[1] Johns Hopkins Univ, Div Pulm & Crit Care Med, Baltimore, MD USA
[2] Univ Utah, Sch Med, Salt Lake City, UT USA
[3] Univ Iowa, Carver Coll Med, Iowa City, IA USA
[4] Weill Cornell Med Coll, New York, NY USA
[5] Univ Calif San Francisco, Med, San Francisco, CA 94143 USA
[6] Columbia Univ, Presbyterian Hosp, Med Ctr, New York, NY USA
[7] Johns Hopkins Univ, Baltimore, MD USA
[8] Univ Michigan Hlth Syst, Internal Med, Ann Arbor, MI USA
[9] Univ Michigan, Ann Arbor, MI 48109 USA
[10] Univ Calif Los Angeles, David Geffen Sch Med, Dept Med, Los Angeles, CA 90095 USA
[11] Univ Calif Los Angeles, David Geffen Sch Med, Dept Physiol, Los Angeles, CA 90095 USA
[12] Univ Iowa, Internal Med Pulm, Iowa City, IA USA
[13] Univ Utah, Salt Lake City, UT USA
[14] Univ Illinois, Chicago, IL USA
[15] Dartmouth Hitchcock Med Ctr, Pulm Crit Care, Lebanon, NH 03766 USA
[16] Univ Washington, Seattle, WA 98195 USA
[17] Univ Washington, Med Epidemiol, Env Occ Hlth, Seattle, WA 98195 USA
[18] Univ N Carolina, Chapel Hill, NC 27515 USA