compared with only 25% of those with diabetes (p = .03, relative risk = 0.53, 95% confidence interval = 0.28-0.98). In a multivariate logistic regression analysis, when we adjusted for several variables including source of infection, the effect of diabetes on the incidence of ARDS remained significant (p = .03, odds ratio = 0.33, 95% confidence interval = 0.12-0.90).

CONCLUSIONS

In patients with septic shock, a history of diabetes is associated with a lower risk of developing ARDS compared with nondiabetics.

Modulation of neutrophil apoptosis by granulocyte colony-stimulating factor and granulocyte/macrophage colony-stimulating factor during the course of acute respiratory distress syndrome

OBJECTIVE

To determine whether bronchoalveolar lavage fluid (BALF) from patients either at risk for the acute respiratory distress syndrome (ARDS) or with sustained ARDS modulates neutrophil apoptosis; to measure the BALF concentrations of the apoptosis inhibitors granulocyte colony-stimulating factor (G-CSF) and granulocyte/macrophage colony-stimulating factor (GM-CSF) before and after the onset of ARDS; and to determine whether the BALF concentrations of G-CSF and/or GM-CSF are associated with clinical outcome.

DESIGN

Prospective cohort study.

SETTING

Tertiary university hospital.

PATIENTS

Twenty patients at risk for ARDS and 45 patients with established ARDS.

INTERVENTIONS

Patients at risk for ARDS underwent bronchoalveolar lavage within 24 hrs of being identified, then again 72 hrs later. Patients with ARDS underwent bronchoalveolar lavage within 24 hrs of meeting ARDS criteria, then again on days 3, 7, and 14 of the disease.

MEASUREMENTS AND MAIN RESULTS

Normal peripheral blood neutrophil were incubated overnight in BALF from normal volunteers, from patients at risk for ARDS, or from patients with ARDS. neutrophil apoptosis was determined by flow cytometric analysis of annexin V binding. G-CSF and GM-CSF were measured in BALF by immunoassays. Compared with normal BALF, BALF from patients on days 1 and 3 of ARDS inhibited neutrophil apoptosis, but BALF from patients at later stages of ARDS, or from patients at risk for ARDS, did not. The BALF concentrations of both G-CSF and GM-CSF were elevated early in ARDS and decreased toward later stages. Patients who lived had significantly higher concentrations of GM-CSF in the BALF than those who died.

CONCLUSIONS

We conclude that the antiapoptotic effect of ARDS BALF on normal neutrophil is highest during early ARDS, and decreases during late ARDS. G-CSF and GM-CSF are present in BALF from patients with ARDS, and their concentrations parallel the antiapoptotic effect of ARDS BALF. These data support the concept that the life-span of neutrophil in the air spaces is modulated during acute inflammation. GM-CSF in the air spaces is associated with improved survival in patients with ARDS.

The effect of acute respiratory distress syndrome on long-term survival

Despite a great deal of information about the risk factors, prognostic variables, and hospital mortality in the acute respiratory distress syndrome (ARDS), very little is known about the long-term outcomes of patients with this syndrome. We conducted a prospective, matched, parallel cohort study with the goals of describing the survival of patients with ARDS after hospital discharge and comparing the long-term survival of patients with ARDS and that of a group of matched controls. The study involved 127 patients with ARDS associated with trauma or sepsis and 127 controls matched for risk factor (trauma or sepsis) and severity of illness who survived to hospital discharge. Time until death was used as the outcome measure. Survival was associated with age, risk factor for ARDS, and comorbidity. There was no difference in the long-term mortality rate for ARDS patients and that of matched controls (hazard ratio for ARDS: 1.00; 95% confidence interval: 0.47 to 2.09) after controlling for age, risk factor for ARDS, comorbidity, and severity of illness. We conclude that if sepsis or trauma patients survive to hospital discharge, ARDS does not increase their risk of subsequent death. Older patients, patients with sepsis, and patients with comorbidities, regardless of the presence of ARDS, have a higher risk of death after hospital discharge. For the purposes of clinical prognosis and cost-effectiveness analysis, the long-term survival of patients with ARDS can be modeled on the basis of age, underlying risk factor for ARDS, and comorbidity.

