[1] Harborview Med Ctr, Dept Anesthesiol & Pain Med, Seattle, WA 98104 USA
[2] Harborview Med Ctr, Div Pulm & Crit Care Med, Seattle, WA 98104 USA
[3] Univ Washington, Dept Med, Seattle, WA USA
[4] Univ Washington, Dept Biostat, Seattle, WA 98195 USA
[5] Univ Washington, Dept Hlth Serv, Seattle, WA 98195 USA