[1] Temple Univ, Sch Med, Dept Pulm & Crit Care Med, Philadelphia, PA 19140 USA
[2] Univ Minnesota, Sch Publ Hlth, Dept Biostat, Minneapolis, MN USA
[3] Univ Minnesota, Data Coordinating Ctr, Minneapolis, MN USA
[4] Univ Minnesota, Dept Pulm Allergy Crit Care & Sleep Med, Minneapolis, MN USA
[5] Mayo Clin, Dept Pulm & Crit Care Med, Rochester, MN USA
[6] Univ Ottawa, Ottawa Hosp Res Inst, Ottawa, ON, Canada
[7] Univ British Columbia, Dept Med, Vancouver, BC, Canada
[8] Univ British Columbia, Inst Heart & Lung Hlth, James Hogg Res Ctr, Vancouver, BC, Canada
[9] Denver Hlth Med Ctr, Dept Med, Denver, CO USA
[10] Natl Jewish Hlth, Div Pulm Crit Care & Sleep Med, Denver, CO USA
[11] Univ Alabama Birmingham, Dept Pulm Allergy & Crit Care Med, Birmingham, AL 35205 USA
[12] Univ Alabama Birmingham, Pulm Sect, Birmingham, AL USA
[13] Harbor UCLA Res & Educ Inst, Los Angeles, CA USA
[14] Vet Affairs Med Ctr, Dept Pulm Med, Ann Arbor, MI USA
[15] Univ Michigan, Ann Arbor, MI 48109 USA
[16] Univ Michigan Hlth Syst, Dept Pulm & Crit Care Med, Ann Arbor, MI USA
[17] Univ Pittsburgh, Med Ctr, Dept Pulm Allergy & Crit Care Med, Pittsburgh, PA USA
[18] Univ Maryland, Dept Pulm & Crit Care Med, Baltimore, MD 21201 USA
[19] Brigham & Womens Hosp, Dept Pulm & Crit Care Med, Boston, MA 02115 USA
[20] Univ Calif San Francisco, Dept Pulm & Crit Care Med, San Francisco, CA 94143 USA