[1] Txagorritxu Hosp, Resp Dept, Vitoria, Spain
[2] Walter Reed Natl Mil Med Ctr, Dept Pulm Crit Care & Sleep Med, Bethesda, MD USA
[3] Duke Univ, Med Ctr, Div Pulm & Crit Care Med, Durham, NC USA
[4] Uniformed Serv Univ Hlth Sci, F Edward Hebert Sch Med, Bethesda, MD 20814 USA
[5] Galdakao Hosp, Resp Dept, Galdakao, Spain
[6] San Pedro Hosp, Resp Dept, Logrono, Spain
[7] Virgen del Rocio Hosp, Resp Dept, Seville, Spain
[8] Hosp La Fe, Resp Dept, E-46009 Valencia, Spain
[9] Hosp Sierrallana, Dept Med, Cantabria, Spain
[10] Hosp Badalona Germans Trias & Pujol, Dept Med, Badalona, Spain
[11] Washington Univ, Sch Med, Div Pulm & Crit Care Med, St Louis, MO USA
[12] Washington Univ, Sch Med, Div Gen Med Sci, St Louis, MO USA
[13] Hosp Ramon & Cajal, IRYCIS, Resp Dept, E-28034 Madrid, Spain