Transforming Growth Factor-b1 (TGF-b1) is involved in the development of acute lung injury and in the fibroproliferation during acute respiratory distress syndrome (ARDS). Procollagen III Peptide (PIIINP) is a validated marker of fibroproliferation. PIIINP is associated with death in ARDS patients. The simultaneous changes of TGF-b1 and PIIINP were never studied in patients with ARDS. The relationships between TGF-b1 and the outcome of ARDS are unknown.

The aim of the study is to analyse the changes of TGF-b1 and PIIINP during ARDS and to show the relationships between TGF-b1 - PIIINP and the outcomes of ARDS.

Primary outcome: To analyse the changes of Transforming Growth Factor b1 and Procollagen III during the acute respiratory distress syndrome.

Inclusion Criteria:

• ARDS with a PaO2/FIO2 < 200 mmHg at a positive end-expiratory pressure (PEEP) ³ 5 cm H2O
• ARDS criteria from less than 24 hours
• Informed consent

Exclusion Criteria:

• Pregnancy
• Chronic interstitial or fibrosis lung diseases
• Hepatic chronic disease
• Neutropenia £1 G/l
• Corticosteroid (more than 200 mg/day of hydrocortisone or equivalent, less than 2 weeks before inclusion)
• Immunosuppressive therapy within the last 30 days
• Participation in any investigational drug or devices study within 30 days prior study entry

patients whom suffered ARDS with a PaO2/FIO2 < 200 mmHg at a positive end-expiratory pressure (PEEP) ³ 5 cm H2O and for which ARDS criteria from less than 24 hours