A 75-year-old patient with end-stage metastatic pancreatic cancer, previously designated her daughter as her healthcare proxy, now presents to the emergency department in respiratory distress. She is intubated, but her prognosis is grim. The daughter states her mother, while competent, repeatedly expressed a desire "not to suffer" and wished to "die naturally" without prolonged life support. The medical team believes further aggressive care is medically futile. What ethical principle should primarily guide the decision-making in this scenario?
✓ Correct Answer: Option C
When a patient lacks capacity, decisions should be guided by the principle of autonomy, respecting the patient's previously expressed wishes and values as communicated through their designated healthcare proxy or advanced directive, especially when medical futility is also a consideration.