Inclusion Criteria:  Patients aged by 18 and more ; Patient with an chronic obstructive respiratory insufficiency, confirmed by clinical and functional criteria ; Patient with exercise-induced oxygen desaturation ; Patient clinical ly stable, with no exacerbation period within the last 2 months before inclusion ; Consent form signed by the patient.  Exclusion Criteria:  Patient in exacerbation period at the inclusion time ; Pregnant and breastfeeding women ; Patient with orthopedic disorder that could limit the ability of stair climbing; Any other disease that could influence exercise capacity of the patient or that could impair exercise test realization ; Patient with law protection (guardianship or protection of vulnerable adults)