[1] Univ Ottawa, Ottawa, ON, Canada
[2] St Michaels Hosp, Li Ka Shing Knowledge Inst, Keenan Res Ctr, Toronto HHT Ctr, Toronto, ON, Canada
[3] Univ Toronto, St Michaels Hosp, Dept Med, Div Respirol, Toronto, ON, Canada
[4] Univ Calif San Francisco, Ctr Cerebrovasc Res, Dept Anesthesia & Perioperat Care, San Francisco, CA 94143 USA
[5] Barrow Neurol Inst, Phoenix, AZ 85013 USA
[6] ICES, Toronto, ON, Canada