Students – Paramedic Practice Exam

The thing being tested is how much oxygen is actually delivered to a patient when using a ventilation device without an oxygen source. A pocket mask, with no supplemental oxygen, doesn’t provide an oxygen reservoir or concentrate the air you’re delivering. The patient ends up breathing a mix of room air and the rescuer’s exhaled breath, and that exhaled breath has a lower oxygen content (roughly around 15–16%). The result is an inspired O2 concentration of about 16–17%. By comparison, supplying oxygen with a mask or reservoir can raise FiO2 substantially—roughly 40–60% with a bag-valve mask with a reservoir, or up toward 90% or more with a nonrebreather mask. Ambient room air is about 21%, but without an oxygen source, a pocket mask doesn’t keep that value; it sits around the mid-teens.