Serial changes in surfactant-associated proteins in lung and serum before and after onset of ARDS

The goal of this study was to determine the changes that occur in surfactant-associated proteins in bronchoalveolar lavage fluid (BAL) and serum of patients at risk for ARDS and during the course of ARDS. We found that the concentrations of SP-A and SP-B were low in the BAL of patients at risk for ARDS before the onset of clinically defined lung injury, whereas the concentration of SP-D was normal. In patients with established ARDS, BAL SP-A and SP-B concentrations were low during the entire 14-d observation period, but the median SP-D concentrations remained in the normal range. Immunoreactive SP-A and SP-D were not increased in the serum of patients at risk for ARDS, but both increased after the onset of ARDS to a maximum on Day 3 and remained elevated for as long as 14 d. The BAL SP-A concentrations were significantly lower in at-risk patients who developed ARDS, and no patient with a BAL SP-A concentration greater than 1.2 microg/ml developed ARDS. On Days 1 and 3 of ARDS, the BAL SP-D concentration was significantly lower in patients who died, and the BAL SP-D concentration was significantly related to the PI(O(2))/FI(O(2)) ratio. Thus, surfactant protein abnormalities occur before and after the onset of ARDS, and the responses of SP-A, SP-B, and SP-D differ in important ways. The BAL SP-A and SP-D measurements can be used to classify patients as high or low risk for progression to ARDS and/or death after the onset of ARDS. Strategies to increase these surfactant proteins in the lungs of patients with ARDS could be useful to modify the onset or the course of ARDS.

Soluble Fas ligand induces epithelial cell apoptosis in humans with acute lung injury (ARDS)

The goals of this study were to determine whether the Fas-dependent apoptosis pathway is active in the lungs of patients with the acute respiratory distress syndrome (ARDS), and whether this pathway can contribute to lung epithelial injury. We found that soluble Fas ligand (sFasL) is present in bronchoalveolar lavage (BAL) fluid of patients before and after the onset of ARDS. The BAL concentration of sFasL at the onset of ARDS was significantly higher in patients who died. BAL from patients with ARDS induced apoptosis of distal lung epithelial cells, which express Fas, and this effect was inhibited by blocking the Fas/FasL system using three different strategies: anti-FasL mAb, anti-Fas mAb, and a Fas-Ig fusion protein. In contrast, BAL from patients at risk for ARDS had no effect on distal lung epithelial cell apoptosis. These data indicate that sFasL is released in the airspaces of patients with acute lung injury and suggest that activation of the Fas/FasL system contributes to the severe epithelial damage that occurs in ARDS. These data provide the first evidence that FasL can be released as a biologically active, death-inducing mediator capable of inducing apoptosis of cells of the distal pulmonary epithelium during acute lung injury.

Effects of ibuprofen on the physiology and survival of hypothermic sepsis. Ibuprofen in Sepsis Study Group

OBJECTIVES

The objective was to compare the clinical and physiologic characteristics of febrile septic patients with hypothermic septic patients; and to examine plasma levels of cytokines tumor necrosis factor alpha (TNF-alpha and interleukin 6 (IL-6) and the lipid mediators thromboxane B2 (TxB2) and prostacyclin in hypothermic septic patients in comparison with febrile patients. Most importantly, we wanted to report the effect of ibuprofen treatment on vital signs, organ failure, and mortality in hypothermic sepsis.

SETTING

The study was performed in the intensive care units (ICUs) of seven clinical centers in the United States and Canada.

PATIENTS

Four hundred fifty-five patients admitted to the ICU who met defined criteria for severe sepsis and were suspected of having a serious infection.

INTERVENTION

Ibuprofen at a dose of 10 mg/kg (maximum 800 mg) was administered intravenously over 30 to 60 mins every 6 hrs for eight doses vs. placebo (glycine buffer vehicle).

