[TSNAPCRACKLEPOP]

there is a test run on a routine Blood Gas Analysis, where a small amount of arterial blood is drawn from an artery, (should be Oxygenated, as opposed to venous blood which is deoxygenated) and the % saturation of the blood with oxygen is measured. also, the carboxyhemoglobinn is measured, which tells how much of your hemoglobin is not available to carry oxygen, because another substance binds to hemoglobin more tightly than oxygen, therefore some of the smokers hemoglobin cannot carry O2 in the blood, never has a chance. this can be low, like 4% or so, but i have seen it up around 12 % in heavy smokers.

remember jim jones and the cyanide....same binding to the cell principle.

also when you quit, you regain this because hemoglobin is recycled about every 90 days.

simplified explanation