Mouth-to-mouth respiration provides an oxygen concentration of:
**Core Concept**
Mouth-to-mouth respiration, also known as mouth-to-mouth ventilation, is a technique used in cardiopulmonary resuscitation (CPR) to provide oxygen to a person who has stopped breathing. The air breathed into the person's lungs is assumed to be 21% oxygen, similar to the atmospheric air.
**Why the Correct Answer is Right**
When performing mouth-to-mouth respiration, the rescuer blows air into the person's mouth, which is then inhaled by the person. The air in the atmosphere contains approximately 21% oxygen, and this oxygen is transferred to the person's lungs and bloodstream during resuscitation. The remaining 79% of the air is nitrogen, which is not utilized by the body. This technique is effective in providing a significant amount of oxygen to the person, but it is not as efficient as using a bag-valve-mask (BVM) device or a ventilator.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because mouth-to-mouth respiration is not designed to provide a specific oxygen concentration, but rather to provide any available oxygen to the person in distress.
* **Option B:** This option is incorrect because the exact oxygen concentration delivered by mouth-to-mouth respiration is not precisely measurable and can vary depending on several factors, including the rescuer's breathing rate and technique.
* **Option C:** This option is incorrect because mouth-to-mouth respiration is not designed to provide a high concentration of oxygen, but rather to provide a sufficient amount of oxygen to sustain a person in distress.
**Clinical Pearl / High-Yield Fact**
It's essential to note that mouth-to-mouth respiration should only be performed by a trained rescuer, as it can pose a risk of infection transmission and other complications. In addition, if a person is suspected to have inhaled a foreign object, mouth-to-mouth respiration should not be attempted.
**Correct Answer: C. 21%**