- respiratory arrest or the need for immediate intubation; - upper airway obstruction; - facial trauma; - inability to cooperate (e.g. agitation or dementia) - inability to give informed consent - participation in another study for covid19 treatments - deterioration due to other reasons than progressive covid19 pneumonia per clinical judgment, e.g. pulmonary thromboembolism, heart failure, renal failure etc. - palliative care or expectation that patient will not survive > 72 hours post randomization per clinical judgment of the investigator.

- respiratory arrest or the need for immediate intubation; - upper airway obstruction; - facial trauma; - inability to cooperate (e.g. agitation or dementia) - inability to give informed consent - participation in another study for covid19 treatments - deterioration due to other reasons than progressive covid19 pneumonia per clinical judgment, e.g. pulmonary thromboembolism, heart failure, renal failure etc. - palliative care or expectation that patient will not survive > 72 hours post randomization per clinical judgment of the investigator.