During respiration, approximately what percentage of carbon dioxide is present in expired air?

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Study for the City and Guilds Dental Nursing Block 2 Test. Use flashcards and multiple choice questions, each with hints and explanations, to prepare effectively. Get ready for your exam!

Multiple Choice

During respiration, approximately what percentage of carbon dioxide is present in expired air?

Explanation:
The amount of carbon dioxide in expired air reflects how much CO2 the body produces and how effectively the lungs remove it. Inspired air contains almost no CO2 (about 0.04%). In the lungs, blood rich in CO2 from tissues releases it into the alveoli, and the gas mix in the alveoli ends up with roughly 4–5% CO2. When we exhale, that CO2-rich air comes out, so expired air is about 4% CO2. The other values are not typical for normal resting breathing: 0.4% would be too low for expired air, while 14% or 40% would be far higher than what healthy lungs expel under normal conditions.

The amount of carbon dioxide in expired air reflects how much CO2 the body produces and how effectively the lungs remove it. Inspired air contains almost no CO2 (about 0.04%). In the lungs, blood rich in CO2 from tissues releases it into the alveoli, and the gas mix in the alveoli ends up with roughly 4–5% CO2. When we exhale, that CO2-rich air comes out, so expired air is about 4% CO2. The other values are not typical for normal resting breathing: 0.4% would be too low for expired air, while 14% or 40% would be far higher than what healthy lungs expel under normal conditions.

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