At what flow rate does a face mask with reservoir allow for approximately 100% oxygen concentration?

A face mask with a reservoir typically provides a higher concentration of oxygen due to the reservoir bag that stores a volume of oxygen for inhalation. For approximately 100% oxygen concentration, a flow rate of at least 10 liters per minute is required. This flow rate ensures that the bag remains inflated and can deliver a sufficient supply of oxygen with each breath.

At lower flow rates, the reservoir bag may not remain adequately filled, which can lead to a dilution of the inspired oxygen concentration with room air, resulting in lower oxygen levels. Thus, the correct answer is associated with the need for a minimum flow to maintain the effectiveness of the oxygen delivery system in delivering high concentrations.