What is the test for liability for misfeasance in medical malpractice cases?

"'Misfeasance is the improper performance of an act that is otherwise proper and nonfeasance is the nonperformance of an act that should be performed.' [Citation.] 'Misfeasance exists when the defendant is responsible for making the plaintiffs position worse, i.e., defendant has created a risk.' [Citation.] '[N]onfeasance is found when the defendant has failed to aid plaintiff through beneficial intervention. [L]iability for nonfeasance is largely limited to those circumstances in which some special relationship can be established. If, on the other hand, the act complained of is one of misfeasance, the question of duty is governed by the standards of ordinary care....' [Citation.]" (Romero v. Superior Court, supra, 89 Cal.App.4th at p. 1079.)