Question:easy
Mouth-to-mouth respiration provides what percentage of oxygen to the recipient?
Mouth-to-mouth respiration provides what percentage of oxygen to the recipient?
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The rescuer's lungs have already taken some oxygen out of the 21% room air before it is blown in.
Updated On: Jun 23, 2026
- 10%
- 16%
- 21%
- 100%
Show Solution
The Correct Option is B
Solution and Explanation
Quick logic: inspired room air is 21% oxygen; the rescuer's body uses some, so expired air must be lower, and the textbook figure for that expired air is 16%.
Eliminate the traps. 21% is the answer for an Ambu bag filled with room air, not for breath given by a person. 100% applies only to a high-flow oxygen source such as a cylinder with a reservoir. 10% would be hypoxic and could not sustain a patient.
So 16% is correct. Practically, mouth-to-mouth ventilation pushes about 0.8 to 1.2 L per breath of this 16% oxygen, 4% carbon dioxide mixture, which keeps a patient oxygenated long enough for resuscitation. The AHA notes tidal volumes of roughly 500 to 1000 mL, with smaller volumes preferred to limit gastric inflation.
Ref: Resuscitation physiology; AHA CPR.
Eliminate the traps. 21% is the answer for an Ambu bag filled with room air, not for breath given by a person. 100% applies only to a high-flow oxygen source such as a cylinder with a reservoir. 10% would be hypoxic and could not sustain a patient.
So 16% is correct. Practically, mouth-to-mouth ventilation pushes about 0.8 to 1.2 L per breath of this 16% oxygen, 4% carbon dioxide mixture, which keeps a patient oxygenated long enough for resuscitation. The AHA notes tidal volumes of roughly 500 to 1000 mL, with smaller volumes preferred to limit gastric inflation.
Ref: Resuscitation physiology; AHA CPR.
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