A recent North-American-European Consensus Conference proposed new, uniform criteria for the definition of acute lung injury, in part to facilitate earlier identification of patients for clinical trials. However, these criteria have not been evaluated prospectively. We designed a prospective cohort study of 123 consecutive patients with acute lung injury prospectively identified on admission to the adult intensive care units of a tertiary care university hospital. The objectives were to determine if selection of patients using the new criteria for acute lung injury results in a significant change in the clinical characteristics, risk factors, or predictors of mortality when compared with prior studies of patients with adult respiratory distress syndrome (ARDS); and to determine if a quantitative index of the severity of acute lung injury has prognostic value in identifying nonsurvivors of acute lung injury. We used three methods: (1) prospective identification of patients with acute lung injury using a PaO2/FIO2 ratio < 300 and bilateral infiltrates on chest radiograph in the absence of left heart failure; (2) evaluation of the severity of lung injury using a four-point scoring system; and (3) stepwise logistic regression analysis to identify variables significantly associated with hospital mortality. Overall hospital mortality was 58%. Sepsis was the most common clinical disorder (50/123 or 41%) associated with the development of acute lung injury. Using the new definition for acute lung injury, 66 of the 123 patients were enrolled with a PaO2/FIO2 ratio between 150 and 299; 57 of the 123 patients had a PaO2/FIO2 < 150 at the time of entry into the study.(ABSTRACT TRUNCATED AT 250 WORDS)

Although intravenous Escherichia coli endotoxin has been used extensively in experimental studies to increase lung endothelial permeability, the effect of E. coli endotoxin on lung epithelial permeability has not been well studied. To examine this issue in sheep, bidirectional movement ofprotein across the lung epithelial barrier was studied by labeling the vascular space with 13"I-albumin and-by instilling 3 ml/kg of an isosmolar protein solution with`-I-albumin into the alveoli. E. coli endotoxin was administered according to one of three protocols: intravenous alone (5-500 ug/kg), intravenous (5 pg/kg) plus low-dose alveolar endotoxin (10 pg/kg), and high-dose alveolar endotoxin alone (50-100 pg/kg). Alveolar liquid clearance was estimated based on the concentration of the instilled native protein.Sheep were studied for either 4 or 24 h. Although intravenous E. coli endotoxin produced a marked increase in transvascular protein flux and interstitial pulmonary edema, there was no effect on the clearance of either the vascular ("3'I-albumin) or the alveolar (1251-albumin) protein tracer across the epithelial barrier. High-dose alveolar E. coil endotoxin caused a 10-fold increase in the number of leukocytes, particularly neutrophils, that accumulated in the air spaces. In spite of the marked chemotactic effect of alveolar endotoxin, there was no change in the permeability of the epithelial barrier to the vascular or alveolar protein tracers. Also, alveolar epithelial liquid clearance was normal. Morphologic studies confirmed that the alveolar epithelial barrier was not injured by either intravenous or alveolar E. coli endotoxin. Thus, the alveolar epithelium in sheep is significantly more resistant than the lung endothelium to the injurious effects of E. coli endotoxin. (J. Clin. Invest. 1991. 88:864-875.) Key words: E. coli endotoxin * alveolar epithelium -lung endothelium * alveolar liquid clearance * acute lung injury

Exogenous administration of fi-adrenergic agonists has previously been reported to increase lung liquid clearance by stimulation of active sodium transport across the alveolar epithelium. We hypothetized for this study that endogenous release of epinephrine in septic shock would stimulate liquid clearance from the airspaces in rats. Liquid clearance from the air spaces was measured by the concentration of protein over 4 h in a test solution of 5% albumin instilled into one lung. Bacteremic rats developed severe systemic hypotension and metabolic acidosis that was associated with a 100-fold rise in plasma epinephrine levels. There was a 100% increase in liquid clearance from the airspaces of the lung in the bacteremic compared with control rats. To determine the mechanisms responsible for this accelerated lung liquid clearance, amiloride (10'-M), a sodium transport inhibitor, was added to the air spaces. Amiloride prevented the increase in liquid clearance from the airspaces, indicating that this effect depended on increased uptake of sodium across the lung epithelium. The addition of propranolol (10-4 or iO' M) to the instillate also prevented the acceleration in alveolar liquid clearance in the bacteremic rats. We conclude that the release of endogenous catecholamines associated with septic shock markedly stimulates fluid clearance from the distal airspaces of the lung by a 8-adrenergic mediated stimulation of active sodium transport across the epithelial barrier. This data provides evidence for a previously unrecognized mechanism that can protect against or hasten the resolution of alveolar edema in pathological conditions, such as septic shock, that are associated with the endogenous release of catecholamines. (J. Clin. Invest. 1994. 94:663-671.)

