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Arterial Blood Gases

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Arterial blood gases (at sea level and breathing room air) 1
Partial pressure of oxygen (PaO2):

Greater than 80 mm Hg (greater than 10.6 kPa)

Partial pressure of carbon dioxide (PaCO2):

35–45 mm Hg (4.6–5.9 kPa)



Bicarbonate (HCO3):

22–26 mEq/L (22–26 mmol/L)

Oxygen content (O2CT):

15–22 mL per 100 mL of blood (6.6–9.7 mmol/L)

Oxygen saturation (O2Sat):

95%–100% (0.95–1.00)

The normal values for children may differ from the adult values listed here.

The concentration of oxygen being breathed, called the fraction of inhaled oxygen (FiO2), is also usually reported. This is only useful if you are receiving oxygen therapy from a tank or are on a ventilator.

Many conditions can change blood gas levels. Your doctor will talk with you about any abnormal results that may be related to your symptoms and past health.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include the following:

  • You have a fever or an abnormally low body temperature (hypothermia).
  • You have a disease that affects how much oxygen is carried in your blood, such as severe anemia or polycythemia.
  • You smoke just before the test or breathe secondhand smoke, carbon monoxide, or certain paint or varnish removers in closed or poorly ventilated areas.

What To Think About

  • Arterial blood gas (ABG) values alone don't provide enough information to diagnose a problem. For example, they can't tell whether low levels are caused by lung or heart problems. Arterial blood gas values are most helpful when they are reviewed with other examinations and tests.
  • An ABG test is often done for a person who is in the hospital because of severe injury or illness. The test can measure how well the person's lungs and kidneys are working and how well the body is using energy.
  • An ABG test may be most useful when a person's breathing rate is increased or decreased or when the person has very high blood sugar (glucose) levels, a severe infection, or heart failure.
  • If several blood samples are needed, a thin tube (arterial catheter) may be placed in an artery. Blood can then be collected when needed.

WebMD Medical Reference from Healthwise

Last Updated: September 09, 2014
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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