The Massachusetts Hospital Association sent a letter to Governor Patrick last week asking him to stop proposed administrative changes the group says would result in cuts of about $40 million to Medicaid payments for hospitals. President Lynn Nicholas wrote to Patrick in a letter dated July 3. The letter points to an ongoing struggle between the hospitals and the state over Medicaid payments, which have fallen since 2006, even as the Affordable Care Act promises to bring Massachusetts nearly $2 billion from the federal government over six years, starting in 2014.