Fingertip measurement of oxygen saturation using an optical sensor, referred to as a pulse oximeter, provides quick and fairly reliable results referred to as SpO2. This measure of oxygen bound to hemoglobin in red blood cells gives results by measuring the amount of red and infrared light absorbed by the blood flowing through the fingertip. The SaO2 result measured directly from a blood sample is more definitive, however, because it is a direct laboratory measurement of the same value.

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