[1] Univ Alabama Birmingham, Lung Hlth Ctr, Div Pulm Allergy & Crit Care, Birmingham, AL 35294 USA
[2] Univ Alabama Birmingham, Dept Radiol, Birmingham, AL 35294 USA
[3] Birmingham Vet Affairs Med Ctr, Birmingham, AL USA
[4] Brigham & Womens Hosp, Div Pulm & Crit Care, Boston, MA 02115 USA
[5] Brigham & Womens Hosp, Channing Lab, Div Network Med, Boston, MA 02115 USA
[6] Univ Michigan Hlth Syst, Div Pulm & Crit Care Med, Ann Arbor, MI USA
[7] Vet Affairs Hlth Syst, Med Serv, Pulm & Crit Care Med Sect, Ann Arbor, MI USA
[8] Temple Univ, Sch Med, Div Pulm & Crit Care, Philadelphia, PA 19122 USA
[9] Natl Jewish Hlth, Div Pulm & Crit Care, Denver, CO USA
[10] Natl Jewish Hlth, Div Biostat & Bioinformat, Denver, CO USA
[11] Univ Colorado, Colorado Sch Publ Hlth, Dept Epidemiol, Aurora, CO USA
[12] Johns Hopkins Sch Publ Hlth, Dept Epidemiol, Baltimore, MD USA