How much oxygen is typically delivered during mouth-to-mouth resuscitation?

During mouth-to-mouth resuscitation, the amount of oxygen delivered is approximately 21%. This is consistent with the oxygen concentration in atmospheric air, which is about 21% oxygen. When performing mouth-to-mouth resuscitation, the rescuer exhales into the patient’s mouth, and the air exhaled will contain this level of oxygen. Even though some air may have been used by the rescuer's body, the majority of the exhaled air remains quite similar to ambient air in terms of oxygen concentration.

The other options do not accurately reflect the oxygen concentration of exhaled air used in mouth-to-mouth resuscitation. Therefore, the best choice is effectively the standard ambient air concentration when providing respiratory support through this method, confirming that the correct answer revolves around the standard value provided by atmospheric conditions.