Now, the question is, how exactly does the binding of carbon monoxide onto hemoglobin affect the oxygen hemoglobin dissociation curve? So, to see what the effect is, let's take a look at the following diagram. So, as always, the Y axis is the percentage saturation of hemoglobin inside our blood plasma, and it ranges from zero to 100%. Now, the x axis is the partial pressure of oxygen inside our tissues given to us in millimeters of mercury. So it ranges from zero to 100. Now, the blue curve describes the normal oxygen hemoglobin dissociation curve.