MEASUREMENTS AND MAIN RESULTS

Forty-four (10%) septic patients met criteria for hypothermia and 409 were febrile. The mortality rate was significantly higher in hypothermic patients, 70% vs. 35% for febrile patients. At study entry, urinary metabolites of TxB2, prostacyclin, and serum levels of TNF-alpha and IL-6 were significantly elevated in hypothermic patients compared with febrile patients. In hypothermic patients treated with ibuprofen, there was a trend toward an increased number of days free of major organ system failures and a significant reduction in the 30-day mortality rate from 90% (18/20 placebo-treated patients) to 54% (13/24 ibuprofen-treated patients).

CONCLUSIONS

Hypothermic sepsis has an incidence of approximately 10% and an untreated mortality twice that of severe sepsis presenting with fever. When compared with febrile patients, the hypothermic group has an amplified response with respect to cytokines TNF-alpha and IL-6 and lipid mediators TxB2 and prostacyclin. Treatment with ibuprofen may decrease mortality in this select group of septic patients.

Expression and function of the chemokine receptors CXCR1 and CXCR2 in sepsis

Neutrophils (polymorphonuclear neutrophils; PMN) and a redundant system of chemotactic cytokines (chemokines) have been implicated in the pathogenesis of the acute respiratory distress syndrome in patients with sepsis. PMN express two cell surface receptors for the CXC chemokines, CXCR1 and CXCR2. We investigated the expression and function of these receptors in patients with severe sepsis. Compared with normal donors, CXCR2 surface expression was down-regulated by 50% on PMN from septic patients (p < 0.005), while CXCR1 expression persisted. In vitro migratory responses to the CXCR1 ligand, IL-8, were similar in PMN from septic patients and normal donors. By contrast, the migratory response to the CXCR2 ligands, epithelial cell-derived neutrophil activator (ENA-78) and the growth-related oncogene proteins, was markedly suppressed in PMN from septic patients (p < 0.05). Ab specific for CXCR1 blocked in vitro migration of PMN from septic patients to IL-8 (p < 0.05), but not to FMLP. Thus, functionally significant down-regulation of CXCR2 occurs on PMN in septic patients. We conclude that in a complex milieu of multiple CXC chemokines, CXCR1 functions as the single dominant CXC chemokine receptor in patients with sepsis. These observations offer a potential strategy for attenuating adverse inflammation in sepsis while preserving host defenses mediated by bacteria-derived peptides such as FMLP.

Reduced quality of life in survivors of acute respiratory distress syndrome compared with critically ill control patients

CONTEXT

Health-related quality of life (HRQL) is reduced in patients who survive acute respiratory distress (ARDS), but whether this decline in HRQL is caused by ARDS or other aspects of the patient's illness or injury is unknown.

OBJECTIVE

To determine if there are differences in the HRQL of ARDS survivors and comparably ill or injured controls without ARDS.

DESIGN

Prospective, matched, parallel cohort study.

SETTING

A 411-bed municipal medical and regional level I trauma center.

PATIENTS

Seventy-three pairs of ARDS survivors and severity-matched controls with the clinical risk factors for ARDS of sepsis and trauma admitted between January 1, 1994, and July 30, 1996.

MAIN OUTCOME MEASURES

The HRQL of ARDS survivors and controls, assessed by generic and pulmonary disease-specific HRQL instruments (Medical Outcomes Study 36-Item Short Form Health Survey, Standard Form [SF-36] and St George's Respiratory Questionnaire [SGRQ], respectively).

RESULTS

Clinically meaningful and statistically significant reductions in HRQL scores of ARDS survivors (n = 73) were seen in 7 of 8 SF-36 domains and 3 of 3 SGRQ domains compared with matched controls (P<.001 for all reductions). The largest decrements in the HRQL were seen in physical function and pulmonary symptoms and limitations. Analysis of trauma-matched pairs (n = 46) revealed significant reductions in 7 of 8 SF-36 domains (P< or =.02) and 3 of 3 SGRQ domains (P< or =.003). Analysis of sepsis-matched pairs (n = 27) revealed significant reductions in 6 of 8 SF-36 domains (P< or =.05) and 3 of 3 SGRQ domains (P< or =.002).

