Oximetry

  • Medical Author:
    George Schiffman, MD, FCCP

    Dr. Schiffman received his B.S. degree with High Honors in biology from Hobart College in 1976. He then moved to Chicago where he studied biochemistry at the University of Illinois, Chicago Circle. He attended Rush Medical College where he received his M.D. degree in 1982 and was elected to the Alpha Omega Alpha Medical Honor Society. He completed his Internal Medicine internship and residency at the University of California, Irvine.

  • Medical Editor: Melissa Conrad Stöppler, MD
    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD

    Melissa Conrad Stöppler, MD, is a U.S. board-certified Anatomic Pathologist with subspecialty training in the fields of Experimental and Molecular Pathology. Dr. Stöppler's educational background includes a BA with Highest Distinction from the University of Virginia and an MD from the University of North Carolina. She completed residency training in Anatomic Pathology at Georgetown University followed by subspecialty fellowship training in molecular diagnostics and experimental pathology.

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What is oximetry?

Oximetry is a procedure for measuring the concentration of oxygen in the blood. The test is used in the evaluation of various medical conditions that affect the function of the heart and lungs.

How is oximetry done?

This is done using an oximeter, a photoelectric device specially designed for this purpose. A reusable probe can be placed on the finger or a single use tape probe is placed on the earlobe or finger.

What are pulse oximeters?

The oximeters most commonly used today are called pulse oximeters because they respond only to pulsations, such as those in pulsating capillaries of the area tested.

How common are oximeters?

Oximeters are now a virtual fixture in intensive care units, pulmonary units and elsewhere in hospitals and health care facilities.

How does a pulse oximeter function?

A pulse oximeter works by passing a beam of red and infrared light through a pulsating capillary bed. The ratio of red to infrared blood light transmitted gives a measure of the oxygen saturation of the blood. The oximeter works on the principle that the oxygenated blood is a brighter color of red than the deoxygenated blood, which is more blue-purple. First, the oximeter measures the sum of the intensity of both shades of red, representing the fractions of the blood with and without oxygen. The oximeter detects the pulse, and then subtracts the intensity of color detected when the pulse is absent. The remaining intensity of color represents only the oxygenated red blood. This is displayed on the electronic screen as a percentage of oxygen saturation in the blood.

Are there other types of oximetry?

Yes. Oximetry can also be done on blood that is within the heart (intracardiac oximetry) or on whole blood that has been removed from the body. More recently, using a similar technology to oximetry, carbon dioxide levels can be measured at the skin as well.

Medically reviewed by Joseph Palermo, DO; American Osteopathic Board Certified Internal Medicine

REFERENCE:

"Pulse oximetry"
uptodate.com

Medically Reviewed by a Doctor on 6/23/2015

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