Blood
About 98.5% of the oxygen in a sample of arterial blood in a healthy human breathing air at sea-level pressure is chemically combined with the hemoglobin. About 1.5% is physically dissolved in the other blood liquids and not connected to hemoglobin. The hemoglobin molecule is the primary transporter of oxygen in mammals and many other species (for exceptions, see below). Hemoglobin has an oxygen binding capacity between 1.36 and 1.40 ml O per gram hemoglobin, which increases the total blood oxygen capacity seventyfold, compared to if oxygen solely were carried by its solubility of 0.03 ml O per liter blood per mm Hg partial pressure of oxygen (about 100 mm Hg in arteries).
Dennis Lewis
In his writing and teaching about breathing, Lewis maintains that many people habitually hyperventilate — by which he means taking rapid shallow breaths from the top of the chest instead of breathing more naturally with the entire abdomen and back — and this reduces carbon dioxide levels in the blood too rapidly and thus causes an oxygen shortage in the brain and body. The result of lower oxygen he claims is, among other things, anxiety, tension, or irritability. There is disagreement about the benefits of increased oxygen blood levels. According to Dr. Mary Purucker, a pulmonary specialist in the U.S. Food and Drug Administration Center for Drug Evaluation and Research, there are no long-term, well-controlled scientific studies that support claims of benefit for increased oxygen in healthy people. There are many like Lewis today, however, including breath therapists, breathing teachers, MDs, and researchers, who maintain that good breathing increases the likelihood of a longer, healthier, more-rewarding life—physically, emotionally, and spiritually.