Jack O. Bovender Jr., who returned to help lead hospital chain HCA Inc. amid a federal fraud investigation in 1997 and most recently oversaw a leveraged buyout that took HCA private, plans to retire as chief executive at the end of the year. Nashville-based HCA Inc. said that Richard M. Bracken, HCA's president and chief operating officer, will become CEO on Jan. 1 while retaining the role of president. The leadership change was announced as HCA and other hospital operators continue to face challenges such as lower inpatient admissions and an increase in patients without insurance coverage.