[1] Univ British Columbia, UBC James Hogg Res Ctr, Vancouver, BC V6Z 1Y6, Canada
[2] McGill Univ, Montreal Chest Inst, Montreal, PQ, Canada
[3] Univ Ottawa, Res Inst, Ottawa Hosp, Ottawa, ON, Canada
[4] Univ British Columbia, Dept Resp Med, Vancouver, BC V6Z 1Y6, Canada
[5] Dalhousie Univ, Dept Med, Halifax, NS, Canada
[6] Univ Calgary, Dept Med, Calgary, AB, Canada
[7] Univ Calgary, Dept Community Hlth Sci, Calgary, AB, Canada
[8] Univ Toronto, Dept Resp Med, Toronto, ON, Canada
[9] Univ Saskatchewan, Div Respirol, Saskatoon, SK, Canada
[10] Hop Laval, Ctr Pneumol, Quebec City, PQ, Canada
[11] Oregon Hlth & Sci Univ, Portland, OR 97201 USA
[12] Queens Univ, Div Resp & Crit Care Med, Kingston, ON, Canada