Inclusion Criteria:  Major patients Patients with chronic hypercapnic respiratory failure with a validated indication of long-term NIV Follow-up at the CHRU of Nancy at "Unité de Médecine Ambulatoire" (UMA) department between 11/01/2020 and 05/30/2021  Exclusion Criteria:  Data not usable / missing Tracheal ventilation Patients' opposition to the use of their data for the purposes of this research