[1] Bethesda North Hosp, Div Pulm & Sleep Med, Cincinnati, OH 20814 USA
[2] Univ Cologne, Inst Pneumol, Ctr Sleep Med & Resp Care, Bethanien Hosp Clin Pneumol & Allergol, Solingen, Germany
[3] Univ New Mexico, Sch Med, Div Pulm Crit Care & Sleep Med, Albuquerque, NM USA