Under a measure drafted by Gov. Deval Patrick's administration, Massachusetts health regulators are expected to make it significantly harder for Boston's teaching hospitals to expand into the suburbs. The move is designed to protect smaller community hospitals that feel under siege from their powerful rivals. The measure is almost certain to win support from the Public Health Council, and will force hospitals to prove that proposed expansions do not duplicate services. Prior to the measure, hospitals hoping to add overnight beds at outpatient facilities faced little scrutiny from the state.