Certified Respiratory Therapist Practice Exam

What is the approximate total output flow from a 35% air-entrainment mask operating at 8 L/min?

1. 32 L/min

2. 48 L/min

3. 64 L/min

4. 40 L/min

The correct answer is: 48 L/min

To determine the approximate total output flow from a 35% air-entrainment mask operating at a flow rate of 8 L/min, it's essential to understand how air-entrainment masks work. These devices mix oxygen with room air to achieve a desired oxygen concentration, in this case, 35%. The total output flow from an air-entrainment mask can be calculated by the formula: Total Output Flow = Flow Rate + (Flow Rate x (air to oxygen ratio)) For a 35% mask, the air-to-oxygen ratio is typically around 3:1, meaning for every part of oxygen, three parts of room air are entrained. When you calculate the total output for a mask like this: 1. The air entering is approximately three times the oxygen flow. 2. Therefore, for a flow-rate of 8 L/min set for oxygen, the flow of air mixed with this would be 3 times that amount, or 24 L/min of air. Adding this to the 8 L/min of oxygen provides the total output flow: Total Output Flow = 8 L/min (oxygen) + 24 L/min (air) = 32 L/min. However, the question asked for an approximation,