How Pulse Oximeter Works

 Did you ever wonder why your veins appear blue, yet blood is red?   The key to the color difference is oxygen.  Blood that is fully saturated with oxygen look bright red, while blood that has released all of it’s oxygen takes on a blue tinge.

Adequate blood oxygen levels are important to keep your body functioning. Without enough oxygen, cells are damaged and eventually die, a potential source o f infection. Vital organs can sustain damage as well.  Most important however, is the delivery of enough oxygen to your brain.

Blood contains hemoglobin, which enables blood to be transported through the body. The hemoglobin molecule has four sites for oxygen to attach.  When all four positions are filled, the hemoglobin is fully (100%) saturated.  The average saturation of a large volume of blood tells the oxygen saturation of your blood. This number indicates how much oxygen is being transported to you body’s vital organs and cells. 

Hemoglobin that is fully saturated with oxygen absorbs light differently that desaturated hemoglobin. Non-invasive detection of the oxygen level in your blood is made possible by using this property.   A finger-tip pulse oximeter device contains both a light source and a detector.  Based on values programmed into the device, the amount of red and infared light that is detected after transmission or reflection through the skin, the level of oxygen saturation of the blood can be calculated. 

The pulse oximeter not only detects the oxygen levels in your blood, but also your pulse rate.  Most pulse oximeters give a visual as well as an audible reading of both pulse rate and oxygen saturation.  Pulse oximetry has been a standard of care in post-anesthesia recovery care since 1990 because  it can quickly alert caregivers of any changes in a patient’s vital signs, offering a higher level of safety.

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