CONCLUSIONS

Survivors of ARDS have a clinically significant reduction in HRQL that appears to be caused exclusively by ARDS and its sequelae. Reductions were primarily noted in physical functioning and pulmonary disease-specific domains.

Elevated transforming growth factor-alpha levels in bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome

The acute respiratory distress syndrome (ARDS) frequently results in a fibroproliferative response that precludes effective alveolar repair. Transforming growth factor-alpha (TGF-alpha), a potent epithelial and mesenchymal cell mitogen, may modulate the response to lung injury. In this study, we determined whether bronchoalveolar lavage fluid (BALF) concentrations of TGF-alpha are increased during the first 2 wk after the onset of ARDS and, if so, whether increased TGF-alpha levels in lavage fluid are associated with increased levels of procollagen peptide III (PCP III), a biological marker of fibroproliferation, and with increased fatality rates. We enrolled 74 consecutive patients with ARDS prospectively identified on admission to the intensive care unit of a tertiary care hospital, and 11 patients with chronic interstitial lung disease. Thirteen healthy volunteers served as control subjects. TGF-alpha concentrations were measured in BALF recovered on Days 3, 7, and 14 after the onset of ARDS (total of 130 lavage samples). TGF-alpha was detected in the lavage fluid of 90% of patients with ARDS (67 of 74), and in 100% of patients with idiopathic pulmonary fibrosis (IPF) (10 of 10), but in none of 13 normal volunteers. At each day tested, the median lavage TGF-alpha level of patients with ARDS was significantly higher than that of normals. The overall fatality rate was 45% (33 of 74 patients). In a univariate analysis, the median TGF-alpha levels in nonsurvivors were 1.5-fold higher at Day 7 (p = 0.06) and 1.8-fold higher at Day 14 (p = 0.048). The fatality rate was 4 times higher (CI 1.6, 17.5) for patients with both increased lavage TGF-alpha and PCP III concentrations at Day 7 than for patients with low TGF-alpha and PCP III values, indicating a synergistic relationship between TGF-alpha and PCP III. We conclude that increased levels of TGF-alpha in BALF are common in patients with ARDS and that lavage TGF-alpha is associated with a marker of the fibroproliferative response in sustained ARDS.

Neutrophil apoptosis in the acute respiratory distress syndrome

Little is known about neutrophil (PMN) apoptosis in the acute respiratory distress syndrome (ARDS). We uses morphologic criteria to count apoptotic PMN in bronchoalveolar lavage fluid (BAL) of 35 patients on Days 1, 3, 7, 14, and 21 of ARDS and 13 patients on Days 1 and 3 of risk for ARDS. We found that the proportion of apoptotic PMN in BAL was low throughout the course of ARDS. There was no significant difference between the percentage of apoptotic PMN in patients at risk and patients with established ARDS or between patients who lived (2.4%) and patients who died (1.8%). When normal human PMN were incubated in ARDS BAL, a significantly lower proportion became apoptotic (50 +/- 4%), as compared with PMN incubated in lavage fluid from normal volunteers (76 +/- 7%, p < 0.05). This antiapoptotic effect of ARDS BAL was blocked by immunodepleting BAL of G-CSF and GM-CSF. We conclude that the proportion of apoptotic PMN recovered from the lungs of patients with ARDS is low throughout the course of ARD S. Furthermore, BAL from patients with ARDS prolongs survival of normal human PMN in vitro, and this effect is partially mediated by G-CSF and GM-CSF.

