Final answer:
Oxygen delivery via nasal cannula is typically limited to 6 L/min to prevent discomfort and injury, and because higher rates do not significantly increase oxygen saturation in the blood.
Step-by-step explanation:
Oxygen delivery via nasal cannula typically should not exceed 6 L/min. This is because higher flows are not well tolerated and can lead to drying of the nasal mucosa, discomfort, and potential injury. Furthermore, in most clinical scenarios, a nasal cannula delivering more than 6 L/min does not significantly increase the arterial oxygen saturation due to the limitations imposed by the anatomy and physiology of the respiratory system. In certain situations, such as when patients have chronic hypercapnia, lower rates of oxygen may be necessary to avoid suppressing their respiratory drive.