Carbon dioxide is a waste product of respiration and moves by diffusion in the other direction. It moves from the cells into the blood and then from the blood into the lungs before it is breathed out.

Red blood cells collect carbon dioxide from the body’s cells and transports it back to the lungs. An exchange of oxygen and carbon dioxide takes place in the alveoli, small structures within the ...

Doctors use lung diffusion tests to measure how well a person’s lungs exchange oxygen and carbon dioxide. The test can detect lung damage and help diagnose lung conditions, including emphysema ...