Pseudomonas aeruginosa, an opportunistic pathogen, is capable of establishing both chronic and acute infections in compromised hosts. Previous studies indicated that P. aeruginosa displays either a cytotoxic or an invasive phenotype in corneal epithelial cells. In this study, we used polarized MDCK cells for in vitro infection studies and confirmed that P. aeruginosa isolates can be broadly differentiated into two groups, expressing either a cytotoxic or an invasive phenotype. In vivo infection studies were performed to determine if cytotoxic and invasive strains displayed differential pathology. Invasion was assayed in vivo by in situ infection of mouse tracheal tissue followed by electron microscopy. Both cytotoxic and invasive strains entered mouse tracheal cells in situ; however, more necrosis was associated with the cytotoxic strain. In an acute lung infection model in rats, cytotoxic strains were found to damage lung epithelium more than invasive strains during the short infection period of this assay. The expression of cytotoxicity requires a functional exsA allele. In the strains tested, the ability to invade epithelial cells in vitro appears to be independent of exsA expression. Since ExsA is a transcriptional regulator of the exoenzyme S regulon, chromosomal preparations from invasive and cytotoxic strains were screened for their complement of exoenzyme S structural genes, exoS, encoding the 49-kDa ADP-ribosyltransferase (ExoS), and exoT, encoding the 53-kDa form of the enzyme (Exo53). Invasive strains possess both exoS and exoT, while cytotoxic strains appear to have lost exoS and retained exoT. These data indicate that the expression of cytotoxicity may be linked to the expression of Exo53, deletion of exoS and perhaps other linked loci, or expression of other ExsA-dependent virulence determinants. In the absence of a functional cytotoxicity pathway (exsA::⍀ strains), invasion of eukaryotic cells is detectable.

In this prospective study of 45 patients, we tested the hypothesis that markedly elevated levels of plasma von Willebrand antigen (vWf-Ag) a marker of endothelial cell injury, might predict the development of acute lung injury in patients with nonpulmonary sepsis syndrome. Acute lung injury was quantified on a four-point scoring system. At the time of entry into the study, none of the 45 patients had evidence of lung injury. Subsequently, 15 patients developed lung injury and 30 patients did not develop lung injury. The mean plasma vWf-Ag level was markedly elevated in the 15 patients who developed lung injury compared with the 30 patients who did not develop lung injury (588±204 vs. 338±196, percentage of control, P < 0.01). Furthermore, a plasma vWf-Ag level 2 450 was 87% sensitive and 77% specific for predicting the development of acute lung injury in the setting of nonpulmonary sepsis. In addition, the combination of a plasma vWf-Ag > 450 and nonpulmonary organ failure at the time of entry into the study had a positive predictive value of 80% for acute lung injury. Also, a plasma vWf-Ag level > 450 had a positive predictive value of 80% for identifying nonsurvivors. Thus, in patients with nonpulmonary sepsis, an elevated level of plasma vWf-Ag is a useful, early biochemical marker of endothelial injury and it has both predictive and prognostic value. (J. Clin. Invest. 1990. 86:474-480.) Key words: endothelial cells * acute lung injury* von Willebrand antigen level * sepsis * adult respiratory distress syndrome -shock

Management of airway infections caused byPseudomonas aeruginosa is a serious clinical challenge, but little is known about the microbial ecology of airway infections in intubated patients. We analyzed bacterial diversity in endotracheal aspirates obtained from intubated patients colonized by P. aeruginosa by using 16S rRNA clone libraries and microarrays (PhyloChip) to determine changes in bacterial community compositions during antibiotic treatment. Bacterial 16S rRNA genes were absent from aspirates obtained from patients briefly intubated for elective surgery but were detected by PCR in samples from all patients intubated for longer periods. Sequencing of 16S rRNA clone libraries demonstrated the presence of many orally, nasally, and gastrointestinally associated bacteria, including known pathogens, in the lungs of patients colonized with P. aeruginosa. PhyloChip analysis detected the same organisms and many additional bacterial groups present at low abundance that were not detected in clone libraries. For each patient, both culture-independent methods showed that bacterial diversity decreased following the administration of antibiotics, and communities became dominated by a pulmonary pathogen. P. aeruginosa became the dominant species in six of seven patients studied, despite treatment of five of these six with antibiotics to which it was sensitive in vitro. Our data demonstrate that the loss of bacterial diversity under antibiotic selection is highly associated with the development of pneumonia in ventilated patients colonized with P. aeruginosa. Interestingly, PhyloChip analysis demonstrated reciprocal changes in abundance between P. aeruginosa and the class Bacilli, suggesting that these groups may compete for a similar ecological niche and suggesting possible mechanisms through which the loss of microbial diversity may directly contribute to pathogen selection and persistence.

In mechanically ventilated, critically ill children, those with ventilator-associated pneumonia had a prolonged need for mechanical ventilation, a longer ICU stay, and a higher mortality rate. Female gender, postsurgical diagnosis, the use of narcotics, and the use of enteral feeds were associated with an increased risk of developing ventilator-associated pneumonia in these patients.

To determine whether exoenzyme S plays a role in alveolar epithelial injury, two parental strains of Pseudomonas aeruginosa, PAK and PA103, were tested that produced large quantities of exoenzyme S. Strains PAK and PA103 differ in the form of exoenzyme S they produce. Strain PAK produces a 53-kDa protein that does not possess ADP-ribosyltransferase activity and large quantities of a 49-kDa protein that expresses ADP-ribosyltransferase activity. Strain PA103 produces the 53-kDa protein and low amounts of exoenzyme S activity. A quantitative experimental protocol was used to measure the protein permeability of the alveolar epithelium and the dissemination of the bacteria to the pleural space and circulation. The results indicate that instillation of PAK and PA103 resulted in significant lung injury. Control experiments utilizing isogenic, exoenzyme S-deficient, regulatory mutants in the infection model reduced the lung injury and the dissemination of instilled bacteria. Taken together these results suggest that alveolar epithelial injury correlated with the production of the 53-kDa form of exoenzyme S or other coordinately regulated factors.