1 Division of Respiratory and Critical Care Medicine, University Medicine Cluster, National University Health System, 1E Kent Ridge Rd, Singapore, 119228, Singapore. mdcliew@nus.edu.sg.
2 Fast and Chronic Programmes, Alexandra Hospital, National University Health System, Singapore, Singapore. mdcliew@nus.edu.sg.
3 Division of Respiratory and Critical Care Medicine, University Medicine Cluster, National University Health System, 1E Kent Ridge Rd, Singapore, 119228, Singapore.
4 Fast and Chronic Programmes, Alexandra Hospital, National University Health System, Singapore, Singapore.
5 Emergency Medicine Department, National University Hospital, National University Health System, Singapore, Singapore.