Inclusion Criteria:  Patients with respiratory failure and indication für High-flow nasal cannula therapy Patients aged between 4 1/7 weeks and 18 years Patients who were treated between 01/01/2017 and 28/02/2021 in the Department of Pediatric Pulmonology, Immunology and Intensive Care Medicine at Campus Virchow- Klinikum, Charité - Universitätsmedizin Berlin  Exclusion Criteria:  Patients aged between 1 and 27 days (neonatal period) Patients with congenital cyanotic heart defects Patients after or in the course of haematopoetic stem cell transplantation Patients with ambulatory respiratory support