Bovine surfactant therapy for patients with acute respiratory distress syndrome

Lung surfactant is deficient in patients with acute respiratory distress syndrome (ARDS). We performed a randomized, prospective, controlled, open-label clinical study of administration of a bovine surfactant to patients with ARDS to obtain preliminary information about its safety and efficacy. Patients received either surfactant by endotracheal instillation in addition to standard therapy or standard therapy only. Three different groups of patients receiving surfactant were studied: patients receiving up to eight doses of 50 mg phospholipids/kg, those receiving up to eight doses of 100 mg phospholipids/kg, and those receiving up to four doses of 100 mg phospholipids/kg. Outcome measures included ventilatory support parameters, arterial blood gases, organ system failures, bronchoalveolar lavage (BAL) analyses, immunologic analyses, survival, and adverse events during the 28-d study period. Fifty-nine study patients were evaluable; 43 in the surfactant group and 16 in the control group. The FI(O2) at 120 h after treatment began was significantly decreased only for patients who received up to four doses of 100 mg phospholipids/kg surfactant as compared with control patients (p = 0.011). Mortality in the same group of patients was 18.8%, as compared with 43.8% in the control group (p = 0.075). The surfactant instillation was generally well tolerated, and no safety concerns were identified. This pilot study presents preliminary evidence that surfactant might have therapeutic benefit for patients with ARDS, and provides rationale for further clinical study of this agent.

The effects of ibuprofen on the physiology and survival of patients with sepsis. The Ibuprofen in Sepsis Study Group

BACKGROUND

In patients with sepsis the production of arachidonic acid metabolites by cyclooxygenase increases, but the pathophysiologic role of these prostaglandins is unclear. In animal models, inhibition of cyclooxygenase by treatment with ibuprofen before the onset of sepsis reduces physiologic abnormalities and improves survival. In pilot studies of patients with sepsis, treatment with ibuprofen led to improvements in gas exchange and airway mechanics.

METHODS

From October 1989 to March 1995, we conducted a randomized, double-blind, placebo-controlled trial of intravenous ibuprofen (10 mg per kilogram of body weight [maximal dose, 800 mg], given every six hours for eight doses) in 455 patients who had sepsis, defined as fever, tachycardia, tachypnea, and acute failure of at least one organ system.

RESULTS

In the ibuprofen group, but not the placebo group, there were significant declines in urinary levels of prostacyclin and thromboxane, temperature, heart rate, oxygen consumption, and lactic acidosis. With ibuprofen therapy there was no increased incidence of renal dysfunction, gastrointestinal bleeding, or other adverse events. However, treatment with ibuprofen did not reduce the incidence or duration of shock or the acute respiratory distress syndrome and did not significantly improve the rate of survival at 30 days (mortality, 37 percent with ibuprofen vs 40 percent with placebo).

CONCLUSIONS

In patients with sepsis, treatment with ibuprofen reduces levels of prostacyclin and thromboxane and decreases fever, tachycardia, oxygen consumption, and lactic acidosis, but it does not prevent the development of shock or the acute respiratory distress syndrome and does not improve survival.

Relationship between soluble CD14, lipopolysaccharide binding protein, and the alveolar inflammatory response in patients with acute respiratory distress syndrome

The effects of bacterial endotoxin (lipopolysaccharide, LPS) are amplified by lipopolysaccharide binding protein (LBP) and CD14, resulting in cellular activation at very low concentrations of LPS. To investigate the importance of this pathway in acute lung injury, we measured LPS, LBP, and soluble CD14 (sCD14) in the bronchoalveolar lavage fluid (BAL) of 82 patients with acute respiratory distress syndrome (ARDS). LBP and sCD14 increased markedly in BAL of patients with ARDS. sCD14 and LBP each were strongly related to BAL total protein and polymorphonuclear neutrophil (PMN) concentration, whereas LPS concentration was not. Multivariate analyses showed sCD14 to be strongly related to BAL total protein, even after controlling for LPS and LBP concentrations. sCD14 was strongly and independently related to PMN concentration, after controlling for BAL LPS, LBP, and interleukin-8 (IL-8). The BAL LPS concentration was not strongly related to either BAL total protein or BAL PMN. The BAL sCD14 and LBP values were similar in all subgroups of patients with ARDS, and were not related to survival. The serum LBP and sCD14 were elevated in ARDS, but were not related to BAL total protein, LBP, sCD14, PMN, or clinical outcome. Thus, LBP and sCD14 reach high concentrations in the lungs of patients with ARDS, and BAL sCD14 is strongly related to two major indices of lung inflammation: total protein and PMN concentration. CD14-dependent mechanisms may contribute to lung inflammation in ARDS.

