As a psychiatric nurse practitioner, Diane Solomon counsels patients in therapy, prescribes medications and practices independently in her medical office in downtown Portland. "I'm completely autonomous," she says. Oregon and Washington are among 16 states with liberal practice laws to allow licensed nurse practitioners to care for patients, order diagnostic tests and prescribe pharmaceuticals without a physician's oversight. As the U.S. extends health coverage to 32 million people, so-called "advanced practice" nurses are likely to be key in areas of medicine with too few doctors, such as primary care, obstetrics, geriatrics and mental health.