Final answer:
Using a high-flow venturi mask to deliver oxygen as prescribed is the nursing action that best promotes adequate gas exchange in a patient with advanced COPD.
Step-by-step explanation:
The nursing action that best promotes adequate gas exchange in a patient with advanced chronic obstructive pulmonary disease (COPD) is C. Using a high-flow venturi mask to deliver oxygen as prescribed. Advanced COPD can significantly compromise the patient's ability to oxygenate their blood and eliminate carbon dioxide. Providing supplemental oxygen through a high-flow venturi mask can help to improve oxygenation and promote adequate gas exchange in these patients.
Other options listed in the question such as encouraging the patient to drink fluids keeping the patient in a semi-fowler's position or administering a sedative are not specifically targeted towards improving gas exchange and may not be as effective in addressing the underlying respiratory impairment.