11.   Breathing pure oxygen under increased pressure allows blood vessels to carry more oxygen deeper into tissue throughout the body, including the brain.

12.   But the number of healthy red blood cells carrying oxygen through her body continued to sink.

13.   Each cell is jam-packed with hemoglobin molecules, which actually carry the oxygen.

14.   EPO is produced naturally by the kidneys to promote production of red blood cells, which are crucial in carrying oxygen throughout the body.

15.   European cycling officials charged the athletes with using erythropoietin, or EPO, which raises red blood cell counts, enabling the blood to carry more oxygen to muscles.

16.   EPO allows more oxygen to reach tired muscles by augmenting the red blood cells that carry oxygen.

17.   For the last six years, since undergoing heart bypass surgery, Stephens has been carrying portable oxygen to help him cope with emphysema.

18.   He was tired and disoriented, but Harris set out to carry oxygen up to them.

19.   If not to carry oxygen, what is the hemoglobin for?

20.   If you breathe in carbon monoxide, it bonds to blood cells and keeps the blood from carrying the oxygen your body needs.