[1] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, Resp Epidemiol Occupat Med & Publ Hlth, London SW3 6LR, England
[2] Univ British Columbia, Heart Lung Innovat Ctr, Vancouver, BC V5Z 1M9, Canada
[3] Paracelsus Med Univ, Dept Pulm Med, Salzburg, Austria
[4] Uppsala Univ, Dept Med Sci Resp Med & Allergol, Uppsala, Sweden
[5] Univ Iceland, Fac Med, Reykjavik, Iceland
[6] Landspitali Univ Hosp, Reykjavik, Iceland
[7] Univ Kentucky, Div Pulm Crit Care & Sleep Med, Lexington, KY USA
[8] Univ Cape Town, Dept Med, ZA-7925 Cape Town, South Africa
[9] Oregon Hlth & Sci Univ, Portland, OR 97201 USA