Fig. 3From: Comparison between high-flow nasal oxygen (HFNO) alternated with non-invasive ventilation (NIV) and HFNO and NIV alone in patients with COVID-19: a retrospective cohort studyKaplan–Meier curve of the survival rate according to the groups. NIV non-invasive ventilation, HFNO high-flow nasal oxygenBack to article page