Not only did the title of Episode 319 get released (it's not confirmed yet, however), but there's also a spoiler about it too! My Favorite Mistake airs sometime in March. From HamAndEggs75 at the ABC Message Boards.

There only appears to be one patient, Cathy. There are also sides for her daughter, Nina. Cathy is sick, coughing, her CT showed that her coughing caused a hairline fracture in her rib and it close to puncturing her lung. She also mentions having cancer at another point in the sides so it could be lung cancer. Her daughter Nina is perfect, regrets taking her mom out to the mall during flu season and says they both knew better. Nina is uptight and bossy and worried the interns do not know what they are doing. Cathy should have surgery to fix her lungs but Nina is worried the risk is too high. There is a scene of Cathy yelling at Nina that "you can't be perfect, no one is perfect."