How much oxygen is delivered through mouth-to-mouth rescue breathing?

The correct answer is that approximately 16% of oxygen is delivered through mouth-to-mouth rescue breathing. This is due to the composition of exhaled air, which contains about 16% oxygen. When a person exhales, they breathe out not only carbon dioxide but also oxygen. Although normal atmospheric air consists of about 21% oxygen, the air exhaled by a person is lower in oxygen concentration because it has already been used by the body.

In the context of life support and rescue breathing, the essential goal is to provide additional oxygen to someone who is unable to breathe adequately. While mouth-to-mouth may not provide pure ambient air, it still delivers a significant amount of oxygen—enough to help sustain life until further medical assistance can be provided. Understanding this percentage is crucial for those practicing immediate life support, as it emphasizes the importance of delivering rescue breaths effectively.