Chronicle obstructive pulmonary disease is a worldwide cause of mortality and morbidity. This systemic disease progressively leads to dyspnea, muscle wasting and exercise capacity impairment.

Pulmonary rehabilitation is a cornerstone in the management of these systemic effects. Unfortunately, access to pulmonary rehabilitation is limited for many people who would benefit from it, primarily because of a lack of pulmonary rehabilitation and assessment centers. Optimal assessment should include cardiopulmonary exercise testing to determine both the optimal training settings as well as any cardiopulmonary contraindications to pulmonary rehabilitation. However, this is not available in most centers and when it is, consultations are limited. Therefore, pulmonary rehabilitation is often delayed for several weeks and patients can lose motivation.

In order to promote pulmonary rehabilitation, the incremental cardiopulmonary exercise testing could be replaced by field tests to individualize pulmonary rehabilitation prescription.

The 6-minute stepper test is a new field tool. Its sensitivity and reproducibility have previously been reported in patients with chronicle obstructive pulmonary disease. It is easy to set up in the clinical setting and could be used to individualize pulmonary rehabilitation.

The aim of this study was to develop and validate a prediction equation to set rehabilitation intensity for patients with severe to very severe chronicle obstructive pulmonary disease attending pulmonary rehabilitation, with the use of a simple, readily available field test. Therefore the investigators sought to determine, if it exists, a relationship between the plateau heart rate from the first and last 3 minutes of the 6-minute stepper test and the heart rate from the first ventilatory threshold from the cardiopulmonary exercise testing in order to individualize pulmonary rehabilitation in patients with severe to very severe chronicle obstructive pulmonary disease.

Experimental design:

The validation of the six-minute stepper test to prescribe endurance training in severe to very severe chronicle obstructive pulmonary disease involves two steps :

1. Patients with severe to very severe chronicle obstructive pulmonary disease who performed an incremental cardiopulmonary exercise testing and are referred to pulmonary rehabilitation will be approached to participate in the study.

   Eligible patients who agree to participate in the study and sign informed consent will perform two six-minute stepper test. Their performance and heart rate (first and last 3minutes) will be compared with those obtained at the first ventilatory threshold from the previously performed incremental cardiopulmonary exercise testing (usually used for the prescription of endurance training in pulmonary rehabilitation) using multiple regression in order to derive a predictive equation.

2. The validity of this predictive equation will be assessed in an independent cross-validation group issued from a completed multicenter observational study (NCT03244137). This cross-validation group will be formed with those patients of this cohort who performed both the incremental cardiopulmonary exercise testing (and had a determined first ventilatory threshold) and the six-minute stepper test. The heart rate prescription for endurance training from the direct measurement of the the first ventilatory threshold will be compared to the heart rate derived from the 6minute-stepper test using the predictive equation determined in step 1. Data will be compared using the mean absolute difference between both prescriptions and a Bland-Altman analysis.

Inclusion Criteria:

• Age > 18 ans ;
• Chronicle obstructive pulmonary disease stage III/IV (FEV1 < 50%) ;
• Weight ≤ 90kg ;
• Eligible for pulmonary rehabilitation ;
• A first ventilatory threshold has been identified during a previously performed incremental cardiopulmonary exercise testing.

Exclusion Criteria:

• Pregnant woman or likely to be ;
• Patient under guardianship ;
• Contraindication to cardiopulmonary exercise testing ;
• Patient medically treated with heart rate modulator (excluding oral B2-agonist) ;
• Patient treated with pacemaker or defibrillator ;
• History of lower limb impairment (i.e. peripheral artery disease, orthopedic disorder etc.).

Patients with severe to very severe chronicle obstructive pulmonary disease reffered for pulmonary rehabilitation.