Sign Up Now For HEALTHbeat Our FREE E-mail Newsletter Sign up for our FREE email newsletter and receive a FREE report, Living to 100: What's the secret? You'll receive weekly briefings with health information you can trust from the doctors at Harvard Medical School. [ Close Window ]

• Harvard Health Publications • Order the Book • Contact Us

Sign up for our free e-mail newsletter, HEALTHbeat.   Email address:     Incontinence Weight Loss Prostate Disease Vitamins and Minerals Aching Hands See All Titles Common Medical Conditions Wellness & Prevention Emotional Well Being & Mental Health Women’s Health Men’s Health Heart & Circulatory Health   contact us		What happens when the test is performed? An estimate of your oxygen saturation can be made easily and painlessly with a clip that fits on your finger. This clip shines a light through one side of your finger; a detector measures the light that comes through the other side. This machine can make a good guess about your oxygen saturation because blood cells that are saturated with oxygen absorb and reflect light differently than those that are not. Blood cells are a bright red when they are loaded with oxygen, and they change to a bluish color when they are no longer carrying a full load. (This is why arteries are red and veins are blue in color.) This machine cannot give a perfect measurement of your oxygen saturation; it can give only a rough estimate, and its measurement can be affected by things as simple as red nail polish on your finger. A better test for measuring your oxygen saturation is an arterial blood gas test. For this test, a small sample of blood must be drawn directly out of an artery. Most routine blood tests use blood that is drawn out of a vein, so this test is a little different. The artery that is sampled most often is the radial artery in your wrist, the one you can feel when you take your pulse. To draw blood from this artery, your doctor or a technician feels your pulse before inserting the needle. Some patients find that it hurts a little more to have blood taken from an artery instead of a vein, but the procedure takes only a few seconds. Your arterial blood can be directly tested for its oxygen level, and other tests (such as the level of carbon dioxide and the pH of the blood) can be done as well.
		Would you like to:
		©2000–2006 President & Fellows of Harvard College

Close window