Oximetry

Oximetry calculates the percent of hemoglobin in your red blood cells that carry oxygen. This measurement is obtained through the use of a sensor. The sensor is connected by a cable to either a device known as an oximeter or a monitor with multiple displays. The measurement helps to:

  • Assess a person's oxygen level and breathing.

  • Assess the need or effectiveness of oxygen therapy or other treatments for lung disease.

  • Assess a person's ability to tolerate increased activity.

If a more accurate measurement is required, a blood sample from an artery should be collected.

HOW IS AN OXIMETRY READING OBTAINED?

For children and adults, a reusable or single use tape sensor is usually placed on such areas as a finger, earlobe, or toe. For infants, a single use tape sensor is usually placed around such areas as the sole of a foot or the palm of a hand. The sensor contains a light source and a light detector. The light source beams both a red and infrared LED light through the skin and blood. More infrared light is absorbed by hemoglobin that contains oxygen (oxyhemoglobin). Conversely, more red light passes through or is transmitted through oxyhemoglobin. Hemoglobin that lacks oxygen absorbs more red light. Conversely, more infrared light is transmitted through hemoglobin that lacks oxygen. The levels of transmitted red and infrared LED light received by the detector is measured. The difference of the transmitted red and infrared light during a heartbeat and between heart beats is calculated. The calculated value is then converted to a percent of hemoglobin that is carrying oxygen.

Oximetry may be used continuously or may be used at specified intervals.

ARE THERE ANY RISKS ASSOCIATED WITH OXIMETRY?

The risks associated with oximetry are rare. The LED lights do not burn or hurt your skin. However, there is a risk of skin breakdown if the sensor is left in the same location for extended periods of time.

Certain factors or conditions can affect the accuracy of the measurements. Accurate measurements can be affected by factors or conditions such as:

  • Extreme warmth or coolness of the area where the sensor is located.

  • Excessive sweating of the area where the sensor is located.

  • Poor blood flow to the area where the sensor is located.

  • Low hemoglobin or red blood cell levels (anemia).

  • A bone marrow disease that causes high levels of red blood cells, white blood cells, and platelets (polycythemia vera).

  • Recent inhalation of smoke or carbon monoxide.

  • Bright artificial lighting.

WHAT IS THE MEANING OF THE OXIMETRY READING?

The normal value depends upon your medical history and your elevation above sea level. For a healthy person at sea level, a saturation level equal to or greater than 92% is normal. However, if the person has a lung condition such as severe chronic obstructive pulmonary disease (COPD), a normal oxygen saturation may be a range between 88–92%. Consistent oxygen saturation levels below 88% is a concern and should be evaluated by your health care provider.