When will an air-entrainment mask deliver an FIO2 higher than intended?

An air-entrainment mask is designed to deliver a specific fraction of inspired oxygen (FIO2) by mixing a controlled amount of oxygen with ambient air. When the air-entrainment ports are functioning properly, they allow ambient air to dilute the oxygen being delivered. However, if these ports become blocked, the mask will not be able to effectively mix ambient air with the oxygen flow. This blockage can lead to a situation where the delivered oxygen concentration increases, resulting in an FIO2 that is higher than intended.

This phenomenon occurs because the oxygen flow remains the same, but the reduction in ambient air intake forces the mask to provide a higher proportion of oxygen compared to the desired mixture. As a result, the patient receives a higher concentration of oxygen than what the mask was designed to deliver.

In the context of the other options, having the flow set too low would actually lead to a lower FIO2, as there would be insufficient oxygen volume to mix effectively with room air. Adding nebulized water can aid in providing humidification but does not directly increase the FIO2 from the mask—it's meant to enhance comfort and prevent airway dryness. Introducing corrugated tubing between the adapter and mask could potentially create dead space, but does not block the