- severe covid pneumonia with fever and bilateral lung infiltrates and respiratory rate>30/min or SpO2<90% on room air (adapted from RKI/WHO)- Condition after surgery/trauma/acute event (stroke, myocardial infarction, acute covid-independent infection) in the last 4 weeks- Known pregnancy - Patients with pre-existing pulmonary disease who were on oxygen prior to infection (e.g., due to pulmonary fibrosis, COPD)- limited ability to give consent (e.g. due to dementia)- limited ability to perform breathing maneuvers independently (e.g. high frailty)- limited ability to provide self-care (care level 2 or 3)- lack of language skills- seizures in the medical history

- severe covid pneumonia with fever and bilateral lung infiltrates and respiratory rate>30/min or SpO2<90% on room air (adapted from RKI/WHO)- Condition after surgery/trauma/acute event (stroke, myocardial infarction, acute covid-independent infection) in the last 4 weeks- Known pregnancy - Patients with pre-existing pulmonary disease who were on oxygen prior to infection (e.g., due to pulmonary fibrosis, COPD)- limited ability to give consent (e.g. due to dementia)- limited ability to perform breathing maneuvers independently (e.g. high frailty)- limited ability to provide self-care (care level 2 or 3)- lack of language skills- seizures in the medical history