Inflammatory cytokines in patients with persistence of the acute respiratory distress syndrome

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.

Proinflammatory activity in bronchoalveolar lavage fluids from patients with ARDS, a prominent role for interleukin-1

Proinflammatory cytokines such as tumor necrosis factor-alpha (TNF) and interleukin-1beta (IL-1) have been found to be elevated in bronchoalveolar lavage (BAL) fluid and in plasma from patients with acute respiratory distress syndrome (ARDS). In order to measure the balance of proinflammatory cytokines and their inhibitors, we quantified the upregulation of intercellular adhesion molecules (ICAM-1) induced by ARDS BAL fluids in human alveolar type II-like (A459) cells, and defined proinflammatory activity as the amount of ICAM-1 induced by the SAL fluids. Proinflammatory activity was detected in 77% of the SAL fluids sampled during the first week of ARDS, was found maximal during the 3 first days after onset of ARDS, and was significantly greater than in BAL specimens from at risk patients. Blocking experiments with specific inhibitors of TNF and IL-1 added to the BAL fluids indicated that the bioactivity measured was mainly due to IL-1. In contrast, proinflammatory activity of conditioned supernates from endotoxin-treated alveolar macrophages was mostly due to TNF. Using a bioassay that measures balance of cytokines with their inhibitors, our results indicate that the net proinflammatory activity in ARDS BAL fluids is attributable to IL-1 and not to TNF.

Pulmonary infection during the acute respiratory distress syndrome

Pulmonary infection is thought to be a common complication of ARDS. We undertook this prospective study to determine the incidence of pulmonary infection in patients with ARDS, and to evaluate the impact of nosocomial pneumonia on severity of ARDS and on survival. Two hundred one bronchoscopies were performed in 105 patients with ARDS with retrieval of distal airway secretions by bronchoalveolar lavage (BAL) and protected specimen brush (PSB). Whenever possible, bronchoscopy was performed at predetermined times: Day 3, Day 7, Day 14, and Day 21 after the onset of ARDS. The majority of patients were receiving antibiotics at the time of study. Changes in bacterial flora over time were determined by quantitative cultures of BAL and PSB. Bacterial growth was common, but usually at small concentrations. Only 16 patients met quantitative culture criteria for pneumonia (PSB > or = 10(3) cfu/ml or BAL > or = 10(4) cfu/ml). Correlation was poor between clinical evidence of pneumonia and pneumonia by quantitative culture criteria: clinical criteria had a very low sensitivity (24%) for predicting positive quantitative culture results, and a low specificity (77%) for predicting negative quantitative culture results. There was no correlation between total colony counts on BAL or PSB and severity of ARDS as judged by Pao2/FIo2 ratios, days receiving ventilation, or compliance. Furthermore, there was no correlation between bacterial growth and survival. We conclude that pneumonia defined by quantitative bacteriology is uncommon in ARDS. The potentially confounding role of broad-spectrum antibiotics should be studied further.

Improved survival of patients with acute respiratory distress syndrome (ARDS): 1983-1993

OBJECTIVE

To analyze temporal trends in acute respiratory distress syndrome (ARDS) fatality rates since 1983 at one institution.

DESIGN

Cohort.

SETTING

Intensive care units of a large county hospital.

PATIENTS

Consecutive adult patients (> or = 18 years of age) meeting ARDS criteria were identified through daily surveillance of intensive care units (N = 918 from 1983 through 1993). The major causes were sepsis syndrome in 37% and major trauma in 25%; 37% had other risks. Sixty-five percent were male. The median age was 45 years (range, 18 to 92 years); 70% were younger than 60 years.

