A growing number of Baltimore residents are being treated in hospitals for illnesses that could be prevented with routine medical care, according to a study. The city's health commissioner says the data show "a fundamental failure" of Baltimore's health system. City residents are being hospitalized or treated in emergency rooms for such conditions as asthma and high blood pressure at rates that are roughly twice those in surrounding counties and statewide, according to the Rand Corp. study. Baltimore's health commissioner says the problem is the inevitable result of clinics that are stretched to capacity and a shortage of primary care doctors to serve the poor.