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Mon, Mar 1, 2021 at 12:00 PM

What is Blood Oxygen and why is it important?

Medical terms we hear but may not fully understand

We’ve heard doctors and nurses use the term Blood Oxygen, but do we understand what it means and why it’s an important part of our overall health snapshot? It may be easier to understand than you think.

Simply put, blood oxygen level is a measure of how much oxygen red blood cells are carrying through arteries. The body closely regulates blood oxygen levels because maintaining the precise balance of oxygen-saturated blood is vital to your good health.

To determine the level of blood oxygen, doctors can test in one of two ways. An arterial blood gas or ABG test requires a small amount of blood drawn from the radial artery in the forearm. Sometimes the femoral artery in the groin or another site is used. Blood for an ABG test is taken from an artery while most other blood tests are done on a sample of blood taken from a vein. Drawing blood from an artery allows oxygen and carbon dioxide levels to be measured before they enter body tissues. The blood is then put into an ABG machine or a blood gas analyzer.

When doctors want a quick answer to blood oxygen levels, they use a small, mobile device known as a pulse oximeter. The pulse oximeter is clipped between any of the fingers for a few seconds. The reading appears on the pulse oximeter screen. This test may be slightly less accurate than ABG but is easier to perform when needed quickly. Normal oxygen levels in a pulse oximeter usually range from 95 to 100 percent.

Levels above 120 are termed hyperoxemia, which is most often seen in hospitals when patients are exposed to high pressures of supplemental oxygen for prolonged periods (3 to more than 10 hours). When the level goes below 90, the condition is generally termed as hypoxemia, which is relatively common in people with advanced chronic obstructive pulmonary disease or COPD. Levels under 60 are considered very low and indicate the need for supplemental oxygen.

Blood oxygen levels can get low due to problems that include:

  • Low air oxygen levels. Atmospheric oxygen becomes extremely low at high altitudes such as mountainous regions.
  • Decreased capacity of the body to take in oxygen. This can be caused by lung conditions that include:
  • Other conditions include:
  • Decreased capacity of the heart to supply the oxygenated blood back to the lungs. The most common causes are congenital heart diseases (heart defects present at birth).

Low blood oxygen causes inadequate oxygen supply to the organs and tissues of the body. Severe hypoxemia can become dangerous. If left untreated for a long time, it can end up affecting the brain or heart.