What relationship does an ethics committee have in enforcing the advance directives of the patients in their care

The Patient Self-Determination Act (PSDA) was implemented to allow patients to state “Do Not Resuscitate” (DNS), or to assign a surrogate decision maker in the event that the individual is unable to make the decision. What relationship does an ethics committee have in enforcing the advance directives of the patients in their care? Support your analysis with a minimum of one peer-reviewed article.