MAIN OUTCOME MEASURE

Hospital mortality.

RESULTS

Overall fatality rates showed no trend from 1983 to 1987, declined slightly in 1988 and 1989, and decreased to a low of 36% in 1993 (95% confidence interval, 25% to 46%). The crude rates were largely unchanged after adjustment for age, ARDS risk, and gender distribution. While patients both younger than 60 years and 60 years or older experienced declines in fatality rate, the larger decrease occurred in the younger cohort. In sepsis patients, ARDS fatality rates declined steadily, from 67% in 1990 to 40% in 1993 (95% confidence interval, 23% to 57%). The decline in sepsis-related ARDS fatality was confined largely to patients less than 60 years of age. Trauma patients and all other patients also experienced declines in fatality rates after 1987, although these trends were not as strong and consistent as in the sepsis population.

CONCLUSIONS

In this large series, we observed a significant decrease in fatality rates occurring largely in patients younger than 60 years and in those with sepsis syndrome as their risk for ARDS. We are unable to determine the extent to which experimental therapies or other changes in treatment have contributed to the observed decline in the ARDS fatality rate. Institution-specific rates and temporal trends in ARDS fatality rates should be considered in clinical trials designed to prevent ARDS and the high mortality associated with this syndrome.

Improved survival of patients with acute respiratory distress syndrome (ARDS): 1983-1993

OBJECTIVE

To analyze temporal trends in acute respiratory distress syndrome (ARDS) fatality rates since 1983 at one institution.

DESIGN

Cohort.

SETTING

Intensive care units of a large county hospital.

PATIENTS

Consecutive adult patients (> or = 18 years of age) meeting ARDS criteria were identified through daily surveillance of intensive care units (N = 918 from 1983 through 1993). The major causes were sepsis syndrome in 37% and major trauma in 25%; 37% had other risks. Sixty-five percent were male. The median age was 45 years (range, 18 to 92 years); 70% were younger than 60 years.

MAIN OUTCOME MEASURE

Hospital mortality.

RESULTS

Overall fatality rates showed no trend from 1983 to 1987, declined slightly in 1988 and 1989, and decreased to a low of 36% in 1993 (95% confidence interval, 25% to 46%). The crude rates were largely unchanged after adjustment for age, ARDS risk, and gender distribution. While patients both younger than 60 years and 60 years or older experienced declines in fatality rate, the larger decrease occurred in the younger cohort. In sepsis patients, ARDS fatality rates declined steadily, from 67% in 1990 to 40% in 1993 (95% confidence interval, 23% to 57%). The decline in sepsis-related ARDS fatality was confined largely to patients less than 60 years of age. Trauma patients and all other patients also experienced declines in fatality rates after 1987, although these trends were not as strong and consistent as in the sepsis population.

CONCLUSIONS

In this large series, we observed a significant decrease in fatality rates occurring largely in patients younger than 60 years and in those with sepsis syndrome as their risk for ARDS. We are unable to determine the extent to which experimental therapies or other changes in treatment have contributed to the observed decline in the ARDS fatality rate. Institution-specific rates and temporal trends in ARDS fatality rates should be considered in clinical trials designed to prevent ARDS and the high mortality associated with this syndrome.

Type III procollagen peptide in the adult respiratory distress syndrome. Association of increased peptide levels in bronchoalveolar lavage fluid with increased risk for death

OBJECTIVE

To determine whether bronchoalveolar lavage fluid levels of the N-terminal peptide of type III procollagen (procollagen III) are increased in patients with the adult respiratory distress syndrome and, if so, whether increased procollagen III levels in lavage fluid are associated with increased fatality rates.

DESIGN

Prospective cohort study.

SETTING

Intensive care units of a tertiary care hospital affiliated with a medical school.

PATIENTS

117 consecutive patients with the adult respiratory distress syndrome prospectively identified on admission; 6 healthy volunteers served as controls.

MEASUREMENTS

Bronchoalveolar lavage fluid procollagen III levels in 117 patients at 3, 7, and 14 days after onset of the adult respiratory distress syndrome (total of 196 lavage samples).

