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).
Hyperventilation syndrome
People with HVS may feel that they cannot get enough air. In reality, they have about the same oxygenation in the arterial blood (normal values are about 98% for hemoglobin saturation) and too little carbon dioxide (hypocapnia) in their blood and other tissues. While oxygen is abundant in the bloodstream, HVS reduces effective delivery of that oxygen to vital organs due to low--induced vasoconstriction and the suppressed Bohr effect.