Final answer:
Arterial blood contains about 20 percent oxygen by volume, with 98.5 percent of this oxygen bound to hemoglobin. Normal pulse oximeter readings indicating this saturation range from 95-100 percent.
Step-by-step explanation:
Oxygen Content in Arterial Blood
Arterial blood oxygen content is a measurement indicating the percent saturation of hemoglobin with oxygen. Although oxygen dissolves in blood, only a small amount, about 1.5 percent, is transported dissolved in the plasma. The majority of oxygen, approximately 98.5 percent, is bound to hemoglobin in erythrocytes (red blood cells) and carried to the tissues. When measured using a pulse oximeter, normal readings for oxygen saturation range from 95-100 percent. These readings reflect the hemoglobin saturation levels and not simply the dissolved oxygen in the plasma. Therefore, approximately 20 percent (by volume) of oxygen is carried by hemoglobin in arterial blood, which corresponds to the high percentage of oxygen saturation usually found in healthy individuals.
Additionally, a patient's hematocrit value indicates the proportion of blood composed of erythrocytes. For example, if a patient's hematocrit is 42 percent, the percentage of the patient's blood that is plasma would be approximately 58 percent, since plasma and erythrocytes make up the total blood volume.