Written preferences regarding the use of artificial life prolonging measures is called ________.

The term that refers to written preferences regarding the use of artificial life-prolonging measures is a living will. This legal document allows an individual to specify the types of medical treatments and interventions they wish to receive or decline in the event they become unable to communicate their wishes due to illness or incapacity. A living will focuses specifically on end-of-life care decisions, ensuring that the individual's preferences are honored.

The other terms mentioned have different meanings: an advance directive is a broader category that includes living wills and may encompass other instructions related to healthcare; a health care proxy designates an individual to make healthcare decisions on someone’s behalf if they are unable to do so; and a palliative care plan generally refers to a comprehensive approach to managing symptoms and improving quality of life for individuals with serious illnesses, rather than specifically addressing life-prolonging measures.