[1] Vet Affairs Palo Alto Hlth Care Syst, Pulm & Crit Care Sect 111P, Hlth Serv Res & Dev Serv, Palo Alto, CA 94304 USA
[2] Stanford Univ, Sch Med, Div Pulm & Crit Care Med, Stanford, CA 94305 USA
[3] Stanford Univ, Sch Med, Dept Hlth Res & Policy, Stanford, CA 94305 USA
[4] Stanford Univ, Sch Med, Ctr Primary Care & Outcomes Res, Stanford, CA 94305 USA
[5] Vet Affairs Palo Alto Hlth Care Syst, Ctr Hlth Care Evaluat, Palo Alto, CA 94304 USA