The purpose of this study is to determine whether the 6-minute walk test (6MWT) could be a prognostic factor for cystic fibrosis patients.

The 6-minute walk test is a simple exercise test, reproducing a daily physical activity. The utility of this test is described in several chronic lung diseases (chronic obstructive pulmonary disease, idiopathic pulmonary arterial hypertension). The distance performed during the 6MWT and / or desaturation during the 6MWT is a prognostic factor that contributes to the assessment of patients for lung transplantation indication.

The 6MWT is practiced routinely in cystic fibrosis centers but its usefulness in this disease has not been shown. Also the results of this test are not part of the decision-making criteria for lung transplantation.

A single-center study performed in adults CRCM at Cochin Hospital suggests the prognostic value of the 6MWT in patients with adult's cystic fibrosis.

The principal objective of this study is to assess the prognostic of 6MWT as part of the cystic fibrosis. The primary endpoint will be to assess the survival without lung transplant during the follow up period of 3 years. In this context, this prognostic tool could be used to help to determine the best time to consider a lung transplant in cystic fibrosis patient.

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