What is the expected FiO2 from a simple face mask?

A simple face mask delivers an expected fraction of inspired oxygen (FiO2) of approximately 40% to 60%. This range is considered appropriate because the mask utilizes oxygen from a supplemental source while also allowing atmospheric air to enter through side ports. As the patient breathes, they receive a mixture of the supplemental oxygen and ambient air.

The design of the simple face mask allows for an adequate flow of oxygen, typically set at 5 to 10 liters per minute, which helps maintain the desired FiO2. The exact value can vary based on the patient's respiratory pattern, the fit of the mask, and the flow rate of oxygen being used. It is commonly used for patients who require moderate levels of oxygen therapy but do not need high concentrations, making it suitable for various clinical situations, such as managing patients with mild hypoxia.

In contrast, values like 10% to 20% would be too low for any effective oxygen therapy, and options suggesting higher FiO2 percentages, such as 70% to 90% or 80% to 100%, typically pertain to other delivery systems like non-rebreather masks or mechanical ventilation, which provide a more concentrated oxygen source. Overall, the simple face mask is designed to