Partial Pressure Oxygen (PaO2) Test: Use, Procedure, Results


The partial pressure of oxygen, also known as PaO2, is a measure of the pressure of oxygen in the arterial blood. It reflects how well oxygen can move from the lungs into the bloodstream, and this often changes due to serious illness.

PaO2 is one of the components measured in the arterial blood gas (ABG) test , which also reports oxygen (O2), bicarbonate (HCO3) saturation, carbon dioxide (CO2) partial pressure , and red blood cell pH. …

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The purpose of the test

The PaO2 test can be used to assess the effect of breathing problems on oxygen supply, especially in a hospital or during an episode of severe respiratory distress.

The results are often used to determine the need for emergency care, such as supplemental oxygen or mechanical respiratory support . PaO2 values can also be used (in conjunction with other tests) to help diagnose a variety of chronic conditions.

Some conditions under which a PaO2 test may be required include :

In some situations, such as when oxygen therapy or ventilation (mechanical respiratory support) has been started, a repeat PaO2 test is used to assess whether the respiratory condition is improving or worsening and whether treatment needs to be adjusted.

Risks and contraindications.

There are very few risks associated with a PaO2 test. Because the test uses blood from a perforated artery rather than blood from a vein, the risk of bleeding or bruising is slightly higher .

If you are taking a blood thinner or have a bleeding disorder , your healthcare team may take special precautions during this test, such as controlling bleeding at the puncture site for a longer period of time or avoiding the test if absolutely necessary. …

Before the test

If you will have a PaO2 test as part of an outpatient diagnostic exam, you will need to make an appointment to do it.

If you have a breathing problem, you may need an urgent PaO2 test. When you are hospitalized and have this test to monitor your treatment or to track the progression of your disease, it can be scheduled at a specific time in relation to your treatment (for example, by adjusting oxygen support).


It takes about five minutes to draw blood for this test, but you should allow about an hour if you are testing on an outpatient basis. This will give you time to register, wait in line, and make sure the puncture site is not bleeding.


Outpatient PaO2 tests are performed in a healthcare provider's office, clinic, or laboratory where blood is drawn.

If you have this test done in a hospital or emergency, you may be able to stay in the hospital bed while your arterial blood is drawn.

What to wear

You can dress comfortably to perform the PaO2 test. Blood is often drawn from the radial artery , which runs along the inner surface of the wrist, so it is recommended that you wear a short-sleeved shirt or a shirt with sleeves that are easy to lift.

Food and drink

You can eat and drink whatever you want before this test because your diet will not affect the results.

Cost and health insurance

If possible, it is recommended that you check with your doctor or insurer if your health plan will cover the cost of the test and if it has a copayment.

The total cost of PaO2 can range from $ 12 to nearly $ 150. When you pay for the test yourself, you should ask about the cost in advance and think about finding out the price if you have the time.

During the exam

Whether you are in a hospital or have an outpatient PaO2 measurement, your procedure will be performed by a healthcare provider, skilled nurse, or technician.

Preliminary test

First, you need to check your arterial pulse. Although blood is usually drawn from the radial artery in the wrist, this is not always ideal. If your pulse is very weak due to serious illness or blood loss, you can use the femoral artery in your groin .

Sometimes a catheter (tube) is inserted into an artery during surgery or during long-term illness. In this case, your PaO2 can be controlled without sticking with a needle.

Throughout the test

The skin around the intended puncture site will be cleaned, usually with an alcohol wipe. A small needle is then inserted into the artery and connected to a tube. The pressure or pain is a bit uncomfortable, more unpleasant than the pain you feel when blood is drawn from a vein. However, most people tolerate this test.

Blood is generally pumped rapidly through the arteries. This allows you to quickly collect the volume of blood needed for analysis. Once a sufficient amount of blood has been collected, the needle is removed and a cotton ball or gauze is applied to the puncture site.

Your doctor will put pressure on the puncture site to stop the bleeding.

Post test

After the exam, your puncture wound will be bandaged. You may also need to wrap gauze around your wrist for a few hours.

After the test

Your wrist may hurt a little for a few days after the test.

Many people are able to return to their normal activities after taking a PaO2 test. However, it is best not to lift weights with your hand that is used to draw blood for several days after the procedure .

Management of side effects

If you feel pain, you can gently place an ice pack on your wrist. Ask your doctor if you can use mild pain relievers for pain and pain. Be careful with medications that also thin the blood (such as aspirin or ibuprofen ), as they can cause additional bleeding.

When to call your healthcare provider

If you experience any of the following symptoms, tell your healthcare provider immediately:

  • Severe pain in the wrist, hand, or arm.
  • Persistent bleeding
  • Pale or bluish fingers or hands
  • Numbness, tingling, or decreased feeling in the hand or fingers.
  • Swelling of the fingers, hand, or arm.
  • Weakness in fingers, hands, or arms

If arterial blood is drawn from an artery other than radial, be sure to tell your doctor if you experience these symptoms near the puncture site.

interpretation of results

With each breath, air is sent to the alveoli in the lungs. There, oxygen and carbon dioxide are transported between the lungs and the blood. Because the pressure of oxygen in the alveoli is higher than in neighboring capillaries (tiny blood vessels), it enters the capillaries .

When the body functions normally, the PaO2 is between 75 and 100 mmHg. Art. (At the sea level). A result in this range means that a sufficient amount of oxygen is supplied from the alveoli to the blood.

If your PaO2 is below the normal range, it is not. Lung diseases and breathing problems can increase your risk of developing low PaO2 .

Factors Affecting PaO2 Levels

Several factors can reduce PaO2 levels, including :

  • Partial pressure of oxygen in inhaled air: At high altitudes (for example, in mountainous regions), a decrease in atmospheric pressure reduces the availability of oxygen and the pressure of oxygen in the lungs.
  • A neurological disorder such as Guillain-BarrĂ© syndrome or amyotrophic lateral sclerosis (ALS) .
  • Lung damage due to injury or cancer.
  • Decreased hemoglobin concentration in blood cells : Having iron deficiency anemia means that red blood cells cannot efficiently transport oxygen molecules.
  • Obesity

All of these conditions lower the oxygen pressure in the lungs, which is reflected in the arterial oxygen pressure measured by PaO2.

Follow up

You may need to retest for PaO2, especially if your symptoms do not improve. You may also need to retest when it is time to change your oxygen supply or ventilation assist.

Often when respiratory support is reduced due to improvement, PaO2 is retested to confirm that respiration and oxygenation remain at optimal levels even with less support.

Get the word of drug information

Oxygen pressure is an important reflection of the function of the heart, lungs, and blood. While this test is quick, it can be a bit uncomfortable. Don't worry if you need to take a blood sample to measure PaO2. The results will determine your treatment and resolution of the breathing problem so that you feel more comfortable.

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