Fig. 1From: 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 studyFlowchart of the study. COT conventional oxygen therapy, HFNO high-flow nasal oxygen, NIV non-invasive ventilation. The COT group was used as reference for multivariate Cox regression model adjustmentBack to article page