Quickly measured without a blood draw, pulse oximetry or SpO2 indicates the estimated oxygen saturation of red blood cells. It is an indirect measure, calculated through a clip-on fingertip device that uses visible and infrared light. The SpO2 value, expressed as a percentage, helps clinicians understand how the body is using oxygen once it has been inhaled. A quick check of this value can help clinic and home care personnel understand how well a patient is breathing, and aid a primary care doctor in identifying lung problems and other conditions during routine visits.


1. How SpO2 is measured

The doctor will clip a measurement device onto a fingertip. The device will then shine light through the finger and measure the light received on the other side. Measurement depends on the patient having normal red blood cells and normal, clean fingernails. Abnormal hemoglobin in the blood and nail polish can disrupt the measurement. When the measurement is complete, the device will display both a percentage value for SpO2 and a pulse value in beats per minute.


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