[1] Univ So Calif, Keck Sch Med, Los Angeles, CA 90027 USA
[2] Univ Calif San Francisco, Sch Nursing, San Francisco, CA 94143 USA
[3] Vet Affairs Palo Alto Hlth Care Syst, Palo Alto, CA USA
[4] San Francisco VA Med Ctr, San Francisco, CA USA
[5] Univ Calif San Francisco, Dept Physiol Nursing, San Francisco, CA USA