6 Minute Walk Test in Cystic Fibrosis

Inclusion Criteria: * Patient with Cystic Fibrosis (bronchiectasis with presence of two mutations in the CFTR gene and / or positive sweat test. * Patients aged 18 year or older. * Pre-bronchodilator FEV1 FEV1 ≤ 60% from theoretical value: this FEV1 limits is proposed following the results from our published study (Martin et al. 2013) showing that desaturation during 6MWT and a distance ≤ 475m performed, are almost exclusively found in patients with FEV1 ≤ 60% . * Stable health status ( \>15 days after the start of treatment of a respiratory exacerbation * No indications against the walking test: Left uncontrolled heart failure Severe aortic stenosis acute endocarditis syncope Symptomatic severe arrhythmia stable angina Myocardial infarction \<5 days Acute respiratory distress Resting SpO2≤85% pulmonary edema Uncontrolled asthma Arterial or venous thrombosis of the lower limbs, Severe acute condition that may interfere with the exercise performance (infections, renal failure, hyperthyroidism, unable to cooperate, severe pulmonary arterial hypertension, severe systemic blood pressure (Systolic blood pressure \>200 mm Hg and / or diastolic blood pressure \>120 mm Hg)) Exclusion Criteria: * History of lung transplant * Oxygen Dependence (inability to achieve a 6-minute walk test in ambient air) * Any indication against walk test * Pregnant women, persons deprived of liberty, person under guardianship, person in emergency situation * Person not affiliated to social security system * Refusal to participate in the study