RESULTS

The median procollagen III level was 1.75 U/mL (range, 0 to 13.4 U/mL) in lavage fluid obtained from patients with the adult respiratory distress syndrome. We detected procollagen III levels in lavage fluid from 80% of patients (94 of 117) but not in 6 normal volunteers. The overall fatality rate was 41% (48 of 117 patients). In a univariate analysis, the relative risk (RR) for death was increased in patients with procollagen III levels of 1.75 U/mL or more obtained on day 3 (RR, 2.4; 95% CI, 1.3 to 4.3), day 7 (RR, 2.7; CI, 1.4 to 5.4), and day 14 (RR, 2.7; CI, 1.1 to 6.3). Inclusion of other variables in a multivariate model only minimally decreased the risk associated with increased procollagen III levels.

CONCLUSION

Increased levels of type III procollagen in bronchoalveolar lavage fluid are frequently detected in patients with the adult respiratory distress syndrome and are strongly associated with increased risk for fatal outcome independent of other variables related to fatality in patients with the syndrome.

Evolution of bronchoalveolar cell populations in the adult respiratory distress syndrome

To characterize the evolution of inflammation in the adult respiratory distress syndrome (ARDS) and test the hypothesis that sustained alveolar inflammation is associated with a poor outcome in patients with ARDS, we performed fiberoptic bronchoscopy and bronchoalveolar lavage (BAL) in 125 patients and compared BAL cells and protein concentrations in survivors and nonsurvivors. ARDS followed sepsis syndrome in 35 patients, major trauma in 41, and other causes in 49. When possible, BAL was performed on Days 3, 7, and 14 after the onset of ARDS. Sixty-five patients (52%) had more than one BAL. We first performed analyses on each BAL day using information from all 212 BAL in the 125 patients (cross-sectional analysis). All patients had increased leukocytes and total protein in the first BAL (Day 3 after onset of ARDS). In patients with ARDS following sepsis, the percentage of BAL polymorphonuclear leukocytes (PMN) was higher on Day 7 (p = 0.11) and particularly Day 14 (p = 0.02) in patients who died; there was a consistent trend of a higher PMN concentration on all days in patients who died then in those who lived. In patients with ARDS following trauma and other risks, however, BAL PMN measures did not distinguish survivors from patients who died. Analysis of serial data from the patients with more than one BAL showed that alveolar macrophages (AM) increased in survivors of ARDS, both in absolute numbers and as a percentage of total cells; this pattern was most pronounced in the sepsis patients. The cross-sectional data analysis suggests that sustained alveolar inflammation occurs frequently in patients with ARDS following sepsis and is associated with a high mortality.

Safety of bronchoalveolar lavage in patients with adult respiratory distress syndrome

Although shown to be safe in many other lung disorders, the safety of fiberoptic bronchoscopy (FOB) with bronchoalveolar lavage (BAL) in critically ill patients with adult respiratory distress syndrome (ARDS) remains unproven. We conducted a prospective study to evaluate the safety of BAL in patients with ARDS. There were 438 patients with ARDS at our institution during the study period. Of these, 110 underwent FOB and BAL for either research or clinical purposes. Data were collected at baseline, at 5-min intervals during the procedure, and 1 h after the procedure. We did not detect any statistically or clinically significant changes in PaO2/FlO2, mean arterial pressure, heart rate, peak inspiratory pressure, or static thoracic compliance after the procedure. A small decrease in SaO2 occurred after BAL. Although this change was statistically significant, the magnitude was not of clinical importance. Five patients (4.5%) had transient arterial oxygen desaturation to < 90% during FOB and one patient (0.9%) experienced desaturation to < 80%. There were no prolonged episodes of severe hypoxemia. No serious bleeding occurred. One pneumothorax developed during the procedure. No deaths occurred that were related to the procedure. We conclude that FOB and BAL can be performed safely and are reasonably well-tolerated in patients with ARDS.