Final answer:
The most appropriate nursing action to relieve the dyspnea experienced by the patient is to initiate high-flow oxygen therapy.
Step-by-step explanation:
The most appropriate nursing action to relieve the dyspnea experienced by the 66-year-old patient in palliative care for lung cancer is B) Initiate high-flow oxygen therapy.
Dyspnea, or difficulty breathing, is a common symptom in patients with advanced lung cancer. High-flow oxygen therapy can help improve oxygenation and relieve dyspnea by delivering a higher concentration of oxygen to the patient's lungs. This can alleviate the feeling of breathlessness and provide comfort to the patient.
Administering a bolus of normal saline (A) may not address the underlying cause of the dyspnea and is unlikely to provide immediate relief. Administering high doses of opioids (C) may help manage pain but may not specifically target dyspnea. Administering bronchodilators and corticosteroids (D) may be appropriate for certain types of dyspnea, but in this case, the patient's dyspnea is likely related to the advanced stage of lung cancer and is not likely to be effectively treated with these medications.