Final answer:
The essential nursing action when administering oxygen at 4 L/minute via a nasal cannula is to position the prongs in the patient's nares so they curve upward, ensuring optimal delivery and patient comfort.
Step-by-step explanation:
The question pertains to essential nursing actions when a primary health-care provider orders oxygen administration at 4 L/minute via nasal cannula. The correct action from the given options is A) Position the prongs in the patient's nares so that they curve upward. This position ensures proper delivery of oxygen into the nasal passages and optimizes patient comfort and oxygen uptake. Ensuring oxygen is humidified (B), providing oral hygiene every shift (C), and securing elastic straps (D), are supportive actions that may also be important depending on the clinical situation, but positioning the prongs correctly is essential for effective oxygen therapy. The nasal cavity's ability to warm and humidify air is beneficial for maintaining healthy respiratory function, as it helps ward off infection, decrease sensitivity during breathing, and prevent damage to the lungs.