ARDS, acute respiratory distress syndrome; COVID-19, coronavirus disease 2019; CPAP, continuous positive airway pressure; HFNC, high-flow nasal cannula; ICU, intensive care unit; LPV/RTV, lopinavir/ritonavir; PEEP, positive end expiratory pressure; RCT, randomized controlled trial; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; WHO, World Health Organization.