[1] Intermt Med Ctr, Dept Med, Div Pulm & Crit Care Med, Murray, UT 84107 USA
[2] Univ Utah, Sch Med, Dept Med, Div Pulm & Crit Care Med, Salt Lake City, UT 84132 USA
[3] Univ Utah, Sch Med, Dept Med, Div Epidemiol, Salt Lake City, UT USA
[4] Intermt Med Ctr, Dept Emergency Med, Salt Lake City, UT USA
[5] Univ Washington, Sch Med, Dept Med, Div Pulm & Crit Care Med, Seattle, WA 98195 USA