Chronic cough is defined by its persistence beyond 8 weeks. Many conditions can explain the existence of a bronchial inflammation. In the management of chronic cough, the search for bronchial hyperreactivity (HRB) is recommended. The treatment relies primarily on the prescription of inhaled corticosteroids. It has been shown recently that the existence of an HRB with Methacholine (bronchial provocation test used in routine) does predict the effectiveness of inhaled corticosteroid treatment in no more than 50% of cases.

It is now possible to assess the bronchial inflammation by rapid, non-invasive and reproducible tests such that the fraction of exhaled nitric oxide (FeNO) and bronchial provocation test with mannitol. In a retrospective study, it was shown that an increased value of FeNO (cut-off > 35 ppb) predicts a positive response to treatment with a sensitivity of 90% and a specificity of 80%.

The purpose of this study is to show that the use of the prospective value of exhaled NO can predict response to treatment with inhaled corticosteroids in adult with chronic cough. In addition we will assess the interest of the prognosis of bronchial provocation test with mannitol in this indication.

Inclusion Criteria:

• Chronic Cough during 2 months
• Social Security regimen affiliated
• Consent form signed

Exclusion Criteria:

• Smoking active
• Treatment with angiotensin converting enzyme inhibitor
• Clinical signs of obvious gastroesophageal reflux
• Clinical rhinosinusitis
• Recent respiratory infection (< 1 month)
• Corticosteroid Treatment(oral or inhaled) within 2 weeks
• VEMS < 1 L or < 80% of the theoretical value
• Existence of an obstructive ventilatory disorder defined as a report (FEV/FVC) < 90% of the theoretical value