The illustration shows the so-called oxygen-binding curve. The oxygen-binding curve is a graphic representation of the relationship between the oxygen partial pressure (ppO2) and the arterial oxygen saturation of hemoglobin (SaO2). The oxygen-binding curve relates each oxygen partial pressure to a certain oxygen saturation of hemoglobin. Regarding the pathophysiology a left shift is distinguished from a right shift of the oxygen-binding curve: In case of a right shift of the oxygen-binding curve, less oxygen is bound to hemoglobin under the same ppO2. The situation is reversed in case of a left shift. Here, the bond between oxygen and hemoglobin is stronger. Therefore more oxygen is bound by hemoglobin under the same ppO2.