The purpose of this study is to determine whether pro-adrenomedullin (Mr proADM)in addition to clinical evaluation is effective to predict outcome of acute exacerbations of COPD patients visiting the emergency room(ER).

Acute exacerbation of COPD (AECOPD)are usual and frequent cause of admission in emergency room (ER). No validated clinical or biological predictor of evolution are available.

The main objective is to determine the prognosis value of Mr proADM in addition to the clinical risk stratification for AE COPD patients in ER.

Patients presenting with a AECOPD diagnosis in ER will have a blood sample collected and freezed at their admission. Mr proADM will be assessed at the end of the study. Clinicians in charge of patients will not have the result during the management of their patients. This study implies no change in the patients' management.

Data related to the patients'demographic,current exacerbation and basic COPD characteristics will be collected.

Inclusion Criteria:

• patients > 40 years old
• Acute exacerbation of COPD

Exclusion Criteria:

• Medico social conditions not allowing home discharge
• Other causes of Dyspnea: Pneumothorax, pulmonary embolism, pulmonary oedema, lung cancer
• Pneumonia on chest ray
• acute respiratory distress requiring immediate ICU transfer