New York State Basic Emergency Medical Technician (EMT-B) Practice Exam

What is the approximate oxygen concentration delivered by a non-rebreather mask at a flow rate of 12-15 l/min?

1. 70%

2. 80%

3. 90%

4. 100%

The correct answer is: 90%

A non-rebreather mask is specifically designed to deliver high concentrations of oxygen to patients who are in need of significant respiratory support. When oxygen is administered through a non-rebreather mask at a flow rate of 12 to 15 liters per minute, the mask creates a sealed system that allows for the inhalation of almost pure oxygen. The design of the non-rebreather mask includes a reservoir bag, which captures the high-flow oxygen and provides a supply for the patient to inhale. Additionally, the presence of one-way valves prevents the patient from breathing in room air, ensuring that the concentration of oxygen remains high. At a flow rate of 12-15 l/min, studies and clinical practice indicate that the approximate oxygen concentration delivered to the patient is around 90%. This is crucial in situations such as severe respiratory distress, hypoxemia, or when the patient is in need of urgent oxygen therapy, as it allows for rapid and effective treatment. The ability of the mask to maintain high oxygen levels is further enhanced when it is fitted properly and the reservoir bag is inflated, ensuring that the patient receives the best possible concentration of oxygen.