1 Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University, 1800 Orleans Street, Zayed Tower, Suite 9121, Baltimore, MD 21287, USA. Electronic address: dhager1@jhmi.edu.
2 Department of Emergency Medicine, University of Michigan Health System, 1500 East Medical Center Drive, SPC 5303, B1-354N Taubman Center, Ann Arbor, MI 48109-5303, USA. Electronic address: kgunners@med.umich.edu.
3 Centre for Clinical Research in Emergency Medicine, Harry Perkins Institute of Medical Research, Royal Perth Hospital, University of Western Australia, Level 6, Q Block, Wellington Street, Perth, Western Australia 6000, Australia. Electronic address: stephen.macdonald@health.wa.gov.au.