Inclusion Criteria:

• COPD patients with the waning of exacerbation:

  • Male or Female more than 18 years old
  • VEF1/FCV < 70% or COPD already knew

  • At the moment of the respiratory failure, the day of the enter in hospital:

    • Respiratory frequency >25
    • PaCO2 >45 mmHg
    • pH < 7.35

  • The day of the inclusion in our study:

    • PH > 7.33 at the end of the respiratory failure, or 2 days of continuation, 3 to 7 days post acute exacerbation of continuation
    • Fever < 38.5
  • Patients who have signed the inform consent form

• Stable COPD patients:

  • Men or women more than 18 years old
  • VEF1/FCV < 70% or COPD already knew
  • Patients who have signed the inform consent form

Exclusion Criteria:

• Evolutive obvious infection or CRP >100 at inclusion Cardiac failure considered like the major cause of the exacerbation or cardiac insufficiency with FeVG < 45 %
• Smoker > 10 cigarettes a day Antioxidant catch: N-acetyl-cystein, selenium, ascorbic acid, alpha tocopherol acetate…
• Evolutive neoplasy
• Antioxidant catch: N-acetyl-cystein, selenium, ascorbic acid, alpha tocopherol acetate…
• pregnant women
• patient under supervision or trusteeship
• patient taking part in another clinical trial.