1 Department of Critical Care Medicine, Department of Anesthesiology and Pain Medicine and the Dosseter Ethics Centre, University of Alberta, Edmonton, Canada.
2 Department of Emergency Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep, University of Arizona College of Medicine, Tucson, AZ, USA.
3 Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep, University of Arizona College of Medicine, Tucson, AZ, USA.
4 Department of Emergency Medicine, St Michael's Hospital, University of Toronto, Ontario, Canada.