Fibrocytes In Bronchoalveolar Lavage Fluid Are Associated With Outcome In Patients With Acute Lung Injury

4 5 Fibrocytes are mesenchymal progenitors from hematopoietic origin involved in normal and pathologic organ repair. During Background: acute lung injury (ALI) and acute respiratory distress syndrome (ARDS), an ineffective repair is associated with over-mortality. We investigated whether fibrocyte detection in bronchoalveolar lavage fluid (BAL) could be a predictor of outcome during acute lung injury. We prospectively collected BAL from 122 ventilated patients (62-ARDS, 30-ALI, 30-ventilated patients w/o ALI/ARDS). Fibrocytes, Methods: defined as cells expressing CD45 and collagen 1, were quantified by flow cytometry. Chemokines, growth factors and collagen 1 concentrations were measured in BAL supernatants. Ventilated patients were followed up for 28 days after BAL procedure and clinical data recorded. Fibrocytes were detected in 89% of BAL from ventilated patients. The median percentage of BAL fibrocytes was significantly Findings: increased in patients with ALI and ARDS (5.0 %) in comparison with ventilated controls (0.9%, p<0.0001). Fibrocyte percentage correlated with percentage of monocytes/macrophages in BAL (s=0.35, p=0.007). After adjustment for age, comorbidities, administered treatments and severity of illness in a multivariable COX proportional-hazard model, a percentage of BAL fibrocytes over 6% was independently associated with a lower proportion of patients weaned from mechanical ventilation at 28 days (HR (95% CI)= 0,34 (0,15-0,78), p=0,01) and a higher 28-day mortality in ALI/ARDS patients (HR (95% CI)= 6.15 (2.78-13.64), p<0.0001). Fibrocytes are detectable in the alveolar space during ALI/ARDS. BAL Fibrocytes percentage is an independent marker Interpretation: associated with poor survival and requirement for prolonged mechanical ventilation in patients with ALI/ARDS.