Final answer:
The room air FiO2 set on a ventilator should be at 21%, which is the oxygen concentration of room air. This setting is used when a patient's breathing is to be supported as if they were breathing normal room air. CO and FiO2 are different parameters, the former related to cardiovascular health and the latter to respiratory support.
Step-by-step explanation:
When a surgeon requests the room air FiO2 (Fraction of Inspired Oxygen) to be set on a ventilator, it refers to the oxygen concentration in the air delivered by the ventilator to the patient. Room air has an FiO2 of approximately 21%, since that is the concentration of oxygen in the Earth's atmosphere. Therefore, the ventilator should be set to deliver a FiO2 of 21% to mimic the oxygen concentration the patient would be breathing if not on the ventilator.
The mean Cardiac Output (CO) is separate from the FiO2 setting on a ventilator, as CO refers to the volume of blood the heart pumps each minute. The numbers provided, which specify a mean CO of 5.25 L/min with a range of 4.0-8.0 L/min, are indicative of the heart's function and are not directly related to the ventilator settings. Factors influencing CO can be critical in understanding overall cardiovascular health and are necessary to monitor in patients requiring mechanical ventilation.