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How to measure oxygen saturation using pulse oximeter 
Understand the relationship between oxygen and the blood. 
Oxygen is breathed into the lungs. The oxygen then passes into the blood where the majority of the oxygen attaches to hemoglobin.
Hemoglobin is a protein located inside our red blood cells that transports the oxygen through the bloodstream to the rest of our body and tissues. In this way, our body is given the oxygen and nutrients it needs to function.