[1] McMaster Univ, Michael G DeGroote Sch Med, Hamilton, ON, Canada
[2] McMaster Univ, Div Neurosurg, Dept Surg, Hamilton, ON, Canada
[3] Univ Ottawa, Ottawa Hosp, Res Inst, Dept Med Crit Care, Ottawa, ON, Canada
[4] St George Hosp, Dept Intens Care Med, Blackshaw Rd, London, England
[5] NYU, Dept Med, Div Pulm Med & Crit Care, 550 1St Ave, New York, NY 10016 USA
[6] St Josephs Healthcare Hamilton, 50 Charlton Ave, Hamilton, ON L8N 4A6, Canada
[7] Univ Pittsburgh, Sch Med, Dept Crit Care Med, Pittsburgh, PA USA
[8] McMaster Univ, Dept Hlth Res Methods Evidence & Impact, Hamilton, ON, Canada
[9] McMaster Univ, Div Crit Care, Dept Med, Hamilton, ON, Canada