What is a Blood Oxygen Level?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon
Tanks of supplemental oxygen.
Tanks of supplemental oxygen.

A blood oxygen level is a measurement to determine how much oxygen is present in a patient's blood. At least 95% of the red blood cells in a sample should be carrying oxygen to fully meet the needs of the body. Oxygen is necessary for a number of cellular processes, particularly in the brain. Also known as the oxygen saturation level, this measurement is an important health indicator.

Oxygen being supplied to a patient with an oxygen mask.
Oxygen being supplied to a patient with an oxygen mask.

People may have low levels of blood oxygen because of malfunction in the lungs or the heart. Normally, the heart pumps deoxygenated blood into the lungs, where a gas exchange takes place, switching carbon dioxide, a waste product, for fresh oxygen. At each pass, a few red blood cells will miss the exchange, but a blood oxygen level test should show 95% to close to 100% of the cells getting new oxygen and providing the cells with enough to function.

The human respiratory system.
The human respiratory system.

If the heart is not pumping efficiently or a patient's lungs are functioning poorly, the blood oxygen level will start to drop. Patients can become cyanotic, developing bluish discolorations in their extremities, and may also become short of breath and very tired. Eventually, the lack of oxygen can cause tissue death, not just at the extremities but also in vital organs like the brain. If a patient has low blood oxygen, it is necessary to provide immediate treatment to get the level back up and then find out why so the doctor can correct the cause.

Blood oxygen level is measured by the percentage of red blood cells that are carrying oxygen throughout the body.
Blood oxygen level is measured by the percentage of red blood cells that are carrying oxygen throughout the body.

One method for assessing blood oxygen level is noninvasive and very easy. It involves clipping a device called a pulse oximeter to the patient's finger. It shines a light through the finger and estimates oxygen saturation on the basis of the light's behavior. The invasive option is to take a direct sample of blood from an artery for an arterial blood gas test. In this test, people look at oxygen, carbon dioxide, and bicarbonate levels in a patient's blood.

An oximeter is a non-invasive way of assessing someone's blood oxygen level.
An oximeter is a non-invasive way of assessing someone's blood oxygen level.

Immediate treatment for low blood oxygen level involves increasing the amount of oxygen the patient inhales. Patients can inhale a gas mixture or pure oxygen. A patient may require intubation if her airway is not very stable, or she can breathe from a mask or nasal cannula. As the level starts to rise, the doctor can order diagnostic testing to find out more about what is happening and work on treatments. A patient with asthma, for example, may need a new asthma management program to keep the airways more functional.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a wiseGEEK researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

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Discussion Comments

Sporkasia

I have read that meditation and deep breathing is a good way to raise oxygen levels in the blood. Believe it or not, we sometimes forget how to breathe. I know this sounds ridiculous, but many people do not breathe deeply enough, and this can decrease the amount of oxygen in the blood.

People under a great deal of stress often change their breathing patterns, and they are unaware they are doing do. This is one reason that stress can be so difficult on the body and on a person's general health. One of the best steps you can take to maintain good health is to take deep breaths and release them slowly.

Animandel

@Laotionne - Some people only need the extra oxygen while they are recovering for whatever illness or injury caused the low oxygen levels in the first place. Once their bodies recover and they are healthy again they are able to stop using the oxygen.

On the other hand, when a chronic condition is causing the oxygen levels to drop then the person will probably require additional levels of oxygen on a permanent basis.

Laotionne

My aunt spent a week in the hospital recently and when she left she was set up with an oxygen tank to take home with her because her blood oxygen level was lower than it should have been.

Now in addition to the portable tank, she also has a really long cord that she can use at home so she doesn't have to move the tank around with her. I'm wondering how common is it for people to get off of oxygen once they have gone on it? Is this something she will have to do the rest of her life?

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    • Tanks of supplemental oxygen.
      Tanks of supplemental oxygen.
    • Oxygen being supplied to a patient with an oxygen mask.
      Oxygen being supplied to a patient with an oxygen mask.
    • The human respiratory system.
      The human respiratory system.
    • Blood oxygen level is measured by the percentage of red blood cells that are carrying oxygen throughout the body.
      Blood oxygen level is measured by the percentage of red blood cells that are carrying oxygen throughout the body.
    • An oximeter is a non-invasive way of assessing someone's blood oxygen level.
      An oximeter is a non-invasive way of assessing someone's blood oxygen level.
    • Blood oxygen levels can be measured using an arterial blood draw and sample.
      Blood oxygen levels can be measured using an arterial blood draw and sample.